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.

Problems Arise: Balloons are Inflating the Helium Shortage

 

              It sounds ridiculous to think that something used everyday in birthday parties is in a serious shortage, but helium, an element used in applications ranging from balloons to MRI scanners, is now getting very difficult to find.  That means that very soon, your cousin may have a very disappointing birthday party. Yet that is the least of our problems.

              The most surprising thing about this shortage is that helium is the second most abundant element in our universe.  However, most of this helium is, practically speaking, way out of our reach.  Let’s embark on an exploration of helium to see why it is so hard to find, what Helium does for us, and what we can do in the future to make the search for it a little easier.

              The main trouble that arises when trying to obtain helium is that it’s less dense than air. This means that any helium trapped under the Earth’s surface eventually diffuses into the atmosphere. Once it’s in the air, it’s out of reach; we have yet to create a feasible means of collecting all of this diffused helium.  Currently, a huge build-up of Helium-4 (He-4) is being released in Yellowstone and about 60 tons of helium are released every year.  Some of this helium is diluted into the atmosphere, but the rest of it escapes the atmosphere into space.  Although it seems like we are letting this helium go to waste, there is just simply no viable way to collect it.

                                                                                                                                                                                                                      Yellowstone National Park

              Yet there are other factors that contribute to Helium’s shortage. For one, the production of Helium as a by-product of nuclear decay is not a heavily invested means of production. This is largely because it is not an economically viable option (along with capturing the diffused Helium in the air as mentioned before); however as we will see, the value of Helium just may be priceless.  Another factor contributing to the shortage is the fact that in the past few decades, the demand and use of Helium has skyrocketed, largely ascribed to our squandering ways. With a limited amount, prices of Helium have soared as well.

              So why exactly is helium important anyway?  Helium has a multitude of applications, but its main application is its use to cool superconducting magnets in MRI (magnetic resonance imaging) scanners. Superconducting magnets are magnets that can produce immense magnetic fields, which MRI scanners require to operate and use to construct images of the body. MRIs use superconducting magnets because below a certain temperature, known as a critical temperature, a metal loses its resistance (The reason this happens at low temperatures is because there are lower energy and less frequent atomic collisions). This temperature needed for superconductivity requires cryogenic temperatures.  That’s where helium comes in.  Liquid helium, due to its extremely low (4.2 K) boiling point and high thermal conductivity, is very efficient at capturing heat and is the only medium that can induce superconductivity in metal alloys. In MRI scanners, the wires are bathed in liquid helium at -269.1 °C to capture heat and remove it from the system. This effectively removes the wires’ resistance and allows them to become superconductors. However, a normal MRI scanner uses 1,700 liters of helium which periodically has to be changed. This is a huge amount of helium, especially with the impending shortage. A new method of superconductor cooling was recently developed by a company known as Cryogenic. This method uses a significantly lower amount of helium and may soon significantly reduce the amounts of helium that we waste.

                                                                 

                                                                                 MRI Scanner

              Another important application of helium is its use in oxygen tanks for underwater diving.  Normally air is comprised of approximately 20% oxygen gas and 80% nitrogen gas. Nitrogen gas is a lot more soluble than Helium, and is especially soluble at high pressures – which essentially keeps the gases in solution. The difference in solubility between the two plays a key role in why Helium is used, and is due to their difference in size. In order to dissolve any substance into a solvent, the solute and solvent must have interactions with one another. For non-polar gases like N2 and He, it becomes difficult to create the interactions with polar water molecules. To actually bring one of these gases into solution, an induced dipole must be created in the gas. An induced dipole becomes increasingly easier as the molar mass of the substance increases. This is because there are then more electrons to shift between the atoms thereby creating a strong bond between the solute and solvent. Between N2 and He, nitrogen gas clearly dominates in molar mass and strength of LDF forces. So at these high pressures below the water, the nitrogen gas becomes highly soluble in the bloodstream inducing nitrogen narcosis, a state with similar effects to those of alcohol. Furthermore, as divers begin to rise from the water, the solubility of nitrogen decreases and begin to bubble out of solution (the blood). This is extremely dangerous as it can create bubbles in the bloodstream which wouldn’t be able to pass through fine capillaries in the body. The condition, called the Bends, is life threatening. To prevent this from happening, Helium is used. As stated previously, Helium is less soluble than Nitrogen, so less Helium would get into the bloodstream. Furthermore, Helium is an inert gas, so its narcotic properties are negligible and do not pose any problems of toxicity like Nitrogen does. Helium continues to be the most ideal gas for diving tanks, and the shortage poses a serious threat to the maritime industries.

              With such versatility it seems more likely that the United States will take on currently, non-viable means to produce Helium rather than drastically cut down on usage. There will likely be 3 primary sources that will serve the United States in the future as a source of Helium. As stated before the first source would be through nuclear reactions.  One reaction that results in a formation of a helium atom is plutonium decomposition (Pu-239).  A plutonium nucleus decays into an alpha particle and a uranium nucleus.  The alpha particle immediately captures 2 electrons from the nearby plutonium metal and becomes a helium atom in the midst of a plutonium lattice.  There are 2 main problems with this method of producing helium.  Firstly, this process has a half-life of 24,100 years.  Using the half-life formula for first-order reactions, one could calculate k to be (ln2)/t_1/2 = (ln2)/24,100= 2.88 x 10-5.  Using the first-order integrated rate law, one could determine that in a year, 10,000 g of plutonium will decompose to 10,000 x e^{-2.88×10^-5} = 9,999.71 g.  Therefore, in a year, 10,000 g of plutonium will only decompose to 0.29 g of decay.  That’s a measly 0.0029% decay after an entire year.  This makes generating a profitable amount of helium unfeasible to say the least.  The second problem with this method is that once the helium is produced, it is stuck in the plutonium lattice.  This makes it become very difficult to isolate and extract

              The second source is actually through natural gas. Some natural gas contains amounts of Helium that can be extracted through a complicated process. The reason it is not widely used today is because the extraction process requires strict criteria and many samples of natural gas only contain about 0.3-1.9 percent Helium by volume. Furthermore, there are many economic considerations before uptaking such a project as the extraction process requires facilities. However, in essence there are 3 steps to the extraction process. The first step is to remove the impurities from the natural gas such as water, carbon dioxide and hydrogen sulfide through means such as amine and glycol adsorption. The second step is to extract the high molecular-weight hydrocarbons. Finally, through cryogenic processing the remaining methane gas is extracted. This works because Helium has the lowest freezing point of any element. So as the temperature is sufficiently reduced, all other substances will freeze and can be filtered out. What’s left is crude Helium, containing approximately 50-70% Helium and the rest is Nitrogen gas and other traces of gases. To further purify the Helium to approximately 99.99% purity, Pressure-Swing Adsorption (PSA) is used. PSA separates different gases from each other based on the premise that each gas has a different affinity for different adsorbent materials, and have different vapor pressures. Due to the varying vapor pressures, one gas can be completely transformed into the gas phase at one temperature and pressure and then extracted, while the other gas would remain largely as a liquid.

                                                                                                                                             Pressure Swing Absorption Process

              The final source will actually be where Helium is most abundant: outer space. Observations from lunar missions have concluded that there are about 22 grams of helium in every cubic meter of lunar soil. In the future, if Helium were to ever run dry on Earth, this alternative would likely create a madman’s dash to the Moon in search of this precious yet scarce gas.

              In essence, our lavish uses of Helium without a steady state of supply has caused a shortage that affects many scientific disciplines that rely on the unique characteristics of Helium. As a human race, we must either cut down on our uses of Helium in some shape or form, or begin taking measures to create more Helium for use in the future. Without Helium, many of the opportunities and technology today will float adrift tomorrow, just an arm’s length away from humanity’s struggling grasp for the resources we use so plentifully.

Instruments and Chemistry: Rosin

 In the previous post, we talked about how certain chemicals have properties that allow them to be suitable for maintaining certain instruments. For this last post, we will further explore maintenance, as well as the chemistry behind certain chemicals since they are both complex and vital. Out of the chemicals that are used, rosin is the most complex since it is comprised of various organic and inorganic compounds. The following image shows how complex rosin can be, as well as showing how it is manufactured from the resin found inside trees. The central column only shows two possibilities that the four isomers can undergo since two molecules can be formed by simply arranging one of the bonds next to the additional Hydrogen.

          As one can see, the structure of the original organic compound varies by the location of the two double bonds, causing different concentrations of different acids to be present. These isomeric resin acids belong to the category of tricyclic diterpenes, whose basic structures result from the coupling of four C5-isoprene units (isoprene = 2-methyl-1,3-butadiene). The resin acids are distilled through 20% volatile turpentine and then leave behind some of the needed colophony rosin. However, some non-volatile alcohols and keto compounds are left behind and leave the molecule less pure and stable, so the compounds must undergo steam distillation in order to rearrange the atoms. Mechanistically, the rearrangement entails protonation at a terminal carbon atom of the conjugated double bond system, leading to a resonance-stabilized carbocation. The latter, through proton-transfer to the neighboring (allylic) CH2-group generates a rearranged diene, an unsaturated hydrocarbon with two carbon double bonds. The product ratio in the resulting equilibrium mixture is determined by the relative stabilities of the different conjugated dienes, and the stability gives the rosin the favorable properties that were mentioned in the previous post. While the acids in the final product are more concentrated, they are more stable and pure due to the addition and relocation of the Hydrogen atoms. The original resin is only 72% pure, while the final rosin is 95% pure; the rest of the percentages are non-volatile solids that hinder the rosin’s physical properties. This is why the levopimaric acid is the only substance that becomes less concentrated: it is the least volatile acid out of the four main acids that appear, and it slightly lessens the quality of the rosin as a whole. However, it is needed since the durability of the rosin can be attributed to this acid in particular.

          One of the most important chemicals used in the production of a piano is called lacquer.  Lacquer is more or less a wood polish; it is the chemical added to wood to give it the smooth and shiny properties.  Without it, the wood of a piano would be a lot more difficult to work with, shrinking the lifespan of the common piano by years if not decades.  Without lacquer, the piano and other hammered string instruments may have never become the influential instruments they are today.  But what exactly is lacquer?

          Lacquer is a polymer of many different bases that when coated on a wooden substance, offers a layer of protection and gloss to a piece of wood. The most common lacquer used on piano frames is a urushiol-based lacquer. Urushiol is a common allergen found in many Anacardiaceae plants such as poison ivy.  It has a boiling point of
200˚ C (392˚ F) and can dissolve in substances such as alcohol.  It is composed of a 6 carbon ring with 3 double bonds similar to benzene, 2 hydroxyl groups, and an R group. The R group varies from a large amount of hydrocarbons (such as (CH2)14CH3, (CH2)7CH=CH(CH2)5CH3, (CH2)7CH=CHCH2CH=CH(CH2)2CH3and others).  While harmful to many humans on poisonous plants, urushiol offers a special breed of polymer that can be used as piano frame lacquer.  It is a special type of lacquer in the sense that it settles in a more elaborate and controlled way. While most lacquers dry solely by evaporation, urushiol-based lacquers will oxidize with the air surrounding it and undergo polymerization.  This requires the settling process to be in a humid and warm environment, to avoid any evaporation.  However, if done properly, this lacquer will offer a completely optimized layer of shiny aesthetics and protective lifespan to the frame and other wooden pieces of a piano.

          As mentioned in the string section of our last blog, the best cleaning agents for brass instruments tend to be Trichloroethylene (TRI) and Perchloroethylene (PERC).  Last time, we talked about greases and oils for brass instruments, but sometimes build-ups of these compounds can form in sludge-like globules inside our instruments.  For degreasing and all-purpose cleaning, TRI and PERC are excellent reagents.  These compounds are heavy, maintain constant pH while cleaning, and dissolves quickly due to high solvency. It should also be noted that without adding stabilizing factors, these compounds are rather unstable and can react violently with metals, especially those made from Aluminum and/or Magnesium. These stabilizing factors are also able to protect Aluminum against decomposing.  In addition, more recently ultrasonic cleaning of instruments has been used instead of the degreasers.  This method takes advantage of a phenomenon called ultrasonic cavitation.  When water (or another liquid) is bombarded with the correct ultrasonic frequencies, very small bubbles form causing agitation. This extreme agitation can loosen contaminants sticking to a metal surface.  Adding certain ions to the water can greatly increase the rate of the reaction by reacting spontaneously with the contaminants with the added energy from agitation.  Finally, in the case that you would need to remove the lacquer from your brass instrument, acetone will work well.

Synthesis of Antibiotics

     Antibiotics are agents that are used to kill microorganisms or inhibit their growth. They can either occur naturally or can be synthetically produced. Extremely common today are semi-synthetic modifications of natural compounds. These chemical, biosynthetic antibacterial compounds are classified according to their biological effect on microorganisms. Bactericidal agents kill bacteria altogether while bacteriostatic agents slow down or stall bacterial growth. One specific semisynthetic antibiotic is what is known as Erythromycin.

     Erythromycin is what is considered a macrolide antibiotic. Macrolide antibiotics slow the growth of and often kill sensitive bacteria by reducing the production of important proteins needed by the bacteria to survive. This drug is notorious for being similar to penicillin in what it is used for and how it is synthesized. Often it is used as a substitute for people who are allergic to penicillin being that penicillin is such a common allergy. It is commonly used to treat respiratory tract infections, acne, Gonorrhea, Chlamydia, and other STDs. It is also applied to the eyes of newborn babies in order to prevent ophthalmia neonatorum. Erythromycin works by improving gastric emptying as well as its symptoms, though oral use of this drug is generally for short term use rather than long term.

     The chemical structure of Erythromycin, C38H69NO12, is extremely complicated and elaborate. Its synthesis published by Robert B. Woodward in 1981, the drug consists of a 14-membered lactone ring along with ten asymmetric centers and two sugars, L-cladinose and D-desosamine. The compound’s complexity makes it extremely hard to produce synthetically therefore it is produced by the bacterium Saccharopolyspora erythraea. Synthesis of this drug includes an intricate series of reactions. Reactions include hydrolysis and stereospecific aldolization. Oxidations and reductions are also involved in the synthesis by the pure enone’s conversion to desired dithiadecalin product. This product is further converted to ketone as well as an aldehyde. Overall, the synthesis contains roughly 50 steps split into 4 parts.

     Erythromycin comes in 4 forms: Erythromycin A, B, C and D. Erythromycin A is known for being the most antibacterial, with B, C and D following respectively. As discussed previously, this drug is considered to inhabit bacteriostatic activity, otherwise it inhibits growth of bacteria rather than stopping it or killing in completely. Its bacteriostatic capability is most displayed at high concentrations by interfering with aminoacyl translocation. This process objects to the functionality of important proteins, which is overall how antimicrobial action is put in place. One should be aware of the side effects erythromycin may cause, for example, abdominal pain, nausea, diarrhea, and vomiting.

     Zithromax is a semi-synthetic antibiotic, an example of the subclass, azalides and slightly differs in structure from the classical macrolides. It is used to treat and prevent infection within an area thought to be caused by bacteria. Like all other antibiotics, zithromax has an active ingredient, which in this case is azithromycin, a subclass of macrolide antibiotics. Azithromycin is derived from erythromycin but differs chemically from erythromycin in that a methyl-substituted nitrogen atom is incorporated into the lactone ring and is has improved activity through its glycosylated side chains. In this form, it has a molecular formula of C38H72N2O12. However, when Azithromycin is a dihydrate, which means it contains two molecules of water or its elements, it has a molecular formula of C38H72N2O12*2H2O. Also, Azithromycin contains inactive ingredients such as pregelatinized starch, lactose, sucrose, sodium phosphate, hydroxypropyl cellulose, or xanthan gum that all supplement the active ingredient.

 

     Azithromycin binds to 50s ribosomes and interferes with protein synthesis but does not affect nucleic acid synthesis. It binds to the 23S rRNA of the bacterial 50S ribosomal subunit, which includes the activities such as catalyzation of  peptide bond formation, prevention of premature polypeptide hydrolysis, provision of a binding site for the G-protein factors, assistance of protein folding after synthesis. blocking of protein synthesis by inhibiting the transpeptidation or translocation step of protein synthesis and by inhibiting the assembly of the 50S ribosomal subunit. Azithromycin was the target of an enantioselective synthesis, which is a chemical reaction where one or more new elements of chirality,a molecule that has a non-superposable mirror image, are formed in a substrate molecule and which produces the stereoisomeric products in unequal amounts are formed in a substrate molecule and produces the stereoisomeric products in unequal amounts. Also, all the stereogenic quaternary carbon centers were enhanced by the desymmetrization of 2-substituted glycerols using a chiral imine/CuCl catalyst, otherwise known as copper (I) chloride.

   

     Synthesis of antibiotics such as erythromycin and azithromycin shows how the chemical structure and formula can be modified in order to change its function and its effect on the body accordingly. Although erythromycin was created first, scientists and doctors were able to enhance its molecular formula in order to enhance the process and activity in which it deals with an infected area. Also, these synthetic drugs offset and affect series of reactions such as hydrolysis, which can either interfere or not affect other processes. Overall, the synthesis of such antibiotics require much difficulty due to the fact that many factors such as the complexity of the compound or different incorporated ingredients that change the orientation of each function and process.

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

 

Beyond the Dairy Aisle

Whether it’s with your cereal first thing in the morning, or in a glass with some chocolate syrup at night, milk is a staple part of most people’s diets. If it’s anything like mine, your family probably goes through at least a few gallons of milk every week, if not more. Milk comes in all different forms, too: without milk, you wouldn’t be able to put that whipped cream on your apple pie, or butter your toast during breakfast. Although it seems pretty simple, the physical status of milk is actually extremely complex, especially when it comes to the chemistry behind it.

The Chemistry Behind Milk

If you were to leave a glass of milk to sit for some time on your countertop, you would begin to see a thin layer of cream form on the surface of the milk. What exactly is this? Well, if you were to view this layer under a microscope, you would see shapes floating around in the milk, which is the fat. In chemistry, this is known as an emulsion; specifically, an emulsion of fat in water. An emulsion is a mixture of two or more liquids that are non-mixable. If you were to shake the glass of milk, the emulsion would be broken down and the milk would go back to normal. However, milk does come in more than one form, such as butter – the difference is that butter is an emulsion of water in fat. So when the milk is churned into butter, there is a phase change that is involved in the process.

The fats that are present in milk are there for a reason- they act as a solvent for all of the fat-soluble vitamins in milk that make it so healthy, such as Vitamins A, D, E, and K. In the milk fats, the fatty acid molecules are made up of a hydrocarbon chain along with a carboxyl group, or COOH group, usually, consisting of all single bonds, one double bond, and an even number of carbon atoms. Structurally, these chemical molecules look something like this:

Other properties of milk, such as the melting point and the hardness of the fatty acid, is affected by various factors such as the length of the previously mentioned carbon chain as well as the degree of unsaturation (when a molecule is unsaturated, this means that it does not have the greatest possible amount of hydrogen atoms that it can have for the number of carbon atoms that it has. In other words, fats with a lot of these high-melting fatty acids will be hard; but fats with a high content of low-melting fatty acids can make the spreadable butter that you put on your toast every morning.

Making Your Milk Taste Its Best

Depending on what kind of environment your store your milk in, you may notice that the milk tastes different. Changes in storage can cause different types of chemical changes to occur in the milk, one of them being oxidation. Although most people tend to think that milk changes or goes bad when it is left outside of a refrigerator because of the higher temperatures, there are actually a lot of chemical processes occurring in milk when it is exposed to lower temperatures as well, such as the oxidation of the fats in the milk.

Although the oxidation of the fats in the milk can be counteracted by reducing agents that are present in the milk, such as lactic acid bacteria, there are still many chemical changes that may cause some unwanted things to occur in your milk. For example, chemical change that occurs due to the oxidation of the fats in the milk is the “flavor” of the milk – although plain milk does not actually have a flavor to it, lower storage temperatures usually cause milk to develop an unpleasant flavor. This is why companies that produce milk place great emphasis on precise refrigeration for their milk, because nobody wants their milk tasting funky!

Got Milk?

Among the many beverages that have come to prominence in society throughout history, milk, along with water, is probably among those that will continue to be a mainstay in the diets of people both young and old. The small cardboard milk carton you get at lunch, the glass full of milk that you dip your Oreo in, the milk mustache you get on your upper lip when you take a sip. All of these are iconic images that come to mind when one thinks about milk throughout history. After taking away this information regarding the chemistry behind milk, one could also realize that not only will milk remain a staying force forever, but so will its chemistry.

The Manufacturing Processes of OLEDs

At the recent CES convention in Las Vegas, many new products were unveiled and demonstrated.  Both the public and professional communities were captivated by the new OLED technologies.  However, as the prices were announced, it soon became clear to the techno-savvy consumers at home that it would be many years before OLEDs were a common sight in the average household.  Although the prices seemed daunting, the manufacturing methods used to produce these organic screens have been steadily improving.  As a revolutionary advance in display technology, OLED displays are expected to overtake the LCD market in the near future.  Thus, many researchers have worked tirelessly to develop a more efficient and quicker method in order to make OLEDs a more accessible technology.

Patternable OLEDs operate through a light or heat activated electroactive layer.  This is a polymer that exhibits a physical change when stimulated with an electric field.  A popular polymer for this layer is PEDOT-TMA, which becomes a highly efficiently hole injection layer.  It is a p-type conducting polymer and a modification of the PEDOT monomer, which is based off the EDOT monomer and can be seen below.  PEDOT-TMA is a popular material for this layer because it is noncorrosive and dispersible in organic solvents.  This is due to the methacrylate groups at both ends of the polymer chain.  These caps limit the length of the polymer, making it more soluble in organic solvents and ideal for usage in OLEDs.  These OLEDs are conventionally produced through the use of two main patterning technologies, organic vapor phase deposition (OVPD) and inkjet etching (IJE).

The PEDOT-TMA chain.  The two methacrylate caps at the end are clearly visible.

Organic Vapor Phase Deposition 

The organic vapor phase deposition manufacturing process works by transporting organic molecules to a cold substrate through the use of a hot inert carrier gas.  The final film product can be fine-tuned by altering the gas flow rate and source temperature.  Uniform films are produced by lessening the carrier gas pressure, which creates a larger velocity and mean free path of the gas.  This leads a decrease in the thickness of the boundary layer.  OVPD is also popular for OLED production because the process naturally prevents issues related to contaminants from the walls of the chamber.  This is because the walls are naturally warm, which prevents molecules from sticking to and producing a film.

However, maintaining a uniform film thickness and dopant concentrations over the large surface area needed for many applications is a demanding task in the context of vacuum evaporation, which is currently the most prevalent method of depositing organic molecular solids.   In addition, there is a relatively low yield with OVPD production, which explains the massive production costs.  As a remedy, low pressure organic vapor phase deposition has been proposed as a substitute technique.  This process has a notably improves command over doping and offers a potential method to rapid, particle-free, uniform deposition of organics on large-area substrates.  Further information detailing the uses and advantages of OVPD can be found here.

Inkjet Etching

The most basic method of producing OLEDs incorporates old technology originating from 1976, when the first inkjet printer was created.  Inkjet printing is a cheap and efficient alternative to traditional OLED production and is used by several start-up OLED companies such as Kateeva.

The Kateeva system for inkjet etching.

Kateeva’s system of inkjet printing involves a movable platform capable of holding screen substrates of up to 55” diagonal length.  The movable platform is able to transfer a selected substrate under various print heads, which are then able to spray droplets of organic material from different nozzles.  These drops of organic material are placed precisely (picoliter scale) on a selected substrate to form the pixels on the screen.  Additionally, the inkjet printing system is a versatile procedure, as it can be adapted from large television screens to small handheld devices such as smartphones and tablets.

This process is not as accurate or efficient without the use of a shadow mask on the substrate.

Shadow mask used for consistency and quality of the final display.

A shadow mask is a fine metal stencil drawn on the substrate that directs the material spray into its correct place, ensuring the consistency and quality of the final screen.  However usage of the shadow mask, while convenient and economical, also has its downfalls.  The shadow mask may lead to contamination of the organic materials of the OLED screen.  Because the OLED screen is composed of organic products, it is extremely sensitive to outside particles that may cause a drop in the vibrant image quality.  Nevertheless, inkjet printing is still a viable method for producing OLED displays and further improvements will reduce the risks of contamination.

New Developments in the OLED Industry

Recently, researchers have discovered that utilizing a molecule of a certain shape and structure allows anew type of OLED that has the potential to emit as much light as a commercial OLED, but without the need for costly rare metals normally demanded to make the OLEDs effective. Rare earth metals such as iridium or platinum are currently vital to OLED displays because it increases the efficiently of the display to commercial standards.  The removal of these expensive metals from the production of OLEDs has the potential to significantly reduce the costs of OLEDs.  This improvement in OLED structure is vital to advance the technology and reduce prices as the OLED industry of smartphones, televisions, and solid-state lighting continues to grow.

New developments regarding OLED production also includes metal oxide deposition systems.  These have potential to become leading production methods because they are more efficient and consistent in their output than the currently costly production methods.  For example, the AKT-55KS, a plasma enhanced chemical vapor deposition (PECVD) system that handles 8.5-Gen substrates, is a good option to consider based on its defect-free nature and its ability to keep out unwanted gases.

AKS-55KS

Two systems that hold potential for widespread use is the new physical vapor deposition (PVD) deposition systems, which comes in 2 models: SKT PiVot 25K which controls Gen-6 substrates, and the SKT PiVot 55K which controls 8.5-gen substrates.  The advantages of these systems are derived from the utilization of tubular cathodes of donor material, where the cathodes rotate because of the process of deposition.

Conclusion

Constant innovation is a necessity of a demanding market, especially in an industry that is still attempting to establish itself as a viable consumer market.  The production of OLEDs is still in its infancy, as there are several obvious and monumental obstacles that present itself in the first phases of starting such a market.  The most pressing issue is the costly and inefficient manner in which these organic LED’s are created, which has prompted researchers to find ways to reduce these expenses. This had led to the introduction of the inkjet printer formatted specifically for the production of OLEds as well as the new deposition systems offer viable alternatives that hold promise for a market that contains endless possibilities. One can only speculate the boundless paths that the OLED industry can take, whether it be into solid-state lighting, a lucrative smartphone market, or both.  Consumers can only wait to see what the raw potential of this revolutionary technology can manifest into.

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.

In this post we will discuss antibiotic resistance and how different ‘superbugs’ are being created because of continued use of antibiotics.

Antibiotic resistance is the ability of bacteria to resist the effects of an antibiotic. This usually occurs when bacteria change in some way that reduces or eliminates the effectiveness of drugs, chemicals, or other agents designed to cure infections. These bacteria survive and continue to multiply, causing more harm. This resistance can cause significant danger for people who have common infections that were once easily treatable with antibiotics. Every time a person takes antibiotics, sensitive bacteria are killed, but resistant germs may be left to grow and multiply.

Here is an interesting TED Talk by Dr. Karl Klose, which describes the ‘superbug’ and how different bacteria evolve into ‘antibiotic-resistant menaces’.

The big question is how bacteria become resistant to antibiotics. There are two answers to this question. One way that bacteria become resistant to antibiotics is by mutations in DNA. These mutations occur spontaneously and can have two different effects. A change in DNA of bacteria could lead to the prevention of bacterial protein synthesis. In our previous post we discussed how antibiotics target and attack these proteins. However, if the bacteria is active without the protein, there will be nothing for the antibiotics to attack. Mutations causing variations in the shape or size of the protein prevent antibiotics from being able to properly bind to the target protein. Another change in the DNA of bacteria could lead to the overproduction of protein enzymes. This overproduction could lead to various issues. Firstly, a particular dose of antibiotics would not be able to deactivate an overproduction of protein enzymes. Furthermore, some of the proteins produced may be alter the permeability of the cell membrane of cell wall of the bacteria. Aside from spontaneously occurring mutations in the DNA of bacteria, bacteria can become resistant to antibiotics as a result of gene borrowing. According to microbiologist Doctor John Turnidge,  “They’re the original life forms almost, so for thousands of millions of years they’ve had a chance to work out ways to survive and one of those is to borrow genes from other bacteria to survive.” Antibiotic resistance can result from DNA mutations or gene sharing among bacteria. The image below explains how the population of antibiotic resistant bacteria has increased tremendously. For more information regarding the process and causes of antibiotic resistance, check out this website. 

Since the advent of penicillin in the 1940s, antibiotic use has been steadily increasing. Antibiotics are used far more than necessary; they are used as a precautionary measure ‘just in case’ or as a comfort to patients who have viral or fungal infections. According to the CDC, 50 million of the 150 million prescriptions for antibiotics annually are unnecessary. Doctors would rather sign off on a prescription than spend the extra time trying to educate patients on the strengths and weaknesses of antibiotics. In addition to that, increasing use of hand sanitizer and antibacterial cleaning agents also contributes to the development of superbugs. The excessive use of antibiotics has already started to have devastating effects. But why? In the body, antibiotics kill enough bacteria so that the body can finish the job. Shouldn’t more antibiotics just kill more bacteria? It would seem that we should always take antibiotics and heed the adage ‘better safe than sorry’, right? Wrong.

That type of thinking will only drive us towards the edge faster, and here’s why: As soon as researchers develop new antibiotics, there are always already bacteria with the capabilities to defeat them. These resistant bacteria survive the antibiotic agents to multiply and divide, passing on their antibiotic resistanceto their progeny. As a result, the same antibiotics become less effective with time and it becomes harder and harder to develop antibiotics for these so called ‘superbugs’. The most famous strain of bacteria that has risen due to increasing antibiotic use is methicillin-resistant Staphylococcus aureus, or MRSA.

The CDC is currently working to reduce the amount of antibiotics used, because unchecked, it could become a serious public health issue. Already, 2 million people in the US are infected annually by antibiotic resistant bacteria. Should antibiotics continue to be prescribed at such an alarming rate, we could face a post-antibiotic age, in which antibiotics have been rendered useless.

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!