Neopentyl alcohol (2,2-dimethylpropan-1-ol) is heated with concentrated HBr. The major organic product is:

A1-bromo-2,2-dimethylpropane
B1-bromo-2-methylbutane
C2-bromo-2-methylbutane
D2-bromo-3-methylbutane

Answer: C

Protonated alcohol loses water with a simultaneous methyl shift, giving the tertiary 2-methylbutan-2-yl cation. Bromide captures it to give 2-bromo-2-methylbutane. The unrearranged neopentyl bromide is not the main product because backside

S_{N} 2

attack is blocked and the primary cation is not formed.

Practice General Organic Chemistry III: Reaction Intermediates More on Carbocations: formation, stability, rearrangements

Previous questionNext question

More questions on Carbocations: formation, stability, rearrangements

Select the cation(s) which cannot be converted into a more stable carbocation by any single 1,2-hydride or 1,2-methyl shift. JEE Main level
How many alpha hydrogens (hydrogens on carbon atoms directly attached to the cationic carbon, i.e. hyperconjugating C-H bonds) are present i... JEE Main level
Heating 3,3-dimethylbutan-2-ol with concentrated H2SO4 gives mainly (Saytzeff product after carbocation rearrangement): JEE Advanced level
Assertion (A): the two C-C bonds in the allyl cation CH2=CH-CH2+ have equal length. Reason (R): the allyl cation has four electrons in its t... JEE Advanced level
Match each cation in List I with the effect that is mainly responsible for its stability (or instability) in List II. List I: P: CH3-O-CH2+;... JEE Advanced level
Which of the following is the correct order of decreasing stability? JEE Advanced level