Allylic and Benzyllic sn1 sn2

[virtualmaster999]

Hi everyone!

Quick question on sn1/sn2

How exactly do benzyllic and allylic halides play into effect when determining "which is the best halide for sn1 or sn2"? Is this how you go about it?

for sn2: check primary, then secondary. if there is a tie, say two primary halides, but one is allylic/ benzyllic, that one wins?

for sn1: how does this work if sn1 reactivity is tertiary and secondary, but allylic/benzyllic are neither of these?

Thank you as always!

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[tyjacobs]

allylic and benzylic halides are good alkyl halides for sn2 i believe

 

[DAT Destroyer]

Hi everyone!

Quick question on sn1/sn2

How exactly do benzyllic and allylic halides play into effect when determining "which is the best halide for sn1 or sn2"? Is this how you go about it?

for sn2: check primary, then secondary. if there is a tie, say two primary halides, but one is allylic/ benzyllic, that one wins?



for sn1: how does this work if sn1 reactivity is tertiary and secondary, but allylic/benzyllic are neither of these?

Thank you as always!

Benzylic and allylic halides can do EITHER SN1 or SN2 depending on the conditions. If the solvent is polar such as water or alcohol, the SN1 pathway will operate. If the nucleophile is strong such as CN- or C2H50-....SN2 will take over. Also...a polar aprotic solvent such as DMF, THF, DMSO favors SN2. As the substrate gets more hindered......as in the case of secondary or tertiary......SN1 is more likely. Great question...

Hope this helps

Dr. Jim Romano