Real-time mid-IR monitoring of metathesis reactions by fiber optic FTIR spectroscopy

The real-time monitoring of metathesis reactions using a recently developed fiber optic transmission FTIR technique is reported in this paper, The rin g-opening metathesis polymerization (ROMP) of 1,5-cyclooetadiene, the rin-c losing metathesis (RCM) of 1,7-octadiene and the polymerization of phenylac etylene were investigated. The Schrock carbyne complex, Cl-3(dme)WC drop CM e3, was used as the catalyst for these reactions. The phenylacetylene polym erization was also studied with WCl6 as the catalyst. In the ROMP of 1,5-cy clooetadiene, monomer consumption was followed by monitoring the disappeara nce of the 1486 cm(-1) absorbance, characteristic of the CH, deformation vi bration (delta (s) CH,) in the monomer. In the RCM of 1,7-octadiene, conver sion data was obtained by monitoring the 1832 cm(-1) signal, which is an ov ertone of the wagging absorbance at 910 cm(-1) of the =CH2 end group in the monomer. Phenylacetylene polymerization was monitored by the disappearance of the nu -C drop CH stretch signal at 2110 cm(-1). Polymerization was muc h faster with the Schrock catalyst than with WCl6, but similar conversions were reached in both reactions. Conversion data obtained by the IR techniqu e agreed well with gravimetric product yields. (C) 2001 Elsevier Science Lt d. All rights reserved.