S2 Competes with E2 Depends on the Size of the Base CH:CH2O CH;CH2CH2CH2OEt CH3CH2CH-CH2 str.base 90% 10% CH:CH2CH2CH2Br (CH:)CO CH3CH2CH2CH2OtBu CH3CH2CH-CH2 str.bulky base 15% 85%SN2 Competes with E2 15% 90% 10% C H3C H2C H2C H2Br C H3C H2O (CH3)3C O str. bulky base str. base C H3C H2CH=CH2 C H3C H2CH=CH2 C H3C H2C H2C H2OEt C H3C H2C H2C H2OtBu 85% Depends on the Size of the Base