Butyl bromide, olefin elimination from

The relative partitioning of the carbonium ion between hydration (i.e. exchange) and elimination to olefin is obviously closely related to the proportion of olefin formed in the SN1 hydrolysis of related alkyl halides. The value of 2-8% olefin formation in water at 25°C found on the basis of the exchange experiments agrees very satisfactorily with the value of 3 % found in the solvolysis of t-butyl bromide in water (as calculated by extrapolation from aqueous ethanol solutions). 

Modification of base and solvent can also induce a change from Saytzeff to Hofmann orientation even in alkyl bromide eliminations . In one unimolecu-lar elimination , the least substituted olefin is formed predominantly - ", but in this case it is the thermodynamically more stable product by about 1.8 kcal.mole, due to eclipsing between the /-butyl and methyl substituents in the more substituted olefin , and consequently the Saytzeff pattern is not violated (115). 

---