Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
RAMAN AND FAR-INFRARED SPECTRA, BARRIERS TO INTERNAL-ROTATION AND AB-INITIO CALCULATIONS OF CF(3)CF(2)X, WHERE X=H, CL, BR, AND I
Autore:
ELTAYEB S; GUIRGIS GA; FANNING AR; DURIG JR;
Indirizzi:
UNIV S CAROLINA,DEPT CHEM & BIOCHEM COLUMBIA SC 29208 BAYER CORP,ANALYT RES DEV DEPT,ORG DIV,BUSHY PK PLANT CHARLESTON SC 29411 UNIV MISSOURI,DEPT CHEM KANSAS CITY MO 64110
Titolo Testata:
Journal of Raman spectroscopy
fascicolo: 2, volume: 27, anno: 1996,
pagine: 111 - 126
SICI:
0377-0486(1996)27:2<111:RAFSBT>2.0.ZU;2-Z
Fonte:
ISI
Lingua:
ENG
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
23
Recensione:
Indirizzi per estratti:
Citazione:
S. Eltayeb et al., "RAMAN AND FAR-INFRARED SPECTRA, BARRIERS TO INTERNAL-ROTATION AND AB-INITIO CALCULATIONS OF CF(3)CF(2)X, WHERE X=H, CL, BR, AND I", Journal of Raman spectroscopy, 27(2), 1996, pp. 111-126

Abstract

The far-infrared (360 to 30 cm(-1)) of gaseous CF3CF2H, CF3CF2Cl, CF3CF2Br and CF3CF2I were recorded at a resolution of 0.10 cm(-1). The fundamental torsional transitions were observed at 75, 69.92, 67.35 and 66.72 cm(-1) for CF(3)CF(2)X (X = H, Cl, Br, I), respectively, and each torsional fundamental except for CF3CF2H was observed with accompanying 'hot bands' with decreasing intensity toward lower wavenumber. Utilizing these torsional data, along with reasonably assumed structural parameters (experimental or ab initio adjusted values) to calculate the kinetic constants, the barrier to internal rotation in these molecules was determined. For pentafluoroethane the overtone accompanied by aseries of two quanta 'hot band' transitions of the CF, torsion was observed and these data were used to obtain the internal rotational barrier for this molecule. The threefold periodic barriers for the CF3 rotors are 1190 +/- 4, 1647 +/- 4, 1872 +/- 34 and 1917 +/- 48 cm(-1) forthese CF(3)CF(2)X molecules, where X = H, Cl, Br and I, respectively. The barriers for the CF3 rotors were compared with the corresponding values for the CH3 tops. The Raman (3200 to 20 cm(-1)) and infrared spectral of CF3CF2H and CF3CF2Cl were recorded for the gases and solids. Complete vibrational assignments are proposed based on infrared band contours, relative infrared and Raman intensities and normal coordinate calculations utilizing force constants from ab initio calculations with RHF/3-21G and MP2/6-31G* basis sets. Ab initio calculations were used to obtain optimized geometries and barriers to rotation, which were compared with the experimental values.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 24/09/20 alle ore 04:11:30