The Experts below are selected from a list of 726 Experts worldwide ranked by ideXlab platform
David Lee Phillips - One of the best experts on this subject based on the ideXlab platform.
-
Investigation of the short-time photodissociation dynamics of trans-1-bromo-2-Iodoethane in the A-band absorption
The Journal of Chemical Physics, 1999Co-Authors: Xuming Zheng, David Lee PhillipsAbstract:We have obtained resonance Raman spectra and absolute Raman cross section measurements at five excitation wavelengths within the A-band absorption for 1-bromo-2-Iodoethane in cyclohexane solution. The resonance Raman spectra have most of their intensity in the fundamentals, overtones, and combination bands of six Franck–Condon active vibrational modes; the nominal CCI bend, C–I stretch, C–Br stretch, C–C stretch, CH2 wag with the Br atom attached to the CH2 group, and CH2 wag with the I atom attached to the CH2 group. The resonance Raman intensities and A-band absorption spectrum were simulated using a simple model and time-dependent wave packet calculations. The simulation results and normal mode descriptions were used to find the short-time photodissociation dynamics in terms of internal coordinate displacements. The A-band short-time photodissociation dynamics for trans-1-bromo-2-Iodoethane show that the C–I, C–Br, and C–C bonds as well as the CCI, CCBr, HCC, ICH, and BrCH angles have significant chang...
-
Short-time photodissociation dynamics of 1-chloro-2-Iodoethane from resonance Raman spectroscopy
Laser Chemistry, 1999Co-Authors: Xuming Zheng, David Lee PhillipsAbstract:We have obtained A-band absorption resonance Raman spectra of 1-chloro-2- Iodoethane in cyclohexane solution. We have done preliminary time-dependent wavepacket calculations to simulate the resonance Raman intensities and absorption spectrum in order to learn more about the short-time photodissociation dynamics. We compare our preliminary results for 1-chloro-2-Iodoethane with previous resonance Raman results for Iodoethane and find that there appears to be more motion along non- C—I stretch modes for 1-chloro-2-Iodoethane than for Iodoethane. This is consistent with results of TOF photofragment spectroscopy experiments which indicate much more internal excitation of the photoproducts from 1-chloro-2-Iodoethane photodissociation than the photoproducts from Iodoethane photodissociation.
-
Vibrational spectra and assignments of 1-chloro-2-Iodoethane
Vibrational Spectroscopy, 1998Co-Authors: Xuming Zheng, David Lee PhillipsAbstract:Abstract Infrared absorption and Raman spectra of liquid 1-bromo-2-Iodoethane and 1-bromo-2-Iodoethane in different solvents were taken. Additional infrared absorption and Raman spectra were obtained for solid 1-bromo-2-Iodoethane. Ab initio vibrational frequencies of the anti and gauche conformers have been calculated at the RHF/3-21G* level of theory by using the point group symmetries of C 1 and C S , respectively. Vibrational frequency assignments for seventeen infrared and Raman active modes have been determined for both anti and gauche conformers. The experimental data and the ab initio calculations indicate that the anti conformer is more stable than the gauche conformer. The Raman intensities of the C – I stretch bands as a function of temperature were used to obtain the change of enthalpy between the anti and gauche conformers. The experimentally determined enthalpy difference between the anti and gauche conformers was found to be Δ H =4.81±0.21 kJ/mol for neat liquid 1-bromo-2-Iodoethane.
-
A-band resonance Raman spectra and short-time photodissociation dynamics of trans 1-chloro-2-Iodoethane in cyclohexane solution
Chemical Physics Letters, 1998Co-Authors: Xuming Zheng, David Lee PhillipsAbstract:Abstract Resonance Raman spectra of 1-chloro-2-Iodoethane in cyclohexane solution are presented for three excitation wavelengths. The fundamentals, overtones and combination bands of the nominal CCCl bend ( ν 10 ), the nominal C–I stretch ( ν 9 ), and the C–Cl stretch ( ν 8 ) vibrational modes can account for most of the resonance Raman intensity. The resonance Raman spectra and associated short-time photodissociation dynamics of 1-chloro-2-Iodoethane are compared with Iodoethane and this suggests that the chloroethyl radical receives more internal excitation than the ethyl radical from the A-band photodissociation in as much as the initial dynamics determines the internal excitation of the alkyl radical photoproducts.
-
A-band resonance Raman spectra and short-time photodissociation dynamics of trans 1-chloro-2-Iodoethane in cyclohexane solution
Chemical Physics Letters, 1998Co-Authors: Xuming Zheng, David Lee PhillipsAbstract:Resonance Raman spectra of 1-chloro-2-Iodoethane in cyclohexane solution are presented for three excitation wavelengths. The fundamentals, overtones and combination bands of the nominal CCCl bend (ν 10), the nominal C-I stretch (ν 9), and the C-Cl stretch (ν 8) vibrational modes can account for most of the resonance Raman intensity. The resonance Raman spectra and associated short-time photodissociation dynamics of 1-chloro-2-Iodoethane are compared with Iodoethane and this suggests that the chloroethyl radical receives more internal excitation than the ethyl radical from the A-band photodissociation in as much as the initial dynamics determines the internal excitation of the alkyl radical photoproducts.link_to_subscribed_fulltex
Xuming Zheng - One of the best experts on this subject based on the ideXlab platform.
-
Investigation of the short-time photodissociation dynamics of trans-1-bromo-2-Iodoethane in the A-band absorption
The Journal of Chemical Physics, 1999Co-Authors: Xuming Zheng, David Lee PhillipsAbstract:We have obtained resonance Raman spectra and absolute Raman cross section measurements at five excitation wavelengths within the A-band absorption for 1-bromo-2-Iodoethane in cyclohexane solution. The resonance Raman spectra have most of their intensity in the fundamentals, overtones, and combination bands of six Franck–Condon active vibrational modes; the nominal CCI bend, C–I stretch, C–Br stretch, C–C stretch, CH2 wag with the Br atom attached to the CH2 group, and CH2 wag with the I atom attached to the CH2 group. The resonance Raman intensities and A-band absorption spectrum were simulated using a simple model and time-dependent wave packet calculations. The simulation results and normal mode descriptions were used to find the short-time photodissociation dynamics in terms of internal coordinate displacements. The A-band short-time photodissociation dynamics for trans-1-bromo-2-Iodoethane show that the C–I, C–Br, and C–C bonds as well as the CCI, CCBr, HCC, ICH, and BrCH angles have significant chang...
-
Short-time photodissociation dynamics of 1-chloro-2-Iodoethane from resonance Raman spectroscopy
Laser Chemistry, 1999Co-Authors: Xuming Zheng, David Lee PhillipsAbstract:We have obtained A-band absorption resonance Raman spectra of 1-chloro-2- Iodoethane in cyclohexane solution. We have done preliminary time-dependent wavepacket calculations to simulate the resonance Raman intensities and absorption spectrum in order to learn more about the short-time photodissociation dynamics. We compare our preliminary results for 1-chloro-2-Iodoethane with previous resonance Raman results for Iodoethane and find that there appears to be more motion along non- C—I stretch modes for 1-chloro-2-Iodoethane than for Iodoethane. This is consistent with results of TOF photofragment spectroscopy experiments which indicate much more internal excitation of the photoproducts from 1-chloro-2-Iodoethane photodissociation than the photoproducts from Iodoethane photodissociation.
-
Vibrational spectra and assignments of 1-chloro-2-Iodoethane
Vibrational Spectroscopy, 1998Co-Authors: Xuming Zheng, David Lee PhillipsAbstract:Abstract Infrared absorption and Raman spectra of liquid 1-bromo-2-Iodoethane and 1-bromo-2-Iodoethane in different solvents were taken. Additional infrared absorption and Raman spectra were obtained for solid 1-bromo-2-Iodoethane. Ab initio vibrational frequencies of the anti and gauche conformers have been calculated at the RHF/3-21G* level of theory by using the point group symmetries of C 1 and C S , respectively. Vibrational frequency assignments for seventeen infrared and Raman active modes have been determined for both anti and gauche conformers. The experimental data and the ab initio calculations indicate that the anti conformer is more stable than the gauche conformer. The Raman intensities of the C – I stretch bands as a function of temperature were used to obtain the change of enthalpy between the anti and gauche conformers. The experimentally determined enthalpy difference between the anti and gauche conformers was found to be Δ H =4.81±0.21 kJ/mol for neat liquid 1-bromo-2-Iodoethane.
-
A-band resonance Raman spectra and short-time photodissociation dynamics of trans 1-chloro-2-Iodoethane in cyclohexane solution
Chemical Physics Letters, 1998Co-Authors: Xuming Zheng, David Lee PhillipsAbstract:Abstract Resonance Raman spectra of 1-chloro-2-Iodoethane in cyclohexane solution are presented for three excitation wavelengths. The fundamentals, overtones and combination bands of the nominal CCCl bend ( ν 10 ), the nominal C–I stretch ( ν 9 ), and the C–Cl stretch ( ν 8 ) vibrational modes can account for most of the resonance Raman intensity. The resonance Raman spectra and associated short-time photodissociation dynamics of 1-chloro-2-Iodoethane are compared with Iodoethane and this suggests that the chloroethyl radical receives more internal excitation than the ethyl radical from the A-band photodissociation in as much as the initial dynamics determines the internal excitation of the alkyl radical photoproducts.
-
A-band resonance Raman spectra and short-time photodissociation dynamics of trans 1-chloro-2-Iodoethane in cyclohexane solution
Chemical Physics Letters, 1998Co-Authors: Xuming Zheng, David Lee PhillipsAbstract:Resonance Raman spectra of 1-chloro-2-Iodoethane in cyclohexane solution are presented for three excitation wavelengths. The fundamentals, overtones and combination bands of the nominal CCCl bend (ν 10), the nominal C-I stretch (ν 9), and the C-Cl stretch (ν 8) vibrational modes can account for most of the resonance Raman intensity. The resonance Raman spectra and associated short-time photodissociation dynamics of 1-chloro-2-Iodoethane are compared with Iodoethane and this suggests that the chloroethyl radical receives more internal excitation than the ethyl radical from the A-band photodissociation in as much as the initial dynamics determines the internal excitation of the alkyl radical photoproducts.link_to_subscribed_fulltex
Zadjia Atik - One of the best experts on this subject based on the ideXlab platform.
-
Solubility and Liquid−Liquid Equilibrium of Aqueous Systems of Iodoethane with Methanol, Ethanol, or 1-Propanol at Temperature 298.15 K and Pressure 101.2 kPa
Journal of Chemical & Engineering Data, 2009Co-Authors: Wahiba Kerboub, Zadjia AtikAbstract:A study to attain the solubility and liquid−liquid equilibrium (LLE) data for the ternary mixtures of water + alcohol + Iodoethane (where alcohol = methanol, or ethanol, or 1-propanol) was carried out at temperature 298.15 K and pressure of 0.1 MPa. The consistency of the binodal and phase diagram data were well ascertained by Hand and Othmer−Tobias empirical equations. The NRTL and UNIQUAC thermodynamic models were shown to yield accurate values for the LLE of the three systems. Plait point, distribution coefficient, solvent selectivity, and binary interaction parameters are reported for each ternary system. The selectivity of water for methanol in the ternary studied system is very high. The removal of methanol from the azeotropic binary system of methanol + Iodoethane by means of water is potentially effective to yield pure Iodoethane at ambient temperature. The immiscibility region of the system decreases significantly with increasing of the alcohol molecular chain.
-
solubility and liquid liquid equilibrium of aqueous systems of Iodoethane with methanol ethanol or 1 propanol at temperature 298 15 k and pressure 101 2 kpa
Journal of Chemical & Engineering Data, 2009Co-Authors: Wahiba Kerboub, Zadjia AtikAbstract:A study to attain the solubility and liquid−liquid equilibrium (LLE) data for the ternary mixtures of water + alcohol + Iodoethane (where alcohol = methanol, or ethanol, or 1-propanol) was carried out at temperature 298.15 K and pressure of 0.1 MPa. The consistency of the binodal and phase diagram data were well ascertained by Hand and Othmer−Tobias empirical equations. The NRTL and UNIQUAC thermodynamic models were shown to yield accurate values for the LLE of the three systems. Plait point, distribution coefficient, solvent selectivity, and binary interaction parameters are reported for each ternary system. The selectivity of water for methanol in the ternary studied system is very high. The removal of methanol from the azeotropic binary system of methanol + Iodoethane by means of water is potentially effective to yield pure Iodoethane at ambient temperature. The immiscibility region of the system decreases significantly with increasing of the alcohol molecular chain.
-
Experimental and predicted volumetric and refractive index properties of ternary mixtures of Iodoethane with toluene and alcohols at temperature 298.15 K and pressure 101 kPa
The Journal of Chemical Thermodynamics, 2006Co-Authors: Zadjia AtikAbstract:Excess molar volumes V m E and change in refractive indices Δ mix n of the binary mixtures of (toluene + methanol), (toluene + ethanol), (toluene + 1-propanol), (toluene + Iodoethane), (methanol + Iodoethane), (ethanol + Iodoethane), (1-propanol + Iodoethane), and the ternary mixtures of (toluene + methanol + Iodoethane), (toluene + ethanol + Iodoethane), and (toluene + 1-propanol + Iodoethane) were measured with vibrating-tube densimeters and an Abbe-type refractometer at the temperature 298.15 K and the pressure 101 kPa. The experimental V m E and Δ mix n values of the ternary systems were predicted by empirical equations using binary solution data.
Andrew V. Teplyakov - One of the best experts on this subject based on the ideXlab platform.
-
Temperature-Programmed Desorption (TPD) and Density Functional Theory (DFT) Study Comparing the Adsorption of Ethyl Halides on the Si(100) Surface
The Journal of Physical Chemistry C, 2017Co-Authors: Jing Zhao, Benjamin W. Noffke, Krishnan Raghavachari, Andrew V. TeplyakovAbstract:The differences between the dissociative adsorption of chloroethane-d5 (C2D5Cl) and Iodoethane-d5 (C2D5I) on a Si(100)-2 × 1 surface are compared by analyzing the results of density functional theory (DFT) calculations and temperature-programmed desorption (TPD) experiments. The adsorption mechanism for both chloroethane-d5 and Iodoethane-d5 on a clean Si(100)-2 × 1 surface is based on a dissociative chemisorption following halogen–carbon bond cleavage. Further surface transformations upon heating cause hydrogen elimination by ethyl groups, followed by ethylene and hydrogen desorption. The key difference between iodo- and chloro-derivatives is that the corresponding sticking probabilities of chloroethane-d5 and Iodoethane-d5 in the same reaction system are extremely different. The experimental study reveals that the exposure for the monolayer saturation of chloroethane-d5 is 20 times higher than that for Iodoethane-d5. These differences are attributed to the stability of surface-mediated molecular adsorba...
-
Temperature-Programmed Desorption (TPD) and Density Functional Theory (DFT) Study Comparing the Adsorption of Ethyl Halides on the Si(100) Surface
2017Co-Authors: Jing Zhao, Benjamin W. Noffke, Krishnan Raghavachari, Andrew V. TeplyakovAbstract:The differences between the dissociative adsorption of chloroethane-d5 (C2D5Cl) and Iodoethane-d5 (C2D5I) on a Si(100)-2 × 1 surface are compared by analyzing the results of density functional theory (DFT) calculations and temperature-programmed desorption (TPD) experiments. The adsorption mechanism for both chloroethane-d5 and Iodoethane-d5 on a clean Si(100)-2 × 1 surface is based on a dissociative chemisorption following halogen–carbon bond cleavage. Further surface transformations upon heating cause hydrogen elimination by ethyl groups, followed by ethylene and hydrogen desorption. The key difference between iodo- and chloro-derivatives is that the corresponding sticking probabilities of chloroethane-d5 and Iodoethane-d5 in the same reaction system are extremely different. The experimental study reveals that the exposure for the monolayer saturation of chloroethane-d5 is 20 times higher than that for Iodoethane-d5. These differences are attributed to the stability of surface-mediated molecular adsorbates rather than to the differences in the dissociation barriers based on the DFT investigation
-
Interpretation of temperature-programmed desorption data with multivariate curve resolution: Distinguishing sample and background desorption mathematically
Journal of Vacuum Science & Technology A: Vacuum Surfaces and Films, 2015Co-Authors: Jing Zhao, Jia-ming Lin, Juan Carlos F. Rodríguez-reyes, Andrew V. TeplyakovAbstract:Efficient interpretation of thermal desorption data for complex surface processes is often complicated further by species desorbing from heating elements, support materials, and sample holder parts. Multivariate curve resolution (MCR) can be utilized as an unbiased method to assign specific temperature-dependent profiles for evolution of different species from the target surface itself as opposed to traces evolving from the surroundings. Analysis of thermal desorption data for Iodoethane, where relatively low exposures are needed to form a complete monolayer on a clean Si(100)-2 × 1 surface in vacuum, provides convenient benchmarks for a comparison with the chemistry of chloroethane on the same surface. In the latter set of measurements, very high exposures are required to form the same type of species as for Iodoethane, and the detection and analysis process is complicated by both the desorption from the apparatus and by the presence of impurities, which are essentially undetectable during experiments wi...
Maoping Song - One of the best experts on this subject based on the ideXlab platform.
-
regioselective 2 2 2 trifluoroethylation of imidazopyridines by visible light photoredox catalysis
Journal of Organic Chemistry, 2016Co-Authors: Mei Zhu, Xin Han, Zhiqiang Wang, Xinqi Hao, Maoping SongAbstract:A visible-light-induced C-3 selective trifluoroethylation of imidazoheterocycles using 1,1,1-trifluoro-2-Iodoethane as trifluoroethyl radical sources was developed. The methodology enables the introduction of a trifluoroethyl group in a fast and efficient reaction under mild conditions with excellent regioselectivities and high functional group tolerance.
-
Regioselective 2,2,2-Trifluoroethylation of Imidazopyridines by Visible Light Photoredox Catalysis
2016Co-Authors: Mei Zhu, Xin Han, Zhiqiang Wang, Xinqi Hao, Maoping SongAbstract:A visible-light-induced C-3 selective trifluoroethylation of imidazoheterocycles using 1,1,1-trifluoro-2-Iodoethane as trifluoroethyl radical sources was developed. The methodology enables the introduction of a trifluoroethyl group in a fast and efficient reaction under mild conditions with excellent regioselectivities and high functional group tolerance
