Chapter 24, Problem 18P

Interpretation Introduction

Interpretation:

The products obtained from the following reactions are to be determined: treating tyrosine with excess bromine water, reaction of phenylalanine with ethanol in the presence of hydrogen chloride, and the reaction of alanine and benzoyl chloride in aqueous base.

Concept introduction:

Amino acids contain both carboxyl group and an amino group. Both, carboxyl groups and amino groups donate and accept protons from water, respectively, to form ions. Amino acids form double ionized species by this exchange of protons in a solution between carboxyl group and amino group. These double ionized species are termed as zwitter ions.

Deactivating groups like amine or carboxy groups gives substitution at the meta position. Such electron withdrawing groups increases the electron density at meta position. In case of disubstituted benzene, electrophilic aromatic substitution would favor the position with respect to the most deactivating group. Halogenation reaction would follow this mechanism.

Amino acids reacts with alcohols to produce esters, and follow nucleophilic aryl substitution reaction and the process is called Fischer esterification.

Amino acids react with acid chlorides to form acetylation or benzoylation of amino acids occur.