Dialin

A2-dialins have the opposite orbital symmetries their reactivities cannot therefore be meaningfully compared, inasmuch as their reactions with a common acceptor cannot both be allowed with the same stereochemistry. 

The experiments were conducted batchwise in small stainless-steel pipe-bombs immersed in a molten-salt bath that was maintained at a desired, constant temperature. Pipe-bomb heat-up and quench times, on the order of 1 min each, were negligible compared with reaction times, which were on the order of 1 hr. The reagents used were obtained commercially all were of purity > 98% except for the A2-dialin which had a composition of ( 0)> 0 0 9 Q)) = 9 20, 64) mol%. The proportions of sub-... 

In summary, the A1- and A2-dialin isomers have been shown to be appreciably more active than etralin (and decalin) in transferring hydrogen to anthracene and phenanthrene. The observed selectivity of this hydrogen transfer is in accord with the Woodward-Hoffman rules for group transfer reactions, anthracene conversions being in the ratio ( 3 / 0 ) = 12/1 >> 1 while phenanthrene conversions are in the ratio ( 0/(33 ) = 0.6/1 < 1. The quantitative differences in the selectivities observed with anthracene and phenanthrene are being further explored. 

The dialin donor solvents were also used directly in coal liquefaction studies. Inasmuch as details of coal structure are unknown, the present theory can only be tested in a qualitative way, as follows. First, if the liquefaction of coal occurs under kinetic control with hydrogen-transfer from the donor solvent involved in the rate-determining step, then we should expect the dialin donors to be more effective than the control solvent T.et-ralin (and also Dfecalin). This is suggested by the theory because the dialins possess higher energy HOMOs than Tetralin and... 

Results showing the effectiveness of the A1- and A2-dialins in coal liquefaction relative to control solvents, naphthalene, Decalin, and fetralin, are presented in Tables 3.1 and 3.2. In both these tables, each row provides the conversion of the coal sample to each of hexane-, benzene-, and pyridine-solubles (plus gases) by the indicated solvent. Table 3.1 contains data derived at a temperature of 400 C and a reaction time of 0.5 hr. Among the control solvents, it can be seen that the naphthalene... 

A second series of liquefaction experiments were conducted to test the theoretical suggestion that a mixture of A1- plus A2-dialin isomers might be a more effective solvent than either one of the dialins alone. Preliminary results at 400 C and 0.5 hr reaction time, are shown in Table 4 which quotes the ratio of... 

Table 4. Coal Liquefaction by Mixed Dialin Solvent...

Note r = pm/0.5(p]+P2) where pm, P2 are respectively the wt% conversions obtained with mixed solvent,A -dialin and A2-dialin. 

At typical coal liquefaction conditions, namely temperatures from 300 to 400 C and reaction times on the order of 1 hr, hydrogen transfer from model CIO donors, the A1- and A2-dialins, to model C14 acceptors, anthracene and phenanthrene, occurs in the sense allowed by the Woodward-Hoffman rules for supra-supra group transfer reactions. Thus, in the conversion of the C14 substrates to their 9, 10 dihydro derivatives the dialins exhibited a striking reversal of donor activity, the A dialin causing about twice as much conversion of phenanthrene but only one-tenth as much conversion of anthracene as did A2-dialin. 

The dialins were also found to be more effective donor solvents than Tetralin in the liquefaction of an Illinois No. 6 HVA bituminous coal. For example, at 400 C and 0.5 hr reaction time, A2-dialin yielded 16% more pyridine-solubles and 37% more hex-... 

Finally, a mixture containing equal parts of A1- and A2-dialin was found to be a more effective donor solvent than either of the A1- or A2-dialins separately. At 400 C and 0.5 hr reaction time, the mixture of donors yielded 11% more pyridine-solubles and 8% more hexane-solubles than the average for the separate donors. 

Singlet oxygen reacts through the [4- -2]-cycloaddition mode with the sterically hindered and non-planar 1,3-diene system in l,l -dimenthene (493) to afford the cis-endoperoxide 494, albeit in moderate yield (Scheme 135) ". Cycloaddition of O2 to more planar bis(dialine) (495) proceeds smoothly leading predominantly to the trans-endoperoxide trans-496 (70%), while cis-496, which would be expected to derive from a concerted process, constitutes the minor (15%) product (Scheme 136) . 

Naphthalene does not react with sodium in ether, but Scott found that when sodium is introduced to a solution of naphthalene in dimethyl ether or in ethylene glycol dimethyl ether the metal dissolves to give a deep green solution. Carbonation of the green solution gave a mixture of naphthalene, A -dialin-3,4-dicarboxylic acids, and A"-dialin-l, 4-dicarboxylic acids, and the result led Scott to infer that the solution contains the complex (C,(,HaNa.)C oH8. However, a quantitative study of the reaction in tetrahydrofurane by Paul" indicated that the metal dissolves by... 

Y. Douville, Evaluating the Dialine vascular prosthesis knitted from an alternative source of polyester yarns . Journal of Biomedical Materials Research, vol. 29, no. 5, pp. 595-610, May 1995. 

---