Stereochemistry anti elimination is favored in an E2 reaction Stereoselectivity, example 1: OEt CH?CHCH2 CH2CH CH3CH=CHCH, CH3 CH2=CHCH2 CH2CH3 HOEt Br major product minor product H3CH2C H CH2CH 3 C-C XCH3 B (E)41% CHCH 3 C=C H○3-xQh3c CH2 CH3 B (Z)14%4. Stereochemistry anti elimination is favored in an E2 reaction —— Stereoselectivity, example 1: C H 3CH C H 2CH 2CH 3 Br - O E t + CH 2=CHC H 2CH 2CH 3 major produ c t m ino r pr oduc t C C H H 3 C CH 2CH 3 H C C H H 3 C H CH 2CH 3 ( E ) 41% ( Z ) 14% H 3CH 2 C H H X H CH 3 H H CH 2CH 3 X H CH 3 : B : B - X - X C H 3CH=CH C H 2CH 3 HOEt