In electrophilic additions of hydrogen halides to conjugated dienes, the 1,2-adduct is favored over the 1,4-adduct under kinetic conditions. This excepted mechanism attributed this to the lower the activation energy for 1,2 addition compared to the 1,4 addition. In 1979, Norlander, et.al. published an alternate explanation. He proposed that 1,2 addition was favored due to its proximity to the 1 position. Because of this, organic chemistry textbooks are currently evenly split in which mechanism they present. The goal of our research is to determine which of the the explanations of why the 1,2-adduct is favored under kinetic control is correct. To accomplish this, we will be attempting to synthesize 2-bromohexane from 1-hexene under different temperature conditions, solvents, and molar ratios. Once a significant yield of product has been made with the simple alkene, then we can perform synthesis with 2,5-dimethyl-2,4-hexadiene which may allow us, by analyzing its product ratios, to determine which mechanism is the correct one in this reaction.

Electrophilic addition to conjugated systems: Activation energy theory vs. proximity effect

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