Man's physical universe

xanabras

UNIT VIII

SECTION 9

COVALENT REACTIONS, WHICH INVOLVE THE SHARING

OF PAIRS OF ELECTRONS, ARE CHARACTERISTIC OF

ORGANIC COMPOUNDS

Introduction.

Up to this point our attention has been given largely to electrovalent

compounds and electrovalent reactions, in which there have been transfers

of electrons or protons. We now turn to that branch of chemistry

in which electrons are shared rather than transferred. As already indicated,

such reactions produce what are known as covalent compounds.

Many inorganic compounds are electrovalent, while the majority of

This Section will introduce some of

organic compounds are covalent.

the fundamental principles of organic chemistry.

Organic Chemistry Is the Chemistry of Hydrocarbons and Compounds

of Hydrocarbon Radicals.

The element, carbon, is remarkable for the large number of compounds

that it forms. The number of different carbon compounds is

at least 250,000, or about twice as many as have been discovered for

all of the other elements put together. This large number of compounds

has been accounted for by assuming that carbon atoms are

able to share electrons with each other to form long chains or ringlike

structures.

There are several series of hydrocarbons {i.e., compounds of carbon

with hydrogen) in which carbon atoms form chains. One series of

hydrocarbons, called the paraffins, is found in natural gas and petroleum.

This series is composed of saturated hydrocarbons {i.e., hydrocarbons

which form derivatives only by substitution,

because there

are no unsatisfied valences). The first eight members in this series

are :

^


Every valence bond indicated in structural formulas of organic compounds represents

a pair of shared electrons.

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