1
An organic compound A (C4H9Cl) on reaction with Na/diethyl ether gives a hydrocarbon which on monochlorination gives only one chloro derivative, then A is
- t-butyl chloride
- s-butyl chloride
- iso-butyl chloride
- n-butyl chloride
Answer
(1) t-butyl chloride
Solution
Na/dry ether converts an alkyl halide into the alkane R–R (Wurtz reaction):
2RX + 2Na dry ether R-R + 2NaX
For A = t-butyl chloride, (CH3)3C-Cl:
2(CH3)3C-Cl + 2Na dry ether (CH3)3C-C(CH3)3 + 2NaCl
The product, 2,2,3,3-tetramethylbutane, has six identical -CH3 groups, i.e. all 18 H atoms are equivalent.
Its monochlorination gives only one chloro derivative, (CH3)3C-C(CH3)2-CH2Cl.
The other butyl chlorides give octanes with two or more kinds of H atoms (e.g. n-butyl chloride gives n-octane with four kinds of H), so they give more than one monochloro derivative.
Answer: (1)
AIPMT 2001