Page 47 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)

G R A M M A R I R-2.14

IR-2.14 L O C A N T S

IR-2.14.1 Introduction
Locants a re used to indicate the position of a s ubstituent o n, or a s tructural f eature within,
a p arent molecule. The locants can be arabic numerals o r l etters.

IR-2.14.2 Arabic numerals

Arabic n umerals are used as locants in the following ways.
(a) For numbering skeletal atoms in parent hydrides, to indicate: the placement of hydrogen
atoms when t here are non-standard bonding numbers; u nsaturation; the positions of bridging
hydrogen atoms in a b orane s tructure.

Examples:
1 2 3 4
6
6
6
6
1. H SSSH SH 1l ,3l -tetrasulfane (not 2l ,4l )
5
4
2.
1 2 3 4 5
pentaaz-2-ene
H 2 NN¼NHNNH 2
3.
1
5 2

4 3

2,3:2,5:3,4:4,5-tetra-mH-nido-pentaborane(9)

(b) In replacement nomenclature.

Example:

4.
1 2 3 4 5 6 7 8 9 1 011
CH 3 SCH 2 SiH 2 CH 2 CH 2 OCH 2 CH 2 OCH 3
7,10-dioxa-2-thia-4-silaundecane

(c) In additive nomenclature.

Example:
5.
1 2 3 4 5
SiH 3 GeH 2 SiH 2 SiH 2 SiH 3
1,1,1,2,2,3,3,4,4,5,5,5-dodecahydrido-2-germy-1,3,4,5-tetrasily-[5]catena

(d) In the Hantzsch–Widman nomenclature (Section IR-6.2.4.3), to indicate positions o f
skeletal atoms.

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