Question

In assigning R-S configuration which among the following groups has highest priority ?

• A. $-S{O}_{3}H$
• B. $-COOH$
• C. $-CHO$
• D. $-C_6{H}_5$

Answer 1

The correct option is A $-S{O}_{3}H$

In assigning R-S configuration $-S{O}_{3}H$ group has highest priority.
The decreasing order of priority is $-S{O}_{3}H>-COOH>-CHO>-C_6{H}_5$.
Higher is the atomic number of the atom, higher is its priority. The atomic number of S is maximum. Hence, $-S{O}_{3}H$ group has highest priority.