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Bridged Hydrocarbons

Rule A-32. Polycyclic Systems

32.11 - Cyclic hydrocarbon systems consisting of three or more rings may be named in accordance with the principles stated in Rule A-31.

The appropriate prefix "tricyclo-", "tetracyclo-", etc., is substituted for "bicyclo-" before the name of the open-chain hydrocarbon containing the same total number of carbon atoms. Radicals derived from these hydrocarbons are named according to the principles set forth in Rule A-31.4.

32.12 - A polycyclic system is regarded as containing a number of rings equal to the number of scissions required to convert the system into an open-chain compound.

32.13 - The word "cyclo" is followed by brackets containing, in decreasing order, numbers indicating the number of carbon atoms in:

the two branches of the main ring,

the main bridge,

the secondary bridges.

Examples to Rule A-32.13

32.21 - The main ring and the main bridge form a bicyclic system whose numbering is made in compliance with Rule A-31.

32.22 - The location of the other or so-called secondary bridges is shown by superscripts following the number indicating the number of carbon atoms in the said bridges.

32.23 - For the purpose of numbering, the secondary bridges are considered in decreasing order. The numbering of any bridge follows from the part already numbered, proceeding from the highest-numbered bridge head. If equal bridges are present, the numbering begins at the highest. numbered bridgehead.

32.31 - When there is a choice, the following criteria are considered in turn until a decision is made:

(a) The main ring shall contain as many carbon atoms as possible, two of which must serve as bridgeheads for the main bridge.

Examples to Rule A-32.31(a)

(b) The main bridge shall be as large as possible.

Examples to Rule A-32.31(b)

(c) The main ring shall be divided as symmetrically as possible by the main bridge.

Examples to Rule A-32.31(c)

(d) The superscripts locating the other bridges shall be as small as possible (in the sense indicated in Rule A-2.2).

Examples to Rule A-32.31(d)

See Recommendations'93 R-2.4.2

Hydrocarbon Bridges


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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