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

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.


                       38
   42   43   44   45   46   47   48   49   50   51   52