Organic Chemistry

119 Electrophilic additions

Electrophilic additions are also referred to asaddition reactions.

An additionCH 2 =CH 2 + HX→CH 3 -CH 2 X

Its reverse, an eliminationCH 3 -CH 2 X + base,∆→CH 2 =CH 2

Electrophilic additions are essentially the reverse of an E1 elimination reaction^1 , sometimes
exactly themicroscopic reverse.

Microscopic reverseThis means that the mechanism of the reaction follows each and every step of

the related reaction in reverse order, without deviation.Sometimes, a reaction can be reversed but

using a different series of tiny steps. When that happens, it is NOT called a microscopic reverse.

Addition reactions involve carbocations^2. This intermediate carbocation can rearrange.

Addition reactions follow Markovnikov’s rule^3. (The higher priority substituent adds to the
more highly substituted carbon of the carbon-carbon double bond).

(Series of sample reactions here)

1 Chapter56.2on page 214
2 Chapter 118 on page 381
3 Chapter55.2on page 203