Factors Controlling the Selective Hydroformylation of Internal Alkenes to Linear Aldehydes. 1. The Isomerization Step

Selective hydroformylation of long-chain alkenes to linear aldehydes has long been a synthetic challenge. This process is especially important because it is the first step in the production of detergent alcohols, which are widely used as plasticizers. Major difficulties arise from the fast isomerization processes that these alkenes can undergo and thereby lead to nonlinear aldehydes. Theoretical calculations and modeling of the isomerization process may lead to it fundamental understanding that will thereby contribute toward the improvement of efficiency in the hydroformylation process. The present study uses DFT and hybrid ONIOM calculations to address the following issues: (i) the isomerization mechanism, (ii) the reason for the faster reactivity of octene compared with smaller alkenes, and (iii) the catalyst role in the kinetics of the isomerization reaction. The thus-computed catalytic cycle is used for calculating the turnover frequency of the isomerization process using the recently developed energetic span model for assessment of catalytic cycles.