How to Determine Reaction Type SN2 SN1 E2 E1 Factors to Consider Each factor is equally important 1 Nucleophile Strength SN1 E1 prefer poor nucleophiles SN2 prefers good nucleophile and weak base E2 prefers good nucleophile and strong base Common Weak Bases Poor nucleophiles H2O ROH Good nucleophiles PR3 Halides NH3 RS N3 NC RCOO Common Strong Bases Good nucleophiles HO RO H2N R2N Tip Good nucleophiles will often have a negative charge 2 Steric Hindrance around the reacting carbon Substitution favors sterically unhindered carbon Primary haloalkanes Likelihood of elimination increases with sterically hindered carbon Branched primary secondary tertiary haloalkanes 3 Steric Hindrance in the nucleophile Note only needed for determining if the reaction is SN2 or E2 SN2 is favored with sterically unhindered nucleophile HO CH3O CH3CH2O H2N E2 is strongly favored with sterically hindered nucleophile CH3 3CO aka t BuO CH3 2CH 2N aka LDA Master Chart to determine the reaction Type of Nucleophile Poor Nucleophile ex H2O Weak base good nucleophile e g I Strong base unhindered good nucleophile e g CH3O Strong base hindered good nucleophile e g CH3 3CO Type of Haloalkane Methyl No reaction No reaction SN2 SN2 No reaction SN2 Primary Unhindered Primary Branched Secondary Slow SN1 E1 SN2 Tertiary SN1 E1 SN1 E1 SN2 SN2 E2 E2 E2 SN2 E2 E2 E2 E2
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