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Food Lipids: Chemistry, Nutrition, and Biotechnology

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Table 2 IUPAC Rules for Hydrocarbon Nomenclature<br />

1. Saturated unbranched acyclic hydrocarbons are named with a numerical prefix <strong>and</strong> the<br />

termination ‘‘ane.’’ The first four in this series use trivial prefix names (methane,<br />

ethane, propane, <strong>and</strong> butane), whereas the rest use prefixes that represent the number of<br />

carbon atoms.<br />

2. Saturated branched acyclic hydrocarbons are named by prefixing the side chain<br />

designation to the name of the longest chain present in the structure.<br />

3. The longest chain is numbered to give the lowest number possible to the side chains,<br />

irrespective of the substituents.<br />

4. If more than two side chains are present, they can be cited either in alphabetical order<br />

or in order of increasing complexity.<br />

5. If two or more side chains are present in equivalent positions, the one assigned the<br />

lowest number is cited first in the name. Order can be based on alphabetical order or<br />

complexity.<br />

6. Unsaturated unbranched acycylic hydrocarbons with one double bond have the ‘‘ane’’<br />

replaced with ‘‘ene.’’ If there is more than one double bond, the ‘‘ane’’ is replaced with<br />

‘‘diene,’’ ‘‘triene,’’ ‘‘tetraene,’’ etc. The chain is numbered to give the lowest possible<br />

number to the double bond(s).<br />

Source: Ref. 6.<br />

ignated with numbers before the fatty acid name (�9-octadecenoic acid or simply 9octadecenoic<br />

acid). The � is assumed <strong>and</strong> often not placed explicitly in structures.<br />

Double-bond geometry is designated with the cis–trans or E/Z nomenclature<br />

systems [6]. The cis/trans terms are used to describe the positions of atoms or groups<br />

connected to doubly bonded atoms. They can also be used to indicate relative positions<br />

in ring structures. Atoms/groups are cis or trans if they lie on same (cis) or<br />

opposite (trans) sides of a reference plane in the molecule. Some examples are shown<br />

in Figure 1. The prefixes cis <strong>and</strong> trans can be abbreviated as c <strong>and</strong> t in structural<br />

formulas.<br />

The cis/trans configuration rules are not applicable to double bonds that are<br />

terminal in a structure or to double bonds that join rings to chains. For these conditions,<br />

a sequence preference ordering must be conducted. Since cis/trans nomen-<br />

Figure 1 Examples of cis/trans nomenclature.<br />

Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.

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