CH6: Radical Reactions Flashcards
What is needed for homolytic bond cleavage
Heat or light
Dialkyl peroxides turn into what with cleavage R-O-O-R
Alkoxyl radicals R-O (-)
What are the most stable radicals?
Allylic and benzylic because of resonance
Alkane halogenation
Is very unstable and leads to a multitude of products
Chlorine radical rxn
Not good, use bromination
How to get monosubstituted alkanes with halogen radical reactions
Use an excess of alkanes
Initiation
The initial step where X2 is split into radicals by heat or light
Chain propagation
A) X* steals an H off of an alkyl group forming an alkyl radical
B) The R* radical attacks X2 forming an alkyl halide and another X* which will go steal another H
A/B repeat
What is radical halogenation?
X2 attacks a symmetrical compound with light or heat adding one X
What is hydrobromination with peroxides?
HX with ROOR leads to the less substituted alkyl halide
Compound symmetry leads to?
A multitude of products
Termination
When 2 radicals link up
Monochlorination of higher alkanes
Leads to multiple products…shit
Monobromination of higher alkanes
Much more selective…gives the predicted product
What happens when an achiral carbon radical is attacked by X*
It may lead to enantiomers because it is trigonal planar, it can fill from either side.
