Why does bromination occur exclusively at the allylic position? Allylic H 360 kJ/mol(87 kcal/mol) H H Alkyl 400 kJ/mol (96 kcal/mol) Vinylic 445 kJ/mol (106 kcal/mol) 62004 Thomson Brooks/Cole R R H一C R-C. R—C R-C. H H H R Vinylic Methyl Primary Secondary Tertiary <Allylic (1) (2) (3) Less Stability More stable stable