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Subtractive Nomenclature

Rule C-43

43.1 - In more recent use, particularly for steroids (see Rules 2S-6.1 and 2S-7.1) and higher terpenes, "nor-" denotes (a) elimination of one methylene group from a chain, the highest permissible locant being used, or (b) contraction of a ring by one CH2 unit, the locant being the capital letter identifying the ring. Elimination of two or more methylene groups may be denoted by the prefixes "dinor-", "trinor-", and so on.

Examples to Rule C-43.1

See Recommendations'93 R-1.2.5

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Subtractive Nomenclature
Rule C-44
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This HTML reproduction of Sections A, B and C of IUPAC "Blue Book" is as close as possible to the published version [see Nomenclature of Organic Chemistry, Sections A, B, C, D, E, F, and H, Pergamon Press, Oxford, 1979. Copyright 1979 IUPAC.] If you need to cite these rules please quote this reference as their source.

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