The Epic Interactive Encyclopedia 1998/Epic Interactive Encyclopedia, The - 1998 Edition (1998)(Epic Marketing).iso/O/Organic_chemistry/INFOTEXT

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The chemistry of carbon compounds, in
particular the more complex ones. The basis
of organic chemistry is the ability of carbon
to form long chains of atoms, branching
chains, rings, and other complex structures.
In a typical organic compound, each carbon
atom forms a bond with each of its
neighbouring carbon atoms in the chain or
ring, and two more with hydrogen atoms
(carbon has a valency of four). Other atoms
that may be involved in organic molecules
include oxygen and nitrogen. Compounds
containing only carbon and hydrogen are known
as hydrocarbons. Organic chemistry is largely
the chemistry of a great variety of
homologous series - those in which the
molecular formulae, when arranged in
ascending order, form an arithmetical
progression. The physical properties undergo
a gradual change from one member to the next.
The chain of carbon atoms forming the
backbone of an organic molecule may be built
up from beginning to end without branching;
or it may throw off branches at one or more
points. This division of organic compounds is
known as the open-chain or aliphatic
compounds. Sometimes, however, the ropes of
carbon atoms curl round and form rings. These
constitute the second division of organic
compounds, known as closed-chain, ring, or
cyclic compounds. Other structural varieties
are known. Many organic compounds are made
only by living organisms (for example
proteins, carbohydrates), and it was once
believed organic compounds could not be made
by any other means. This was disproved when
Wohler synthesized urea, but the name
`organic' (that is `living') chemistry has
remained in use. Many organic compounds are
derived from oil, which represents the
chemical remains of millions of microscopic
marine organisms. In inorganic chemistry, a
specific formula usually represents one
substance only, but in organic chemistry, it
is exceptional for a molecular formula to
represent only one substance. Substances
having the same molecular formula are called
isomers, and the relationship is known as
isomerism. Hydrocarbons form one of the most
prolific of the many organic types; fuel oils
are largely made up of hydrocarbons. Typical
groups containing only carbon, hydrogen, and
oxygen are alcohols, aldehydes, ketones,
ethers, esters, and carbohydrates. Among
groups containing nitrogen are amides,
amines, nitro-compounds, amino-acids,
proteins, purines, alkaloids, and many
others, both natural and artificial. Other
organic types contain sulphur, phosphorus, or
halogen elements. The most fundamental of all
natural processes are oxidation, reduction,
hydrolysis, condensation, polymerization, and
molecular rearrangement. In nature, such
changes are often brought about through the
agency of promoters known as enzymes, which
act as catalytic agents in promoting specific
reactions. The most fundamental of all
natural processes is synthesis, or building
up. In living plant and animal organisms, the
energy stored in carbohydrate molecules,
derived originally from sunlight, is released
by slow oxidation and utilized by the
organisms. The complex carbohydrates thereby
revert to carbon dioxide and water, from
where they were built up with absorption of
energy. Thus, a so-called carbon food cycle
exists in nature. In a corresponding nitrogen
food cycle, complex proteins are synthesized
in nature from carbon dioxide, water, soil
nitrates, and ammonium salts, and these
proteins ultimately revert to the elementary
raw materials from which they came, with the
discharge of their energy of chem cal
combination. origami