An organic compound A ($C_4H_9Cl$) on reaction with Na/diethyl ether gives a hydrocarbon which on monochlorination gives only one chloro derivative then, A is : -
A
t-butyl chloride
B
sec. butyl chloride
C
Iso butyl chloride
D
n-butyl chloride
The answer is A.
Solution
In the Wurtz reaction, two alkyl groups join: $2RCl + 2Na \xrightarrow{dry\ ether} R-R + 2NaCl$ A hydrocarbon that gives only one monochloro derivative must have all its hydrogen atoms equivalent. From t-butyl chloride, $(CH_3)_3CCl$: $R-R = (CH_3)_3C-C(CH_3)_3$ (2,2,3,3-tetramethylbutane). All 18 hydrogens are on equivalent methyl groups, so it gives only one monochloro product. The products from the other butyl chlorides (n-octane, 3,4-dimethylhexane, 2,5-dimethylhexane) have different kinds of hydrogen and give several monochloro products. So A is t-butyl chloride.
ConceptSymmetry of Wurtz product
Haloalkanes and Haloarenes in past papers
55 questions from this chapter have appeared across 25 exam years.
