Q11.56 - Chemistry: Molecular Nature Of Matter And Change

Question

Simple proteins consist of amino acids linked together in long chain; a small portion of such a chain 

Experiment shows that rotation about the C—N bond (indicated by the arrow) is somewhat restricted. Explain with resonance structures, and show the types of bonding involved.

Step-by-Step Solution

Answer

The process of delocalization of electrons to achieve more stability in a molecule is called resonance.

A bond formed between the carboxyl group of one molecule reacts with the amino group of other molecules of two molecules with the release of water is known as a peptide bond in a protein chain.

Step 1: Definition

When a molecule or ion with delocalized electrons is represented by different structures is called resonance structure.

Step 2: Resonance structure in peptide bond

A resonance structure forms due to the interaction of electrons of the carbonyl group with the C-N bond which provides the stability in the molecules. The partial double bond character means the bond in C-N is shorter than predicted as well as in  $\mathbf{c}\mathbf{=}\mathbf{o}$ also.

 Besides this, because of the partial double bond character in the amide group no rotation is possible around the C-N bond.

Step 3: Types of bonding

The bonding around nitrogen in peptide has trigonal planar geometry which suggests that it has ${\mathbf{sp}}^{\mathbf{2}}$ hybridized as well as carbon has the same hybridization.