Replacement Nomenclature

Rule C-63

63.1 - (a) In a branched chain to which replacement nomenclature is applied, the principal chain is chosen in accordance with the criteria, applied successively so far as necessary, that are listed in Rule C-13.11, terminal non-carbon atoms being excluded except insofar as choice of the principal group is concerned.

However, the following additional criteria are then inserted in that list:

(i) maximum number of hetero atoms: to be considered immediately after the maximum number of principal groups [C-13.11(a)];

(ii) maximum number of hetero atoms first cited in Rule B-1 (Table B-I): to be considered immediately after the maximum length [C-13.11(c)]; terminal non-carbon atoms being excluded;

(iii) lowest locants for hetero atoms all together, and then for those first cited in Rule B-1 (Table B-I): to be considered immediately after the lowest locants for principal groups [C-13.11(e)];

(b) When replacement nomenclature is used for a principal chain it is used also for all the side chains provided that there is more than one hetero atom in any one of the side chains, but in other cases the customary names are used for side chains.

(c) Locants for the main chain are assigned as described in Rule C-62, and, so far as necessary thereafter, as described in Subsection C-0.13 excepting Rule C-13.11(a) Side chains are numbered from the point of attachment, which has locant 1.

Examples to Rule C-63.1

See Recommendations'93 R-1.2.2

Replacement Nomenclature
Rule C-64
Rule C-65

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