Conformational analysis of gaseous 3-bromopropene from low-frequency Raman data

Durig, J. R.; Jalilian, M. R.

doi:10.1021/j100463a010

Cited by 38 publications

(17 citation statements)

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“…The obtained bond lengths, bond angles, and vibrational frequencies for 3-bromopropene at the employed levels differ in only ±0.04 Å, ±1.1°, and ±18 cm –1 , respectively. A very good agreement between these and reported experimental − and calculated values was also found.…”

Section: Resultssupporting

confidence: 86%

Thermal Decomposition of 3-Bromopropene. A Theoretical Kinetic Investigation

et al. 2016

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A detailed kinetic study of the gas-phase thermal decomposition of 3-bromopropene over wide temperature and pressure ranges was performed. Quantum chemical calculations employing the density functional theory methods B3LYP, BMK, and M06-2X and the CBS-QB3 and G4 ab initio composite models provide the relevant part of the potential energy surfaces and the molecular properties of the species involved in the CH2═CH-CH2Br → CH2═C═CH2 + HBr (1) and CH2═CH-CH2Br → CH2═CH-CH2 + Br (2) reaction channels. Transition-state theory and unimolecular reaction rate theory calculations show that the simple bond fission reaction ( 2 ) is the predominant decomposition channel and that all reported experimental studies are very close to the high-pressure limit of this process. Over the 500-1400 K range a rate constant for the primary dissociation of k2,∞ = 4.8 × 10(14) exp(-55.0 kcal mol(-1)/RT) s(-1) is predicted at the G4 level. The calculated k1,∞ values lie between 50 to 260 times smaller. A value of 10.6 ± 1.5 kcal mol(-1) for the standard enthalpy of formation of 3-bromopropene at 298 K was estimated from G4 thermochemical calculations.

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Section: Resultssupporting

confidence: 86%

Thermal Decomposition of 3-Bromopropene. A Theoretical Kinetic Investigation

et al. 2016

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“…To describe the thermal chemistry of allyl bromide on Pt(111), it is helpful to ascertain the adsorption structures. Gaseous allyl bromide exists in two isomers at room temperature, gauche (90%) and cis (10%) . We assume that the gauche conformation remains the most stable when adsorbed on the surface.…”

Section: Resultsmentioning

confidence: 99%

Thermal Chemistry of Allyl Bromide Adsorbed on Pt(111)

and

White

1997

J. Phys. Chem. B

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Allyl bromide, CH2CHCH2Br, adsorbs both molecularly and dissociatively on Pt(111) at 95 K. The multilayer desorbs at 130 K and the monolayer at 156 K. At exposures >0.63 monolayers (ML), a broad high-temperature parent desorption peak appears, centered at ∼225 K. For exposures below 0.38 ML, complete decomposition occurs, and only H2 and HBr desorb when heated. For these exposures, high-resolution electron energy loss spectroscopy (HREELS) indicates complete C−Br bond cleavage and η3-allyl group, C(a)H2C(a)HC(a)H2, formation by 185 K, followed by rearrangement to propylidyne, C(a)CH2CH3, between 300 and 350 K. Higher exposures result in some hydrogenation of allyl groups to desorb a mixture of propane and propylene at ∼225 K and propylene at 320 K. HREELS suggests that π-bonded propylene may form from η3-allyl and lead to the 225 K propylene and propane desorption. H2 and D2 coadsorption experiments indicate that propane forms only in the presence of surface hydrogen. For these higher exposures, η-allyl (propenyl, C(a)H2CHCH2) fragments form and undergo reductive elimination to propylene at 320 K and reorient in a competing reaction to η3-allyl groups that subsequently rearrange to propylidyne between 320 and 350 K.

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“…The spectral data merely indicated a very slight preference for the cis conformer and the possibility that the gauche form could be preferred was not completely eliminated. 14 The far-infrared and low-frequency Raman spectra of the gas phase of allyl fluoride1IJ3 and chloride14 have been reported from which the asymmetric torsional potential functions governing internal rotation were determined. The asymmetric torsional fundamental and associated upper level transitions for the cis conformer occur as well-defmed Q branches for both molecules in the far infrared spectrum of the gas.…”

Section: Latroductionmentioning

confidence: 99%

Infrared and Raman spectra, conformational analysis, barriers to internal rotation, vibrational assignment, and ab initio calculations of trans-1,3-dichloropropene

Durig¹,

Costner²,

Little³

et al. 1992

J. Phys. Chem.

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The infrared (3200-50 cm-') and Raman (3200-10 cm-I) spectra of gaseous and solid trans-l,3-dichloroprope.ne, CIHC-CH(CH2Cl), have been recorded. Additionally, the Raman spectrum of the liquid has been obtained and qualitative depolarization ratios have been measured. The fundamental CH2CI torsion for the more stable gauche conformer has been observed in the far-infrared spectrum of the gas and has a hybrid contour centered at 84.0 cm-I. The corresponding mode for the cis conformer (allylic chlorine atom oriented cis to the double bond) gives rise to a series of well defined C-type. Q branches beginning at 129.8 cm-' and proceeding to lower frequencies. From these data the potential function for internal rotation of the asymmetric top has been determined and the following potential constants have been obtained: VI = -558 f 7, V, = -38 f 10, V3 = 637 f 9, V, = 174 f 7, V, = -16 f 4 cm-'. This potential function has the gauche rotamer more stable by 318 f 26 cm-l (909 f 74 cal/mol). The gauche to gauche, gauche to cis, and cis to gauche barriers have been determined to be 397,957, and 639 cm-', respectively. From studies of the Raman and infrared spectra of the gas at variable temperatures, the conformational enthalpy difference has been determined to be 342 f 36 cm-l(978 f 103 cal/mol). A complete assignment of the vibrational fundamentals is proposed. All of these data are compared to the corresponding quantities obtained from ab initio HartretFock gradient calculations employing either the 3-21GS or 6-31G5 basis sets. Additionally, complete equilibrium geometries have been determined for both rotamers. The results are discussed and compared with the corresponding quantities obtained for some similar molecules. latroductionThe vibrational and rotational spectra of the allyl halide molecules have been of interest for a number of Additionally, the electron diffraction patternP and the NMRL7J8 shifts have been invdigated. Allyl fluoride, chloride, and bromide have been determined to exist tts a mixture of cis and gauche conformers. For the ~apeous state of the fluorideI3 and chloride14 the cis conformer is slightly more stable, but for the b r o m i d~'~ the gauche form is the thermodynamically preferred rotamer. For 3chloropropme, however, the value of the energy difference was inferred to be leas than 100 cm-' (286 cal/mol). The spectral data merely indicated a very slight preference for the cis conformer and the possibility that the gauche form could be preferred was not completely eliminated.14 The far-infrared and low-frequency Raman spectra of the gas phase of allyl fluoride1IJ3 and chloride14 have been reported from which the asymmetric torsional potential functions governing internal rotation were determined. The asymmetric torsional fundamental and associated upper level transitions for the cis conformer occur as well-defmed Q branches for both molecules in the far infrared spectrum of the gas. For 3-fluoropropene the Av = 2 transitions for the cis conformer were also observed in the Raman spectrum of the g...

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Conformational analysis of gaseous 3-bromopropene from low-frequency Raman data

Cited by 38 publications

References 5 publications

Thermal Decomposition of 3-Bromopropene. A Theoretical Kinetic Investigation

Thermal Decomposition of 3-Bromopropene. A Theoretical Kinetic Investigation

Thermal Chemistry of Allyl Bromide Adsorbed on Pt(111)

Infrared and Raman spectra, conformational analysis, barriers to internal rotation, vibrational assignment, and ab initio calculations of trans-1,3-dichloropropene

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