SynopsisCatalytic activities of benzyl sulfonium salts with nonnucleophilic anions (BFL, PF;, AsF;, SbF;) for epoxy polymerization were examined. The order of reactivities correlated well with nonnucleophilicity of anions. Epoxy resins catalyzed by these salts are characterized by longer shelf-life and shorter gel time at high temperature. Some physical properties of cured product were compared with those cured by a commonly used BF, amine complex.

Thermal isomerization of cyclooctatetraene to semibullvalene 6 has been studied theoretically by the MINDO methods. The reaction is predicted to be exothermic by comparison of the calculated heats of formation and to be allowed as a concerted cyclization by constructing a complete MO correlatiom diagram. These findings together with the knowledge of thermal interconversion of cyclooctatetraene and bicyclo[4.2.0]octa-2,4,7-triene 5 suggest a tentative mechanism for thermal dimerization of cyclooctatetraene in which dimers 2, 3, and 4 are formed by coupling of the two isomers 5 and 6 of cyclooctatetraene.

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A photo-precursor (4) of [4]annulene (1) has been irradiated at 4–10 K in argon. The infrared spectrum of the photolysate shows two strong bands at 1240 cm−1 and 570 but, in contradiction to an earlier claim, one at 650 cm−1 is missing. The discrepancy between this and the earlier observation is explained, and comments on the infrared spectrum of 1 are made.

SATORU MASAMUNE, MITSURU SAKAI, and KAZUHIKO MONO. Can. J. Chem. 53,784(1975).1-Phenyl-2,2-dimethyl and 1-phenyl-2,2-diethyl vinyl cations have been generated. Their n.m.r. spectral data indicate (i) the presence of C , , symmetry in these cations, (ii) the positive charge being mostly localized a t the vinyl a-carbon (and the aromatic ring) but not a t the p-position, and (iii) the bisected geometry for the aromatic ring of the system. SATORU MASAMUNE, MITSURU SAKAI et KAZUHIKO MORIO. Can. J. Chem. 53,784(1975). On a genere les cations phenyl-1 dimethyl-2,2 et phknyl-1 dikthyl-2,2 vinyles. Leur spectre r.m.n. indique (i) la presence d'une symktrie C2,., (ii) que la charge positive est localisee principalement sur le carbon cu du groupe vinyle (et sur le cycle aromatique), mais pas en position p e t (iii) que le systeme de cycle aromatique a une gkometrie bisectke.[Traduit par le journal]The successful generation and direct observation of a vinyl cation has very recently been reported by Hanack and co-workers (1). This has prompted us to disclose the results of our investigation in this area (2). Our findings are mainly in accord with theirs but offer additional information, theoretically important and experimentally advantageous: ( i ) readily available vinyl chlorides rather than the corresponding fluorides serve equally well as precursors for the generation of vinyl cations, thus the latter halides that are synthetically less accessible are not required, (ii) the chemical shifts of both the a-and P-carbons of the vinyl cation are unambiguously determined, (iii) two different cations are generated to display (to the limit of the n.m.r. time scale) the linearity of the system, a feature that requires further confirmation of this unstable and elusive system, and finally (iv) our quenching experiments involve direct trapping of the cations rather than the isolation of secondary products.We have chosen (I-chloro-2,2-dimethylethenyl)benzene(l)' and (1-chloro-2,2-diethyleth-'Proton magnetic resonance spectr~im of 1 (CDCI,): 6 1.73 (s.3H), 2.00 (s.3H), and 7.32 ( b r s 5H): c.m.r. (CDCI,, TMS), 6 21. 8, 22.1, 125.6, 127.8, 128.1, 129.3, 130.4, and 139.6. eny1)benzene (2) (3) as precursors and have generated the corresponding carbocations in a manner similar t o that previous1 y described (4). Methylene chloride solutions of 1 and 2 were NOTE: The numbering of the cation is arbitrary.separately mixed with a 1 : 5 mixture of SbF,-S0,ClF at -130". The resulting dark orange lower layers contained the corresponding cations 1' and 2' and exhibited the spectra as shown below. The p.m.r. spectra of 1' and 2' in Fig. 1 clearly demonstrate the equivalence of the two methyl and ethyl groups, respectively. Furthermore, the chemical shifts of the aromatic protons suggest that the i~ system of the aromatic ring conjugates more effectively with the empty Can. J. Chem. Downloaded from www.nrcresearchpress.com by 52.36.4.81 on 05/10/18For personal use only.