ch.7 Flashcards
Sn2
nucleophilic attack, loss of a leaving group
methyl
3 hydrogen attached to alpha carbon
primary 1
2 hydrogen attached to alpha carbon
secondary 2
1 hydrogen attached to alpha carbon
tertiary 3
no hydrogens attached to alpha carbon
strong nucleophiles
I, BR, Cl, HS, RS, HO, RO, CN
weak nucleophiles
H2O, ROH
Sn2 preferred solvent.
polar aprotic
protic solvents
water, methanol, ethanol, ammonia, acetic acid
polar aprotic solvents
Acetone, Dimethylsulfoxide (DMSO), Dimethylformamide (DMF), acetonitrile, Hexamethylphosphoramide (HMPA)
protic solvents
H-bonding stabilize anions (like good nucleophiles) and also cations
Aprotic solvents
stabilize cations only
E2
proton transfer, loss of a leaving group
Sn1
lose of a leaving group, nucleophilic attack (proton transfer)
E1
loss of leaving group and proton transfer
strong base; weak nucleophile (1-3)
E2
strong base; strong nucleophile 1
E2 minor, Sn2 major
strong base; strong nucleophile 2
E2 major; Sn2 minor
strong base; strong nucleophile 3
E2
weak base; strong nucleophile (1-2)
Sn2
weak base; strong nucleophile 3
Sn1
weak base; weak nucleophile (sterically hindered) 3
E1
weak base; weak nucleophile (non-sterically hindered) 3
Sn1
most stable to least stable carbocations
tertiary>secondary>primary>methyl
least reactive to most reactive
I>Br>Cl>F
water solvent type
protic
ethanol solvent type
protic
ammonia solvent type
protic
acetic acid solvent type
protic
acetone solvent type
polar aprotic
DMF solvent type
polar aprotic
HMPA solvent type
polar aprotic
DSMO solvent type
polar aprotic
acetonitrile solvent type
polar aprotic
what is the major product for a substitution reaction with a sterically hindered substrate and sterically hindered base?
the less substituted alkane
bredt’s rule
a small bicyclo ring cannot have alkenes at the bridgeheads
strong bases; weak nucleophiles
DBN;DBU
strong bases; strong nucleophiles
OH-;EtO-;MeO-
weak bases, strong nucleophiles
I; Br; Cl; RS; HS; RSH;
weak bases, weak nucleophiles
H2O, MeOH, EtOH
what does the rate of an Sn2 reaction depend on?
the strength of the nucleophile
what does the rate of an E2 reaction depend on?
concentration of the alkyl halide and of the base
what is the RDS for E1 and Sn1 reactions?
loss of a leaving group
