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preface to fifteenth edition

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1.10 SECTION 1<br />

1.1.1.6 Bridged Hydrocarbons. Saturated alicyclic hydrocarbon systems consisting of two rings<br />

that have two or more a<strong>to</strong>ms in common take the name of the open-chain hydrocarbon containing<br />

the same <strong>to</strong>tal number of carbon a<strong>to</strong>ms and are preceded by the prefix bicyclo-. The system is<br />

numbered commencing with one of the bridgeheads, numbering proceeding by the longest possible<br />

path <strong>to</strong> the second bridgehead. Numbering is then continued from this a<strong>to</strong>m by the longer remaining<br />

unnumbered path back <strong>to</strong> the first bridgehead and is completed by the shortest path from the a<strong>to</strong>m<br />

next <strong>to</strong> the first bridgehead. When a choice in numbering exists, unsaturation is given the lowest<br />

numbers. The number of carbon a<strong>to</strong>ms in each of the bridges connecting the bridgeheads is indicated<br />

in brackets in descending order. Examples are<br />

Bicyclo[3.2.1]octane<br />

Bicyclo[5.2.0]nonane<br />

1.1.1.7 Hydrocarbon Ring Assemblies. Assemblies are two or more cyclic systems, either single<br />

rings or fused systems, that are joined directly <strong>to</strong> each other by double or single bonds. For identical<br />

systems naming may proceed (1) by placing the prefix bi- before the name of the corresponding<br />

radical or (2), for systems joined through a single bond, by placing the prefix bi- before the name<br />

of the corresponding hydrocarbon. In each case, the numbering of the assembly is that of the corresponding<br />

radical or hydrocarbon, one system being assigned unprimed numbers and the other<br />

primed numbers. The points of attachment are indicated by placing the appropriate locants before<br />

the name; an unprimed number is considered lower than the same number primed. The name biphenyl<br />

is used for the assembly consisting of two benzene rings. Examples are<br />

1,1-Bicyclopropyl or 1,1-bicyclopropane<br />

2-Ethyl-2-propylbiphenyl<br />

For nonidentical ring systems, one ring system is selected as the parent and the other systems<br />

are considered as substituents and are arranged in alphabetical order. The parent ring system is<br />

assigned unprimed numbers. The parent is chosen by considering the following characteristics in<br />

turn until a decision is reached: (1) the system containing the larger number of rings, (2) the system<br />

containing the larger ring, (3) the system in the lowest state of hydrogenation, and (4) the highes<strong>to</strong>rder<br />

number of ring systems set forth in Table 1.2. Examples are given, with the deciding priority<br />

given in parentheses preceding the name:<br />

(1) 2-Phenylnaphthalene<br />

(2) and (4) 2-(2-Naphthyl)azulene<br />

(3) Cyclohexylbenzene<br />

1.1.1.8 Radicals from Ring Systems. Univalent substituent groups derived from polycyclic hydrocarbons<br />

are named by changing the final e of the hydrocarbon name <strong>to</strong> -yl. The carbon a<strong>to</strong>ms<br />

having free valences are given locants as low as possible consistent with the fixed numbering of the

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