1
The incorrect IUPAC name is
- CH3- O \|C- CH3 |CH-CH3 2-methyl-3-butanone
- CH3- CH3 |CH- CH2CH3 |CH-CH3 2,3-dimethylpentane
- CH3-C CCH(CH3)2 4-methyl-2-pentyne
- CH3 Cl |CH Br |CHCH3 2-bromo-3-chlorobutane
Answer
(1) CH3- O \|C- CH3 |CH-CH3 2-methyl-3-butanone
Solution
(1) Principal functional group (C=O) must get the lowest locant; the chain is numbered from the end nearer to the carbonyl carbon:
1CH3- 2CO- 3CH(CH3)- 4CH3 ⇒ correct name 3-methylbutan-2-one (3-methyl-2-butanone). ∴ '2-methyl-3-butanone' is incorrect.
(2) Longest chain = 5 C (through CH2CH3), methyl groups at C-2 and C-3 ⇒ 2,3-dimethylpentane ⇒ correct.
(3) 1CH3- 2C 3C- 4CH(CH3)- 5CH3 ⇒ 4-methylpent-2-yne (4-methyl-2-pentyne) ⇒ correct.
(4) Both numberings give locants 2, 3; then the substituent cited first in alphabetical order (bromo) gets the lower number ⇒ 2-bromo-3-chlorobutane ⇒ correct.
Answer: (1)
AIPMT 2001