Free Radical and SN and E Flashcards
Alkyl halide alternative term
Haloalkane
Name of cleavage for free radical mechanism
Homolytic cleavage
How long does the propagation step last?
It can go on forever, until free radical hits free radical - termination.
Why is the tertiary radical the most stable?
Inductive Effect and Hyperconjugation.
Regioselective
One pathway is more likely to occur than the other.
Problems with conventional Allylic Bromination and Solution
Br likes to go to double bond, and requires a lot of heat to do reaction. Allylic Bromination with NBS solves both problems.
NBS
N-Bromosuccinimide
The allylic radical is more stable than the normal primary radical because
of resonance
Resulting product from free radical mechanism (stereochemistry)
Racemic
3 steps of SN1
- Ionization of alkyl halide (rate determining step)
- Nucleophile Attacks
- Proton Extraction
Solvolysis
Solvent is nucleophile
Factors affecting the rate of SN1/SN2
- Substrate = alkyl halide 2. Nucleophile (no affect on SN1) 3. Solvent 4. Leaving Group
Polar Aprotic Solvents favor what reaction? Why?
Favors SN2, will not solvate Nu
Strongest Halogen nucleophile for PAS
F (opposite for PPS)
Best leaving group, why?
Iodine, most stable anion, weakest base
2 steps in elimination reaction
- Dehydrohalogenation (removal of X & ß Carbon)
2. Formation of a double bond
How to increase E1 product?
Increase temperature
E2 requirements
ß Hydrogen and Halogen must be anticoplanar (can still be done in eclipse, but needs a lot of energy to beat steric effect).
Which ß elimination reaction takes place on a tertiary alkyl halide (substrate)? Why?
E1 - weak base
E2 - Strong base
Reason: Backside size doesn’t come into play like SN1/2
1º alkyl halide, strong nu/base, which reaction is favored?
SN2 (1 bond broken) > E2 (2 bonds broken)
Hoffmann Product
Least substituted double bond (opposite of Zaitsev’s Rule)
When do we get Hoffmann Product?
Bulky Base
