Each of these were removed through extraction,
isolating the organic layer (containing the ester) from the aqueous layer.
We performed 4 extraction experiments.
Gierasch stated, “The environment in a cell is extremely complex and challenging for the process of protein folding, leading to a need for a network of species that protect protein states that are susceptible to aggregation—the protein homeostasis network. We are working with colleagues and collaborators to understand the underlying mechanisms of protein homeostasis from the level of the molecular chaperone machines that act on protein clients to the coordinated action of the network in all of its complexity. We would love to witness and contribute to new discoveries related to these questions, both because of the fascinating basic science involved and because failures in these systems are implicated in a wide array of diseases, including neurodegenerative diseases.”
on the purity and synthesis of an ester
After a reaction is completed, the solution often times does not only contain the desired product, but also undesired byproducts of the reaction, unreacted starting material(s) and the catalyst (if it was used). These compounds have to be removed in the process of isolating the pure product. A standard method used for this task is an extraction or often also referred to as . Strictly speaking, the two operations are targeting different parts in the mixture: while the extraction removes the target compound from an impure matrix, the washing removes impurities from the target compound i.e., water by extraction with saturated sodium chloride solution. Washing is also used as a step in the recrystallization procedure to remove the impurity containing mother liquor adhering to the crystal surface.
Many liquid-liquid extractions are based on acid-base chemistry. The liquids involved have to be immiscible in order to form two layers upon contact. Since most of the extractions are performed using aqueous solutions (i.e., 5 % NaOH, 5 % HCl), the miscibility of the solvent with water is a crucial point as well as the compatibility of the reagent with the compounds and the solvent of the solution to be extracted. Solvents like dichloromethane (=methylene chloride in older literature), chloroform, diethyl ether, or ethyl ester will form two layers in contact with aqueous solutions if they are used in sufficient quantities. Ethanol, methanol, tetrahydrofuran (THF) and acetone are usually not suitable for extraction because they are completely miscible with most aqueous solutions. However, in some cases it is possible to accomplish a phase separation by the addition of large amounts of a salt (“salting out”). Commonly used solvents like ethyl acetate (8.1 %), diethyl ether (6.9 %), dichloromethane (1.3 %) and chloroform (0.8 %) dissolved up to 10 % in water. Water also dissolves in organic solvents: ethyl acetate (3 %), diethyl ether (1.4 %), dichloromethane (0.25 %) and chloroform (0.056 %). Oxygen containing solvents are usually more soluble in water (and vice versa) because of their ability to act as hydrogen bond donor and hydrogen bond acceptor. The higher water solubility lowers the solubility of weakly polar or non-polar compounds in these solvents i.e., wet Jacobsen ligand in ethyl acetate. Other solvents such as alcohols increase the solubility of water in organic layers significantly because they are miscible with both phases and act as a mediator. This often leads to the formation of emulsions.
The most important point to keep in mind throughout the entire extraction process is which layer contains the product. For an organic compound, it is relatively safe to assume that it will dissolve better in the organic layer than in most aqueous solutions unless it has been converted to an ionic specie, which makes it more water-soluble. If a carboxylic acid (i.e., benzoic acid) was deprotonated using a base or an amine (i.e., lidocaine) was protonated using an acid, it would become more water-soluble because the resulting specie carries a charge. Chlorinated solvents (i.e., dichloromethane, chloroform) exhibit a higher density than water, while ethers, hydrocarbons and many esters possess a lower density than water (see solvent table), thus form the top layer . One rule that should always be followed when performing a work-up process:
Never dispose of any layer away until you are absolutely sure (=100 %) that you will never need it again. The only time that you can really be sure about it is if you isolated the final product in a reasonable yield, and it has been identified as the correct compound by melting point, infrared spectrum, etc. Keep in mind that it is always easier to recover the product from a different layer in a beaker than from the waste container or the sink. In this context it would be wise to label all layers properly in order to be able to identify them correctly later if necessary.
In order to separate compounds from each other, they are often chemically modified to make them more ionic i.e., convert a carboxylic acid into a carboxylate by adding a base. Standard solutions that are used for extraction are: 5 % hydrochloric acid, 5 % sodium hydroxide solution, saturated sodium bicarbonate solution (~6 %) and water. All of these solutions help to modify the (organic) compound and make it more water-soluble and therefore remove it from the organic layer. More concentrated solutions are rarely used for extraction because of the increased evolution of heat during the extraction, and potential side reactions with the solvent.
Synthesis of Isopentyl (Amyl) Acetate Ester (Banana Oil)
The dissociative chemisorption of methane on a metal catalyst is the rate limiting step in the steam reforming of natural gas, our primary source for the molecular hydrogen used in the Haber-Bosch process. In collaboration with the experimental group of Rainer Beck at the École Polytechnic Fédéral de Lausanne, we examined this reaction on a Pt surface containing step defects. We were able to differentiate between reactions at the step edges and the terrace sites, using both UHV molecular beam experiments and high-dimensional quantum scattering theory. Both approaches were also able to resolve the reaction probability with respect to the velocity and vibrational state of the methane molecule and the surface temperature, providing additional details about the reaction mechanism.
Synthesis of Isopentyl (Amyl) Acetate Ester (Banana Oil) Resources ..
Filtration with cotton plug because of anhydrous calcium chloride
Boiling point was lower than expected, but consistent between both Reaction A and B (at 143 C)
Same amount of distillate collected at this temperature
Simultaneous fractional distillation
Malfunction of fractional column for reaction B
Recorded temperatures as distillate collected in graduated cylinder.
loss of product during distillation and extraction
residual impurities after extraction
What we would do next:
Run a sample of pure pentyl acetate to compare
Run more experiments using more variable amounts of sulfuric acid.