Amino Acid

Glutamic acid is one of the twenty proteinogenic amino acids. It can be abbreviated either Glu or E. This amino acid is a non-essential amino acid. Glutamic acid is a key molecule in cellular metabolism, and is abundant in both animal and plant protein. However, in humans it is a non-essential amino acid because the body is able to produce it's own glutamic acid. In addition to this, the dietary proteins are broken down by digestion into amino acids which play as a metabolic fuel for other functional roles in the body.  A picture of glutamic acid is shown below:

The pKa value of carboxyl group for glutamic acid in a polypeptide is about 4.3. This may be a little high for a pKa value due to the inductive effect of the additional methylene group. The isoelectric point is around 5.65. Pka values are shown below in the diagram:

 

Glutamic acid can be easily converted to proline; due to the carboxyl group is reduced to the aldehyde. From here the aldehyde can react with the alpha-amino group which eliminates water. A diagram of this is shown below:

Electrophilic Substitution

This weeks goal was to find a peer review journal which shows a picture of an electrophilic substitution and why it is important in Organic Chemistry. After doing research on electrophilic substitution it can be defined as: a form of substitution reaction in which the leaving group (normally hydrogen) is replaced with an electrophile. It is important because it a way of introducing functional groups onto a benzene ring. There are two types of substitution one known as electrophilic aromatic substitution and electrophilic aliphatic substitution. Common aromatic substitution include: aromatic nitration, aromatic halogenation, aromatic sulfonation, and Friedel-Crafts, and common ones for aliphatic substitution include: nitrosation, ketone halogenation, and ketol-enol tautomerism,   A picture is shown below which shows electrophilic substitution:

This digram shows electrophilic aromatic substitution in which the final step is a decarboxylation rather than a deprotonation. This is due to the ketone carbonyl. 

References:

1. UC Davis ChemWiki. Section 15.5 Electrophilic aromatic substitution. 4 Feb. 2011. 6 March 2011.

<http://chemwiki.ucdavis.edu/Organic_Chemistry/Organic_Chemistry_With_a_Biological_Emphasis/Chapter_15:_pi_electrons_as_nucleophiles/Section_15.5:_Electrophilic_aromatic_substitution>.