Bridged Hydrocarbons

Bridged Hydrocarbons

Rule A-31. Bicyclic Systems 

31.1 - Saturated alicyclic hydrocarbon systems consisting of two rings only, having two or more atoms in common, take the name of an open chain hydrocarbon containing the same total number of carbon atoms preceded by the prefix "bicyclo-". The number of carbon atoms in each of the three bridges connecting the two tertiary carbon atoms is indicated in brackets in descending order.

Examples to Rule A-31.1

 

31.2 - The system is numbered commencing with one of the bridgeheads, numbering proceeding by the longest possible path to the second bridgehead; numbering is then continued from this atom by the longer unnumbered path back to the first bridgehead and is completed by the shortest path from the atom next to the first bridgehead.

Examples to Rule A-31.2

31.3 - Unsaturated hydrocarbons are named in accordance with the principles set forth in Rule A-11.3 When after applying Rule A-31.2 a choice in numbering remains unsaturation is given the lowest numbers.

Examples to Rule A-31.3

(See Rule A-3.1 for double locants)

31.4 - Radicals derived from bridged hydrocarbons are named in accordance with the principles set forth in Rule A-11 The numbering of the hydrocarbon is retained and the point or points of attachment are given numbers as low as is consistent with the fixed numbering of the saturated hydrocarbon.

Examples to Rule A-31.4

(See Rule A-3.1 for double locants)

See Recommendations'93 R-2.4.2

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 RuleA-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

Rule A-34. Hydrocarbon Bridges 

34.1 - Polycyclic hydrocarbon systems which can be regarded as "ortho-fused" or "ortho- and peri-fused" systems according to RuleA-21 and which, at the same time, have other bridges, are first named as "ortho-fused" or "ortho- and peri-fused" systems. The other bridges are then indicated by prefixes derived from the name of the corresponding hydrocarbon by replacing the final "-ane", "-ene", etc., by "-ano", "-eno", etc., and their positions are indicated by the points of attachment in the parent compound. If bridges of different types are present, they are cited in alphabetical order.

Examples of bridge names to Rule A-34.1

Butano
Benzeno (o-, m-, p-)
Ethano
Etheno
Methano
Propano

Examples to Rule A-34.1

34.2 - The parent "ortho-fused" or "ortho- and peri-fused" system is numbered as prescribed in Rule A-22. Where there is a choice, the position numbers of the bridgeheads should be as low as possible. The remaining bridges are then numbered in turn starting each time with the bridge atom next to the bridgehead possessing the highest number.

Example to Rule A-34.2

34.3 - When there is a choice of position numbers for the points of attachment for several individual bridges, the lowest numbers are assigned to the bridgeheads in the order of citation of the bridges and the bridge atoms are numbered according to the preceding rule.

Example to Rule A-34.3

34.4 - When the bridge is formed from a bivalent cyclic hydrocarbon radical, low numbers are given to the carbon atoms constituting the shorter bridge and numbering proceeds around the ring.

Examples to Rule A-34.4

34.5 - Names for radicals derived from the bridged hydrocarbons considered in Rule A-34.1 are constructed in accordance with the principles set forth in Rule A-24. The abbreviated radical names naphthyl, anthryl, phenanthryl, naphthylene, etc., permitted as exceptions to Rules A-24.2 and A-24.4, are replaced in such cases by the regularly formed names naphthalenyl, anthracenyl, phenanthrenyl, naphthalenediyl, etc.

Examples to Rule A-34.5

See Recommendations'93 R-2.4.1.2