for a substitution reaction, nucleophilic strength ____ as you go down thje periodic table
increases, because of size and polarizability increase
for an Sn2 reaction, bulky molecules are _____ nucleophiles
weak
polar protic solvents
reduce the strength of the nucleophile (which
makes it more favorable for Sn1 and less favorable for Sn2). The hydrogen bonds
between the solvent and the nucleophile must be broken before the nucleophile
can attack the carbon
polar aprotic solvents
do not form hydrogen bonds with the nucleophile.
Favors Sn2 reactions and disfavors sn1 reactions
Does Sn2 (walden inversion) always result in a change in the configuration of the chiral carbon? (ex. if the original molecule was in (S) configuration but changed to (R)
after the halogenation)
inversion doesn't always result in a change i
nthe configuration of the chiral carbon, but 99% of the time it does.
Does racemization occur in an sn1 reaction?
yes
what is the rate law for an Sn1 reaction?
rate = k[R-X]
so, concentration of nucleophile doesn't play a role in the rate, only the
concentration of the alkyl halide does.
what is the order of reactivity for an Sn1 reaction?
tertiary>secondary>primary>>>methyl
does sn1 reaction prefer weak or strong nucleophile?
weak
How does the Sn1 mechanism work?
unimolecular (meaning only one molecule is involved in the transition stat eof the rate limiting step) nucleophilic substitution. it is a multi-step reaction (2-3 steps) that involves a carbocation intermediate.
Ex.
Step 1 formation of carbocation (slow step)
Step 2 nucleophilic attack
Step 3 Loss of Hydrogen ion (H+) if needed
what is a unimolecular reaction?
there is only one molecule involved in the transition state of the rate-limiting step