Functional Classes II, Reactions - Organic Chemistry Concepts: An EFL Approach - page 137

Q 7.4 Draw structures for the alkene(s) which are produced by E2 elimination
if the following alkyl halides are treated with sodium ethoxide (NaOEt).
PROGRAM 21 Nucleophilic Addition
A Substitution does not change the bond order, but elimination causes an increase
in bond order. Both of these reaction types have a saturated center which has a leaving
group, and both proceed by reaction with an electron pair donor nucleophile/base.
An addition reaction is the opposite of elimination. Therefore it must cause a decrease in
the bond order. Addition can follow two main mechanisms. Which mechanism is followed
depends on the type of unsaturation (double bond). The double bond may be the dipolar
type found in carbonyl groups, or largely non-polar as found in alkenes and alkynes.
A dipolar carbonyl group has both electrophilic and nucleophilic centers. Nucleophilic
attack needs an electrophilic center. The example reaction of cyanide with an aldehyde
shows the general outcome (see Program 15C and D).
Because the reaction is started by a nucleophile, it is called nucleophilic addition. The
main feature of addition is the decrease in bond order. This happens when two new
single bonds form to complete the valency requirements.
There are many different nucleophiles, and many different addition products can be
made. Nucleophilic additions can occur under acid or base conditions. This depends
on the exact nucleophile-electrophile pair in the reaction.
For example, the addition reaction of water to aldehydes or ketones to give hydrates
can be done under basic conditions in a way similar to the cyanohydrin formation.
Can you draw the acid-catalyzed process?