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Alkanes: Introduction and Chemical Bond

Alkanes: Introduction

Alkanes are a sub-category of hydrocarbons, i.e. organic compounds that consist only of carbon and hydrogen atoms. They are also called saturated hydrocarbons and contain only C-C single bonds. Examples for other sub-categories of hydrocarbons are alkenes, alkynes and aromatic compounds. This group is referred to as unsaturated hydrocarbons as they contain C-C double and C-C triple bonds.

Fig.1
Overview of hydrocarbon sub-categories

By clicking on a structure in the table, the 3D model of the corresponding molecule will be displayed.

Tab.1
Examples of saturated (alkanes) and unsaturated hydrocarbons (alkenes, alkynes, aromatic compounds)
Alkanes
Fig.
ethane
Fig.
isobutane
Fig.
cyclopentane
Alkenes
Fig.
ethene
Fig.
2-methyl-1-butene
Fig.
cyclohexene
Alkynes
Fig.
ethyne
Fig.
1-butyne
Fig.
ethynylcyclopentane
Aromatic compounds
Fig.
benzene
Fig.
para-ethylmethylbenzene
Fig.
phenanthrene

Table of names and notations of various alkanes

Alkanes are the essential part of crude oil and natural gas. Therefore, they represent not only the main energy source but also the most important resource for the chemical industry. In former times, alkanes were referred to as paraffines (from the Latin parum affinis , little related), because they exhibit very low reactivity and do not mix with water.

Alkanes are divided into linear n-alkanes, branched alkanes, and cycloalkanes. Linear and branched alkanes have the empirical formula CnH2n+2 while cyclic alkanes CnH2n are richer in carbon atoms.

Tab.2
n-Alkanes (CnH2n+2) Branched alkanes (CnH2n+2) Cycloalkanes (CnH2n)

Toxicology of alkanes

Many higher alkanes exhibit a characteristic odor. Proteins embedded in the membranes of olfactory nerves are able to bind the scents. Initiated by a conformational change of these proteins, a signal containing information about the scent is sent to the brain. Therefore, alkanes belong to a group of compounds which act as pheromones, i.e. signalling compounds that are used in nature to allow communication between members of the same species.

Insect traps containing sexual attractants are an environmentally sound and ecologically safe method used in pest control. For example, 2-methylheptadecane and 17,21-dimethylheptatriacontane are the sexual attractants to attract tiger moth and tsetse fly.

Historical background.

The Roman scholar Plinius d. Ä. (AD 23-79) gave an early report on crude oil. He named it naphtha, from the Greek, a word which has its origins in the Babylonian word naptu, to burn.

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