Fused Polycyclic Hydrocarbons

Fused Polycyclic Hydrocarbons

Rule A-21. Trivial and Semi-trivial names 

21.1 - The names of polycyclic hydrocarbons with maximum number of non-cumulative double bonds end in "-ene". The following list contains the names of polycyclic hydrocarbons which are retained. This list is not limiting.

Examples to Rule A-21.1

(1) Pentalene	(2) Indene
(3) Naphthalene	(4) Azulene
(5) Heptalene	(6) Biphenylene
(7) as-Indacene	(8) s-Indacene
(9) Acenaphthylene	(10) Fluorene
(11) Phenalene	(12) Phenanthrene
(13) Anthracene	(14) Fluoranthene
(15) Acephenanthrylene	(16) Aceanthrylene
(17) Triphenylene	(18) Pyrene

(19) Chrysene

(20) Naphthacene

(21) Pleiadene

(22) Picene

(23) Perylene

(24) Pentaphene

(25) Pentacene

(26) Tetraphenylene

(27) Hexaphene

(28) Hexacene

(29) Rubicene

(30) Coronene

(31) Trinaphthylene

(32) Heptaphene

(33) Heptacene

(34) Pyranthrene

(35) Ovalene

21.2 - The names of hydrocarbons containing five or more fused benzene rings in a straight linear arrangement are formed from a numerical prefix as specified in RuleA-1.1 followedby "-acene".

Examples to Rule A-21.2

21.3 - "Ortho-fused" or "ortho- and peri-fused" polycyclic hydrocarbons with maximum number of non-cumulative double bonds which contain at least two rings of five or more members and which have no accepted trivial name such as those of Part .1 of this rule, are named by prefixing to the name of a component ring or ring system (the base component) designations of the other components. The base component should contain as many rings as possible (provided it has a trivial name), and should occur as far as possible from the beginning of the list of Rule A-21.1. The attached components should be as simple as possible.

Examples to Rule A-21.3

(not Naphthophenanthrene: benzo is "simpler" than naphtho, even through there are two benzo rings and only one naphto)

21.4 - The prefixes designating attached components are formed by changing the ending "-ene" of the name of the component hydrocarbon into "-eno"; e.g.,"pyreno" (from pyrene). When more than one prefix is present, they are arranged in alphabetical order. The following common abbreviated prefixes are recognized (see list in Part.1 of this rule):

Acenaphtho	from	Acenaphthylelle
Anthra	from	Anthracene
Benzo	from	Benzene
Naphtho	from	Naphthalene
Perylo	from	Perylene
Phenanthro	from	Phenanthrene

For monocyclic prefixes other than "benzo" the following names are recognized, each to represent the form with the maximum number of non-cumulative double bonds: cyclopenta, cyclohepta, cycloocta, cyclonona, etcWhen the base component is a monocyclic system, the ending "-ene" signifies the maximum number of non-cumulative double bonds and thus does not denote one double bond only. 

Examples to Rule A-21.4

21.5 - Isomers are distinguished by lettering the peripheral sides of the base component a, b, c, etc., beginning with "a" for the side "1,2", "b" for "2,3" (or in certain cases "2,2a") and lettering every side around the periphery. To the letter as early in the alphabet as possible, denoting the side where fusion occurs, are prefixed, if necessary, the numbers of the positions of attachment of the other component. These numbers are chosen to be as low as is consistent with the numbering of the component, and their order conforms to the direction of lettering of the base component. When two or more prefixes refer to equivalent positions so that there is a choice of letters, the prefixes are cited in alphabetical order according to Rule A-21.4 and the location of the first cited prefix is indicated by a letter as early as possible in the alphabet. The numbers and letters are enclosed in square brackets and placed immediately after the designation of the attached component. This expression merely defines the manner of fusion of the components.

Examples to Rule A-21.5

The completed system consisting of the base component and the other components is then renumbered according to Rule A-22, the enumeration of the component parts being ignored.

Example to Rule A-21.5

21.6 - When a name applies equally to two or more isomeric condensed parent ring systems with the maximum number of non-cumulative double bonds and when the name can be made specific by indicating the position of one or more hydrogen atoms in the structure, this is accomplished by modifying the name with a locant, followed by italic capital H for each of these hydrogen atoms. Such symbols ordinarily precede the name. The said atom or atoms are called "indicated hydrogen". The same principle is applied to radicals and compounds derived from these systems. 

Examples to Rule A-21.6

See Recommendations'93 R-2.4.1, R-9.1, Tables 20 and 20(a)

Rule A-22. Numbering 

22.1 - For the purposes of numbering, the individual rings of a polycyclic "ortho-fused" or "ortho- and peri-fused" hydrocarbon system are normally drawn as follows: 
 
 
and the polycyclic system is oriented so that (a) the greatest number of rings are in a horizontal row and (b) a maximum number of rings are above and to the right of the horizontal row (upper right quadrant). If two or more orientations meet these requirements, the one is chosen which has as few rings as possible in the lower left quadrant.

Example to Rule A-22.1

 

The system thus oriented is numbered in a clockwise direction commencing with the carbon atom not engaged in ring-fusion in the most counter-clockwise position of the uppermost ring, or if there is a choice, of the uppermost ring farthest to the right, and omitting atoms common to two or more rings.

Examples to Rule A-22.1

22.2 - Atoms common to two or more rings are designated by adding roman letters "a", "b", "c", etc., to the number of the position immediately preceding. Interior atoms follow the highest number, taking clockwise sequence wherever there is a choice.

Examples to Rule A-22.2

 

22.3 - When there is a choice , carbon atoms common to two or more rings follow the lowest possible numbers.

Examples to Rule A-22.3

  
 

Notes:
I 4, 4, 8, 9 is lower than 4, 5, 9, 9.
II 2, 5, 8 is lower than 3, 5, 8.
III 2, 3, 6, 8 is lower than 3, 4, 6, 8 or 2, 4, 7, 8.

22.4 - When there is a choice, the carbon atoms which carry an indicated hydrogen atom are numbered as low as possible.

Examples to Rule A-22.4

22.5 - The following are recommended exceptions to the above rules on numbering:

Examples to Rule A-22.5

  

See Recommendations'93 R-2.4.1, R-9.1, Tables 20 and 20(a)

Rule A-23. Hydrogenated Compounds 

23.1 - The names of "ortho-fused" or "ortho- and peri-fused" polycyclic hydrocarbons with less than maximum number of non-cumulative double bonds are formed from a prefix "dihydro-", "tetrahydro-", etc., followed by the name of the corresponding unreduced hydrocarbon. The prefix "perhydro-" signifies full hydrogenation. When there is a choice for H used for indicated hydrogen it is assigned the lowest available number.

Examples to Rule A-23.1

  

Exceptions:The following names are retained:
 
 
 

23.2 - When there is a choice, the carbon atoms to which hydrogen atoms are added are numbered as low as possible.

Examples to Rule A-23.2

23.3 - Substituted polycyclic hydrocarbons are named according to the same principles as substituted monocyclic hydrocarbons (see Rules A-12 and A-61).23.5 (Alternate to part of Rule A-23.1) - The names of "ortho-fused" polycyclic hydrocarbons which have (a) less than the maximum number of non-cumulative double bonds, (b) at least one terminal unit which is most conveniently named as an unsaturated cycloalkane derivative, and (c) a double bond at the positions where rings are fused together, may be derived by joining the name of the terminal unit to that of the other component by means of a letter "o" with elision of a terminal "e". The abbreviations for fused aromatic systems laid down in Rule A-21.4 are used, and the exceptions of Rule A-23.1 apply.

Examples to Rule A-23.5

 

See Recommendations'93 R-2.4.1, R-9.1, Tables 20 and 20(a)

Rule A-24. Radical Names  from Trivial and Semi-trivial Names 

24.1 - For radicals derived from polycyclic hydrocarbons, the numbering of the hydrocarbon is retained. The point or points of attachment are given numbers as low as is consistent with the fixed numbering of the hydrocarbon.24.2 - Univalent radicals derived from "ortho-fused" or "ortho- and peri-fused" polycyclic hydrocarbons with names ending in "-ene" by removal of a hydrogen atom from an aromatic or alicyclic ring are named in principle by changing the ending "-ene" of the names of the hydrocarbons to "-enyl".

Examples to Rule A-24.2

 

Exceptions:

	5,6,7,8-Tetrahydro-2-naphthyl

24.3 - Bivalent radicals derived from univalent polycyclic hydrocarbon radicals whose names end in "-yl" by removal of one hydrogen atom from the carbon atom with the free valence are named by adding "-idene" to the name of the corresponding univalent radical.

Examples to Rule A-24.3

1(4H)-Naphthylidene
(for 4H see Rule A-21.6)
or 1,4-Dihydro-1-naphthylidene

24.4 - Bivalent radicals derived from "ortho-fused" or "ortho- and peri-fused" polycyclic hydrocarbons by removal of a hydrogen atom from each of two different carbon atoms of the ring are named by changing the ending "yl" of the univalent radical name to "-ylene" or by adding "-diyl" to the name of the ring system Multivalent radicals, similarly derived, are named by adding "-triyl", "-tetrayl", etc., to the name of the ring system.

Examples to Rule A-24.4

See Recommendations'93 R-9.1, Table 22

Rule A-28. Radical Names for Fused Cyclic Systems with Side Chains 

28.1 - Radicals formed from hydrocarbons consisting of polycyclic systems and side chains are named according to the principles of the preceding rules.See Recommendations'93 R-9.1, Table 22