1. NMR and Raman spectroscopic study of CDCl3 in cyclohexane solutions in the presence of pyridine, quinuclidine or triethylamine
- Author
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Magnus Sandström, Jozef Kowalewski, and Stephen Bagley
- Subjects
Cyclohexane ,Stereochemistry ,Rotational diffusion ,Deuterated chloroform ,Nuclear magnetic resonance spectroscopy ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,symbols.namesake ,chemistry ,Materials Chemistry ,symbols ,Physical chemistry ,Physical and Theoretical Chemistry ,Raman spectroscopy ,Triethylamine ,Spectroscopy ,Equilibrium constant ,Quinuclidine - Abstract
NMR and Raman spectroscopic methods have been used to study deuterated chloroform (ca. 10 mol%) with added pyridine (py), quinuclidine (Q) or triethylamine (Et 3 N) (0 – ca. 15 mol%) in cyclohexane solutions. In the Raman spectra of the CDCl 3 solutions new bands shifted to lower wavenumbers appear for the CCl and CD stretching vibrations when the above N-donor Lewis bases are added. These bands age ascribed to the formation of 1:1 hydrogen bonded complexes with CDCl 3 . A quantitative evaluation of the band areas, using the breathing mode of cyclohexane as internal standard, allowed relative molar scattering coefficients to he evaluated for the displaced CCl bands of the CDCl 3 hydrogen bonded species by fitting calculated to experimental concentrations. Equilibrium constants were then obtained for the 1:1 complex formations CDCl 3 + N-donor ⇌ CDCl 3 ·N-donor: K py = 0.8 ± 0.2, K Q = 0.8 ± 0.2, and K Et 3 N = 0.53 ± 0.05 dm 3 mol −1 . The NMR relaxation times of 2 D and 35 Cl for CDCl 3 have been measured and analyzed in terms of anisotropic rotational diffusion, in addition the perpendicular rotational diffusion constant of CDCl 3 in cyclohexane has been estimated from the Raman CD stretching band widths. Using the concentrations of the free and hydrogen bonded CDCl 3 species from the Raman experiment the rotational correlation times for the CDCl 3 ·N-donor complexes have been obtained.
- Published
- 1992
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