Bibenzyls

Since lunularic acid which is found in the more primitive liverworts and abscisic acid (622) which occurs in mosses and in all higher plants both promote dormancy and inhibit growth in liverworts as well as higher plants, and since the structures of (598) and abscisic acid (622) are similar as shown 

1) EtONa/EtOH 2) HCl/EtOH 3) H2O, 60° 4) ACOH/H2SO4 5) Zn-HgClj/HCl 

A bibenzyl (599) has also been isolated from Pellia species its structure was established by TLC comparison of Rf values with those of an authentic sample 164). 

Twenty-five Frullania species were investigated chemically bibenzyls derivatives (595—597, 600—608) were detected in twelve species and five species contained methylenedioxy bibenzyls as shown in Table I (27). 

Analysis of the mass spectrum (M 360 mjz 107 and 234) led to the conclusion that (613) was 3,5,4 -trihydroxy-4-(3,7-dimethyl-2,6-octa-dienyl)-bibenzyl. 

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The first application of the time-resolved CIDNP method by Closs and co-workers involved tire Norrish 1 cleavage of benzyl phenyl ketone [24, 25]. Geminate RPs may recombine to regenerate the starting material while escaped RPs may fonn the starting ketone (12), bibenzyl (3), or benzil (4), as shown below. 

Bibenzyl [103-29-7] M 182.3, m 52.5-53.5 . Crystd from hexane, MeOH, or 95% EtOH. It has also been sublimed under vacuum, and further purified by percolation through columns of silica gel and activated alumina. 

Carbocations can also be generated during the electrolysis, and they give rise to alcohols and alkenes. The carbocations are presumably formed by an oxidation of the radical at the electrode before it reacts or diffuses into solution. For example, an investigation of the electrolysis of phenylacetic acid in methanol has led to the identification of benzyl methyl ether (30%), toluene (1%), benzaldehyde dimethylacetal (1%), methyl phenylacetate (6%), and benzyl alcohol (5%), in addition to the coupling product bibenzyl (26%). ... 

Only about 1% of bibenzyl is formed during the reaction and it was suggested that this reflects the high reactivity of phenazine toward benzyl radicals. Evidently direct attack on the nitrogen atom occurs with relative ease in this case. 

Methyl Acrylate CH2=CHCOOCH3 Non-inhibitors such as Biphenyl, Bibenzyl, Tri-phenyl, etc Methyl Acrylate Vap plus air > Ambient > 120 Inhibitor—H ydro quino ne or Methyl Ether of Hydro-quinone 10-20ppm. Store Store below 10° no inert atmosphere. No sparks 18.58-18.8 463 Self polymerizing above ambient press temp accelerates polymerization... 

Temp. (° C) PhH PhMe PhEt Ph-i-Pr Ph-t-Bu Tetralin Bibenzyl Naphthalene Biphenyl... 

Thus irradiation of benzophenone in toluene gives the photoreduction product 19, benzpinacol, and bibenzyl [equation (59)] of which only 19... 

Chromium atoms were cocondensed with benzyl sulfide at 77 K (35), the primary result being desulfurization to form bibenzyl and trans-stilbene. Coordination compounds were not characterized in this system. 

Rycroft et al. (1999) identihed the major components of plants from six locations in western Scotland and four from the Azores using nuclear magnetic resonance (NMR) fingerprinting and GC-MS. The terpene P-phellandrene [129], which may be responsible for the aroma of material crushed in the held, was detected in all specimens. The major components, which appear in Fig. 5.6, were shown to be methyl eveminate [444], the four methyl orcellinate derivatives [445 8], the two 9,10-dihydrophenanthrene derivatives [449] and [450], the newly described phthalide killamiensolide [451], and the bibenzyl [453]. Methyl eveminate was the major compound in all 10 specimens other compounds were more varied in their occurrence. Killamiensolide was not isolated as such but was detected when extracts were acetylated yielding, among other compounds, [452]. The presence of the bibenzyl compound [453] in more than trace amounts in P. killarniensis raises the possibility that it represents contamination from P. spinulosa with which it was growing at the one site. 

Model compound studies were also carried out in MeOH/KOH, and the results are shown in Table VI. Phenanthrene and biphenyl were quantitatively recovered unchanged by the reactions, and bibenzyl was recovered in 95% yield, with small amounts of toluene observed. Anthracene and diphenyl ether, on the other hand, were converted respectively to 9,10-dihydroanthracene and a mixture of polymethyl-phenols similar to that observed in the work with coal. The cleavage of diphenyl ether via hydrogenolysis should yield both benzene and phenol as products we saw no benzene in our study, and our... 

Model Component Studies. Model compound work with this system showed that anthracene was reduced to its 9,10-dihydro derivative (35% yield). Bibenzyl, on the other hand, was recovered unchanged, with only a trace of toluene observed. 

However, as pointed out above, the commonly proposed free radical mechanism is not entirely consistent with the observed behavior of H-donor solvents and coal. Further, a thermally promoted C-C or C-0 bond-scission is inconsistent with our observations in the -PrOH work at 335°C. As also mentioned, a major fraction of the coal was converted in this system to a product with a number-average molecular weight of less than 500. If we consider that the rate constant for the unimolecular scission of the central bond in bibenzyl is expressed (5) as... 

Note. In a recent paper, Miller and Stein have provided values for both C-C and C-0 bonds for a variety of coal model compounds, including bibenzyl and benzyl phenyl ether (11). Their rate constant for bibenzyl provides half-life values at 335°C and 400°C even larger than those discussed here, and it would seem on the basis of their data that at those low temperatures C-C scission in bibenzyl itself is too slow for thermal scission to be significant. 

On the other hand, they find that the ether and substituted bibenzyls are thermalized faster than bibenzyl itself, and thus thermal scission of such bonds could play a role in a free radical route. 

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