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Vol. 86
COMMUNICATIONS TO THE EDITOR
method of Weldon and Wilson,6 was dissolved in a 1,2dimethoxyethane-tetrahydrofuran mixture and reduced to the anion radical with a sodium-potassium alloy using the procedure of B01ton.~ An X-band superheterodyne spectrometer8 was employed wit11 R sample temperature of -100". The spectruln is is over 8 A , and we assume t h a t it is a t least as large in [Ni(detu)iCIz]. readily interpreted as arising from C a H J - with about MetaI--metal bonding is therefore not evident, nor is a p a t h for superexchange interaction apparent in the structurelo of [Ni(tu)4C1~1. We also assume its a 4% impurity of CBHG-. The latter serves as a conabsence here. Furthermore t h e spectra (Fig. 1) are similar t o other comvenient internal standard, and the hyperfine splittings pounds with a tetragonal field," such a s [Ni(etu)rl(ClOa)n. Lastly, t h e relative to benzene, r X i = Uxi (C6H6D)/uH (CsHs), are: effects of magnetic coupling on spectra are not well known, h u t appear t o he rH2 = rHs = rH6 = rH6 = 1.046 f 0.002, rH4 = 0.908 T h e temperature dependence of t h e spectrum therefore does not small appear to he due t o exchange effecta f 0.005, and rlD = 0.148 f 0.002. Using uH (C6H6)= (15) J . W Stout, J . Chem. P h y s , 31, 709 (1959); D. S. McClure, ibid., 3.73 gauss417 gives (in gauss): uHp = 3.92 i 0.01, 38, 2289 (1963) aH4= 3.41 f 0.01, andaD1= 0.55 0.01. The widths METCALF CHEMICAL LABORATORIES S. L. HOLT,JR. of both the deuterated and undeuterated benzene BROWN UXIVERSITY R. J , BOUCHARD anion absorption lines were the same within experiR . L. CARLIN PROVIDENCE 12, RHODEISLAND mental error and had the value 0.3 gauss between points RECEIVED OCTOBER 30, 1963 of extreme slope. The symmetry of the C6H6Dspectrum about the central line of the C6Ha- spectrum implies an equality of the g-values of the two radicals Orbital Degeneracy and the Electron Spin Resonance t o within three parts in lo6. Spectrum of the Benzene-1-d Negative Ion' The spectrum of the monodeuteriobenzene anion thus shows t h a t the twofold degeneracy of the ground Sir: electronic state of the benzene negative ion is lifted on In recent years there has been considerable interest deuterium substitution. The increase relative to the in the Jahn-Teller theorem2 and in the simpler molebenzene negative ion of the spin densities from posicules such as the negative ion radical of benzene to which tions 2, 3, 5, and 6, and the decrease at the other it is a p p l i ~ a b l e . ~ The ground electronic state of this positions, indicates that the orbital which is antiradical is doubly degenerate, but the substitution of a symmetric with respect to reflection in the plane through methyl group as in the toluene and p-xylene anions has the 1 and 4 positions makes a greater contribution a large enough effect t o remove the d e g e n e r a ~ y . ~ ' ~ than the symmetric orbital. The antisymmetric Although the substitution of deuterium for hydrogen in orbital is also predominant, and to a miwh larger a free radical normally has a negligible effect on the extent, in the toluene and p-xylene a n i o m 5 The direcspin-density distribution, it is possible that the detion of the changes that we have found 011 deuterium generacy of the benzene anion would be lifted by substitution is consistent with the secondary isotope deuterium substitution, and we consequently have effects observed on rates and equilibria.9 In the investigated the electron spin resonance spectrum of the methyl-substituted anions, the stabilization of the negative ion of benzene-1-d. antisymmetric orbital is thought to arise from the electron-repelling effect of the methyl groups,5,'0but the importance of vibronic interactions is not fully understood. The role of these interactions in the deuteriobenzene anions is currently under investigation. Adding together the hyperfine splittings in the monodeuteriobenzene anion gives ('/6)(4rHz 2rH4) = 1.0K~ d= 0.001, so that a constant value of Qc" in McConnell's" relation aHi = QHCHpi for C6Hn.- arid C6H6D- implies the equality of the spin densities at, the 1- and 4-positions in the deuterated radical. These is thus a small but significant isotope effect since aH4!ar>l = 6.15 f 0.11 while the value of 6.514 is expected if the difference in proton and deuteron splittings is caused only by the magnetic properties Of the two isotopes. l 2 Fig. 1.-First derivative of the e.s.r. spectrum of the benzeneThe anion of benzene-l,4-d* has also beeii observed, I d anion The reconstruction includes dotted lines correspondbut the sample was contaminated with an appreciablr ing to a 470 impurity ,of-CeHe-. amount of benzene-1-d. Preliminary studies indicate the spectrum is consistent with predictions based OE The e.s.r. spectrum of the benzene-1-d anion is shown the spectrum of the benzene-i-d anion. Furthr.1 in Fig. 1. Benzene-1-d, which was prepared by the aspects of the effect of deuterium substitution on the benzene anion spectrum are being actively investj (1) Supported in part by t h e Sational Science Foundation through Grant NSF-GP- 1370. gated. Acknowledgment.-This research has been supported by a grant from the National Science Foundation, and by the ARPA program at Brown. We thank Professor A. Wold for arranging the measurement of the powder patterns at Lincoln Laboratory.
15
*
+
(2) H . A Jahn and E . Teller, Proc. R o y . Soc. (London), A161, 220 (1937); H . A Jahn, ibid.,8 1 6 4 , 117 (1937). (3) W . D Hobey and A . U . h l c l a c h l a n , J . Chem. P h y s . . 33, 1695 (1960); H. M McConnell and .4. 1). .McLachlan, i b i d . . 34, 1 (1961); H . M. McConnell. ibid.. 34, 13 (1961) (4) T K T u t t l e , J r . , and S I . Weissman, J . A m . Chem. SOL.,80, 5342 (1958) ( 5 ) ,T K Boltrin and A . Carrington, mol. Phys , 4, 497 (1961); T . R . Tuttle, J r . J . A m C h e m Soc , 84. 1492 (1962); V . V Voevodskii, S P Solodovnikov, and 1.. M . Chibrikin, Dokl A k a d . r a u k S S S R , 129, 1982 (1959). (6) L. H. P . Weldon a n d C. L. Wilson, J . Chem. Soc., 235 (1946)
(7) J R. Bolton. Mol. Phys., 6 , 210 (1963) (8) J . M . Hirshon and G. K . Fraenkel, Rev. S c i . Insrv , 2 6 , 34 (1955: J . W .H . Schreurs and G . K . Fraenkel, J . Chem. P h y s . , 34, 756 (1961). (9) E . A Halevi in "Progress in Physical Organic Chemi>try," \ < , I L lnterscience Publishers, Inc., New York. N. Y., 1963. (10) T . H Brown, M. Karplus, and J . C. Schug, J Chem P h y s . , 38, 1146 (1963); T . H. Brown and M. Karpliis, i b i d . , 39,1115 (19631. (11) H McConnell, ibid., 24, 633, 764 (19%); H. Ni. McConnr!: atld H H. Dearman, i b i d . , 2 8 , 51 (19583; €1 l4. h1cConne:I and U B. Chesnut i b i d . , 28, 107 (1958). (12) B.Venkataraman and G . R . Fraenkel, ibid., 88, 688 (1445)
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COMMUNICATIONS TO THE EDITOR
52 1
A n a l . Found: N, 5.411. The n.m.r. spectrum (100 Mc./sec., CDCl, solution) clearly points to structure I b ; it consists of two symmetrical 1-proton triplets a t (13) National Science Foundation Postdoctoral Fellow 15.25 and 14.85 r ( J = 13.5 c.P.s.) assigned to the RONALD G. LAWLER'S DEPARTMENT OF CHEMISTRY H3 protons, a 3-proton multiplet a t 1.30 7 asinner JAMES R. BOLTON COLUMBIA UNIVERSITY NEW YORK27, NEWYORK GEORGE K . FRAENKEL signed to HI, a 3-proton multiplet a t 0.33 r due to H 2 , UNIONCARBIDE RESEARCH INSTITUTE THOMAS H. BROWN and a 1-proton doublet a t -0.43 T ( J = 13.4 c.P.s.) due to H2' (the proton adjacent to the substituent). UNIONCARBIDE CORPORATIOX NEW YORK TARRYTOWN, Sulfonation of Ia with oleum in dioxane a t room RECEIVED DECEMBER 21, 1963 temperature gave a water-soluble sulfonic acid (Azp-,"," 314, 440, and 590 mp), which was converted to t h e silver salt with aqueous silver nitrate and then methylElectrophilic Substitution of Aromatic Fourteenated with methyl iodide. The resulting monomethyl Membered Ring Cyclic Conjugated Systems' sulfonate (IC),formed in ca. 30% yield, crystallized as red needles, m.p. 168-169' dec. [A~,O?'a"' 315, 442, and Sir : 591 mp ( E 179,000, 20,400, and 7700); 321, 1,8-Bisdehydro [14]annulene (Ia)2-4 and monode448, and 591 mp; Anal. Found: C, 66.80; H, 4.731. hydro[14]annulene (I1 or III)2Jhave been shown to be The n.m.r. spectrum (100 Mc./sec., CDC13 solution). aromatic compounds, since they sustain an induced consists of two incompletely resolved symmetrical 1ring current as demonstrated by nuclear magnetic proton triplets at 14.95 and 14.71 T ( J = 13.2 c.P.s.) resonance (n.m.r.) ~ p e c t r o s c o p y . ~On , ~ the other hand, [14]annulene (IV)2 on this basis is n o n a r ~ m a t i c . ~ . ~due to the inner H 3 protons, a 3-proton singlet a t 5.99 T due to the methyl hydrogens, a 3-proton multiplet a t Aromatic character has usually been associated with the 1.33 T assigned to Hi, a 3-proton multiplet a t 0.25 T ability to undergo electrophilic substitution reactions assigned to H2, and a 1-proton doublet a t -0.11 T (although this need not necessarily be true for all aro( J = 13.4c.P.s.) due to H2'. matic We now report that the two aroAcylation of Ia with acetic anhydride and boron matic dehydroannulenes Ia and I1 (or 111) in fact do untrifluoride etherate in methylene chloride a t room dergo such substitution reactions, whereas the nonarotemperature gave an acetyl compound in low yield, matic [14]annulene (IV) under analogous conditions to which structure Id is tentatively assigned by analogy; does not. '321, 451, and 608 mp it formed brown crystals ;:A:[ H' (relative intensities, ca. 20 : 3 : 1) ; 2,4-dinitrophenylhydrazone:' "": :A: 505 and 619 mp]. The amount of material was insufficient for further investigation, Another acetyl compound with unusual ultraviolet properties was also formed, as will be described in a H / H H \ H later publication. Monodehydro [14]annulene (I1 or 111) on nitration H \ A H under the above-mentioned conditions gave ca. 20% of a mononitro compound as dark brown needles, H H lo , R=H IC ,R=S03Me 328 and 425 mp ( E 59,500 m.p. 185-186' dec. [A:oXCtane I t d , R=COMe b , RzN02 and 8300) ; 335 and 435 mp; Anal. Found : N , 6.671. The n.m.r. spectrum (56.4 Mc./sec., CDCI3 solution) consists of two double doublets a t 10.61 and H H 10.72 T assigned to the two inner protons, as well as a H H complex band in the 2.67-0.91 T region due to the outer protons. Nitration must have resulted in substitution of one of the outer protons, but the exact point of attack has not been determined. Sulfonation of monodehydro [ 14lannulene and subse quent methylation, as above, gave a ca. 4 : 1 mixture of two isomeric monomethyl sulfonates as dark red plates, m.p. 153-154' [ A ~ ~ ? t a n e314, 367, and 400 mp ( E 74,500, H H 6000, and 5300); Akz!ene321, 371, and 406 mp; A n a l , m Found: C, 65.32; H, 4.991. That this was in fact Ip a mixture was shown by thin layer chromatography l&Bisdehydro [14]annulene (la) underwent substi(two spots of very similar polarity) and by the fact tution at the position adjacent to the acetylene. Nitrathat the methyl proton signals in the n.m.r. spectrum tion with cupric nitrate in acetic anhydride a t room (60 Mc./sec., CDC13 solution) appeared as two distinct temperature yielded ca. 25% of mononitro compound peaks a t 6.12 and 5.91 T . Acylation of monodehydroI b as black needles, which decomposed above 200' on [14]annulene with acetic anhydride, as above, led in heating [A2,0Yne327, 467, and 605 mp (E 85,500, low yield to an acetyl derivative 329 and 420 mp 337, 476, and 608 mp; 19,000, and 7800); (relative intensities, ca. 7.5 : 1) 1. (1) This is Part X X X I in the series "Unsaturated Macrocyclic Com[ 14JAnnulene (IV) on attempted nitration, sulfonapounds"; for Part X X X , see F. Sondheimer, Pure A p p l . C h e m . , 7 , 363 tion, and acylation under the conditions used with the (1963). (2) F Sondheimer and Y Gaoni, J . A m . Chem. SOC.,81,5765 (1960). dehydro compounds gave no comparable substitution (3) F. Sondheimer, Y. Gaoni, L M. Jackman, N . A . Bailey, and R products. In no case did we observe the formation of a Mason, i b i d . , 84, 4595 (1962) substance with a higher wave length maximum in the (4) N . A Bailey and R . Mason, Proc. Chem Soc., 180 (1963). ultraviolet than the starting material, and decomposi(5) L M Jackman, F . Sondheimer, Y . ilmiel, D A Ben-Efraim, Y . Gaoni, R . Wolovsky, and A . A. Bothner-By, J . A m , Chem. Soc., 84, 4307 tion of the latter usually resulted. (1962). 1&Bisdehydro [14 lannulene (Ia) was found to form (6) J. Bregman, Nature, 194, 679 (1962) 1: 1 n-complexes with compounds such as 1,3,5-trinitro(7) F . Sondheimer, R . Wolovsky, and Y Amiel, J . A m . Chem SOL.,84, benzene ; the complex with the latter crystallized as 274 (1962) Acknowledgment.-We wish to thank Prof. Martin Karplus for many helpful discussions.
