266 Substitution and Elimination Table

266 Substitution - Substitution and Elimination reactions with different alkyl halides Substrate Methyl Possible Reaction SN2 SN2 Sterically

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1 Substitution and Elimination reactions with different alkyl halides Substrate Methyl Primary (1 o ) Secondary (2 o ) Tertiary (3 o ) Possible Reaction S N 2 S N 2 E2 S N 2, E2, S N 1/E1 S N 1/E1 E2 Explanation S N 2: Sterically unhindered electrophile easy access for nucleophilic attack An elimination reaction cannot occur S N 2: Main reaction with strong nucleophiles (e.g., RS¯, I¯, ¯CN) or strong bases (e.g., RO¯). The alkyl halide is sterically unhindered and will readily undergo an S N 2 E2: An E2 reaction will mainly occur with a hindered strong base (e.g., (R 3 CO¯) S N 1/E1 generally does not occur because a primary carbocation will not form S N 2: main reaction when using good nucleophiles/weak bases (e.g., RS¯, I¯, ¯CN, RCO 2 ¯). An aprotic solvent. (e.g., acetone, DMF,THF) enhances the reactivity of a nucleophile E2 internal double bond: Main reaction when an strong base (e.g., RO¯) is used. Do not forget ( E ) and ( Z ) isomers may form S N 1: main reaction if a weak base/poor nucleophile (e.g., ROH) is used in a polar protic solvent (e.g., ROH). Solvent is most likely the nucleophile. E1 products will also form. Remember to think about regiochemistry and stereochemistry . Anytime a carbocation forms rearrangement can occur S N 1: main reaction if a weak base/poor nucleophile (e.g., ROH) is used in a polar protic solvent (e.g., ROH). Solvent is most likely the nucleophile. E1 minor products will also form. Remember to think about regiochemistry and stereochemistry . Anytime a carbocation forms rearrangement can occur E2: Main reaction with a strong base (e.g., RO¯, R 3 CO¯) Remember to think about regiochemistry and stereochemistry An S N 2 reaction can not
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This note was uploaded on 10/31/2011 for the course CHEM 266 taught by Professor Pols during the Fall '07 term at Waterloo.

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266 Substitution - Substitution and Elimination reactions with different alkyl halides Substrate Methyl Possible Reaction SN2 SN2 Sterically

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