Mid-Infrared Monitoring of Gas-Liquid Reactions in Vitamin D Analogue Synthesis with a Novel Fiber Optical Diamond ATR Sensor

Abstract

A novel mid-infrared optical sensor enabling in situ ATR measurements was applied to investigate several steps of a vitamin D analogue synthesis. The probe based on silver halide fibers coupled to a diamond prism was connected to a conventional FTIR spectrometer with internal MCT detector. All steps of the reaction were monitored by real-time in situ FTIR measurements. The steps carried out were the dissolution of SO 2 in a CH 2 Cl 2 /CH 3 OH solvent mixture as well as the addition of SO 2 to a vitamin D analogue, the subsequent ozonation of the double bond in the SO 2 addition product, and the following reduction of the formed hydroperoxide with triphenylphosphine. The dissolving process of SO 2 and the addition of SO 2 to the vitamin D analogue were monitored by changing the characteristic m as (SO 2 ) and m s (SO 2 ) modes of dissolved and incorporated SO 2 . It was found that during ozonation of the SO 2 addition product the formation of hydroperoxide is accompanied by the simultaneous formation of the corresponding aldehyde identified by the typical m(C=O) band at 1720 cm -1. Extended ozone exposure favors the formation of the corresponding acid detected by an additional carbonyl band at lower wavenumbers. During the reaction with triphenylphosphine the increasing intensity of the aldehyde band and the appearance of the m(P=O) mode of the formed triphenylphosphine oxide indicate the progressive reduction of hydroperoxide. The hydroperoxide band disappears completely during the reaction whereas the m as (SO 2 ) band remains unaffected.

Linking Simultaneous In Situ WAXS/SAXS/Raman with Raman/ATR/UV–vis Spectroscopy: Comprehensive Insight into the Synthesis of Molybdate Catalyst Precursors

“…Raman spectra were recorded using the Kaiser RXN spectrometer mentioned above. Mid-infrared spectra were collected using a FTIR spectrometer Nicolet Avatar 370 (Thermo Electron) equipped with an fiber optical diamond ATR probe (infrared fiber sensors, Aachen) [23].…”

Reaction Monitoring in Multiphase Systems: Application of Coupled In Situ Spectroscopic Techniques in Organic Synthesis

“…However, this system is expensive and therefore not always the tool of choice. Standalone diamond ATR probes can also be readily used in conjunction with standard FTIR spectrometers via respective coupled optics [11,38,39].…”

Recent Advances in Microflow Photochemistry

“…Likewise, the irradiation period is precisely controlled via the flow rate of the pumping system. For rapid reaction monitoring, online UV- [ 35 , 36 ] and IR-analysis [ 37 ] have both been realized. On demand, microflow systems can be automated, up-scaled or run in parallel.…”