How does an #"S"_"N"1# reaction work?

1 Answer
Sep 10, 2017

Well, an #S_(N)1# reaction is essentially a reaction where BOND-BREAKING is the rate determining step.........they are usually invoked to describe organic reactivity.......

Explanation:

#S_(N)1# reactions are thus presumed to occur thru the intermediacy of a 3-coordinate carbocation:

#CR_1R_2R_3X stackrel("rate determining step")rarr""^(+)CR_1R_2R_3 +X^-#

And as the #"RDS"#, this is the slow step, i.e. the formation of a carbocation.....and the formation of a bond between the three-coordinate carbocation and a nucleophile is usually the fast step......

#R_1R_2R_3C^(+) + Nu^(-) stackrel("fast")rarrR_1R_2R_3C-Nu#

Because the carbocation is three-coordinate it cannot (normally) support optical activity, and an optically active substrate would give rise to a racemic product......