Thermal isomerizations of 1-(13)c-2,2,3,3-d(4)-cyclopropane to isotopically labeled trimethylene diradicals, 1-propylidenes, and propenes.

The gas-phase thermal isomerizations of 1-13C-2,2,3,3-d4-cyclopropane lead to isotopically labeled propenes characteristic of both the traditional reaction mechanism involving a trimethylene diradical intermediate and a previously predicted, but never observed, path involving rate-limiting conversion of the cyclopropane to singlet 1-propylidenes, followed by a [1,2]-deuterium shift. The isomerizations give mixtures of both 1-13C-2,3,3,3-d4-propene and 1-13C-1,2,3,3-d4-propene, products characteristic of the two mechanisms that are clearly observable by 13C{1H} NMR spectroscopy.

Silicate complexes of sugars in aqueous solution.

Certain sugars react readily with basic silicic acid to form soluble 2/1 (sugar/silicic acid) silicate complexes. Failure of monohydroxy compounds to give soluble products under these conditions indicates that the sugar silicates are chelates: five-membered diolato rings. Only furanose forms react.