Pure organic compound exercises

In summary, we selected one database (Pedley s) to quote the standard enthalpies of formation of the pure organic compounds and another database (NBS) to derive the solution enthalpies. Although these databases are not mutually consistent, that did not affect our final result because the experimental enthalpies of solution were calculated with NBS data only. The exercise illustrates the sort of caution one should keep in mind whenever two or more nonconsistent databases are used. 

Exercise 11-8 Consider that it is necessary to synthesize pure samples of d.l-hexane-3,4-D2 and meso-hexane-3,4-D2. Show how this might be done both with diimide and catalytic-type reductions, assuming that any necessary deuterium-iabeled reagents and six-carbon organic compounds are available. 

The organic esters have a greater order of stability, but it is difficult to prepare completely acylated compounds without concurrently anhy-drizing the hexitol unless one uses acid anhydrides or chlorides. Early attempts to prepare higher aliphatic esters of D-mannitol resulted in the formation of mixtures of mannitans and mannides. It is for this reason that caution must be exercised in interpreting some of the work in the literature. The analytical values of the pure compounds and the mixtures are such that one cannot differentiate between them. 

Journal of Fluorine Chemistry, published monthly by Elsevier Science (Amsterdam), contains original papers and short communications describing both pure and applied research on the chemistry and applications of fluorine and of compounds where fluorine exercises significant effects. The journal covers inorganic, organic, organometallic and physical chemistry and also includes papers on biochemistry and environmental industrial chemistry. 

It should be noted that the compatibility of aluminum alloys with mixtures of organic compoimds cannot always be predicted from their compatibility with each of the compounds. For example, some aluminum alloys are corroded severely in mixtures of carbon tetrachloride and methyl alcohol, even though they are resistant to each compoimd alone. Caution should be exercised in using data for pure organic compoimds to predict performance of the alloys with commercial grades that may contain contaminants. Ions of halides and reducible metals, commonly copper and chloride, frequently have been found to be the cause of excessive corrosion of aluminum alloys in commercial grades of organic chemicals that would not have been predicted from their resistance to pure compounds. 

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