Applicability of laser-induced Raman microscopy for in situ monitoring of imine formation in a glass microfluidic chip

Abstract

Laser‐induced Raman microscopy has been used to illustrate its applicability for the in situ monitoring of imine formation reaction in a glass microfluidic chip. In order to monitor the diffusion process in a micro channel, the Raman spectra were measured at various points along the channel with a constant flow rate of 2.7 µl min−1. Time‐dependent Raman spectra were also measured without flow in order to monitor the variation of Raman peaks to a complete conversion. The disappearance of the CO stretching peak at 1700 cm−1 of the reactant, benzaldehyde, and the appearance of the Raman peak for the product, an imine, at 1628 cm−1 were successfully monitored. In addition, the intensity increases of three phenyl stretching modes in the 1550–1630 cm−1 region were also observed. The increase in Raman intensity for this vibrational mode is caused by an effective π‐electron conjugation between two phenyl rings through the —CN—bridging group of the product. Laser‐induced Raman microscopy enables us to monitor in situ product formation and to obtain detailed structural information in a glass microfluidic chip.