SN1 vs SN2 Simplified Guide

If SN1 and SN2 always confuse you on exams, this will fix that in under a minute. First question:

one step or two? SN1 = two steps. SN2 = one step. SN1 starts by forming a carbocation,

so it loves tertiary carbons. SN2 can’t handle carbocations — it attacks directly

— so it loves primary carbons. Next: nucleophile strength. SN2 needs a strong

nucleophile to hit fast. SN1 doesn’t care — once the carbocation forms,

anything can attack. Now the biggest exam giveaway: stereochemistry. SN2 = inversion only.

SN1 = racemic mixture because the carbocation is planar. Finally, rate laws.

SN2 depends on substrate AND nucleophile. SN1 depends on substrate only. If you see tertiary