Introduction To Organic: Reaction Mechanisms

Question 1

Free radical substitution description

Answer 1

No curly arrows required here! Just three stages: (1) Initiation by UV light to form two radical species; (2) Propagation where the radical moves from one species to another;(3) Termination where radicals join to form a stable species.

• Alkanes

Question 2

Electrophilic addition description

Answer 2

Always involves addition to a double bond. Usually H2, HBr, Br2 or H20 will be added.

• Alkenes

Question 3

Nucleophilic substitution description

Answer 3

A nucleophile attacks an electrophilic atom. A leaving group is replaced.

• halogenoalkanes and alcohols

Question 4

Nucleophilic addition description

Answer 4

A nucleophile attacks a carbonyl group. The nucleophile is usually H- or CN-

• ketones and aldehydes

Question 5

Nucleophilic addition-elimination description

Answer 5

Two stages: Attack of an amine on either an acyl chloride or acid anhydride followed by the elimination of either the chloride or acid.

-acyl chlorides

Question 6

Electrophilic substitution description

Answer 6

Involves a benzene ring. The electrophile must be produced first because the delocalised n system is very stable. The electrophile (E*) replaces H+ on the benzene ring

Question 7

Elimination description

Answer 7

Starts with a halogenoalkane. Ethanolic NaOH is added. The product is an alkene, water, and sodium halide.

-halogenoalkanes (to make an alkene)