In IUPAC nomenclature, the correct order of decreasing priority of functional group is :
- -CONH2, >C=O, -CHO, -NH2, -C C-
- -CONH2, -COOCH3, -CHO, -NH2, -OH
- -CONH2, -CHO, >C=O, -NH2, -C C-
- -CONH2, -CHO, -CN, -NH2, -C C-
Answer
(3) -CONH2, -CHO, >C=O, -NH2, -C C-
Solution
As per NCERT, the decreasing order of priority of functional groups is:
–COOH > -SO3H > –COOR > –COCl > -CONH2 > –CN > –CHO > >C=O > –OH > -NH2 > >C=C< > -C C-
Checking each option:
(1) >C=O placed before –CHO ✗
(2) –COOCH3 (ester) placed after -CONH2 ✗ (ester > amide)
(3) -CONH2 > –CHO > >C=O > -NH2 > -C C- ✓
(4) –CN placed after –CHO ✗ (nitrile > aldehyde)
Answer: (3)