Question

Which of the following is the correct order of priority of groups of D-glyceraldehyde?

• A. $OH\left(1\right),CHO\left(2\right),{CH}_{2}OH\left(3\right)$ and $H\left(4\right)$
• B. $OH\left(1\right),{CH}_{2}OH\left(2\right),CHO\left(3\right)$ and $H\left(4\right)$
• C. ${CH}_{2}OH\left(1\right),CHO\left(2\right),OH\left(3\right)$ and $H\left(4\right)$
• D. $CHO\left(1\right),OH\left(2\right),{CH}_{2}OH\left(3\right)$ and $H\left(4\right)$

Answer 1

The correct option is A $OH\left(1\right),CHO\left(2\right),{CH}_{2}OH\left(3\right)$ and $H\left(4\right)$

The priority of groups is decided by the following rules:

(i) Atom having higher atomic number gets higher priority.

(ii) If priority cannot be decided by rule $1$ then the next atoms are considered for priority assignment.

(iii) Where there is a $=$ bond or $\equiv$ bond both atoms are considered to be duplicated or triplicated ($-\stackrel{H|}{C}=O$ has higher priority than $-{CH}_{2}OH$).

Hence, the correct order of priority of groups in D-glyceraldehyde:

$OH\left(1\right),CHO\left(2\right),{CH}_{2}OH\left(3\right)$ and $H\left(4\right)$