Chapter 3.8, Problem DQ

Interpretation Introduction

Interpretation:

The correct stereochemical descriptor for the given amino acids has to be given.

Concept Introduction:

Priority rules:

• Priorities based on atomic number

$\begin{array}{l}\stackrel{\text{-}\text{H,}{\text{-CH}}_{\text{3}}\text{,}{\text{-NH}}_{\text{2}}\text{,}\text{-OH,}\text{-SH,}\text{-Cl,}\text{-Br,}\text{-I}}{\to }\\ \text{Increasing}\text{priority}\end{array}$

• When priority cannot be assigned on the basis of the atoms bonded directly to the chiral center

$\begin{array}{l}\stackrel{{\text{-CH}}_{\text{2}}\text{H,}{\text{-CH}}_{\text{2}}{\text{CH}}_{\text{3}}\text{,}{\text{-CH}}_{\text{2}}{\text{NH}}_{\text{2}}\text{,}{\text{-CH}}_{\text{2}}\text{OH,}{\text{-CH}}_{\text{2}}\text{Cl}}{\to }\\ \text{Increasing}\text{priority}\end{array}$

• Atoms participating in a double or triple bond are considered to be bonded to an equivalent number of phantom atoms.

For example,

• Priority assignment is made at the first point of difference between groups (should not be based on the larger group).