5 Hydrocarbon Ring Assemblies
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The
term ring assembly denotes a polycyclic hydrocarbon in which two or more rings (or fused ring systems) are joined directly by single or double bonds and in which the number of such direct ring junctions is one less than the total number of rings and ring systems. For example, two benzene rings joined by a single bond, or two cyclohexane rings joined by a single or double bond, are classed as ring assemblies. O n the other hand two benzene rings joined by two single bonds form a fused polycyclic system (see Chapter 4).
Recommended Nomenclature Practice Hydrocarbon ring assemblies consisting of two identical rings or ring systems joined by a single or double bond are named by placing the prefix bi before the name of the component ring system, except that the name biphenyl is commonly used for the assembly consisting of two benzene rings. Alternative names based on the substituting group name of the component hydrocarbon are also recognized in the 1957 I U P A C Rules. Numbering of a ring assembly is based on that of the component ring or ring system, unprimed numbers being assigned to one ring or ring system and primed numbers to the other. When necessary, to avoid ambiguity the points at which the component rings are joined are indicated by placing appropriate locants before or within the name. If the two rings are joined by a double bond, a capital Greek delta (Δ) with superscript number locants is required in the hydrocarbon-type name to denote such joining. 43 In Nomenclature of Organic Compounds; Fletcher, J., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.
44
NOMENCLATURE OF ORGANIC COMPOUNDS
3 I
r \
3
1
%
Downloaded by UNIV OF GUELPH LIBRARY on June 21, 2012 | http://pubs.acs.org Publication Date: June 1, 1974 | doi: 10.1021/ba-1974-0126.ch005
5*
f ^ \ = ^ J 3r \ ^ 4
g
2
\ 4
\ 3
) 7
a*
5'
1
A ' -B icy clopentane Bicyclopentylidene
2
4
5'
Bicyclopentane Bicyclopentyl
i \
v
e
1
1
A ' ' - Bi-2,4-cyclopentadiene Bi-2,4-cyclopentadien-l-ylidene
3
^ / 5
Biphenyl (Bibenzene, though correctly formed, is hardly ever used). not Diphenyl
r t ^ — ^ ^V'^7 ~72 3 \ A / e 8
4'
4
2,2'-Binaphthalene 2,2'-Binaphthyl
5
When there is a choice in numbering, unprimed numbers are given to the ring or ring system which has the lower-numbered point of joining.
1,2' -B inaphthalene 1,2'-Binaphthyl
When component ring systems having the same point of attachment contain substituents at various positions, lowest possible numbers are given to the substituents, an unprimed number being considered to be lower than the same number when primed. Primed and unprimed numbers are arranged in a single series in ascending numerical order.
In Nomenclature of Organic Compounds; Fletcher, J., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.
5.
45
Hydrocarbon Ring Assemblies CH CH CH 3
2
CH CH
2
2
3
2-Ethyl-2 -propylbiphenyl
