Reactivity of a Carene-Derived Hydroxynitrate in Mixed Organic/Aqueous Matrices: Applying Synthetic Chemistry to Product Identification and Mechanistic Implications

β-hydroxynitrates (HN) are a major class of products formed during OH and NO3 initiated oxidation of terpenes. Their production contributes significantly to secondary organic aerosol (SOA) formation and NOx sequestration. However, studying the condensed phase reactions of this important class of molecules has been hindered by the lack of commercially available authentic standards. The goal of this work was to examine the influence of water concentration and solvent identity on product yields of a tertiary HN derived from 3-carene prepared in house. To assess the role of water on conversion chemistry, bulk-phase reactions were conducted in DMSO-d6, a non-nucleophilic solvent, with a gradient of water concentrations, and analyzed with 1H NMR. Product identifications were made by comparison with authentic standards prepared in house. Four major products were identified, including an unexpected diol produced from carbocation rearrangement, diol diastereomers, and trans-3-carene oxide, with varying yields as a function of water concentration. Product yields were also measured in two protic, nucleophilic solvents, MeOD-d4 and EtOD-d6. Finally, reactions with added chloride formed alkyl chloride products in yields approaching 30%. These results are among the first to highlight the complexities of nucleophilic reactions of hydroxynitrates in bulk, mixed aqueous/organic media and to identify new, unexpected products.

ZnCl2/PhI=O Mediated Selective ortho-Chlorination of Amides

: A new ortho-chlorination system consisted of zinc(II) and hypervalent iodine(III) reagent was developed for ortho-chlorination of amides, and the desired products were obtained in moderate to good yields (38 - 85%). This highly facile and convenient methodology was tolerant of aromatic amide and alkyl amide with diverse substituted groups. A plausible mechanism was illustrated in which carbocation rearrangement and metal salt coordinate facilitated ortho-chlorination were involved.

What causes the nonclassical structure of 2-norbornyl ion?

A recent publication of a general carbocation rearrangement mechanism highlighted protonated cyclopropane (PCP+) intermediates, whose structures are meso between the nonclassical hypotheses of edge-PCP+ and corner-PCP+. Unlike the nonclassical structures, which possess 3-centre–2-electron bonds, the meso-PCP+ structures appear as closed classical structures. The 2-norbornyl ion, however, is known to have a nonclassical corner-PCP+ structure, and here we explore (using computational chemistry) the reasons why. The main reasons are due to the three 5-membered carbon rings, whose ring strain resist relaxation to a meso-PCP+ structure, but an additional reason is the trisubstitution on one side of the PCP+ face, which causes unfavourable C–C bond eclipsing.