Question

When 3,3-dimethyl-2-butanol is heated with $H_{2}S{O}_4,$ the major product obtained is

• A. 2,2-dimethyl-l-butene
• B. 2,3-dimethyl-l-butene
• C. 2,3-dimethyl-2-butene
• D. $cis$ and trans isomers of 2,3-dimethyl-2- butane

Answer 1

Answer: (C)

$H_{3}C-\underset{\begin{array}{c}|\\ C{H}_3\end{array}}{\stackrel{\begin{array}{c}C{H}_3\\ |\end{array}}{C}}-\underset{\begin{array}{c}|\\ OH\end{array}}{\mathrm{CH}}-C{H}_3+cone{H}_{2}S{O}_4$ $\stackrel{\Delta }{\to }\underset{(minor)}{H_{3}C-\underset{\begin{array}{c}|\\ C{H}_3\end{array}}{\stackrel{\begin{array}{c}C{H}_3\\ |\end{array}}{C}}-CH=C{H}_2}+\underset{(major)}{C{H}_3-\stackrel{\begin{array}{c}C{H}_3\\ |\end{array}}{C}=\stackrel{\begin{array}{c}C{H}_3\\ |\end{array}}{C}-C{H}_3}$ Mechanism
Note Most stable alkene is the major product of the reaction. C is and trans isomerism is not possible because similar groups are present on both double bonded carbon atoms.