Chemistry, Third edition

Organic Chemistry:

Hydrocarbons

Objectives

Explains what is meant by ‘organic chemistry’

Introduces you to some families of hydrocarbons

Describes the sources of hydrocarbons and that hydrocarbons form the

starting materials for many synthetic organic compounds

Distinguishes between ‘aliphatic’ and ‘aromatic’ compounds

One element in the periodic table, carbon, forms so many compounds that it has an

entire branch of chemistry devoted to it. Most of the chemistry of this element

comes under the heading organicchemistry. The reason that carbon forms such a

huge number of compounds is that it has the ability to form chains of carbon atoms

(or the ability to catenate) – the carbon atoms are covalently bonded to one another

and to other elements, such as hydrogen, oxygen and nitrogen.

The name ‘organic’ originates from the days when chemical compounds were

divided into two classes, depending on their origin: ‘inorganic’ and ‘organic’. In-

organic compounds were obtained from mineral sources, whereas organic chemi-

cals were derived from living things. It was believed that organic compounds

contained a ‘vital force’ and could not be made from inorganic compounds, until F.

Wöhler (1800–1882) made the organic compound urea, CO(NH 2 ) 2 , from the in-

organic salt ammonium cyanate, NH 4 CNO. Urea is formed as a waste product

when proteins are metabolized. Today, organic chemistry refers to most of the

chemistry of carbon compounds. Some exceptions include the chemistry of metal

carbonates, carbon dioxide and carbon monoxide, which are included within in-

organic chemistry.

Organic compounds can be organized into families of compounds with similar

structural formulae and similar properties. This makes the study of organic chem-

istry easier, since there is such a large number of individual organic compounds.

Alkanes

The first family we shall look at is called the alkanes. They were originally called the

paraffins (which comes from the Latin ‘little affinity’) because, as you will see, apart

17.1

Contents

17.1Alkanes 307

17.2Alkenes 315

17.3Alkynes 321

17.4Aromatic

hydrocarbons 322

17.4Revision questions 328

17

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