MATRIX-ISOLATION INFRARED-SPECTROSCOPY OF ORGANIC-PHOSPHATES

Matrix-isolation infrared spectra of trimethyl phosphate (TMP), trieth yl phosphate (TEP), and tri-n-butyl phosphate (TBP), in argon and nitr ogen matrices, are reported for the first time. The peak widths of the sharpest features in our matrix-isolated spectra are typically 2 cm(- 1), compared with peak widths of 40 cm(-1) seen in liquids for these c ompounds. Comparison with the vapor-phase spectrum of TMP reported ear lier indicates that TMP is trapped in two different conformations in t hese matrices. Similar spectra were also obtained for TEP. Our matrix- isolated spectra indicate that the intramolecuIar hydrogen bonding (wh ich is believed to be responsible for the lowering of the P=O frequenc y in the C-3v conformer relative to the C-3 conformer in these compoun ds) is stronger in TEP than in TMP. In the case of TBP, the peak width s were larger (8-10 cm(-1)) than those obtained for TMP and TEP. This observation is probably due to a distribution of conformers that may b e trapped in the matrix, as a result of the increased alkyl chain leng th in TBP.