RESUMO
Diatomic carbon (C2) is historically an elusive chemical species. It has long been believed that the generation of C2 requires extremely high physical energy, such as an electric carbon arc or multiple photon excitation, and so it has been the general consensus that the inherent nature of C2 in the ground state is experimentally inaccessible. Here, we present the chemical synthesis of C2 from a hypervalent alkynyl-λ3-iodane in a flask at room temperature or below, providing experimental evidence to support theoretical predictions that C2 has a singlet biradical character with a quadruple bond, thus settling a long-standing controversy between experimental and theoretical chemists, and that C2 serves as a molecular element in the bottom-up chemical synthesis of nanocarbons such as graphite, carbon nanotubes, and C60.
RESUMO
The iodoform reaction has long been used as a qualitative test for acetyl and/or ethanol units in organic molecules. However, its synthetic applications are quite limited. Here, we describe a tuned iodoform reaction for oxidative demethylation reaction with I2 and t-BuOK in t-BuOH, in which in situ-generated t-BuOI serves as the chemoselective iodinating agent. This system enables one-step conversion of levulinic acid to succinic acid, a major four-carbon chemical feedstock. This oxidative demethylation is also applicable to other compounds containing an acetyl group/ethanol unit, affording the corresponding carboxylic acids in a selective manner.
