Man's physical universe

xanabras

I

I I I I II

H

H

H

H

612 MAN IS MASTERING HIS MATERIAL WORLD

There Are Many Isomers among Covalent Compounds.

Two butanes of different structural formulas are known:

H H H H H H H

I I I

i

H—C—C—C—C—

H—C—C—C—

H H H H H H

H—C—

These compounds have the same empirical formula, C4H10, but their

structural formulas and their properties are somewhat different. Such

compounds are called isomers. Three pentanes, six hexanes, and nine

heptanes are known. As the number of carbon atoms increases, the

possibilities of isomerism likewise increase very rapidly. Thus there

are 75 theoretically possible decanes, and a hydrocarbon with thirteen

carbon atoms could exist in 802 isomeric forms. Isomerism thus helps

to account for the large number of organic compounds.

Isomerism is even more pronounced among the compounds of

hydrocarbon radicals, as we shall see later.

Chain Hydrocarbons May Be Cracked.

Large molecules of chain hydrocarbons may be heated under pressure

and cracked to form smaller molecules. This discovery has been

of tremendous importance in the petroleum industry, because it makes

possible the production of gasoline in large quantities, when desired,

by cracking kerosene, fuel oils, and the other fractions of petroleum

for which there is relatively little demand.

When saturated hydrocarbons are cracked, unsaturated compounds

are produced. Thus, if butane were cracked, it might produce an

unsaturated hydrocarbon, as follows:

H H H H H H

H—C—C—C—C—H

—>- H—C—C—H + H—C=C—

II

I

H

HHHH HH HH

Every carbon atom must share four electrons. In case there is nothing

with which to share one or more of its electrons, it shares two or more

electrons with other carbon atoms, but the most stable arrangement is

made by sharing only one electron with another carbon atom. A

double union would seem to indicate strength, but it actually creates

weakness for reasons which are now understood but which we need not

More magazines by this user
Similar magazines