Evonik’s ULTRASIL Tires increase fuel efficiency

Company Profile:

Evonik Industries is one the world’s lead specialty chemical companies. One of the main goals of the company is to provide product that solve problems and provide a maximum benefit to customers and society. Recently, they have developed a more fuel efficient tire that does not compromise on performance through the implementation of a silica-silane system, known as ULTRASIL.

ULTRASIL:

The greenhouse effect is a natural process in which radiant heat from the sun is captured in the lower half of the atmosphere, directly resulting in higher temperatures and thus global warming. In order to reduce this greenhouse effect, most companies are working towards minimizing carbon dioxide emissions from transportation. Carbon emissions from combustion of energy fuels has accounted for 81.5% of total greenhouse gas emissions over the last several years, and global warming is quickly becoming a major problem throughout the world. Transportation contributes to this on a large scale, and it is responsible for 31% of the CO₂ emissions from the United States. However, Evonik’s silica-silane system (ULTRASIL) is a unique approach to this problem. ULTRASIL is created in several different forms and is applicable in many different situations, however its primary purpose is to serve as a coating for tires. This advanced tire technology can reduce the rolling resistance of tires, increase traction in wet conditions, and reduce carbon dioxide emissions. In general, tires have been targeted as quick way to reduce carbon dioxide emissions, as simple changes in size and shape can increase fuel efficiency by up to 15%.

ULTRASIL is able to reduce rolling resistance between tires and wet or icy road conditions due to the presence of intermolecular forces (IMFs), which can determine whether a solid will be hydrophobic (resists water) or hydrophilic (attracts water). This is an important concept to the concept of ULTRASIL because it is produced with hydrophobicity in mind. Being hydrophobic, water will adhere to the ULTRASIL coated tires, resulting in increased traction between the tires and the road. The major types of intermolecular forces that impact hydrophobicity include dipole-dipole forces, hydrogen bonding, ionic interactions, and London dispersion forces.

Dipole-dipole forces, hydrogen bonding, and ionic interactions are all known to be hydrophilic interactions. The larger presence of these forces in a molecule, the more the solid will attract water molecules. Dipole moments in a molecule are dictated by the polarity of a molecule. Polarity is the sum of all of the bond polarities in a molecule, resulting in dipole moments. The dipole moment is measured in a vector as the sum of the individual vector movements. For example, CO₂, a linear and non-polar molecule, has no dipole moment. Hydrogen bonds are the interactions of a hydrogen atom with a nitrogen, oxygen, or fluorine atom. They are a much more powerful force than dipole-dipole forces, resulting in a larger increase on the hydrophilicity of the molecule. Similarly, the presence of ionic bonds (interactions between positive and negative ions) can have the same effect.

London dispersion forces, the weakest of the intermolecular forces, are the sole forces that can raise the hydrophobicity of a molecule. This force, also called an induced dipole-dipole force, is a temporary attractive force that results when the electrons in two adjacent positions occupy positions that make the atoms form temporary dipoles. These forces occur in all molecules. In the production of ULTRASIL, Evonik has created a silica-silane system, where the hydrophobic regions of the molecule dominate, causing adhesive forces to arise and increase the tension between tires and wet/icy road conditions. More information about intermolecular forces can be found here, or

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Also, the chemical structures of the silica helps contribute to its unique properties. Silicon dioxide can exhibit one of the largest varieties of crystal structures among the compounds commonly available and used. These many different crystalline forms allow silica to be used in a broad range of applications, including ULTRASIL. Precipitated silica, which is key to this product’s functionality, is a specially prepared form that has an amorphous structure, similar to silica gel or glass, both of which are predominantly silicon dioxide, or silica. As already discussed, adding these silicon dioxide granules to the surface of rubber tires has many beneficial effects on vehicle performance, but binding this hydrophilic molecular solid to the long, continuous, and hydrophobic polymer chains that make up vulcanized rubber can be difficult. It is up to sulfur, linking the polymers of vulcanized rubber to make it more resistant to temperature extremes, to act as a coupling agent for silica, since the hydrocarbon polymers will not bond to it by themselves.

From what we know, however, ULTRASIL production takes a rather different approach to solving the problem of coupling silica to rubber: the silica-silane system. By treating the original rubber  material with various organosilanes, a surface that silica particles can easily bond to is created, making it possible to form the desired composite with more cross-links to the silica granules and a higher overall thermal stability than without the treatment. Organosilanes usually have both a nonpolar and polar end and can not only bond with vulcanized rubber, but also with the silicon dioxide particles, through dehydration synthesis of their hydroxyl groups with the hydroxyl groups that cover the surface of the silica particles.

While many of the specific details of the ULTRASIL manufacturing process are trade secrets of Evonik, the company does share the basic concept of how it obtains the very pure amorphous silica needed for its products: precipitation from solution. Precipitated silica is widely used in industrial processes around the world, and Evonik Industries is its largest producer. Just like in ULTRASIL, these fine silica grains are often used in rubber products like tires and shoe soles for benefits similar to those of Evonik’s products. Generally, an aqueous silicate salt is reacted with an inorganic acid (like H₂SO₄) to form insoluble silica in the following reaction:

Na₂SiO_3(aq) + H₂SO_4(aq) → SiO_2(s) + Na₂SO_4(aq) + H₂O_(l)

    After the silica precipitate has been dried, it still contains no more than 88% silicon dioxide according to Evonik, with most of the rest being water. The ensuing treatment to purify the product varies depending on the desired size and quality of the particles obtained, but eventually a fine powder consisting of 99% silica can be obtained. The precipitated silica used in the ULTRASIL product line consists of miniscule, porous granules often of nanoparticle size to allow a high surface area to volume ratio, with the 7000 GR variant having a surface area of 170 m² per gram. It is this kind of fine silica that allows for the reinforced rubber of the emerging “Green Tire” that advances in silica rubber have created.

Further Reading:

If you are interested in the chemistry behind Evonik’s ULTASIL, there is a lot of in depth reading available in scientific journals. A thorough account of this technology and the chemistry that drives it can be found

• In this study by Brinke, Debnath, Reuvkamp, and Noordermeer
• And this article by Park and Cho

Essentials of Fragrance Chemistry

By Matthew Tittensor, Nicholas Lang, and Sohum Sanghvi

Two more common hygiene products are perfume and cologne.  We know that these sprays smell nice and permeate throughout a room, but what is it that gives them their scent and more importantly why does it disperse?  In today’s blog post we will get into this by discussing the organic structures of esters, specific scents, commercial uses for esters, and the process of diffusion.

           An ester follows the format follows the format of the image to the right, with the R group being any hydrocarbon.  This is written a RCO2R’.  The alcohol component makes up the basis of the alkyl component and R’OH’s root name and is based on the longest chain with an OH attached to it. Meanwhile, RCO2H is the carboxylic acid, from which the –oate in the name is derived from.  The full name for an ester is an alkyl alkanoate. Now that the nomenclature is out of the way, what do esters smell like and would they be used in perfumes?

Esters often have a pleasant fruity aroma as can be seen in the chart to the right.  However, that does not necessarily make them ideal for perfumes.  Most simple esters give off these pleasant smells, but problems arise because they are not prepared to handle the sweat that a human body releases.  This sweat hydrolyzes the simple ester and can replace this seemingly nice smell with a harsh one.  A common example is that butyric acid smells like rancid butter, but ethyl butyrate, an ester it can be derived from, smells like pineapples.  This is one reason that simple esters are not utilized in the perfume industry.  However, perfumeries get around this by often including many esters in their products as well as essential oils to prevent the hydrolysis of the esters.  Esters serve a role in the food and beverage industry as well.

           Would you rather eat a delicious food that smells rancid or a mediocre food that smells delicious, if you did not know how each one tasted?  This is a problem that major manufacturers come to face when they make their products.  These companies utilize a combination of esters and essential oils as well to produce a scent that is please to both smell and taste.  It is not so simple as getting one pleasant odor and taste either, as the human has over 9000 taste receptors on its tongue and smell plays a large role in perception of taste.  To create an ideal, it takes a lot of testing and a wide variety of organic and synthesized compounds to be used.

           Diffusion is the movement of molecules from an area that contains a higher concentration to one with a lower concentration of the molecule.  These molecules are already in constant motion and move in random directions due to the random collisions that they experience with each other and other particles.  The net movement is always towards the lower concentrated expanse as more collisions occur on a more highly concentrated zone, making it more likely for the molecule to be pushed over to the other area.  Dynamic Equilibrium only comes to exist after the concentration gradient, difference in molecule distribution, is removed.  This applies to perfumes and colognes as they emanate from their more highly concentrated location on the wrist or neck to the areas surrounding the wearer.  This creates a nice scent around the user and fulfills the purpose of removing or covering up body odors.

We have taken a look at the concept of esters, specific scents, commercial uses for esters, and basics about the process of diffusion. Using the right ester is vital for obtaining the scent that is wanted, and diffusion is important for making sure the scent remains on the user and covers the body odors. In our next blog post, we will continue our discussion on fragrances and continue to unveil interesting chemistry behind perfumes and colognes.

Chemistry of Flow Batteries

Technology is progressing more and more with each passing day. In order to support these changes, advancements regarding power supply must also be made. At the moment, the trend is moving towards more efficient and sustainable sources of energy. The rechargeable, low-cost, and long-lasting flow battery seems to fit the bill perfectly. Of course, it is not as well known as the common lithium-ion battery because it is used on a larger scale rather than for small everyday items. It can be used to store excess electrical grid power which is then released during periods of high demand.

When you hear the word “battery”, the first thing that comes to mind is probably a package of AA or AAA batteries — you know, the ones with the adorable Energizer bunny on the front? Flow batteries are neither portable nor small. In fact, they consist of two liquid-filled tanks that are separated from the actual cell of the battery. These “tanks”, or electrolyte reservoirs, pump liquid electrolytes into two half cells separated by a membrane, as can be seen in the image below.

A reduction reaction takes place on one side and an oxidation reaction in the other, similar to the reactions within the fuel cells we mentioned in our last post. The membrane between the two half cells  keeps  the electrolytes separate, but is thin enough to allow certain ions to pass through in order to complete the redox reaction. Ions from both sides flow through the membrane and react with the electrodes on both sides of the cell, drawing energy from them. To store more power, the batteries can be stacked in a bipolar arrangement. At this point, they essentially provide unlimited electrical storage capacity. The only limit is the capacity of the electrolyte reservoirs.

Sounds pretty simple, right? Now for the interesting, and slightly more complex, part: how the actual energy storage takes place. The liquid electrolytes that flow through the cell are mixed with energy storing materials such as iron, vanadium, zinc, or bromine. Zinc-bromine flow batteries, for example, have a zinc anode in one half cell and a bromine cathode in the other. Aqueous zinc bromide is circulated through the two half cells. In discharge, (bottom image on right) a load is applied to the cell and the zinc metal on the anode is oxidized (Zn_(s)↔ Zn²⁺_(aq) + 2e^–) to form zinc ions and bromine is reduced to bromide ions at the cathode (Br_2(aq)+ 2e^– ↔ 2Br^–_(aq)). When the battery is completely discharged, the metal zinc on the anode dissolves in the electrolyte. It is stored there until the battery is recharged (top image on right), during which the reactions involving zinc and bromine are reversed. The zinc ions are reduced back to metal (Zn²⁺_(aq) + 2e^– ↔ Zn_(s)), thus plating metallic zinc back onto the electrode. On the cathode side, bromide ions are oxidized into molecular bromine in the aqueous solution (2Br^–_(aq) ↔ Br_2(aq) + 2e^–) which combines with an oil to form a dense, oily liquid called a polybromide complex. As more polybromide complex is created and more zinc metal is plated onto the anode, the energy stored in the system increases. Because there are always fresh electrolytes in both half cells, the system is always ready to produce full power, even when the pumps are off. The electrodes in the zinc-bromine batteries don’t take part in thereactions but rather function as substrates, so repeated cycling won’t cause the electrode materials to deteriorate, as it would in most other rechargeable batteries.

So far, flow batteries seem like the best option available. The only problem is that they’re not quite available — not commercially, at least. Right now, the main issue is cost. The most commercially developed flow battery utilizes the rather expensive metal vanadium. For this reason, a team of Harvard researchers have recently developed a new type of metal-free flow battery that instead uses organic molecules called quinones, specially those found in rhubarb. According to Harvard author Roy Gordon, there is a limited number of metal ions that can be put into solution and used to store energy, none of which can store large amounts of renewable energy. For this reason, researchers have turned to organic molecules. The quinone used by the Harvard team is known as 9,10-anthraquinone-2,7-disulfonic acid (AQDS). What is unique about AQDS is its capacity for rapid reactions. It is able to undergo quick and reversible two-electron two-proton reduction on a glass-like carbon electrode in sulfuric acid. Although the small battery prototype has only run through about a hundred cycles, so far it has exhibited little to no losses. The model displays nearly the same performance as vanadium flow battery, but is much less expensive.

Flow batteries have a promising future, though they are not widely available at the moment and there are still unresolved issues regarding cost and production. Eventually, large quantities of energy will need to be stored and conserved in order to sustain our population and the great demand for power. Flow batteries will undoubtedly provide the best and most efficient solution.

The Antidepressant

Kinetic and mechanistic evaluation of antidepressant medication

A Brief Overview 

Neurons in the human brain transfer information through an electrochemical process that culminates in the brain interpreting the transmitted data.  Between normal human neurons there exists a synapse through which envoy neurochemicals cross. The presynaptic, or initial neuron taking part in communication, produces chemical courier neurotransmitters. After being transported to the neuron’s external surface, these neurotransmitters are sent into the synapse and find a receptor area on the secondary, or postsynaptic, neuron. By doing so, the chemical messengers have now relayed their message, which will catalyze processes in the secondary neuron, among which include further construction of new neurotransmitters. When a surplus amount of neurotransmitters are put into the synapse, the initial neuron has the ability to reclaim this excess. Portions that go through reuptake are destroyed in the neuron and used as crude product for future undertakings. At the origin of antidepressants were the monoamine oxidase inhibitors, or MAOIs, which stemmed from the tuberculosis drug iproniazid. This medication became a treatment for depression, having the ability to obstruct the elimination of recycled neurotransmitters. A heightened sense of positive mood and energy in those who were medicated came from blockage of the enzyme that disintegrated norepinephrine, serotonin and dopamine.

Tricyclic antidepressants

In an analogous manner, tricyclic antidepressants hinder reprocessing of norepinephrine and serotonin, both expanding the success of the message in traveling to the second neuron and permitting neurotransmitter excess to remain in the synapses. Tricyclic antidepressants (TCAs) categorize a set of antidepressant medications that have homologous chemical structures and efficacy. Due to depression’s perceived roots in the disproportion of neurotransmitter levels, tricyclic antidepressants promote levels of norepinephrine and serotonin while impeding the function of acetylcholine. Anafranil, Elavil, Norpramin, Pamelor, Sinequan, and Tofranil are all
commercial names of tricyclic antidepressanst that are currently on the market, representing a now aged class of treatments combating depression. Muscarinic, histaminergic and α1-adrenergic receptors are antagonized in the action of classical TCA drugs, leading to anticholinergic (rendering inactive the neurotransmitter acetylcholine), sedative, and cardiovascular effects. In vitro, fluoxetine unites with the aforesaid receptors in the brain tissue with less efficacy than TCA drugs. As identifiable through their names, these TCAs have a three-ring chemical structure. For example,

in imipramine (tofranil), the crucial portions of antidepressant activity include the ring system, sidechain extent, and location of the substituent groups. In this way, the most vigorously occupied compounds are the secondary methylamines (organic compound) and a small amount of primary amines (functional group with a atom of nitrogen coupled with a lone pair). In terms of sedative action apart from imipramine’s antidepressant properties, the tertiary amines deal with this mechanism while not taking part in the prime purpose.

Mechanism of Action in Tricyclic Antidepressants

Selective Serotonin Reuptake Inhibitors

As opposed to TCAs, there exists a class of compounds termed selective serotonin reuptake inhibitors(SSRIs), now the most prescribed antidepressant medications in numerous countries. In the creation of the SSRIs the method of rational drug design was used for the first time among the psychotropic drug class (psychoactive drugs traverse the blood-brain barrier, affecting the central nervous system of the human body and altering brain activity), where a definitive biological mark was identified and made an objective to a treatment.  An example of a prominent selective serotonin reuptake inhibitor, working by delaying the reuptake of serotonin into the human platelets so the serotonin that is released remains for a longer period of time, is Prozac. The chemical formula of Prozac is C₁₇H₁₈F₃NO (systematic name: N-Methyl-3-phenyl-3-[4-(trifluoromethyl)phenoxy]-1-propanamine. Prozac is the trade name for Fluoxetine.  The fluoxetine molecule contains a variety of functional groups. There are two phenyl groups (benzene rings), an ether, and an amine.  Prozac is also a chiral molecule, meaning that they display a symmetry to their mirror image, often caused by the location of an asymmetric carbon atom in the general structure. This is a feature to be noted due to its usages in inorganic, organic, physical, and biological chemistry. It is metabolized by CYP2D6 by the liver, characterized by its slow rate and a long half-life in the confines of the system. Slow aggregation leads to delay in the manifestation of meaningful effect. It is also an agonist for 5HT2C receptors, linking back to the first blog post on beta-agonists.

Agonists, as aforementioned in the previous post, are chemical compounds that bind to receptor area and initiate the receptor to a form of action. Contrary to an antagonist which thwarts an action, the agonist strength is strongly linked to its half maximal effective concentration, otherwise known as EC50. This is the concentration of the substance that causes an intermediate effect between a minimum and maximal point after a definite period of time. In research regimens that follow a dose response, this represents the 50% efficacy point, and correlates to the IC50 that ascertains a substance’s inhibition. The slowing of the increasing ligand concentration response is an inflection point at which the EC50 occurs. This is pertinent due to the fact that the ligand is the functional group molecule or ion that connects to a center metal atom in the creation of a coordination complex, where there is a transfer of electron pairs from the ligand to the metal element. The bonds created in the process can be characterized as ranging from the covalent strength to ionic bonds, while the bond order is conventionally from one 1-3. In most circumstances, these ligands are also Lewis bases, and in Gilbert N. Lewis’ definition, are characterized as electron-pair acceptors that have the capacity to react with a Lewis base and result in the Lewis adduct. Furthermore, the ligand is what prescribes the reactivity of the central metal atom and redox. In conditions where the oxidation state is unclear, the ligand is non-innocent, present in heme proteins and with redox not focused on the ligand. (The innocent ligand does not change in oxidation state, for example in the the reduction of MnO₄^– to MnO₄^2-. As you can see, the transformation occurs in the change in oxidation state of manganese from 7+ to 6+. The oxide ligand remains at an oxidation state of 2-, though a meticulous analysis would show that the ligand is changed in an alternate way by the redox).

3D animated view of Prozac Molecule

The Mechanism of Prozac

 

Chemistry in Cleaning Instruments

Instrument cleaning products generally rely on similar properties of the solutions used. For instance, the type of water used (tap, distilled, de-ionized, etc.), the temperature and pH of the solution, buffering agents, catalysts or inhibitors, etc. are all heavily considered when a chemist is creating the cleaning product. To fully clean most instruments, it is best to place the instrument in a tank full of the solution and shake or stir the water, as long as it does not damage the instrument. Generally, these solutions function best at 100-140º F, and are basic with a pH of about 9 in order for the chemicals to stay stable and dissolve protein and fatty residues (since a few chemicals in cleaning products are less stable at lower temperatures).

As far as brass instruments go, cleaning is usually as simple as submerging the instrument and running a snake brush through it, with maybe some soap. However, the maintenance of a hunk of metal that moves and requires precise tuning can be more laborious.  When you go to purchase a brass instrument, depending where you go, they’ll often offer to sell you a starter’s pack at a great deal (which is usually a rip off). But in those kits there is one thing that is definitely essential and you would have to buy anyhow. This is valve oil, an essential lubricant for your instrument. There are many types of valve oil, some specialized for rotary valves (like french horn, some tubas, bass trombones, and some strange trumpets), and others for the standard piston valve. In addition to this, a slide grease is also desirable for you slides (tubes of metal that you can pull out and push in varying amounts to affect tuning).  Both these substances have a similar basic goal, allow smooth movement of a part on the horn, and create a bit of a seal that ensures there are no air leaks.  The difference, is the valve oil is designed for the valves to move quickly, swiftly, and quietly, whereas the slide grease is to cause the slide to stay stuck in the same position, yet still be adjustable later.  You’ll notice the physical difference between these substances is valve oil is an oil in a bottle, and slide grease is a lard-like material in what looks like a chapstick (be warned, do not make that mistake!).  These substances are both lubricants, and you should noticed that they are both best described when equated to common fats (oil and lard), and this is because a lubricantis a fat or a lipid.

It is comprised of saturated carbon chains (see above), and has the useful quality of being adhesive to both surfaces (so that it is not rubbed of the contact surface), but still provides separation between the two surfaces. This separation allows for smooth motion.

Now, you should be able to tell that some oils are thicker than others, and you should especially be able to tell that slide grease is much thicker than valve oil. As stated on the same site where these wonderful images come from, oils tend to have carbon chains of 15-20 carbons, whereas greases have carbon chains from 20-25 carbons. By adding more carbons, you make it so that the chains get ‘tangled’ together more, causing the material to move more slowly. Imagine taking a bunch of short 1/2″ snippets of string laid out, and rolling them around with the heel of you palm. Nothing would really happen. But if you did this with a bunch of 6″ strips, they’ll start to tangle around each other, inhibiting further motion.

As far as lubricating instruments goes, there’s no need to work outside of room temperature (or roughly near that), however since we are on the topic of lubricants, there is one other thing that needs mention. Now we know that as the energy of the system (a lubricant) increases, such as by temperature increase, the molecules begin to move around more and overcome their Inter Molecular Forces (IMF). If we look at any standard saturated carbon chain,  you’ll see that being perfectly symmetrical and only containing C-C and H-C bonds, the only IMF present would be LDF.  So, if as the temperature increases, the energy increases to a point where the lubricant vaporizes by overcoming IMF, the simplest way to counteract that and allow our lubricant to work at higher temperatures is to use a longer carbon chain which would result in a higher IMF.  Therefore, thicker lubricants are used in the presence of heat, such as in the engines of the machines that shape brass or in the equipment that handles the melted metal alloys at extremely high temperatures.

Although brass elements are generally cleaned with trichloroethylene and perchloroethylene, violins are usually cleaned with phenolic resin solutions, resorcin/formaldehyde solutions, or saligenin/formaldehyde solutions. The resorcin/formaldehyde solution is mainly used to give the wood an “outside shell” and keep the wood strong so it does not erode. The saligenin/formaldehyde is used to hydrolyze with the debris on the instrument so it may be removed after being rinsed. The phenolic resin solution ( (HOC6H4CH2)2O + H2O ) is the most common one since its the most active in the cleaning process. The solution does not only also give the instrument is sturdy shell, but its alkaline properties enable it to also remove debris the most effectively. Further, this solution generally decreases the dampening of the sound produced. After the violin is soaked in these solutions, it is rinsed off and dried so it may be used like it is brand new once again.

While the tuning of a piano is a more complex process than that of any mobile string instrument, the cleaning of piano strings is that of very intricately detailed work.  It is much more necessary than cleaning of, say, violin strings, as the metal materials that make piano strings and their coiling are much more prone to rust and environmental decay.  The copper strings in the lower register of the piano, specifically, can be ruined over time without proper cleaning in areas with a high amount of sulfur in the air.  Sulfur and Copper combined make for a very volatile and rapid chemical reaction, one that can easily ruin the quality of a piano string.  To avoid any strings, copper or steel, from rust or any other collateral damage, it is a good idea to clean the strings with a cleaning solution once every now and then.  Anything that will remove any slight black or rusty residue from the strings should suffice.

Now… if you’re unfortunate enough to stumble upon a piano that seems to have lost any hope in being well restored, there are a few options. While buying and replacing strings is the simplest option, it is much more expensive and may not be worth it in the long run, especially if the poor piano is like this due to an environmental factor like the sulfur prevalent air as mentioned before.  You wouldn’t want something like that to happen all over again to a set of brand new strings. Your best bet is to clean them with a more strenuous process.

It is best at this point to remove the strings and separate them from each other. This is easier said than done, however necessary to remove a majority of the rust or residue.  The easiest way to remove most of it is to simply hang the strings on a clothesline outdoors and hose them down.  Afterwards, it is a good idea to pour hot water on the strings and immediately douse them in a generous amount of cleaning material used in items such as ovens.  The boiling water will make the outer surface of the strings warmer, making reactions between cleaning products and residue happen much faster and more spontaneously.

The Chemistry behind Mascara:

What really is in your vanity?

Mascara, the dark pigment inside a tube that one paints across their eyelashes, is not a simple cosmetic. Used to draw attention to the eyes by darkening and thickening eyelashes, mascara enhances and beautifies one’s appearance. Tracing back to ancient Egypt in 4000 B.C. as a dark pigment formed from natural ingredients such as plants, fruits, and animals, mascara can now be found in a liquid, cream, or cake form. Varying chemical compounds dictate the properties of mascara, whether they be hydrophilic or hydrophobic. However, the most basic components, including pigments, oils, waxes and preservatives, are always prevalent.

But what is it that allows mascara to hold these chemical properties? How does it display such beautifying effects? What is the difference between hydrophilic and hydrophobic mascara?

 

Compounds/Ingredients

The main ingredients of mascara include a pigment to darken lashes, such as carbon black or iron oxide, polymers to film the individual lashes and stiffen the mascara (ceresin, gum tragacanth, methyl cellulose), thickening waxes or oils for enhancing lashes, and preservatives to maintain shelf life. Mascara is made of a heavy base of wax (usually beeswax but also paraffin, carnauba or palm wax), oils (mineral, sesame, eucalyptus, or turpentine oil), and lanoil (moisturizer) nylon or rayon microfibers. Therefore, carbon blackand beeswax are among the most prominent ingredients in mascara. Iron oxide is used to add a brownish tint to mascara, while carbon black adds a deep black  pigment.

Electron Microscope image of carbon black

Chemical structure of beeswax

Carbon Black

• Produced by incomplete combustion of hydrocarbons, carbon black usually exists in pellets or powder form and is used in rubber, plastic products, and pigments. It is made of fine particles, mainly carbon, and carbon black has a complex structure with spherical particles fused together. It has different functional groups like the hydroxyl and carboxyl group found on its surface. The diameter of the particles affects the blackness and how dispersible the substance is once mixed with resins. The smaller the particle size, the darker the compound is. Therefore, the small particle size of carbon black allows it to be prominently dark and black.

Carbon black pigment in a powder form

• Increasing the size of the structure lessens the blackness of carbon black but makes its dispersibility properties stronger. Since it also has a relatively large structure, carbon black is very conductive. Because of the vast amount of hydroxyl groups in carbon black, it has a strong affinity to inks and paints, and this increases dispersibility.

• Carbon black is a network solid, which is formed by atoms or molecules held together in large network (lattice structure) by covalent bonds. Network solids are characterized by having high melting points and boiling point temperatures because of their strong bonds. In mascara, carbon black was used as a pigment due to its dark color. Its other properties prove themselves useful in composition of mascara; for example, the high boiling point prevents mascara from evaporating off the lashes.

Beeswax

• Manufactured naturally by bees, beeswax (approximate chemical formula: C15H31CO2C30H61) is made up of fatty acids, esters, long-chain alcohols, and carbohydrates (fructose, glucose, and sucrose) and it can be used in painting.

• It is a tough wax made of many compounds, the most prominent ones being palmitate, palmitoleate, and oleate esters with long-chained aliphatic alcohols  (30-32 carbons). It has a melting point of around 62 °C. In mascara, the wax keeps the eyelashes separated, lengthened, and thickened. It keeps the color attached to the lashes because it is the heavy base.

• Wax-based mascaras are able to lift and bend eyelashes, and they are often preferred over dryer mascaras, as the wax prevents the mascara from crumbling and falling off the lashes. Since wax is a nonpolar substance, its molecules are able to stick together due to London dispersion forces (LDFs). As discussed in our previous post, LDFs create attractions between molecules by creating a dipole between separated electrons and nuclei of atoms. In larger molecules such as fats and waxes, LDFs play a major role in creating intermolecular attractions, since larger molecules contain more electrons and protons for producing a greater dipole. Therefore, the LDFs in wax help to keep the mascara together, preventing it from falling off the lashes.

Polymers

• A polymer is a large molecule that is made up of repeating monomers, commonly called subunits. One commonly used polymer in mascara is polyvinylpyrrolidone (PVP).

• Polymers are added to mascaras to create a film to encapsulate each individual lash. Some polymers are able to do this because of their binding and film forming properties. Polymers create a film around eyelashes because of their transport properties. Molecules rapidly move through the polymer matrix with the property of diffusivity. PVP is water soluble and is therefore able to cling on to other polar molecules.

Waterproof vs. Non-waterproof

Mascara can be split into two categories: waterproof and non-waterproof. Non-waterproof mascaras are hydrophilic, making them soluble in water. Meanwhile, waterproof mascaras can be called  hydrophobic. What exactly is the difference between these two?

Water soluble (hydrophilic) mascara contains water, glyceryl stearate, ammonium acrylates copolymer, polyvinyl alcohol, and alcohol. Ammonium acrylates copolymer contains nitrogens bonded to hydrogens. Since nitrogen is very electronegative, the hydrogens attached to nitrogen can form highly polar bonds, and this allows these hydrogen to participate in hydrogen bonding with other molecules. Hydrogen bonding occurs when hydrogens are bonded to an extremely electronegative element like oxygen, fluorine or nitrogen. The hydrogens obtain a high partial positive charge, as their electrons have been pulled far away from them, while the electronegative atom has a much stronger pull on the electrons, giving them a high partial negative charge. Since these charges are relatively large, they can participate in very strong dipole-dipole interactions with other polar molecules, and this is known as hydrogen bonding. Water (H2O) is a polar molecule that can participate in hydrogen bonding. It will easily form hydrogen bonds with the nitrogen-hydrogen bonded atoms in ammonium acrylates copolymer. Since these two compounds attract each other, the mascara can easily become dissolved in water, explaining why non-waterproof mascara can be removed upon contact with water.

Ammonium acrylates copolymer

Meanwhile, waterproof (hydrophobic) mascara contains petroleum distillate, polyethylene, carnauba wax, pentaerythrityl hydrogenated rosinate, and tall oil glycerides. The large presence of waxes and oils automatically indicates that the substance contains nonpolar components, as these waxes and oils consist of only carbon-hydrogen bonds. Since these molecules are nonpolar, they will not be able to dissolve in water, which is polar. Instead, other nonpolar molecules, such as petroleum distillate oil, are required to remove the mascara from the lashes. Often, stores will sell special makeup removers containing these nonpolar oil molecules, and these makeup removers must be bought in order to sufficiently remove waterproof mascara.

The next time you are considering which mascara to purchase, think about how much chemistry influences your decision. What ingredients make up the luscious substance, how mascara forms a film around your eye lashes, and what prevents your tears from running waterproof mascara down your face?

Coming up next: An interview with cosmetic chemist Mr. Stephen Herman!

Manufacture of Local Anesthesia: Cocaine

by: Sol Lim, Anthony Xu, Miguel Zevallos

Introduction:

Cocaine, also known as benzoylmethylecgonine, is a very controversial drug today because although it can  be used as a local anesthetic, usually in optic or nasal surgery, it is actually used primarily as an expensive, addictive, and extremely detrimental illegal substance. It is usually seen as a white powder; typically cocaine is transported as a salt known as cocaine hydrochloride.Cocaine is a powerful nerve stimulant, as referenced in the last post, and is usually associated with euphoria, alertness, and increased energy. However, its side effects include cardiac arrests, myocardial infarctions, hallucinations, hypothermia, and through chronic usage, most likely death.

Origins:

The production of cocaine begins from the leaves of a South American plant known as the Erythroxylon coca, or coca plant. The indigenous peoples of South America have been chewing the leaves of the coca leaf for centuries, as they contain many vital nutrients, as well as several alkaloids, precursors to cocaine. The leaves of the coca plant are consumed by millions of people in the Andes, where it grows, and has no negative side effects. In fact, coca leaves are prescribed to help with altitude sickness, dizziness, and headaches. It is considered a staple crop in the countries surrounding the Andes Mountains and sold in various forms.

However, complete isolations of the cocaine alkaloid from the coca leaves was not achieved until the mid-1850’s by Friedrich Gaedcke. Throughout the late 1800’s, doctors and businessmen alike became interested in both the medicinal and the economic potential of the isolated cocaine molecule. By the early 1900’s, cocaine had become a widespread local anesthetic, and was sold commercially until its prohibition in the later 20th century.

Synthesis of Cocaine:

The illicit synthesis of cocaine involves three primary steps:

1. Extraction of crude coca paste from the coca leaf

2. Purification of coca paste to coke base

3. Conversion of coke base to cocaine hydrochloride.

Extraction: 

The most popular way of producing coca paste is through the solvent extraction technique.

In this process, coca leaves are macerated, dampened, and placed in a maceration pit. Alternately, there is a pre-mixed aqueous solution of the inorganic base which is then poured over the macerated leaves, ensuring that the cocaine is in its free-base form. A water-immiscible organic solvent such as gasoline is later added  to the already dampened coca leaves. This mixture is then either stirred occasionally for the process of 3 days or vigorously mixed, taking only several hours. One of the biggest determinants in the extraction is highly dependant on how fine the leaves were chopped up because this increases the efficiency of the transferring of the cocaine base to the solvent. After the extraction process is complete, the solvent is then removed from the mixture causing the new solution to be mostly organic with the occasional aqueous layer. this new large volume of organic solvent is then back-extracted with a significantly smaller volume of dilute sulfuric acid. This acid is essential because it converts the cocaine-free base into a new substance, that dissolves in the aqueous layer, called cocaine sulfate. The organic solvent then separates, which leaves only the dilute sulfuric acid solution of cocaine sulfate, forming a new solution called “agua rica”. An excess of base is then slowly added to the solution while stirring. This base is responsible for the neutralization of the sulfuric acid, converting the cocaine sulfate back to the free base, which leaves the solution due to its precipitation. This free base, however, precipitates out of the solution in solid form with moldy and yellowish complexion. This is what is known as the coca paste. After this process is done, the coca paste is then dried, filtered, packaged, and is ready to bes sent a lab for the next step.

Purification:

Once the coca paste is made, the next step is to convert this paste to what is known as the coke base through a purification process. The level of cocaine purity once the coca paste is made lies between 30 and 80%. The rest is made up of alkaloidal impurities and inorganic salts that are alter to be removed in order for there to be the highest possible concentration of purified cocaine. The first step in the conversion to the coke base is to redissolve the coca paste in dilute sulfuric acid. The solution formed is then titrated with a fairly concentrated aqueous solution of a powerful oxidizing agent called potassium permanganate.  This potassium permanganate is reduced to manganese dioxide when it reacts with the oxidizable alkaloidal impurities of the coca paste. Once this manganese dioxide is formed in the solution, it quickly proceeds to precipitate out of the solution. The best way to do this reaction is by slowly adding the solution of potassium permanganate to the solution of dissolved coca paste in dilute sulfuric acid and vigorously stirring. The key is to add the exact amount of potassium permanganate so that the final solution is colorless, indicating that the manganese dioxide is fully precipitated out of the solution. If too much potassium permanganate is added, it can cause in decomposition and loss of cocaine, which is the ultimate goal of the entire process. After the solution is complete, it is still acidic and therefore needs to be treated by stirring with a solution of base, for the most part ammonia. The ammonia neutralizes any and all of the remaining sulfuric acid as well as the cocaine sulfate. This final product is called the coke base and is dried, filtered, and packaged.

Conversion:

The final step is known as conversion, where the cocaine base is undergoes several chemical procedures to finally synthesize cocaine hydrochloride in its crystalline form. Unlike the previous steps, cocaine hydrochloride processing is much more dangerous as it requires the use of hazardous, rare chemicals and equipment. In order to convert cocaine base to cocaine hydrochloride, the base is dissolved into diethyl ether to create a solution, allowing the extraction of any impurities or undesirable material from the solution through filtration.  Next, hydrochloric acid is diluted in acetone and the resulting solution is mixed with the cocaine solution. The presence of hydrochloric acid allows ion-pairs to be formed with the cocaine base, precipitating cocaine hydrochloride out of the mixed solution as shiny white, flaky crystals. This precipitation process usually takes between 3 to 6 hours to fully complete the crystallization process. However, if time is limited, the rate of ion-pair reaction can be accelerated by placing the solution in a hot water bath called a “bańo maria”. Though the total reaction time is reduced to a favorable 30 minutes, the use of this technique has been reported to demean the quality of cocaine hydrochloride. After crystallization, the cocaine hydrochloride is then dried using heat lamps or microwaves and prepared for distribution.  Illicitly synthesized cocaine hydrochloride usually ranges 80%-97% purity, with many alkaloidal impurities (present in the coke base) appearing in the final product.

Bańo maria pictured above

Especially in South America, the acquiring of the solvents used in this step (diethyl ether and acetone) is difficult therefore manufacturers resort to alternatives that will be an adequate substitution. When choosing the alternatives, the manufacturers must keep three concepts in mind in order to successfully synthesize cocaine hydrochloride:

1.       Solubility of coke base in diethyl ether alternative

2.       Miscibility of acetone alternative with hydrochloric acid

3.       Insolubility of cocaine hydrochloride in combined solvent mixture (diethyl ether alternative + acetone alternative)

The most common substitutes for the solvents include methyl ethyl ketone, ethyl acetate, toluene, and so forth.

Crack Cocaine:

               A rising, popular trend in modern society is to convert cocaine hydrochloride into crack cocaine: a more potent form of cocaine has been recorded to induce a very intense high within a matter of seconds. Though the response is immediate making it addictive, it is short lived and followed by an intense period of depression and desire for more. Common impurities within crack also release toxic fumes when combusted therefore posing a health risk to using crack cocaine. Opposed to powder cocaine hydrochloride, crack cocaine vaporizes (90^o C) at a much lower temperature therefore allowing it to be inhaled and triggering an immediate response by the body to its effects. The cause for this change in melting point is a result of how crack cocaine is produced. Crack cocaine is synthesized by dissolving cocaine hydrochloride in a mixture of water and baking soda and heating the solution until all the hydrochloride is removed. The remaining product is a waxy substance that hardens when dried: crack cocaine.  The color generally ranges from white to a yellowish cream to a light brown.

Newlight Technologies: Plastic from Thin Air

Company Profile: Newlight Technologies, LLC

Newlight Technologies, founded in 2003 has just recently brought its innovative, game changing products to market. Through a patented carbon-sequestration process using biocatalysts, Newlight technologies is able to extract carbon from greenhouse gasses in the air and convert them to AirCarbon, a high performance thermoplastic that serves as a highly viable substitute to oil-based plastics. AirCarbon plastics aren’t simply low carbon, or carbon neutral; requiring less carbon emissions to produce than used in production, AirCarbon is carbon-negative, having the net result of reducing greenhouse gas pollution. Amazingly, eco-friendly AirCarbon plastics are less expensive than oil-based alternatives. To this extent Newlight Technologies succeeds in creating a product that is eco-friendly, high performance, and commercially competitive; a recipe for success.

Check out this quick video from Newlight.

Thermodynamics

It is truely remarkable to consider the thermodynamic challenges to creating a product such as AirCarbon plastics. Qualitatively speaking, sequestering carbon from the atmosphere and using it to produce plastics represents a huge decrease of entropy within the system. Gaseous carbon dioxide and methane mixed in the atmosphere have a great amount of positional entropy, with gaseous molecules flying around in the atmosphere near-evenly mixed with a **tail of gasses that compose Earth’s atmosphere. To contrast, consider the neatly arranged polymer chain of carbon molecules that make up AirCarbon, the end result of Newlight’s process. The latter has considerably less entropy.

While the highly significant change in entropy of the system (the carbon used to make the plastics) by no means makes the process of converting gaseous carbon to plastic impossible, it is important to consider the constraint that the whole process is carbon negative — they have to expend less carbon emissions to make the plastic than carbon they sequester and transform into plastic.

Consider Gibb’s free energy equation:

In order for the reaction converting gaseous carbon emissions into carbon polymers to occur in a forward direction, free energy (G) must be negative. Given a large negative entropy (S) characteristic of a conversion from a gas to a solid, there must be an even greater negative change in enthalpy (H). In basic terms, the system must give off a lot of energy, making the reaction highly exothermic.

 

Molecular Structure of AirCarbon

The end product is Newlight’s trademarked AirCarbon, a high performance thermoplastic that can serve as an affordable and effective substitute to polypropylene, polyethylene, ABS, polystyrene, and TPU. AirCarbon is a thermoplastic, it is a plastic polymer that becomes pliable when heated. This makes AirCarbon appropriate for a number of industrial applications and makes it versatile for producing many products in many different ways.

A polymer is a macromolecule composed of small repeating subunits, called monomers. Step 3 of Newlight’s GHG to Plastic process gives an example of a monomer. A polymer is made by covalently bonding many monomers together, which could theoretically be extended infinitely. Through polymerization, monomers can be used to build long polymer chains or three dimensional networks. The example below shows a polymer chain of polyethylene, showing how the individual ethylene molecules are connected to create a continuous chain. An important difference to consider between the individual monomers and the polymer chain in this example is how the double bonded carbons in the monomer units become single bonds in the polymer. For a good introduction to polymer chemistry watch this video.

Because polymer chains are only covalently bonded in long linear chains, there are other molecular forces to account for in three dimensional plastics, primarily Van der Waals forces. Illustrated by the dotted lines, Van der Waals forces are relatively weak attractive forces that occur due to partial charges in polar molecules. Van der Waals forces can hold together lengths of a polymer chain, allowing it to form three-dimensional solids.

This also provides a ready explanation for how thermoplastics can be malleable when heated and solid, or even brittle when cooled. At high temperatures the kinetic energy of the polymer chain is able to overcome the Van der Waal forces holding it in a particular arrangement, so it becomes malleable. Once the polymer is arranged into its desired shape it is allowed to cool, allowing the Van der Waal forces to take hold and set the polymer in its shape. At very cold temperatures, there is less and less kinetic energy in the molecule to oppose the Van der Waals forces making them play a very significant role. At these low temperatures the forces are relatively strong, and make the material brittle, explaining why plastics crack easily at cold temperatures.

So What?

The beauty of Newlight Technology is that it is truly sustainable and truly convenient. Newlight offers a cost effective solution to create eco-friendly plastics, completely turning the tables when it comes to environmental sustainability. Plastic, normally seen as an eco-unfriendly and destructive material can now be part of the solution to pollution and global warming. AirCarbon is biodegradable, making it eco-friendly cradle to grave. It gets extracted from the atmosphere in a carbon-negative process, gets turned into a useful material for human expenditure, and then when it is put to waste (as it inevitably will) it breaks down back to the earth and the atmosphere. What is particularly promising about Newlight is the fact that its products are less expensive than their oil based counterparts, again defying the expectation that eco-friendly means more expensive or less convenient.

Midazolam: The Anesthetic That Makes You Forget

  It is amazing how far medicine has progressed. Can you imagine that only a little over 100 years ago the most common form of treating an illness was bloodletting? Today there are thousands of different medications and drugs available to make a successful treatment. For example, midazolam, often called by its brand name Versed, is a type of oral or injectable drug that is used prior to medical procedures. It is well known for its fast-acting anxiolytic and amnestic properties (MedlinePlus). “I use it for all of my cases from simple hernia operations to complex cardiac procedures…and I imagine [it is used in] over 95% of all cases done in the OR,” says Dr. Kaya Sarier, an anesthesiologist at the Hackensack University Medical Center. This common yet crucial anesthetic causes drowsiness, reduces anxiety, and most interestingly erases the memory of an event. How exactly? Let’s take a closer look.

The Molecule

The molecular formula for midazolam is C₁₈H₁₃ClFN₃. This specific structure with the core of a benzene ring bonded to a diazepine ring allows it to be categorized as a benzodiazepine. If you are interested, this article from the Handbook of Experimental Pharmacology gives a general background on benzodiazepine.

When midazolam is taken, it moves through the body and into the cerebrospinal fluid. There, cytochrome P450 3A4 enzymes metabolize the midazolam. The end product binds to the gamma-aminobutyric acid (GABA) receptor on a neuron. This opens up a channel, and higher concentrations of GABA are released, which bind to the GABA receptors. As a result, this causes chlorine ions to enter the neuron, and the sudden presence of electronegative chlorine ions in the neuron stops the neuron from sending signals to the brain. The neural inhibition that results is the reason why midazolam relaxes the mind and makes you forget the events that transpire under its effects. Check out the animation in this link to see how benzodiazepines react with GABA receptors.

Action Potentials

Now that the general pharmacokinetics of midazolam have been established, let’s compare it to the regular process of a neuron’s response to stimuli. Neurons have a certain point called rest potential, which is the potential difference between two sides of a neuronal membrane when the neuron is not transmitting a signal. The approximate rest potential is -70mV. Neurons naturally respond to events in the environment by depolarization, which starts by the opening of Na⁺ channels. If enough pass through the membrane and reach -55mV, the neuron will proceed to send the signal. This point is called the action threshold. Voltage-gated channels will allow more Na⁺ ions to increase the interior potential to +30mV. Then repolarization starts. The voltage-gated channels of Na⁺ close while those of K⁺ open. The K⁺ ion channels are much slower than the Na⁺ channels, and so more K⁺ions can leave the neuron. The repolarization aims to go back to rest potential, but the process will typically go to -90mV. This is called hyperpolarization. What this does is stops the neuron from receiving and transmitting any other source of stimuli during this time besides the one it is in the process of sending. If hyperpolarization did not occur, the first stimulus that is being sent may change directions and be sent back down the axon to the neuron instead of to the brain; the result would be an unceasing loop of stimuli never being processed and transmitted. The releasing and receiving of K⁺and Na⁺ ions by diffusion eventually bring the neuron back to its rest potential, the stimulus information sent. However, if the interior potential incessantly decreases, the neuron will forever be in hyperpolarization and cease to carry out its functions. A step-by-step description of this process is available on this link and this video as well.

How does this tie into midazolam? Midazolam causes hyperpolarization. The Cl^– ions that are released due to the GABA are brought into the neuron via the GABA receptors. These chlorine ions have a negative charge, causing hyperpolarization in neurons at rest potential and increasing the time needed to send a signal when a neuron is in the process of sending an impulse to the brain. Therefore, the anxiolytic and amnestic effects of midazolam at the correct dosage are not damaging, as all neurons themselves go through hyperpolarization. The main difference is that midazolam causes hyperpolarization in neurons that are not even active, eradicating any chance of an impulse being sent. This is why no stimuli are being received while under the drug’s effects, no memories to remember.

Production of Midazolam

Since midazolam is such a common drug, it is made through a relatively simple process called a condensation reaction. This process is used for producing most benzodiazepine rings, and it involves reacting two amine groups with a ketone. During this reaction, water is lost, classifying it as a condensation reaction. Sulfamic acid is used as a catalyst during the reaction to help the reactants bond and to stabilize the complex.

For the reaction itself, two amine groups bond to the ketone, forming a double bond between the nitrogen and carbon atoms. Then an intramolecular reaction occurs that forms the diazepine ring. The resulting products are benzodiazepine and water. The figure to the below shows the synthesis of a benzodiazepine from o-phenylenediamine.

Drawbacks and the Antidote

While midazolam has its benefits, there are many cases of overdosage due to various factors, such as the patient’s age and metabolism. “The most common side effect would be hypoventilation,” says Dr. Sarier. “This can happen quite often. [The anesthesiologist] would assist in the patient’s ventilation and could administer oxygen via a nasal cannula or place a mask over both the mouth and nose to force oxygen into the lungs.”

In addition to this method, research in the British Journal of Clinical Pharmacology shows that a rising alternative solution is the use of a GABA receptor antagonist/ partial agonist called flumazenil. This drug works by binding to the GABA receptors, thereby reducing the amount of receptors that the midazolam binds to. This reverses the effects of midazolam with proven swiftness of recovering from the side effects. Therefore, flumazenil has been called the “antidote” to any benzodiazepine. For more information on flumazenil, take a look at Netdoctor and PubChem.

The Chemistry of Hydrogen Fuel Cells

In cities like Beijing, citizens have to live every day with a suffocating layer of smog in the atmosphere. Fortunately for most Americans, this is not a very prominent issue. However, with the immense amount of pollution produced from the industries that continuously provide for the needs and luxuries of Americans, it could be.

Pollution has been a problem ever since global warming was coined as a term. There are so many ways to contribute to this problem that is growing at such a fast rate that there seems to be no significant way to stop it.

One small step towards solving this problem is the implementation of fuel cells in vehicles. Fuel cells, specifically hydrogen fuel cells, are one of the most environmentally friendly power sources available. The byproducts of their electricity-making process are solely water and heat! Although frequently compared to the battery, technically speaking, the fuel cell is an electrochemical energy conversion device. It converts hydrogen and oxygen into water, producing energy in the form of electricity in the process. Now, how does energy enter into the equation?

This energy actually comes from the reverse of a relatively familiar process – electrolysis. Electrolysis uses electricity to separate a molecule into its original components. By sending an electric current into a solution through an electrolyte, which ionizes when dissolved in a solvent, the flow of ions is stimulated and allows for the non-spontaneous reaction (the break-up of the molecule) to occur. In 1839, a Welsh scientist named Sir William Robert Grove reversed this process and generated electricity and water from hydrogen. He called his creation a gas voltaic battery, now known today as a hydrogen fuel cell.

There are many types of fuel cells that serve different purposes, but they all have the same general setup. In a hydrogen fuel cell hydrogen atoms enter at the anode, where their electrons are stripped by an oxidation reaction: 2H2 –> 4H++ 4e-. As a result, the hydrogen atoms are ionized and carry a positive charge. The electrons then travel through a wire where they produce a direct electric current (DC) output. In some fuel cells, the positively charged hydrogen ions move through the electrolyte (represented by the proton exchange membrane pictured below) and join with oxygen molecules that enter from the cathode and the electrons returning from the wire. Other fuel cells have the oxygen molecules pick up the electrons first before moving through the electrolyte to the cathode, where the electrons combine with the hydrogen ions to form water, as can be seen in the reduction reaction O2 + 4H+ + 4e- –> 2H2O. In this process, water and heat are formed as a result, meaning that the reaction is exothermic. All these steps can be summarized in the net, or “redox” reaction: 2H2 + O2 => 2H2O + energy. Both products are released from the exhaust and are harmless in terms of pollution.

Graphic credit to Marc Marshall, Schatz Energy Research Center/

Not only are fuel cells eco-friendly, but, in comparison with batteries, they have the ability to last much longer. Unlike batteries, fuel cells can be used as long as there is access to hydrogen and oxygen. Batteries, on the other hand, can’t be refueled. The one exception is rechargeable batteries, but even these will eventually die. Additionally, since fuel cells create electricity chemically, they are not subject to the thermodynamic laws that greatly restrict efficiency. Fuel cells are, thus, more efficient than batteries.

There are six main types of fuel cells: polymer exchange membrane (PEMFC), solid oxide (SOFC), alkaline (AFC), molten-carbonate (MCFC), phosphoric acid (PAFC), and direct methanol (DMFC). They each have advantages and disadvantages and hold different futures in the ever-changing world of technology. For more specific information on each type, check out this link.

Let’s explore one of them. Utilizing the simplest reactions, PEMFC is one of the more promising of the fuel cell family and will most likely be used in homes and transportation. It consists of an anode, a cathode, an electrolyte, and a catalyst, and follows the aforementioned description of how a fuel cell works. Hydrogen gas enters the fuel cell on the anode side and is split into H+ ions and electrons once it comes into contact with the catalyst. The electrons move through the anode to the external electric circuit where they produce an electric current, then return to the cell on the cathode side, where oxygen gas is pumped through. Because of oxygen’s high electronegativity, it attracts and pulls the H+ ions through the exchange membrane and forms, along with the electrons that return to the cell, water molecules. This reaction will produce about 0.7 volts. To increase this voltage to a more useful level, several fuel cells are layered on top of each other and connected by bipolar plates, forming a fuel-cell stack. Try out the simulation here!

Now for how they work in cars! Fuel cell vehicles consist of five distinct components: the fuel cell stack, electric motor, high-output battery, hydrogen storage tank, and power control unit. The fuel cell stack converts the highly pressurized hydrogen gas (to increase driving range) stored in the hydrogen storage tank with the oxygen from the air into electricity, which powers the electric motor. Compared to a conventional internal combustion engine, the electric motor is much quieter, more efficient, and more smooth. The high-output battery stores energy that is generated from regenerative braking and provides supplemental power to the electric motor. Lastly, the power control unit controls and oversees the flow of electricity.

It is clear that hydrogen fuel cells have a bright future ahead, Of course, there are disadvantages to every new breakthrough in science, but with time, those are ensured to be addressed. Even now, these issues are being acknowledged and improved. Recently, an article from USA Today detailed Toyota’s advancement in fuel cell technology with an increase in range and shortening of the time it takes to refuel. With improvements already being seen, this technology is sure to make its way into the transportation and home infrastructure in no time. So keep your eyes peeled for any mention of fuel cells!