Transcript Chapter 12 Alcohols, Phenols, Ethers, Aldehydes, and Ketones

Chapter 12 Organic Compounds
with Oxygen and Sulfur
12.2
Properties of Alcohols, Ethers,
and Thiols
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
1
Boiling Points of Alcohols
Alcohols
• contain polar OH
groups.
• form hydrogen bonds
with other alcohol
molecules.
• have higher boiling
points than alkanes and
ethers of similar mass.
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
2
Boiling Points of Ethers
Ethers
• do not have a polar
group.
• have an O atom,
but there is no H
attached.
• cannot form
hydrogen bonds
between ether
molecules.
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
3
Solubility of Alcohols and Ethers in
Water
Alcohols and ethers
• are more soluble in water than alkanes because the
oxygen atom can hydrogen bond with water.
• with 1-4 C atoms are soluble, but not with 5 or more
C atoms.
4
Comparing Solubility and Boiling
Points
Compound
Alkane CH3─CH2─CH3
Ether
CH3─O─CH3
Alcohol CH3─CH2─OH
Molar
Mass
Boiling
Point (°C)
Soluble
in Water?
44
-42
No
46
-23
Yes
46
78
Yes
5
Reactivity of Alkanes vs. Alcohols
Hydrocarbon + O2  carbon dioxide + water + heat energy
D
Ex. CH4 + 2O2  CO2 + 2H2O
D
Heat released is 802 kJ/mol
of methane
Effect of partially oxidizing a hydrocarbon, let’s look at the
combustion reaction of CH3OH (methanol), in which 1 H has
been replaced by an –OH group.
2CH3OH + 3O2  2CO2 + 4H2O
D
Heat released is 640 kJ/mol
of methanol
(1.5 moles of O2 required to with 1 mole of CH3OH!)
6
These reactions illustrates two important principles.
1st, the more reduced a molecule, the more energy is
released during oxidation on a molar basis.
Methane is fully reduced and gives off more energy during
combustion than methanol.
2nd, the number of oxygen molecules required to react
with a fuel molecule can give an estimate of how much
energy is available.
More highly reduced molecules require more oxygen during
combustion and produces more energy.
7
Reduction of
hydrocarbons vs. their oxidation
OH
CH3OH
Partially Oxidized
8
Solubility of Phenol
Phenol
• is soluble in water.
• has a hydroxyl group that ionizes slightly (weak acid).
• is corrosive and irritating to skin.
OH
O-
+ H2O
+ H3O+
9