Advices For Studying Organic Chemistry

Figure 13.10 A schematic free-energy versus reaction coordinate diagram for the
1,2 and 1,4 addition of hbr to 1,3-butadiene. An allylic carbocation is
common to both pathways. The energy barrier for attack of bromide
on the allylic cation to form the 1,2-addition product is less than that
to form the 1,4-addition product. The 1,2-addition product is
kinetically favored. The 1,4-addition product is more stable, and so
it is the thermodynamically favored product.