Chemistry Reference
In-Depth Information
15
Organic chemistry 2
Alcohols (R—OH)
Combustion
Oxidation
Cholesterol - a complex molecule that contains the -OH group
Biotechnology
Baking - an important use of biotechnology
New applications of biotechnology
Condensation polymers
Some biopolymers
Starch
Amino acids
DNA
Pharmaceuticals
Drug abuse
Checklist
Carboxylic acids
Other carboxylic acids
Soaps and detergents
Soapless detergents
Manufacture of soapless detergents
Additional questions
In Chapter 14 we discussed the organic compounds
that are obtained from oil, the alkanes, and how they
are converted into another homologous series of
hydrocarbons called the alkenes. If you replace one
of the hydrogen atoms on an alkane molecule with
a group such as -OH, the hydroxyl group, then you
get a new homologous series called the alcohols. If
you replace one of the hydrogen atoms on an alkane
molecule with a -COOH group (Figure 15.1) then
you get a homologous series called the carboxylic
acids or alkanoic acids. Whichever group you have
attached, it will bring with it a new set of physical
and chemical properties. These groups are known
as
functional groups
. The functional group is the
group of atoms responsible for the characteristic
reactions of the organic compound.
Table 15.1 shows some examples of functional
groups. In the table, R represents an alkyl group or
a hydrogen atom. An alkyl group has the general
formula based on the alkanes, i.e. C
n
H
2
n
+1
. When
n
= 1, R = CH
3
; when
n
= 2, R = C
2
H
5
, and so on.
Table 15.1
The functional groups present in some homologous series of
organic compounds.
Class of compound
Functional group
Alcohols
R—OH
Carboxylic acids
R—COOH
Esters
R—COOR
Halogenoalkanes
R—X
(where X is a halogen atom such as
Cl, Br, etc.)
●
Alcohols (R—OH)
The alcohols (alkanols) form another homologous
series with the general formula C
n
H
2
n
+1
OH (or R—
OH, where R represents an alkyl group). All the
alcohols possess an -OH as the functional group.
Table 15.2 shows the names and condensed formulae
of the first four members along with their melting
and boiling points.
Table 15.2
Some members of the alcohol family.
Alcohol
Formula
Melting point/
°C
Boiling point/
°C
Methanol
CH
3
OH
−94
64
Ethanol
CH
3
CH
2
OH
−117
78
Propanol
CH
3
CH
2
CH
2
OH
−126
97
Butanol
CH
3
CH
2
CH
2
CH
2
OH
−89
117
Figure 15.2 shows the arrangement of the atoms
in the fully displayed (structural) formulae of these
members of this family or homologous series.
The alcohols are named by reference to the
corresponding alkane (see Chapter 14, p. 219),
always ensuring that the hydrocarbon chain is
numbered from the end that gives the lowest
Figure 15.1
This fruit juice contains plenty of vitamin C or ascorbic acid,
which contains the functional group -COOH.
