Structural and vibrational study of the Ci(1) conformation of 18-crown-6.
Optimized geometry, vibrational frequencies and IR absorption intensities were calculated for the Ci(1) conformation of 18c6. Optimized geometry was compared with the experimental geometry and that of the Ci(2) conformation of 18c6. The Ci(1) conformation is more planer than the Ci(2) conformation of 18c6, which provides an explanation that free 18c6 in the crystal phase has a Ci(1) conformation. Vibrational frequencies were scaled using an unvaried one-scale-factor scaling of 0.928. Calculated vibrational frequencies were compared with the experimental vibrational frequencies. The root-mean-square deviation of the difference between the calculated and experimental frequencies was only 15 cm(-1). This excellent agreement between the calculated and experimental frequencies is an indication of the proper assignment of the fundamental vibrational frequencies of the Ci(1) conformation of 18c6.
Temperature study of the intramolecular interactions in 15-crown-5 and 18-crown-6
Abstract The Raman CH stretching spectra of 15-crown-5 and 18-crown-6 in water solution are studied in the temperature interval 5–80°C. The method of Fourier deconvolution is applied to resolve the overlapped bands in the complex isotropic and anisotropic spectra. The intramolecular coupling constants and the unperturbed CH stretching frequency are calculated for all studied temperatures. The temperature dependencies are discussed in comparison with the temperature dependencies for 12-crown-4 obtained previously.
Deconvolution versus Derivative Spectroscopy
The set of functions that can be deconvoluted is extended. An explicit form of the deconvolution operator is obtained by generalization of the operator of even derivation. The advantages of the deconvolution to derivation, when the former is used for resolution enhancement, are given analytically.