Synthesis and Nmr Data of Some Variously Substituted Diphenylmet hanes and Di benzylbenzenes GlORGlO MONTAUDO’, PAOLO FINOCCHIARO, SALVATORE CACCAMESE, and FRANCESCO BOTTINO Institutes of Industrial and Organic Chemistry, University of Catania, Viale A. Doria, Catania, Italy Fifty-four new compounds-methyl and halo derivatives of diphenylmethane and o,rn,p-dibenzylbenzene-were prepared under mild conditions. The identity of com- pounds prepared was established by nmr, and spectral assignments are reported. In connection with a study on the conformational proper- ties of molecules containing substituted diarylmethane units zyxwvutsr (II), a number of such compounds were prepared. Com- pounds in Tables I-VII, hitherto unreported by other authors, were prepared through Friedel and Crafts reactions starting from appropriate aromatic hydrocarbon and chloro- methyl derivatives. The choice of mild conditions (low temperature and reac- tion time, catalyst, solvent, excess of hydrocarbon, and nitrogen steam) was crucial to avoid or minimize isomeriza- tion and disproportionation. This was pointed out also by Olah (14, 15). Nmr spectra were used to provide unequiv- ocal structure proof for our compounds-Le., to test for eventual rearrangements of methyl groups which occurred during the alkylation reaction. To build up reliable assignment maps from the analysis of the spectra, a number of diphenylmethane and dibenzyl- benzene derivatives already known (prepared by other authors by different synthetic procedures) were used as references. These compounds, reported in Table VIII, were prepared and their nmr spectra were recorded and analyzed, together with the other compounds which were synthesized. In our opinion, the Friedel and Crafts reaction represents a satisfactory route to the synthesis of diphenylmethane and dibenzylbenzene derivatives, and is somewhat simpler with respect to alternative methods (ketone reduction, Gri- gnard synthesis). EXPERIMENTAL Nitroethane and aromatic hydrocarbons-commercial products of high purity-were dried, distilled, or crystallized before use. Chloromethyl derivatives, where not available commercially, were prepared according to the literature zyxwvuts (13). Aluminum chloride was sublimed, stannic chloride was vacuum distilled, and zinc chloride was fused before use. Melting points (uncorrected) were obtained in glass capil- lary tubes sealed under vacuum, and checked with a Kofler hot stage microscope. The following instruments were used in the present work: Varian A-60, X-100 and Jeol C-6OHL nmr spectrometers, Mechrolab V.P.O. 302, and Perkin-Elmer zyxwvutsrq 237 infrared spectrometer. Elemental analyses were obtained commercially (Institute of Organic Chemistry of the University, Milan). Infrared data, although omitted here, are available on request. Method. A mixture of chloromethyl derivative and hydro- carbon, dissolved in nitroethane, was added to the catalyst under stirring, and a nitrogen stream was maintained through the reaction, at constant temperature. Workup consisted of pouring the reaction mixture into an excess of methanol or water, filtering the solvent, washing the residue with diluted HC1 and water, and vacuum drying. Liquid products were purified by chloroform extraction, drying-off the solution, evaporation of the solvent, and vacuum distillation. Criteria of Purity. The characteristics and specific reaction conditions used in the preparation of all compounds reported are listed in Tables I-VII. All compounds described analyzed correctly for elemental analysis. It has to be realized, however, that in many cases the presence of sizable impurities (hydrocarbons of higher or lower molecular weight) could be masked by small deviations in the analytical data. Under these cir- cumstances, in judging the purity of a product, we have relied more upon the molecular weight determinations. NMR SPECTRA The identity of the compounds prepared was established by their nmr spectra. The spectra consist of three types of signals corresponding to methyl, methylene, and nuclear aromatic protons. Methyl and methylene peaks appear as sharp singlets. Aromatic protons have various appearances according to the nuclear substitution pattern. In many cases, peak assignments follow in a straightforward manner from the relative intensities and positions of signals. This is the case of polysubstituted rings zyxw (1,2,4,5; 1,2,3,4,5; 1,2,3,5) where nuclear protons appear as singlets. In less substituted rings, aromatic protons may show up as multispin systems. For nuclear protons, in 1,2,4- and 1,2,5-trisubstituted rings (strictly AA’B), no sensible JAA, was detected, and the analysis was carried out as for a pure AB system. Aromatic protons in 1,4-disubstituted rings (strictly zy AZBZ) were also analyzed as AB systems, a particularly good approximation due to the absence of extra lines. Aromatic protons in 1,2,6-trisubstituted rings (halo-derivatives) showed the characteristic pattern of AB, systems. b/J values were estimated according to standard procedures zy (8). Aromatic protons in 1,2-disubstituted and mono- substituted rings appear, in general, as complex multiplets and, in these cases, no complete analysis was attempted. Sometimes, however, the analysis of this type of spectra becomes, for reasons discussed elsewhere (11), simpler To whom correspondence should be addressed (Continued on page 254) Journal of Chemical and Engineering Data, Vol. 16, No. 2, 1971 249