3,3-Dimethyl-2-butanol cannot be prepared by : Choose the correct answer from the options given below :
- B and E Only
- B, C and E Only
- B and C Only
- B Only
Answer
(1) B and E Only
Solution
Target: (CH3)3C-CH(OH)-CH3 (3,3-dimethylbutan-2-ol, 6 C)
A. (CH3)3C-CHO [H3O+]CH3MgBr, dry ether (CH3)3C-CH(OH)-CH3 can be prepared.
B. 3,3-Dimethylpent-1-ene has 7 C atoms. Acid-catalysed hydration gives a 2° carbocation which rearranges (1,2-methyl shift) to a 3° carbocation 2,3-dimethylpentan-3-ol (a C7 alcohol) cannot give the target.
C. Ozonolysis: (CH3)3C-C(CH3)=C(CH3)-C(CH3)3 O3/Zn-H2O 2 (CH3)3C-CO-CH3
(CH3)3C-CO-CH3 NaBH4/MeOH (CH3)3C-CH(OH)-CH3 can be prepared.
D. (CH3)3C-CO-CH3 LiAlH4/H3O+ (CH3)3C-CH(OH)-CH3 can be prepared.
E. (CH3)3C-C CH H2O, Hg2+/H+ (CH3)3C-CO-CH3 (enol tautomerises to the ketone); no reduction occurs the alcohol is not formed.
B and E cannot give 3,3-dimethyl-2-butanol.
Answer: (1)