Honors Chemistry II
REACTIONS OF ALKANES
Reactions of Alkanes

Are alkanes and cycloalkanes generally reactive or unreactive?
1. Alkane molecules usually assume the most _______________ conformations.
2. The bonding of alkanes is considered “_______________” bonding, which
means that the electron pairs are shared directly _______________ the atoms,
so it is _______________ for reagents to get to these electrons.
3. There are __________ non-bonded electrons (lone pairs) to participate in
reactions.

Therefore, alkanes are _______________ to normal chemical reactions.
1. Combustion

What types of fuels do we burn in our homes, in our BBQ grills, and gas camping
stoves?

What do we call a reaction in which something is burned?

What is needed to burn something?
Examples:
o Write a balanced equation for the combustion of propane.
o Write a balanced equation for the combustion of 2,3-dimethylhexane.
o Predict the products of the following reaction:
2 C3H8 (g) + 7 O2 (g) 
o If alkanes are burned with insufficient oxygen, _______________
_______________ is produced instead of carbon dioxide.
Biological Combustion of Hydrocarbons

What types of biomolecules contain long chains of hydrocarbons, with a carboxyl
group at the end?

What are the by-products of the burning of these fats and lipids in our bodies?
o
o
o
2. Halogenation

Alkane halogenation is the substitution of a _______________ with a
_______________. Fluorination is strongly exothermic and difficult to control,
while iodination is endothermic and nonspontaneous. Chlorination and
bromination are the most widely used halogenation reactions.

Chlorination and bromination follow radical halogenation mechanisms (see
handout), and need visible or UV light to get started (h). A similar mechanism
can be used to explain the reaction of chlorofluorocarbons (CFCs) with ozone
(O3) in the atmosphere (see handout).
Examples:
Cl2
h
Br2
h

Chlorine will replace any hydrogen on the hydrocarbon, where bromine will
replace the hydrogen that is bonded to the carbon that has the most carbons
bonded to it. This is called _______________.
Examples:
Cl2
h
Br2
h