Mechanistic Study on the Efficient Conversion of d-Sorbitol to Iodohexanes Mediated by Hydroiodic Acid

Abstract

As an important biomass-derived chemical, D-sorbitol can be converted to a variety of useful chemicals and fuels. Because of the strong nucleophilicity of I − and reducibility of hydrogen iodide (HI), hydroiodic acid has been used for polyol hydrogenolysis with high selectivity. Here, D-sorbitol was converted by HI, rhodium, and hydrogen to give a high yield of iodohexanes (94.2%) at 373 K in a water/cyclohexane biphasic system. Rhodium and hydrogen were used to regenerate HI in situ. The reaction mechanism was studied in detail by using model molecules. The substitution−elimination−addition (SEA) mechanism was proven to be the most possible pathway. The high concentration of both proton and iodide was found to be necessary for the efficient conversion of D-sorbitol and the selective formation of iodohexanes. Besides, water could inhibit the conversion of D-sorbitol dramatically. These findings were explained by kinetic study and demonstrated in the reaction kinetic equation. This catalytic system, including HI and RhCl 3 , was proven to be reusable. In addition, iodohexanes can be quantitatively converted to hexenes over ZrO 2 at 473 K.

Iodine and Iodide in Reductive Transformations

“…More recently, Yang converted glyceric acid into 3‐iodopropionic acid using HI (regenerated by H 2 and Rh/C) and a substitution‐elimination‐addition mechanism was proposed [41] . A similar pathway was suggested for the reductive conversion of D‐sorbitol to isomeric iodohexanes (Scheme 14c) [42] …”

“…[41] A similar pathway was suggested for the reductive conversion of D-sorbitol to isomeric iodohexanes (Scheme 14c). [42] Similarly, D-saccharic acid potassium salt was converted to 3-iodoadipic acid (3-IAA), a promising platform chemical, which was then converted to other products such as adipic acid and 3-hydroxy adipic acid (Scheme 15). [43] In addition to Yang's research on iodide-mediated processing of biomass derivatives to added-value chemicals, a disproportionation of alcohols catalyzed by iodide was also described.…”

The Future of Biomass Utilization Technologies Special Issue Editorial

“…Thus, as the energy demand and serious environmental concerns increase, the technologies including torrefaction, catalytic conversion, gasification, and hydrothermal liquefaction (HTL) have attracted more and more attention and have developed rapidly in recent years. A variety of reactions, including hydrogenation, oxidation, deoxygenation (hydrodeoxygenation, decarboxylation and decarbonylation), catalytic cracking, dehydrogenation, aromatization, reforming, pyrolysis, ketonization, and so on have been achieved. − Various products including biochar, bio-oil, hydrogen, aromatics, CO 2 , CO, CH 4 and other gaseous hydrocarbons have been obtained. − …”