medchem 5 Flashcards
the energy difference between the ground state and the transition state is the
activation energy ( g++)
- primary alkyl halide have lower activation energy than secondary bc the reaction will be faster by decreasing the transition energy
SN2 will not take place if
carbon has no H bc it’ll be too crowded for the nucleophile to enter
if -ve charged nucleophile attack the molecule
the molicule will become neutral
if a neutral nucleophile ( aka has lone pair ) attacks the molecule
positive molecule will form and the charge will be removed by losing the proton by deprotonation
strong nucleophiles are
strong bases
nucleophiles and their rate of reactions
CN- > Aloxide ( Ch30-) > OH- > cl > Nh3 > h20
best leaving groups are those that
stabilise the -ve charge since they leave w it
weak bases are
good leaving groups
lower the pka of the leaving group of conjugate acid
better leaving group
reactivity of the leaving groups:
TosO- > I > Br> Cl> F> OR- > NH2- > OH-
SN2 follows
second order of kinetic ( if we double the rate the concentration will double )
SN1
-unimolicular
-slow determine step is the: formation of carbonation
- 2nd fastest step is nucleophile reaction w/ carbonation
secondary alkyl halide can undergo
SN2 and SN1
- its more favourable for SN1 if it contains: benzene ring or bulky substituents bc it prevents the backside attack of the nuclephile, stabilises the carbonation
the more substiuents in the carbon
the more stabilised carbonation will be ( that’s why tertiarty is the most reactive and alpha carbon aka CH3X does not react )
chiral alkyl halide in SN1 gives
racemic mixture
