Record number :
Title of article :
Vibrational spectra, conformations, ab initio calculations and vibrational assignments of 3-pentyn-2-ol
Author/Authors :
Horn، نويسنده , , Anne and Klaeboe، نويسنده , , Peter and Nielsen، نويسنده , , Claus J. and Guirgis، نويسنده , , Gamil A.، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2008
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Abstract :
The infrared spectra of 3-pentyn-2-ol, CH3CCCH(OH)CH3, have been recorded as a vapour and liquid at ambient temperature, as a solid at 78 K in the 4000–50 cm−1 range and isolated in an argon matrix at ca. 5 K. Infrared spectra of the solid phase at 78 K were obtained before and after annealing to temperatures of 120 and 130 K. The IR spectra of the solid were quite similar to that of the liquid. spectra of the liquid were recorded at room temperature and at various temperatures between 295 and 153 K. Spectra of an amorphous and annealed solid were recorded at 78 K. In the variable temperature Raman spectra, some bands changed in relative intensity and were interpreted in terms of conformational equilibria between the three possible conformers. Complete assignments were made for all the bands of the most stable conformer in which OH is oriented anti to C1(aMe). From various bands assigned to a second conformer in which OH is oriented anti to Hgem(aH), the conformational enthalpy differences was found to be between 0.4 and 0.8 kJ mol−1. The highest energy conformer with OH anti to C3(aC) was not detected. m-chemical calculations have been carried out at the MP2 and B3LYP levels with a variety of basis sets. Except for small basis set calculations for which the aH conformer had slightly lower energy, all the calculations revealed that aMe was the low energy conformer. The B3LYP/cc-pVTZ calculations suggested the aMe conformer as more stable by 0.8 and 8.3 kJ mol−1 relative to aH an aC, respectively. Vibrational wavenumbers and infrared and Raman band intensities for two of the three conformers are reported from B3LYP/cc-pVTZ calculations.
Keywords :
Conformational stability , 3-pentyn-2-ol , Infrared and Raman spectra , Ab initio calculations
Journal title :
Journal of Molecular Structure
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