Question

Can I get somebody to explain SN₁ vs SN₂ reactions in terms of both what happens and how the rate law applies? Thank you

Answer 1

SN1: it represents nucleophillic unimolecular substitution.

it happen through 2 steps.

step:1 R-X ------------> R⁺   + X^-   formation of carbocation intermediate slow step

step 2: R⁺   + Nu --------------> R-Nu reacting intermediate with Nu fast step.

as we know rate of multi step reaction depends on the step which occuer slowly.

in above case in slow step only alkyl halide present. so rate law as follows

rate = K [R-X]

so it if first order kinetics.

SN2) nucleophillic bimolecular substitution

R-X + Nu --------------> R-Nu + X^-      it is one step reaction

rate is depends on both alkyl halide and nucleophile

rate = K[R-X][Nu]

it follows second order kinetics