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The nomenclature of hydrocarbons

The basic structure of a name

Example: PVC is made out of the following substance:

chloroethène

Its scientific name has three parts: chloroethene - the substituent prefix chloro (which designates the chlorine atom) - the root eth (which designates the number of carbon atoms) - the functional group suffix ene (which designates the carbon-carbon double bond)

The main chain

It is the longest continuous chain of carbon atoms. If there are double or triple bonds, it is the chain which contains most of them. chaîne In the name of the substance, the number of carbon atoms of the main chain determines the root.
1..meth..
2..eth..
3..prop..
4..but..
5..pent..
6..hex..
7..hept..
8..oct..
9..non..
10..dec..

The numbering

The main chain is numbered in order to mark the positions of substituents attached to this chain or the position of double and triple bonds. These locants (numbers) are arranged in increasing order as to give the lowest number at the first difference. ( see examples ).

chaîne

false

chaîne

correct

Indeed: 23 < 34

chaîne

false

chaîne

correct

Indeed: 278 < 349

Multiple bonds

The type of bonds between carbon atoms is determined by substituent prefixes arranged in alphabetic order. Double bond: ....ene Triple bond: ....yne Only single bonds: ....ane

propènee

Propene

butadiene

Buta-1,3-diene

2..di..
3..tri..
4..tetra..
5..penta..
6..hexa..
7..hepta..
8..octo..
9..nona..
10..deca..
oct-2-en-5-yne

Oct-2-en-5-yne

Note the elision of e after en by euphonious reasons!

Rings

Rings are given the prefix cyclo..

cyclobutane

Cyclobutane

cyclohexadiène

Cyclohexa-1,3-diene

Alkyl substituents

- Branches are designated by the suffix ..yl. - They are arranged like substituent prefixes before the root. - They are always numerotated from there attachment point.

methylpropane

Methylpropane

3-methylpentane

3-Methylpentane

2,2-dimethylbutane

2,2-Dimethylbutane

2,3,4,4-tetramethylhexane

2,3,4,4-Tetramethylhexane

methylcyclobutane

Methylcyclobutane

1-cyclobutyl-3,3-dimethylcyclopent-1-ène

1-Cyclobutyl-3,3-dimethylcyclopent-1-ène

prop-1-enylocta-

Prop-1-enylocta--1,3,5-triene

- Some side chains have common trivial names: $(CH_3)_2CH-$ isopropyl.. prefered to methylethyl.. $(CH_3)_3C-$ tertbutyl.. prefered to dimethylethyl.. $CH_2=CH-$ vinyl.. prefered to ethenyl..

Aromatic rings

- The important aromatic rings (cycles with resonance) have trivial names:

benzene

Benzene

naphtalene

Naphtalene

Toluène

Toluene

- The benzene as substituent is called phenyl:

Toluene

Diphenylmethane