Kinetic and Thermodynamic Control The addition of HBr to 1,3-butadiene is temperature dependant(ie.the ratio of the products is greatly affected by variations in temperature). 入∠+H-Br 80c 40C Br Br 80% 15% Br Br 20% 75% At the lower temperature,the 1,2-addition product dominates,whereas at the higher temperature the 1,4-addition product is major. The more stable product would be predicted to be the 1,4-addition product since it has an internal double bond. Notice that at lower temperatures the more stable product is not the major product formed. Ch15 Conjugated Systems (landscape) Page 11 Ch15 Conjugated Systems (landscape) Page 11 Kinetic and Thermodynamic Control The addition of HBr to 1,3-butadiene is temperature dependant (i.e. the ratio of the products is greatly affected by variations in temperature). At the lower temperature, the 1,2-addition product dominates, whereas at the higher temperature the 1,4-addition product is major. The more stable product would be predicted to be the 1,4-addition product since it has an internal double bond. Notice that at lower temperatures the more stable product is not the major product formed. H-Br Br Br 80% 20% + Br Br 15% 75% -80 oC 40 oC