Fischer Esterification of An Unknown Alcohol

As I love jumping from here and there, let's talk about Fischer Esterification!

While you may think that chemical reactions go in one way and never turn back. The truth is that a chemical reaction is always in an equilibrium!

Here is the Fischer Esterification, which is always a reaction between a carboxylic acid and an alcohol. Note that the source of the oxygen of the ester group and the reaction is always in an equilibrium.

Fisher Esterification 
Now, let's revise the concept of equilibrium and the math behind it like how to calculate the Keq.


We consider concentration when we look at an equilibrium. The initial concentration is Mi for both the acetic acid and the ethanol. When the equilibrium is established, a concentration of x of ester and water is formed. In a closed environment, the product can only be formed from the reactants. So the reactants lost a concentration of x to form the product. The final concentration of the reactants is Mi-x.

To calculate the Keq of the reaction, we divided the concentration of the products by the concentrations of the reactions. As the concentration of the ester formed is the same as the water formed, we can simply the product concentration using the square of the concentration of the ester only. Same put for the concentration of the reactants, we can replace the concentration by the concentration of the alcohol.


*The reason we are replacing the concentration using the ester and the alcohol is because water and carboxylic acid will dissolve together in the aqueous layer, while the other two will remain in the organic layer. By extraction, we can separate the organic layer out and do Chromatography to analyze their relative concentration.

*The reason that carboxylic acid is more dissolved in water rather than in the alcohol or the acid is that hydrogen bonding occurs between the carboxylic acid and the water.

The following is some useful notes related to this reaction. Btw, we add sulfuric acid to assure a sufficient proton source to catalyze the reaction or the equilibrium will not be established before a month or longer!



*we add NaHCO3 afterwards to neutralize the sulfuric acid left and assures it dissolves in the aqueous layer. 

*the organic layer is above the aq. layer because it is less dense (less heavy) than the aqueous layer. Usually, when there is a dicloro-sth in the organic layer will it be below the aq. layer.

+ Further GC & NMR analysis is required

Comments

Post a Comment

Popular posts from this blog

What is Pepsin?

Image
In Your Body... Pepsin is a digestive enzyme that performed the best in the acidic condition (pH 2) produced by the gastric juice. It digests and breaks down protein (e.g. meat, seeds, eggs, dairy products, etc.). Keep in mind that pepsin digests proteins (not carbohydrates, not fat) into peptides. These peptides are then either absorbed in the intestine or further break down by enzymes from pancreas. In small intestine (pH around 7), pepsin is no longer effective and no longer digests proteins. Hormones Hormones that regulate digestion and hunger such as gastrin and secretin stimulates the production of pepsinogen, the proenzyme of pepsin. In other words, when pepsinogen is activated, it becomes pepsin.
Read more

Intro to 4 Basic Types of Reaction: SN1 SN2 E1 E2 - Updated 2024!

Image
After introducing electrophile and nucleophile, let's talk about SN1 , SN2 , E1 and E2 . Let's see what they mean first: SN1: First-Order Nucleophilic Substitution SN2: Second-Order Nucleophilic Substitution E1: First-Order Elimination E2: Second-Order Elimination   So basically, these 4 types of reactions are categorized into   Nucleophilic Substitution and Elimination .  Nucleophilic Substitution means one thing is substituted by something else, which is a nucleophile (to make it nucleophilic) Elimination always form a double bond product because as something is eliminated, the remained  electrons form a double bond  The condition for each of these reactions are different (solvent, leaving group, reactant bulkiness, etc) and the ability to classify them is crucial. Here is a table summarized all we need to know about them.   source: www.pinstopin.com Our team at Chemistery uses NordVPN every day and we highly recommend it.
Read more

The structure of Chimeric Antigen Receptor (CAR) III - Transmembrane Domains

Image
Transmembrane Domains Among the four components of a chimeric antigen receptor (CAR), the transmembrane domain is the least studied one. How different transmembrane domains affect and contribute to each other's functions is also not well studied. That being said, we will go through the function of a transmembrane domain of a CAR, the CD3ζ transmembrane domain, and the CD8α transmembrane domain.  Introduction of the transmembrane domain The transmembrane domain is where the transmembrane proteins are located. In a CAR, the transmembrane domain has the function to anchor the CAR to the T cell membrane. How strong the CAR is anchored to the T cell membrane affects the CAR expression level and stability.  Currently, the commonly used transmembrane domain is derived from proteins such as CD3ζ, CD4, CD8α, and CD28. The CD3ζ transmembrane domain Among the transmembrane domains mentioned, the CD3ζ transmembrane may improve CAR-mediated T cell action as the CD3ζ transmembrane mediates CAR d
Read more