Reactions of Alkanediazotic Acids at Near Neutral and Basic pH in H2O

Article abstract of DOI:10.1021/ja00319a027

The reactions of propane-1-diazotic acid (1) and optically pure (S)-1-phenylethanediazotic acid (2) are investigated in <(18)O>H2O at near neutral (pH 7.0-8.5) and basic (pH > 14) conditions.At near neutral pH, 1 yielded 1- and 2-PrOH (2:1), with both alcohols showing complete incorporation of (18)O from solvent.In the presence of NaN3 the isomeric ratios of azides and alcohols were independent of the ->.The ratio of PrN3 to PrOH is linearly related to ->/ for both primary and secondary products.In basic medium, 1 yields the same isomeric propanol ratio, but both alcohols contain significant and similar amounts of (16)O label. 2 in pH 8.5 buffer gives 1-phenylethanol with 20percent net inversion and containing ca. 4percent (16)O-labeled conservation product.In contrast the ethanolysis of 2 in a basic environment yields 29percent conservation (alcohol) product and the overall stereochemistry of conservation and exchange (ether) products is 1percent net inversion.These results indicate that the extent of (16)O conservation is not dependent on structure, but rather on the degree of proton-transfer-mediated equilibration of the original (16)OH counteranion with <(18)O>H2O, prior to C-N bond cleavage.It is also apparent that a nitrogen-separated ion pair, formed in a two-step process, is responsible for the high yield of rearrangement product, while the stereochemical outcome is determined at the ion-pair stage after nitrogen extrusion.