What is the major product formed when HBr is added to Pent-2-ene?

On adding HBr to Pent-2-ene (CH3-CH2-CH=CH-CH3); The major product formed is 2-Bromopentane whose carbocation has 5- Hyperconjugates and it is in accordance with MARKOWNIKOVA rule which states electrophilic addition to an unsymmetrical alkene always occurs through the formation of a more stable carbocation intermediate which I agree, but at the same time, I get confused when I apply the other statement of M.rule, which says the negative part of the addendum goes to the carbon with lesser H atoms. But here both carbons have one H each.. so please correct me!

1 Answer
Oct 17, 2017

see below

Explanation:

Markovnikov rule is only an empirical rule to forecast the addition on a double bond of an alchene. It is regulated from the inductive effect, and the carbocation that is more stable will be formed. between
#CH_3-CH_2-CH^+ -CH_2-CH_3# and #CH_3-CH_2-CH_2 -CH^+ -CH_3# ,
the second carbocation is more stabe than the first, and you will have preferably it.

This is because #CH_3-# has an inductive effect +I bigger than #CH_3-CH_2-# and stabilizes better the carbocation. However both the two compounds are formed may be in proportion about 60%-40% depending also from the temperatura and the catalyst