2-Bromo-2,3-dimethylbutane, $(CH X_{3}) X_{2} CBr - CH (CH X_{3}) X_{2}$ , is treated separately with sodium ethoxide in ethanol and with potassium tert-butoxide in tert-butanol. The major alkenes are respectively

A2,3-dimethylbut-1-ene and 2,3-dimethylbut-2-ene
B2,3-dimethylbut-2-ene and 2,3-dimethylbut-1-ene
C2,3-dimethylbut-2-ene in both cases
D2,3-dimethylbut-1-ene in both cases

Answer: B

Small bases such as ethoxide give the more stable, more substituted alkene (Saytzeff): the tetrasubstituted 2,3-dimethylbut-2-ene. The bulky tert-butoxide removes the more accessible methyl hydrogen (Hofmann), giving the disubstituted 2,3-dimethylbut-1-ene as major product.

Practice Hydrocarbons More on Alkenes: preparation and addition reactions

Previous questionNext question

More questions on Alkenes: preparation and addition reactions

A hydrocarbon C5H10 gives 2-methylbutan-2-ol on oxymercuration-demercuration and a secondary alcohol on hydroboration-oxidation. The hydroca... JEE Advanced level
But-1-ene is treated with HBr (no peroxide) to give A. A is heated with alcoholic KOH to give B as the major product. B is treated with O3 a... JEE Advanced level
(Z)-But-2-ene is (i) treated with cold dilute alkaline KMnO4 to give the diol P, and (ii) treated with Br2 in CCl4 to give the dibromide Q. ... JEE Advanced level
Consider the alkenes (I) ethene, (II) propene, (III) 2-methylpropene and (IV) 3,3,3-trifluoropropene. The order of reactivity towards electr... JEE Advanced level
Which of the following statements are correct? JEE Advanced level
In which of the following reactions is the major product formed with a rearranged carbon skeleton (compared with the starting alkene)? JEE Advanced level

2-Bromo-2,3-dimethylbutane, (CHX3​)X2​CBr−CH(CHX3​)X2​, is treated separately with sodium ethoxide in ethanol and with potassium tert-butoxide in tert-butanol. The major alkenes are respectively

Answer: B

More questions on Alkenes: preparation and addition reactions

2-Bromo-2,3-dimethylbutane, $(CH X_{3}) X_{2} CBr - CH (CH X_{3}) X_{2}$ , is treated separately with sodium ethoxide in ethanol and with potassium tert-butoxide in tert-butanol. The major alkenes are respectively