Question

29 multiple choice 2 points which of the following are acceptable fischer projections for s - alanine, nh₂ch(ch₃)cooh? ii only i only iii only i and iii

Explanation:

Step1: Determine priority of groups

For S - alanine, the priority of groups around the chiral center is: $-NH_2 > -COOH> -CH_3 > -H$. In Fischer projection, when the lowest - priority group ($-H$) is on the vertical line, a counter - clockwise arrangement of the remaining groups gives the S - configuration.

Step2: Analyze projection I

In projection I, when we assign priorities and check the direction of the three higher - priority groups, it gives an R - configuration.

Step3: Analyze projection II

In projection II, with the $-H$ on the vertical line, the arrangement of $-NH_2$, $-COOH$ and $-CH_3$ is counter - clockwise, which is the S - configuration.

Step4: Analyze projection III

In projection III, when we assign priorities and check the direction of the three higher - priority groups, it gives an R - configuration.

Answer:

A. II only