1,1-Diphenylethanes

Figure C2.3.9. Product distribution of dissymmetrical ketone photolysis as influenced by cefyltrimethylammonium chloride (CTAC) micelles. The initial ketone, A(CO)B is photolysed to lose the carbonyl group and to produce tliree products, AA, AB and BB. These data are for benzyl (A) 4-methylbenzyl (B) ketone. Product AA is 1,2-diphenylethane, product BB is 1,2-ditolylethane and product AB is l-phenyl-2-tolyl-ethane. At low CTAC concentration, in the absence of micelles, a random distribution of products is obtained. In the presence of micelles, however, the AB product is heavily favoured. Adapted with pennission from 1571.

Dowtherm J is a mixture of isomers of an alkylated aromatic that contains only carbon and hydrogen. Dowtherm J can be used in Hquid-phase systems at temperatures as low as —73° C and in vapor-phase systems at temperatures from 185 to 315°C. Dowtherm Q is a mixture of diphenylethane and alkylated aromatics intended for Hquid-phase systems. It can be used at temperatures as low as —34°C. Dowtherm HT is a mixture of hydrogenated terphenyls intended for Hquid-phase systems. Dowtherm HT and Therminol 66 are essentially identical. 

Styrene undergoes many reactions of an unsaturated compound, such as addition, and of an aromatic compound, such as substitution (2,8). It reacts with various oxidising agents to form styrene oxide, ben2aldehyde, benzoic acid, and other oxygenated compounds. It reacts with benzene on an acidic catalyst to form diphenylethane. Further dehydrogenation of styrene to phenylacetylene is unfavorable even at the high temperature of 600°C, but a concentration of about 50 ppm of phenylacetylene is usually seen in the commercial styrene product. 

The piefeiied route depends upon the avajlabihty of a hydrogen atom in the beta-position to the thiol group. In other words, a-toluenethiol (in toluene) decomposes to give 1,2-diphenylethane and hydrogen sulfide, via the homolytic route, whereas 2-methyl-2-propanethiol decomposes to give 2-methyl-1-propene and hydrogen sulfide. 

Bromine can function as a solvent. One of the very few metal bromides that has significant solubiUty in bromine is cesium bromide, 19.3 g/100 g of solution, thus providing a method of separating cesium bromide from the other alkah bromides (12). Aluminum bromide also is reported to have significant solubiUty in bromine but the pubUshed solubiUty values are not in good agreement (13). Bromine serves as the solvent in some brominations of organic compounds, such as 1,2-diphenylethane (14). 

Benzyl chloride readily forms a Grignard compound by reaction with magnesium in ether with the concomitant formation of substantial coupling product, 1,2-diphenylethane [103-29-7]. Benzyl chloride is oxidized first to benzaldehyde [100-52-7] and then to benzoic acid. Nitric acid oxidizes directly to benzoic acid [65-85-0]. Reaction with ethylene oxide produces the benzyl chlorohydrin ether, CgH CH20CH2CH2Cl (18). Benzylphosphonic acid [10542-07-1] is formed from the reaction of benzyl chloride and triethyl phosphite followed by hydrolysis (19). 

Nitrogen cannot be eliminated from the latter by further methylation, but (VIII) on catalytic hydrogenation has its vinyl group converted into ethyl and the product, on methylation followed by reduction with sodium amalgam, yields 6-dimethylamino-3 4 3 4 -tetramethoxy-6 -ethyl-a)3-diphenylethane (X), and this, on repetition of the methylation, and reduc-... 

Base-promoted E2 eliminations involving 1,2-dibromo-1,2-diphenylethane have been used to learn about the stereochemical preferences of this reaction. The meso starting material gives one alkene and the dl starting material gives another. 

Step through the sequence of structures depicting rotation about the carbon-carbon bond in the two dibromoethane isomers l,2-dibromo-l,2-diphenylethane A andfi). For each, plot energy (vertical axis) vs. BrCCBr torsion angle (horizontal axis), and identify all minimum-energy structures. Which of these are reactive conformers , that is, conformers which are set up for either syn or anti elimination of HBr Which are non-reactive conformers , that is, which do not meet the requirements for elimination Do the reactive conformers correspond only to syn elimination, only to anti elimination, or are both pathways represented Which alkene would these reactive conformers lead to Are your results consistent with the observation that each isomer of the starting material gives only one alkene Explain. 

Tliere is only one report concerning the reaction of A -(l-chloroalkyl)-pyridinium chlorides with secondary diamines (92BSB233). 2-Substituted 1,3-dimethyl- and 1,3-diphenyl-imidazolidines 79 have been prepared (75-95% yields) starting from either -dimethyl- or A, A -diphenylethane-1,2-diamines, respectively (Scheme 25). Reactions are particularly fast for the preparation of the 1,3-dimethylimidazolidines. Reaction times as short as 5 min have been claimed. 

In an attempt to study the behavior and chemistry of coal in ionic liquids, 1,2-diphenylethane was chosen as a model compound and its reaction in acidic pyri-dinium chloroaluminate(III) melts ([PyHjCl/AlCb was investigated [69]. At 40 °C, 1,2-diphenylethane undergoes a series of alkylation and dealkylation reactions to give a mixture of products. Some of the products are shown in Scheme 5.1-40. Newman also investigated the reactions of 1,2-diphenylethane with acylating agents such as acetyl chloride or acetic anhydride in the pyridinium ionic liquid [70] and with alcohols such as isopropanol [71]. 

What stereochemistry do you expect for the alkene obtained by E2 elimination of (IS,25)- l,2-dibromo-l,2-diphenylethane ... 

Draw (lSP2S)-l,2-clibromo-l,2-diphenylethane so that you can see its stereochemistry and so that the —H and —Br groups Lo be eliminated are anti periplanar. Then carry out the elimination while keeping ail substituents in approximately their same positions, and see what alkene results. 

The reaction of butyllithium with 1-naphthaldehyde cyclohexylimine in the presence of (/C )-l,2-diphenylethane-1,2-diol dimethyl ether in toluene at —78 °C, followed by treatment with acetate buffer, gave 2-butyl-1,2-dihydronaphthalene-l-carbaldehyde, which was then reduced with sodium borohydride in methanol to afford (1 R,2.S)-2-butyl-1 -hydroxymcthyl-1,2-dihydronaphthalene in 80% overall yield with 91 % ee83. Similarly, the enantioselective conjugate addition of organolithium reagents to several a,/J-unsaturated aldimines took place in the presence of C2-symmetric chiral diethers, such as (/, / )-1,2-butanediol dimethyl ether and (/, / )- ,2-diphenylethane-1,2-diol dimethyl ether. 

In general the chiral additive (l/ ,2/J)-l,2-dimethoxy-l,2-diphenylethane was the most effective while (.S )-2.2 -diniethoxy-1,1 -binaphthalene and (1 / ,27 )-/V,/V,/V, A"-tetramethyl-1,2-diphcnyl-ethylenediamine induced only very low levels of enantiofacial differentiation. In the case of the acyclic enimines competing 1,2-addition products were also obtained7. 

Gas chromatography on a 200 cm. by 0.6 cm. column packed with 10% Apiezon L on Chromosorb W (AW, DMCS) using a flame-detector instrument, at a 40 ml./minute helium carrier gas flow rate, gives a trace peak at 9.9 minutes (diphenylmethane), a major peak at 11.7 minutes (1,1-diphenylethane), and a trace peak at 15.4 minutes (1.1-diphenylethanol) when the oven is held at 190° for 10 minutes and then programmed at 10°/minute to 290°. 

In addition to the present method, other procedures have been reported for the synthesis of 1,1-diphenylethane.5-7... 

We shall discuss in detail only one example, and for the sake of simplicity we shall take the (actually undissociated) sym. diphenylethane. Let us first consider what happens when the ethane dissociates. In the first step, the C —C bond breaks and there are formed two phenyl-methyl radicals, which however can resonate between only the structures A and B of Fig. 3. 

Fig. 4. Catalytic reduction of mew-l,2-dibromo-l,2-diphenylethane (DBDPE) at poly-/J-coated Pt. cyclic voltammograras in 0.1 M TBAP/acetonitiile at 0.1 V s- scan rate. A 16 at bare Pt B DBDPE at poly-/J (F = 1 x 10" mol cm" ) C poly-f5 in clean el trolyte (from ref.

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