Reaction Mechanisms

Question 1

Homolytic fission

Answer 1

• When a covalent bond breaks by homolytic fission, each of the bonded atoms takes one of the shared pair of electrons from the bond.
• Each atom would have a single unpaired electron shows by a dot.

Question 2

Radicals

Answer 2

An atom or groups of atoms with unpaired electron is called a radical.

Question 3

Heterolytic fission

Answer 3

• When a covalent bond breaks by heterolytic fission, one of the bonded atoms takes BOTH the electrons from the bond.
• The atom that takes both electrons becomes a negative ion.
• The atom that does not take the electrons becomes a positive ion.

Question 4

Curly arrows

Answer 4

A curly arrow shows the movement f an electron pair, showing either heterolytic fission or formation of a covalent bond.
* Half curly arrows represent the movement of single, unpaired electron in mechanisms involving radicals (homolytic fission).

Question 5

Addition reactions

Answer 5

2 reactants join together to form 1 product. Usually a double bond is turned to 2 single bonds.

Question 6

Substitution reactions

Answer 6

An atom or group of atoms is replaced by another atom or group of atoms. Same number of products and reactants.

Question 7

Elimination reactions

Answer 7

The removal of a small molecule from a larger one. 1 reactant molecule forms 2 products. Usually a single bond to double bond.