examples

R-4.2.1
R-4.2.2
R-4.2.3

Basic numerical terms

Table 11 Basic numerical terms (multiplying affixes)

Number	Numerical term	Number	Numerical term
1	mono-	90	nonaconta-
2	di-	100	hecta-
3	tri-	200	dicta-
4	tetra-	300	tricta-
5	penta-	400	tetracta-
6	hexa-	500	pentacta-
7	hepta-	600	hexacta-
8	octa-	700	heptacta-
9	nona-	800	octacta-
10	deca-	900	nonacta-
11	undeca-	1000	kilia-
12	dodeca-	2000	dilia-
20	icosa-	3000	trilia-
30	triaconta-	4000	tetralia-
40	tetraconta-	5000	pentalia-
50	pentaconta-	6000	hexalia-
60	hexaconta-	7000	heptalia-
70	heptaconta-	8000	octalia-
80	octaconta-	9000	nonalia-

hydrocarbon

A. Hydrocarbons

 Acyclic Hydrocarbons

 A-1. Saturated Unbranched-chain Compounds and Univalent Radicals  A-2. Saturated Branched-chain Compounds and Univalent Radicals  A-3. Unsaturated Compounds and Univalent Radicals  A-4. Bivalent and Multivalent Radicals

Acyclic Hydrocarbons

Rule A-2. Saturated Branched-chain Compounds and Univalent Radicals 

2.1 - A saturated branched acyclic hydrocarbon is named by prefixing the designations of the side chains to the name of the longest chain present in the formula.

Example to Rule A-2.1

The following names are retained for unsubstituted hydrocarbons only:

Isobutane
Isopentane
Neopentane
Isohexane

2.2 - The longest chain is numbered from one end to the other by Arabic numerals, the direction being so chosen as to give the lowest numbers possible to the side chains. When series of locants containing the same number of terms are compared term by term, that series is "lowest" which contains the lowest number on the occasion of the first difference. This principle is applied irrespective of the nature of the substituents.

Examples to Rule A-2.2

2.25 - Univalent branched radicals derived from alkanes are named by prefixing the designation of the side chains to the name of the unbranched alkyl radical possessing the longest possible chain starting from the carbon atom with the free valence, the said atom being numbered as 1.

Examples to Rule A-2.25

1-Methylpentyl
2-Methylpentyl
5-Methylhexyl

The following names may be used for the unsubstituted radicals only:

Isopropyl
Isobutyl
sec-Butyl
tert-Butyl
Isopentyl
Neopentyl
tert-Pentyl
Isohexyl

2.3 - If two or more side chains of different nature are present, they are cited in alphabetical order .
The alphabetical order is decided as follows:
(i) The names of simple radicals are first alphabetized and the multiplying prefixes are then inserted.

Examples to Rule A-2.3(i)

ethyl is cited before methyl,
thus 4-Ethyl-3,3-dimethylheptane

(ii) The name of a complex radical is considered to begin with the first letter of its complete name.

Examples to Rule A-2.3(ii)

dimethylpentyl (as complete single substituent) is alphabetized under "d",
thus 7-(1,2-Dimethylpentyl)-5-ethyltridecane

(iii) In cases where names of complex radicals are composed of identical words, priority for citation is given to that radical which contains the lowest locant at the first cited point of difference in the radical.

Examples to Rule A-2.3(iii)

2.4 - If two or more side chains are in equivalent positions, the one to be assigned the lower number is that cited first in the name.

Examples: to Rule A-2.4

2.5 - The presence of identical unsubstituted radicals is indicated by the appropriate multiplying prefix di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona-, deca-, undeca, etc.

Example to Rule A-2.5(a)

The presence of identical radicals each substituted in the same way may be indicated by the appropriate multiplying prefix bis-, tris-, tetrakis-, pentakis-,etc. The complete expression denoting such a side chain may be enclosed in parentheses or the carbon atoms in side chains may be indicated by primed numbers.

Examples to Rule A-2.5(b)

(a) Use of parentheses and unprimed numbers:
5,5-Bis(1,1-dimethylpropyl)-2-methyldecane
(b) Use of primes:
5,5-Bis-1',1'-dimethylpropyl-2-methyldecane

(a) Use of parentheses and unprimed numbers:
7-(1,1-Dimethylbutyl)-7-(1,1-dimethylpentyl)tridecane
(b) Use of primes:
7-1',1'-Dimethylbutyl-7-1",1"-dimethylpentyltridecane

2.6 - If chains of equal length are competing for selection as main chain in a saturated branched acyclic hydrocarbon, then the choice goes in series to:(a) The chain which has the greatest number of side chains.

Example to Rule A-2.6(a)

(b) The chain whose side chains have the lowest-numbered locants.

Example to Rule A-2.6(b)

(c) The chain having the greatest number of carbon atoms in the smaller side chains.

Example to Rule A-2.6(c) 

(d) The chain having the least branched side chains.

Example to Rule A-2.6(d)

hydrocarbon

Acyclic Hydrocarbons

Rule A-1. Saturated Unbranched-chain Compounds and Univalent Radicals 

1.1 - The first four saturated unbranched acyclic hydrocarbons are called methane, ethane, propane and butane. Names of the higher members of this series consist of a numerical term, followed by "-ane" with elision of terminal "a" from the numerical term. Examples of these names are shown in the table below. The generic name of saturated acyclic hydrocarbons (branched or unbranched) is "alkane".
Examples of names:
(n = total number of carbon atoms)

n	n
1 Methane	22 Docosane
2 Ethane	23 Tricosane
3 Propane	24 Tetracosane
4 Butane	25 Pentacosane
5 Pentane	26 Hexacosane
6 Hexane	27 Heptacosane
7 Heptane	28 Octacosane
8 Octane	29 Nonacosane
9 Nonane	30 Triacontane
10 Decane	31 Hentriacontane
11 Undecane	32 Dotriacontane
12 Dodecane	33 Tritriacontane
13 Tridecane	40 Tetracontane
14 Tetradecane	50 Pentacontane
15 Pentadecane	60 Hexacontane
16 Hexadecane	70 Heptacontane
17 Heptadecane	80 Octacontane
18 Octadecane	90 Nonacontane
19 Nonadecane	100 Hectane
20 Icosane	132 Dotriacontahectane
21 Henicosane

1.2 - Univalent radicals derived from saturated unbranched acyclic hydrocarbons by removal of hydrogen from a terminal carbon atom are named by replacing the ending "-ane" of the name of the hydrocarbon by "-yl". The carbon atom with the free valence is numbered as 1. As a class, these radicals are called normal, or unbranched chain, alkyls.

Examples to Rule A-1.2