Agriculture Reference
In-Depth Information
Table 3.3. Functional Groups Derived from the Acid Functional Group
Family Name
Composition
Structure and IUPAC Name
Acid halides
Carbon, hydrogen, single bonds
with at least one —COX
a
in
the molecule (may include
double and triple bonds and
other structures)
H
H
O
H
CCC
Cl
H
H
Propanoyl chloride
Anhydrides
Carbon, hydrogen, single bonds
with at least one —COOOC—
in the molecule (may include
double and triple bonds
and other structures)
H
OOH
H
H
CCOC
H
H
Ethanoic anhydride
Amides
Carbon, hydrogen, single bonds
with at least one —CONH
2
b
in the molecule (may include
double and triple bonds and
other structures)
H
O
H
H
H
CC
N
H
Ethanamide
Esters
Carbon, hydrogen, single bonds
with at least one —COOC—
in the molecule (may include
double and triple bonds and
other structures)
O
CH
3
C
CH
3
O
Methyl ethanoate
a
X is always used as a general representation for any of the halogens.
b
Hydrogens on the nitrogen can be substituted with alkyl groups.
In addition to methane, other simple organic compounds will be found in
soil from two different sources. They can be either exuded from roots into the
rhizosphere of plants or derived from the decomposition of any organic matter
present. During decomposition all organic matter is broken down into smaller
and smaller organic molecules until it is finally completely converted into
carbon dioxide, water, and humus.
2
The same is true for anaerobic decompo-
sition, except that one of the final decomposition products is methane. Thus,
at any given time, intermediate decomposition products from these two
sources can be found in the soil solution.
Plant roots excrete a mixture of simple and complex compounds and mate-
rials, which differ for different plant species. First, simple acids, both fatty and
amino; sugars; and phenolic compounds are commonly detected as exudates
from plant roots. Each of the these groups may be composed of a complex
mixture of compounds; thus, the most common amino acids can be found along
with many common sugars. In addition, a high-molecular-weight compound
called
mucigel
is secreted by root tip cells and is thought to lubricate root pen-
etration into soil. Mucigel is somewhat slower to decompose but can also be
2
Although seldom mentioned, this process is characterized by the release of energy that is uti-
lized by the organism carrying out the decomposition.
