The Correct von Baeyer Name for (Buckminster)fullerane David Eckroth Brooklyn, NY 11217 Nomenclature of bridged cyclic hydrocarbons i s accounted for by t h e von Baeyer system Rule A-32 (esp IUPAC Rule A-32.31) ( I ) . The bridged ring system can be simplified when applied to two-dimensional multi-ring systems with secondary bridges.
IUPAC Rule A-32.31 (the von Baeyer System) (2) 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. (b) The main bridge shail be as large as possible. (c) The main ring shail be divided as symetrically as possible by the main bridge. (d) The superscripts locating the other bridges shall be as small as possible.
The ring systems shown in Figure 1are drawn easily in two-dimensional form. Of course, the largest possible ring contains all of the carbons. If the hydrocarbon is depicted a s a planar graph (Schlegel diagram), a ring passing through every carbon (vertex) once and only once is called a Hamiltonian line. Hamiltonian lines of the Platonic solids tetrahedrane, cubane, and dodecahedrane were shown in a n earlier paper ( I ) . Each Hamiltonian line outlines a multi-ring system t h a t can be connected by secondary bridges to give the Platonic solid. However, when the multi-ringed molecule cannot be drawn readily i n two-dimensional form (Schlegel dia-
"Bullvalene"
Figure 2. Prismane" Telracyclo\2.2.00' '.03 7nexane 1650-42-01 "Aoamantane' ~rzyclo13.3.1 .I3 ldecane [281-23-2] 11005-51-21. BJ lvalene' Tr cyc 0[3.3.2.0~~ldeca-3.6,9-triene RegLkW%Iid
Sdliegei diagram (pimar graph) Hdltonian-line diagram
Bicydo[2.2.1]heptane [26808-81
Figure I. Chemical Abstracts Service Registry Numbers allow reference to ComDuterized databases.
Figure 3. The regular (Platonic)solids. Volume 70 Number 8 August 1993
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The Platonic solids (regular solids) are spherically symmetical solids whose faces Name of Solid Name of Figure Vertices Faces Edges Hydrocarbon are regular polygons. Each hydrocarbonPlatonic solid ( I ) has a circuit, containing Hydrocarbon Formula every vertex, that is called a Hamiltonian line. A Hamiltonian line for a spherically Platonic (Regular)Solids symmetrical solid can be located by fmding the overlay (string) of contiguous faces 3 4 4 6 C6H4 Tetrahedron Tetrahedrane (rings) that, when geometrically positioned, Cube Cubane 3 8 6 12 CsH6 give rise to the solid. A Hamiltonian line (hexahedron) outlines half the faces in a spherically symmetical solid. It can be combined (in three3 20 12 30 CzoHzo Dodecahedron Dodecahedrane dimensional form) with an identical half to plus two others give all of the faces of the spherically symmetrical solid. The Schlegel diagram-HamArchimedean (Semiregular)Solids (with Two Types of Faces) iltonian line procedure was first described in 1967 (1). 4 12 8 18 CizHiz Truncated Truncated Hamiltonian lines also exist on hydrocartetrahedon tetrahedrane bons t h a t a r e semi-regular solids 4 24 14 36 C24H24 Truncated Truncated (Archimedean solids) such as truncated octahedron octahedrane icosahedrane (fulleranel and the two semiregular solids that have not yet been syn6 60 32 90 CsoHso Truncated (Buckminster) icosahedron fulllerane thesized: truncated tetrahedrane and truncated octahedrane (see Fig. 4). The Plus ten others semiregular solids are spherically symmetrical and have two or more types of faces (regular polygons) (3). gram), finding the main ring bewmes difficult. Shown as The Platonic hydrocarbons: tetrahedrane, cubane examples of increasing difficultyin Figure 2 are prisman% (hexahedrane), and dodecahedrane (Fig. 3). The other two adamantme, and bullvalene, and in Figure 3 are the regPlatonic solids are unlikely hydrocarbons because "ocular (Platonic) uniform solids: tetrahedrane, cubane tahedranen requires four C* bonds one C-H bond for (hexahedrane), and dodecahedrane. each carbon and "icosahedrane" requires an even more unEach compound in Figures 2 and 3 is shown as a planar likely fifth C-C bond plus a C-H bond for each carbon. graph (Schlegel diagram) that presents the wmpound in The similarity of hydrocarbons that are regular and two-dimensional form. The Schlegel diagrams show the semiregularsolids is their spherical symmetry, mehydromolecules in an easily seen form similar to those molecules gens of the molecules lie on the surfaces of spheres, Every shown in Figure 1. solid that can be a hydrocarbon (CXHJmust have three The main ring is the circuit drawn through the planar edges (c-c bonds) leading to a vertex. platonic (regular) graph containing as many vertices (carbon atoms) as passolids have three members having this structural requiresible. ment. In addition. there are three Archimedean (semireeular, solids that also have this structural requirement (i.e.. those havine a hexagon as the lareest face, (see Table 1,. The first Archimedean solid known to exist as a hvdrocarbon is truncated icosahedrane, (~uckminster)fullekme, t h e most comolex hvdrocarbon of the oossible Archimedean sofids. FuI"lerane is the saturated form of fullerene that has been called 1991's "Molecule of the Year" by Science magazine (5).Several derivatives of fullerane are described in a recent oaoer bv - Curl and Smallev (6). The nomenclature of derivatives of fullerane will be chaotic if the numbering of the wmpound is not standardized. The wrrect von Baeyer name, shown in Figure 5, assigns each carbon a specifically numbered position. Further structural details of the molecule are reoorted elsewhere. Two Hamiltonian lines (see Figs. 5 and 6) can be drawn through fullerane: starting with five of the six faces surrounding a hexagon, either (1)hexagon-pentagon-hexagon-pentagon-hexagon (Fig. 5) or (2)pentagon-hexagonpentagon-hexagon-pentagon(Fig. 6)which is the same as starting, a t the other end of the string of polygons, with four of the five hexagons surrounding a pentagon. The Hamiltonian line shown in Figure 5 is the only Hamiltonian line that allows symmetric splitting of the major ring: i.e., [29.29.0.. . .I. Fullerane's Hamiltonian lines were described by Castells and Serratosa in 1983and 1986(8Jbefore the molecule fullerene was reported. They used the name "soccerane" and the Hamiltonian line shown in Figure 6 from Figure 4. A is truncated tetrahedrane and Bis truncated octahedrane whose three-demensionalstructuresare shown in a paper by Schultz which the best name they could obtain was the unsymmetrical [30.28.0. . . .I. system. (7). Table 1. Spherically Symmetrical Solids (4)
~
-
-
-
-
A
610
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Figure 6. Hamiltonian line drawin that roduces the incorrect name 0~26.05~13.06~26.07~24.08B12.09922: Hentriacontac clo[30.28 0 02,30
O$J,i4
,010.19 o l t l 6 0y5.60 017.59'oi8.56 ~20,55~021,52,023,51,025.49,027,P1,029.46 0 3 1 , 4 i 033.56 034.i3,035.57,036~54,037,42,038,53,039,50,040,48,041.45~
hexacontane. Figure 5. Buckminsterfullerane represented in three-dimensions (above),as a Schlegel diagram (below),and as the Hamiltonian line (right)that produces the correct name.
Table 2. Faces (Secondary Rings) Outlined by Hamiltonian Lines Figure
Number of faces in solid
Faces outlined by Hamiltonian line
Tetrahedrane
4
2
3
Cubane
6
3
3
Dodecahedrane Truncated tetrahedrane Truncated octahedrane Fullerane
Table 2 shows that a Hamiltonian line consists of half the races of n spherically symmetical sol~d.A combination of two Hamilronian line6 in thrw-dimensional form mvcs a model of the solid. Conclusion The goal of this paper bas been to show the usefulness of a Hamiltonian line in the derivation of the correct von Baeyer name of a bridged hydrocarbon. For a carbon skeleton that does not make possible a Hamiltonian line, the main ring can be obtained froma Schlegel diagram. Literature Cited 1. Eekmth. DavldR. J Or#. Chem. 1967,32(11),3362-3365. 2. From N o m n c l o f l m of OrgonC Chmisfv; J. Rigavdy and S. D. mesnex Eds. Permmon Press: NY,1979. 6. Wenninger, M m a J.Polyhodmn Mode&, Cambridge Univ Press: NY,1971. 4. Schultz,HamyP J. Org Chom. lPBS,30(5),1361-1365. 5. Koshland, Jr.,D.E. Secenn 1991,254, 1705-1707. 6. Curl. R. F:Smallex R. E. Scr. Am. Oct.1991, 265(4), 5 6 6 3 . 7. Burgess,Ken". Chem ond h d fhndonl 19W 122),733: G. E. Scuseria, 0. E. Chem. Ph.w Loft. 1991,17615),423427; Lee, Rob. Chmz andInd. IhndonJ 1991,95(15), 5769-5773: B a n . Rudv M. C & E N 1991.691501. 17-20. 8, Casteus, Josep; Sematosa, Felix. J. Chem. E&. 19&, 60,941: 63,630
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