Question

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

• A. $- SO_3 H$
• B. $- COOH$
• C. $- CHO$
• D. $- C_6 H_5$

Answer 1

Answer: (A)

$- SO_3 H$

Answer 2

In R-S configuration, priority sequence is decided by the atoms directly attached to the chiral carbon arranged in decreasing atomic number.
From the given groups, sulphur (S) has the highest atomic number i.e., 16 therefore, it gets highest priority.