JEE Main levelOne or more correct optionsDifficulty 2 of 3g3196
Buta-1,3-diene reacts with one equivalent of HBr. Which statements are correct?
AAt 40∘C (equilibrated) the major product is 1-bromobut-2-ene
BBoth adducts arise from the same resonance-stabilised allylic cation
CAt −80∘C the major product is 3-bromobut-1-ene
DThe 1,4-adduct forms faster than the 1,2-adduct at every temperature
Answer: A, B, C
The kinetic 1,2-adduct dominates at low temperature, and the more stable 1,4-adduct at higher temperature. Both come from one allylic cation. The 1,4-adduct forms more slowly at low temperature, so the last statement is false.