Hydroformylation of Oct‐1‐ene in Novel Ionic Liquid Crystals

Abstract

AbstractHydroformylation of oct‐1‐ene leading to nonanal (denoted by n) and 2‐methyloctanal (denoted by iso), in a novel series of caprolactam‐based and common imidazolium‐based ionic liquid crystals (ILCs; see Fig. 1) carried out for the first time (caprolactam=hexahydro‐2H‐azepin‐2‐one) (Scheme). Variation of the chain length (n) of the alkyl substituent (Cn) at the caprolactam cation (CP+) from n=12 to 18 caused the n/iso ratios to vary from 1.7 to 2.9. Meanwhile, the TOF (turnover frequency) decreased from 148 to 122 mol mol−1 h−1. Hydroformylation in the imidazolium‐based ILCs revealed that [C16MIm]⋅BF4 (n/iso 5.2, TOF 969 mol mol−1 h−1) was more favorable than [C16MIm]⋅MsO (n/iso 3.7, TOF 969 mol mol−1 h−1) for the formation of the unbranched aldehyde. Although the n/iso ratio in caprolactam‐based ILCs was lower than that in imidazolium‐based ILCs, the conversions are higher in the former ILCs on the whole. It should be noted that the lamellar mesophase has a strong effect on the regioselectivity and TOF of the hydroformylation. Also, it is evident that the influences of different ILCs on the hydroformylation under the various reaction conditions are greatly different. The identification of the reaction products was established by GC and GC/MS analyses.