| Abstrakt: |
Four different FTIR methods&sbd;single-bead FTIR, beam condenser, macro attenuated total reflection (macro-ATR), and KBr pellet methods&sbd;and macro and single-bead FT Raman methods have been investigated, and the relative utility was compared for the analysis of resin-bound organic compounds and the monitoring of solid-phase organic reactions. Furthermore, the comparison includes two additional methods from the literature: diffuse reflectance infrared Fourier transform spectroscopy and photoacoustic spectroscopy. While all of these methods have some utility for solid-phase sample analysis, the relative merits of these methods vary particularly in such areas as the information content, spectral quality, sensitivity, speed, sample requirement, and the instrument cost. Both single-bead FTIR and beam condenser FTIR methods have been found to be superb methods in each of these aspects. In the following way, these methods meet many of the essential requirements for a thin layer chromatography (TLC) equivalent for solid-phase synthesis: (1) Only a single bead or 50−100 beads are needed for analysis so that reaction is not interrupted and is monitored in real-time. (2) A high-quality spectrum can be recorded within a few minutes. (3) No sample preparation is required, making the analysis time even shorter than that for TLC analysis. (4) These two FTIR methods provide qualitative, quantitative (the percentage of conversion), and kinetics information on organic reactions carried out on resin supports. Finally, from the synthetic chemist's point of view, the additional advantages of the beam condenser method, such as the low cost and the ease of operation, make it a more suitable choice as a TLC equivalent for solid-phase organic synthesis applications. |
