organic chem - chapter 6

methane

CH4

chloromethane

CH3Cl

methylene chloride

CH2Cl2

chloroform

CHCl3

carbon tetrachloride

CHCl4

primary halide

attached to one other carbon

secondary halide

attached to two other carbons

tertiary halide

attached to three other carbons

allylic position

third carbon is in blank position

SN2 reaction

• no intermediate; concerted

• backside attack

• 2nd order reaction - rate depends on concentration of both reactants

• CH3 > 1 > 2> 3

• inverts configuration of chiral carbon

strong nucleophiles

CH3O- , OH - , SH - , I - , CN - 

moderate nucleophiles

Br - , Cl -, NH3

weak nucleophiles

F- , H2O, ROH, CH3COO -

nucleophilicity trends

increases down and to the left

smaller nucleophile - stronger nucleophile

SN1 reaction 

• has intermediate (carbocation 

• carbocation forms quickly. second step is slow

• 3 > 2 >1> CH3

• reactivity depends on halide. Nucleophile completes reaction

• yields racemic mixture

• potential for rearrangement

racemic mixture

half R and half S

SN2

if it’s a strong nucleophile

SN1

if it’s a weak nucleophile