Summary CHEM 222 Mechanisms of Organic Chemistry Review

Mechanisms of Organic Chemistry

Note that for all reactions, the charges may vary, but must make sense - the net charge on both
sider of the equation must balance. Lone pairs can be assumed, but charges are always required.
Note that at the beginning I have used colored arrows, bonds, and lone pairs to track the electrons
and reflect the thinking that goes along with mechanisms. The arrows always have this meaning.

1. Acid-base Reactions
generic
A—H + :B A: + H—B

specific
Ph H + NH2
Ph C + H—NH2


2. Steps for free radical reactions. (The odd electrons for radicals are never assumed.)
homolysis
Br Br Br Br

H abstraction
H
Br + Br H +


Rxn w/ e.g. Br2 Br Br Br + Br
+

Termination
Br Br Br Br


3. E2 Eliminations
H Br
O H O +
+ Br


R
H
HO H OH H R O +
H 2O
+ H
OH R OH2

Note that R at the beginning is nPr, at the end is H. There is very little water early in the
reaction and very little alcohol at the end.
cont.

, Mechanisms of Organic Chemistry

H +
H2N H H2N
Br
+ Br

4. E1 elimination of alkyl halide or of protonated alcohol
R H
R O
HO H R OH H
H
+ H 2O
OH2 +
OH
Ph Ph
Ph
Ph
See note in previous mechanism
R
O R H
H R O
H +
Cl + R
Cl
Ph Ph Ph


Colors now omitted; the meaning of the arrows is still the same.
5. SN2 reaction of alkyl halide or of protonated alcohol (inversion)

Br OAc OH2 Br

AcO- Br


note: epoxide and bromonium ion opening is SN2-like

O CN CN Br OH2
O Br
-CN
same OH2
as
O

6. SN1 reaction of alkyl halide or of protonated alcohol

Br OHMe
MeOH


H
Br H OHMe
Ph Ph MeOH
Ph