Publications (66)160.34 Total impact
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Article: Synthesis, Microwave Spectrum, and Conformational Properties of 2-Fluoroethylazide (FCH(2)CH(2)N(3)).
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ABSTRACT: A novel synthesis producing neat 2-fluoroethylazide (FCH2CH2N3) is described. A conformational analysis using microwave spectroscopy augmented by quantum chemical calculations at the CCSD(T)/cc-pVTZ, B3LYP/aug-cc-pVTZ, and B3LYP/cc-pVTZ levels of theory has been performed for this compound. The spectra of the ground vibrational state and two vibrationally excited states of one rotameric form were assigned. A large number of transitions were assigned and very accurate values were obtained for the rotational and quartic centrifugal distortion constants. The identified conformer has synclinal orientations for the F‒C‒C‒N and C‒C‒N‒N chains of atoms bringing the fluorine atom and the azido group into close proximity. It is concluded from consideration of absolute intensities that this conformer is indeed the preferred form of the molecule in accord with the theoretical calculations. The experimental and CCSD(T) rotational constants are in very good agreement, whereas much larger discrepancies were seen for the experimental and B3LYP quartic centrifugal distortion constants.The Journal of Physical Chemistry A 02/2013; · 2.95 Impact Factor -
Article: Microwave Spectra, Planarity, and Conformational Preferences of cis- and trans-N-Vinylformamide.
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ABSTRACT: The microwave spectra of a mixture of cis- and trans-H‒N‒C‒O forms of N-vinylformamide, (H2C=CHNHC(=O)H) have been measured at room temperature in the 18 - 75 GHz spectral range. The spectra of two forms were assigned. The first of these forms has a cis arrangement for the H‒N‒C‒O chain of atoms, whereas the second form has a trans arrangement. The C‒C‒N‒C chain of atoms is antiperiplanar (180º) in both forms. The inertial defect of the ground vibrational state of cis is ‒0.142(5) × 10‒20 u m2, whereas this parameter is ‒0.087098(26) × 10‒20 u m2 for trans. It is concluded that the equilibrium structures of both cis and trans are completely planar. The dipole moment determined from Stark effect measurements is a = 9.96(8), b = 2.22(3), c = 0 (by symmetry), and tot = 10.20(8) × 10‒30 C m [3.06(2) D], for cis, while a = 7.64(16), b = 9.24(10), c = 0 (by symmetry), and tot = 12.0(2) × 10‒30 C m [3.59(5) D] for trans. The spectrum of one vibrationally excited state, presumably the first excited state of the torsion about the C‒N bond of cis, was assigned and the frequency of this state was determined to be 76(15) cm‒1 by relative intensity measurements. The spectra of two vibrationally excited states of trans were assigned. These states are assumed to be the first excited state of the torsion about the C‒N bond, and a low bending vibration. Relative intensity measurements yielded 101(20) and ca 300 cm‒1, respectively, for the frequencies of these normal vibrations. Accurate values of the quartic centrifugal distortion constants, the dipole moments, and the vibration-rotation constants have been obtained for both cis and trans. The experimental work has been augmented by high-level quantum chemical calculations at the B3LYP/cc-pVTZ and CCSD(T)/cc-pVTZ levels of theory. The theoretical calculation performed without symmetry restrictions correctly predict that cis and trans are both planar. The CCSD(T) rotational constants are in excellent agreement with their experimental counterparts, whereas the B3LYP quartic centrifugal distortion constants and the vibration-rotation constants are in fairly good agreement with experiments. The CCSD(T) dipole moments deviate more than expected from the experimental dipole moments. It is estimated that further conformers of cis and trans must be at least 4 kJ/mol higher in energy.The Journal of Physical Chemistry A 11/2012; · 2.95 Impact Factor -
Article: Microwave spectra and barriers to internal rotation of z- and e-1-propenyl isocyanide.
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ABSTRACT: A synthetic procedure yielding a mixture of Z- and E-1-propenyl isocyanide (CH(3)CH═CHNC) is described. The microwave spectrum of this mixture has been recorded in the 12-100 GHz spectral range, and the spectra of the Z and E isomers have been assigned for the first time. Most transitions of the Z form were split into two components of equal intensity due to tunneling of the methyl group, which allowed the barrier to internal rotation of this group to be determined as 4.0124(12) kJ/mol by fitting 568 transitions with a maximum value of J = 46 using the computer program Xiam. This fit had a root-mean-square deviation as large as 4.325. The same transitions were therefore fitted anew using the more sophisticated program Erham. This fit has a rms deviation marginally better (4.136) than the Xiam fit. No split MW lines were found for E-1-propenyl isocyanide. The absence of splittings is ascribed to a barrier to internal rotation of the methyl group that is significantly higher than the barrier of the Z isomer. It is concluded that the barrier must be larger than 6 kJ/mol for the E form. The experimental work was augmented by quantum chemical calculations at CCSD/cc-pVTZ, B3LYP/cc-pVTZ, and MP2/cc-pVTZ levels of theory. The CCSD method predicts rotational constants of the Z and E forms well. The B3LYP barriers to internal rotation of a series of substituted propenes were calculated and found to be in good agreement with experiments. Calculations of the quartic centrifugal distortion constants of the two 1-propenyl isocyanides by the B3LYP and MP2 methods were less successful.The Journal of Physical Chemistry A 07/2012; 116(35):8833-9. · 2.95 Impact Factor -
Article: Synthesis and microwave spectrum of vinyl isoselenocyanate (H2C═CHNCSe), a compound with a quasilinear CNCSe chain.
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ABSTRACT: The first α,β-unsaturated isoselenocyanate, vinyl isoselenocyanate (H(2)C═CHNCSe), has been synthesized, and its microwave spectrum has been investigated in the 11.5-77.0 GHz spectral range. The microwave work was augmented by quantum chemical calculations using four different methods, namely, CCSD(T), CCSD, B3LYP, and M062X, with the cc-pVTZ basis set. It is generally assumed that two rotamers having the isoselenocyanide group in an antiperiplanar or a synperiplanar position can exist for this compound. However, these four methods all predict that there is only one rotameric form of the molecule, namely, the antiperiplanar form. The CNC angle of the antiperiplanar rotamer is calculated to vary from 151° to 170° depending on the quantum chemical methodology. CCSD(T) and B3LYP potential functions of the in-plane CNC bending vibrations were calculated. These functions have one shallow minimum corresponding to the antiperiplanar form. The spectra of the ground and one vibrationally excited state of this rotamer were assigned. Spectral searches for the synperiplanar form were performed but were not successful, so this form must have a relatively high energy, if it exists at all. The vibrationally excited state is presumably the lowest in-plane bending vibration of the CNC angle. Relative intensity measurements yielded a very low frequency of 18(25) cm(-1) for this vibration. The large-amplitude vibration of this mode suggests that this compound should rather be regarded as having a quasilinear CNCSe link of atoms than a rigid, bent antiperiplanar form.The Journal of Physical Chemistry A 03/2012; 116(16):4074-81. · 2.95 Impact Factor -
Article: Rotational spectrum and conformational composition of cyanoacetaldehyde, a compound of potential prebiotic and astrochemical interest.
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ABSTRACT: The rotational spectrum of cyanoacetaldehyde (NCCH(2)CHO) has been investigated in the 19.5-80.5 and 150-500 GHz spectral regions. It is found that cyanoacetaldehyde is strongly preferred over its tautomer cyanovinylalcohol (NCCH═CHOH) in the gas phase. The spectra of two rotameric forms of cyanoacetaldehyde produced by rotation about the central C-C bond have been assigned. The C-C-C-O dihedral angle has an unusual value of 151(3)° from the synperiplanar (0°) position in one of the conformers denoted I, while this dihedral angle is exactly synperiplanar in the second rotamer called II, which therefore has C(s) symmetry. Conformer I is found to be preferred over II by 2.9(8) kJ/mol from relative intensity measurements. A double minimum potential for rotation about the central C-C bond with a small barrier maximum at the exact antiperiplanar (180°) position leads to Coriolis perturbations in the rotational spectrum of conformer I. Selected transitions of I were fitted to a Hamiltonian allowing for this sort of interaction, and the separation between the two lowest vibrational states was determined to be 58794(14) MHz [1.96112(5) cm(-1)]. Attempts to include additional transitions in the fits using this Hamiltonian failed, and it is concluded that it lacks interaction terms to account satisfactorily for all the observed transitions. The situation was different for II. More than 2000 transitions were assigned and fitted to the usual Watson Hamiltonian, which allowed very accurate values to be determined not only for the rotational constants, but for many centrifugal distortion constants as well. Two vibrationally excited states were also assigned for this form. Theoretical calculations were performed at the B3LYP, MP2, and CCSD levels of theory using large basis sets to augment the experimental work. The predictions of these calculations turned out to be in good agreement with most experimental results.The Journal of Physical Chemistry A 03/2012; 116(16):4047-56. · 2.95 Impact Factor -
Article: Microwave spectrum and conformational composition of 3-fluoropropionitrile (FCH2CH2CN).
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ABSTRACT: The microwave spectrum of 3-fluoropropionitrile, FCH(2)CH(2)C≡N, has been investigated in the whole 17-75 GHz spectral region. Selected portions of the spectrum in the 75-95 GHz have also been recorded. The microwave spectra of the ground state as well as of three vibrationally excited states of each of two conformers have been assigned. The spectra of the vibrationally excited states belong to the lowest torsional and bending vibrations. The F-C-C-C chain of atoms is exactly antiperiplanar in one of these rotamers and synclinal in the second conformer. The F-C-C-C dihedral angle is 65(2)° in the synclinal form. The energy difference between the two forms has been obtained from relative intensity measurements performed on microwave transitions. It was found that the antiperiplanar conformer is more stable than the synclinal form by 1.4(5) kJ/mol. It is argued that the gauche effect is a significant force in this compound. Quantum chemical calculations at the high CCSD(full)/cc-pVTZ, MP2(full)/cc-pVTZ, and B3LYP/cc-pVTZ levels of theory have been performed. Most, but not all, of the theoretical predictions are in good agreement with experiment.The Journal of Physical Chemistry A 12/2011; 116(3):1015-22. · 2.95 Impact Factor -
Article: Microwave spectrum and conformational composition of 2-chloroethylisocyanide.
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ABSTRACT: 2-Chloroethylisocyanide (ClCH(2)CH(2)N≡C) has been synthesized, and its microwave spectrum has been investigated in the 20-97 GHz spectral region. The spectra of (35)Cl and (37)Cl isotopologues of two conformers have been assigned. The Cl-C-C-N chain of atoms is antiperiplanar in one of these rotamers and synclinal in the second. The energy difference between the two forms has been obtained from relative intensity measurements. It was found that the antiperiplanar conformer is favored over the synclinal form by 4.3(8) kJ/mol. Quantum chemical calculations at the CCSD/cc-pVTZ and B3LYP/cc-pVTZ levels of theory have been performed. Most, but not all, of the spectroscopic constants predicted in these calculations are in good agreement with their experimental counterparts. The theoretical calculations correctly predict that the 2-chloroethylisocyanide exists as a mixture of an antiperiplanar and a synclinal conformer, with the former about 3.5 kJ/mol more stable than the latter. Both methods of calculations find that the antiperiplanar rotamer has a symmetry plane. The dihedral angle formed by the Cl-C-C-N link of atoms of the synclinal form is 67° according to the CCSD calculations. It is estimated from a comparison with the experimental rotational constants that this dihedral angle is uncertain by ±3°.The Journal of Physical Chemistry A 11/2011; 115(46):13474-81. · 2.95 Impact Factor -
Article: Microwave spectrum and conformational composition of 2-fluoroethylisocyanide.
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ABSTRACT: The microwave spectrum of 2-fluoroethylisocyanide, FCH(2)CH(2)N≡C, has been investigated in the whole 50-120 GHz spectral region. Selected portions of the spectrum in the range of 18-50 GHz have also been recorded. The microwave spectra of the ground state and vibrationally excited states of two conformers have been assigned. Accurate spectroscopic constants have been derived from a large number of microwave transitions. The F-C-C-N chain of atoms is antiperiplanar in one of these rotamers and synclinal in the second conformer. The energy difference between the two forms was obtained from relative intensity measurements. It was found that the synclinal conformer is favored over the antiperiplanar form by 0.7(5) kJ/mol. Quantum chemical calculations at the high CCSD/cc-pVTZ and B3LYP/cc-pVTZ levels of theory were performed. Most, but not all, of the spectroscopic constants predicted in these calculations are in good agreement with the experimental counterparts. The theoretical calculations correctly indicate that the F-C-C-N dihedral angle in the synclinal form is about 67° but underestimate the magnitude of the gauche effect and erroneously predict the antiperiplanar rotamer to be 1.3-1.6 kJ/mol more stable than the synclinal conformer.The Journal of Physical Chemistry A 07/2011; 115(33):9192-8. · 2.95 Impact Factor -
Article: Synthesis, microwave spectrum, and dipole moment of allenylisocyanide (H2C═C═CHNC), a compound of potential astrochemical interest.
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ABSTRACT: An improved synthesis of a compound of potential astrochemical interest, allenylisocyanide (H(2)C═C═CHNC), is reported together with its microwave spectrum, which has been investigated in the 8-120 GHz spectral range to facilitate a potential identification in interstellar space. The spectra of the ground vibrational state and of five vibrationally excited states belonging to three different vibrational modes have been assigned for the parent species. A total of 658 transitions with a maximum value of J = 71 were assigned for the ground state and accurate values obtained for the rotational and quartic centrifugal distortion constants. The spectra of five heavy-atom ((13)C and (15)N) isotopologues were also assigned. The dipole moment was determined to be μ(a) = 11.93(16) × 10(-30) C m, μ(b) = 4.393(44) × 10(-30) C m, and μ(tot) = 12.71(16) × 10(-30) C m. The spectroscopic work has been augmented by theoretical calculations at the CCSD/cc-pVTZ and B3LYP/cc-pVTZ levels of theory. The theoretical calculations are generally in good agreement with the experimental results.The Journal of Physical Chemistry A 06/2011; 115(27):7978-83. · 2.95 Impact Factor -
Article: Microwave spectrum and conformational composition of 1-vinylimidazole.
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ABSTRACT: The microwave spectrum of 1-vinylimidazole has been investigated in the 21-80 GHz spectral region. The spectra of two conformers have been assigned. One of these forms is planar, while the other is nonplanar with the imidazole ring and the vinyl group forming an angle of 15(4)° from coplanarity. The planar form is found to be 5.7(7) kJ/mol more stable than the nonplanar rotamer by relative intensity measurements. The spectra of 10 vibrationally excited states of the planar form and one excited-state spectrum of the nonplanar form were assigned. The vibrational frequencies of several of these states were determined by relative intensity measurements. The microwave work has been augmented by quantum chemical calculations at the CCSD/cc-pVTZ, MP2/cc-pVTZ, and B3LYP/cc-pVTZ levels of theory. The B3LYP calculations predict erroneously that both forms of 1-vinylimidazole are planar, whereas the MP2 and CCSD calculations correctly predict the existence of a planar and a nonplanar conformer of this compound.The Journal of Physical Chemistry A 06/2011; 115(26):7559-65. · 2.95 Impact Factor -
Article: Microwave spectrum, conformational composition, and intramolecular hydrogen bonding of (2-chloroethyl)amine (ClCH2CH2NH2).
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ABSTRACT: The microwave spectrum of (2-chloroethyl)amine, ClCH(2)CH(2)NH(2), has been investigated in the 22-120 GHz region. Five rotameric forms are possible for this compound. In two of these conformers, denoted I and II, the Cl-C-C-N chain of atoms is antiperiplanar, with different orientations of the amino group. The link of the said atoms is synclinal in the three remaining forms, III-V, which differ with respect to the orientation of the amino group. The microwave spectra of four of these conformers, I-IV, have been assigned. In two of these rotamers, III and IV, the amino group is oriented in such a manner that rare and weak five-membered N-H···Cl intramolecular hydrogen bonds are formed. The geometries of conformers I and II preclude a stabilization by this interaction. The energy differences between the conformers were obtained from relative intensity measurements of spectral lines. The hydrogen-bonded conformer IV represents the global energy minimum. This rotamer is 0.3(7) kJ/mol more stable than the other hydrogen-bonded conformer III, 4.1(11) kJ/mol more stable than II, and 5.5(15) kJ/mol more stable than I. The spectroscopic work has been augmented by quantum chemical calculations at the CCSD/cc-pVTZ and MP2/6-311++G(3df,3pd) levels of theory. The CCSD rotational constants and energy differences are in good agreement with their experimental counterparts.The Journal of Physical Chemistry A 04/2011; 115(17):4334-41. · 2.95 Impact Factor -
Article: Microwave spectra and structures of 1,2-(ortho)- and 1,7-(meta)-carborane, C2B10H12.
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ABSTRACT: The microwave spectra of 1,2- and 1,7-dicarba-closo-dodecaborane(12), C(2)B(10)H(12) (ortho- and meta-carborane), have been recorded for the first time at room temperature in the 32-88 and 24-80 GHz spectral ranges, respectively. The spectra of the parent species (1,2-C(2)(11)B(10)H(12) and 1,7-C(2)(11)B(10)H(12)) have been assigned, together with those of four monosubstituted ((10)B) 1,2-C(2)(10)B(11)B(9)H(12) and 1,7-C(2)(10)B(11)B(9)H(12) isotopologues. The microwave spectra confirm that the structures of each of these two molecules are slightly distorted icosahedrons of C(2v) symmetry. A previous determination of the gaseous structures of these two carboranes by the gas electron-diffraction method was based on several assumptions about the B-B bond length differences. All B-B bond lengths have now been redetermined using the substitution (r(s)) method, which is independent of such restraints. Although several of the r(s) and electron-diffraction bond lengths are in good agreement, there are also differences of up to 0.026 Å. Quantum chemical calculations at the B3LYP/6-311++G(3df,3pd) level of theory have also been performed.The Journal of Physical Chemistry A 03/2011; 115(15):3380-5. · 2.95 Impact Factor -
Article: Microwave spectrum, and conformational composition of (chloromethyl)phosphine (ClCH2PH2).
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ABSTRACT: (Chloromethyl)phosphine, (ClCH(2)PH(2)) has been studied by microwave spectroscopy at -30 °C in the 22-80 GHz spectral interval. The experimental study has been augmented by quantum chemical calculations at the MP2/aug-cc-pVQZ and B3LYP/aug-cc-pVTZ levels of theory. The spectra of the ground as well as of several vibrationally excited states of the (35)ClCH(2)PH(2) and (37)ClCH(2)PH(2) isotopologues of two rotameric forms, denoted I and II, have been assigned. These conformers have different orientations of the phosphino group. I has a symmetry plane, consisting of the Cl-C-P link of atoms, whereas the phosphino group is rotated out of this symmetry plane in II. Conformer I was found to be 4.3(5) kJ/mol more stable than II by relative intensity measurements. The rotational and quartic centrifugal distortion constants calculated using the MP2/aug-cc-pVQZ procedure are in very good agreement with their experimental counterparts. Less good agreement is found in the B3LYP/aug-cc-pVTZ calculations. Both computational procedures predict energy differences between I and II that are close to the experimental energy difference. It is suggested that I is the preferred form of this molecule because it is stabilized by weak intramolecular hydrogen bonding between the chlorine atom and the hydrogen atoms of the phosphino group. Repulsion between the lone electron pair of the phosphorus atom and the chlorine atom also stabilizes I relative to II.The Journal of Physical Chemistry A 10/2010; 114(39):10612-8. · 2.95 Impact Factor -
Article: High resolution millimeter-wave spectroscopy of vinyltellurol.
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ABSTRACT: The millimeter-wave rotational spectrum of vinyltellurol has been recorded and assigned for the first time. To support the spectrum assignment, high level ab initio calculations have been carried out. Geometries, total electronic energies, and harmonic vibrational frequencies have been determined at the MP2 level. A small-core relativistic pseudopotential basis set (cc-pVTZ-PP) was employed to describe the tellurium atom. Two stable conformers, synperiplanar (sp) and anticlinal (ac), have been identified. The sp conformer is planar with a small negative inertia defect of -0.025 u Å(2). The ac conformer was found to be nonplanar with a C-C-Te-H dihedral angle of about 140° from sp. This conformer exhibits a large amplitude motion associated with the torsion about the C-Te bond. The barrier to internal rotation is about 1 kJ/mol, according to the theoretical calculations. For the ac conformation, a torsional potential function consisting of quartic and quadratic terms of the torsional angle has been partially determined from the observed rotational constants.The Journal of Physical Chemistry A 10/2010; 114(46):12202-7. · 2.95 Impact Factor -
Article: Microwave and quantum chemical study of allyldifluorosilane (H(2)C=CHCH(2)SiF(2)H).
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ABSTRACT: The microwave spectrum of allyldifluorosilane (H(2)C=CHCH(2)SiF(2)H) has been investigated for the first time in the 28-80 GHz spectral interval at a temperature of -30 degrees C. The spectrum of the ground vibrational state of one conformer characterized by an anticlinal orientation for the C=C-C-Si chain of atoms and a synclinal conformation for the C-C-Si-H link has been assigned. This rotamer was found to be at least 2 kJ/mol more stable than further rotameric forms. The spectroscopic investigation has been augmented with quantum chemical calculations employing the MP2 and B3LYP methods using the 6-311++G(3df,3pd) basis set. The theoretical predictions are generally in good agreement with the experimental results.The Journal of Physical Chemistry A 06/2010; 114(24):6608-12. · 2.95 Impact Factor -
Article: Microwave and Quantum Chemical Study of Allyldifluorosilane (H2C═CHCH2SiF2H)
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ABSTRACT: The microwave spectrum of allyldifluorosilane (H2C═CHCH2SiF2H) has been investigated for the first time in the 28−80 GHz spectral interval at a temperature of −30 °C. The spectrum of the ground vibrational state of one conformer characterized by an anticlinal orientation for the C═C−C−Si chain of atoms and a synclinal conformation for the C—C—Si—H link has been assigned. This rotamer was found to be at least 2 kJ/mol more stable than further rotameric forms. The spectroscopic investigation has been augmented with quantum chemical calculations employing the MP2 and B3LYP methods using the 6-311++G(3df,3pd) basis set. The theoretical predictions are generally in good agreement with the experimental results.05/2010; -
Article: Microwave spectrum and intramolecular hydrogen bonding of propargyl selenol (HC[triple bond]CCH2SeH).
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ABSTRACT: The microwave spectrum of propargyl selenol, HC[triple bond]CCH(2)SeH, has been investigated in the 19-80 GHz spectral range at -30 degrees C. The spectra of five isotopologues of one conformer, which has a synclinal conformation for the C-C-Se-H link of atoms, were assigned. This conformational preference allows for the formation of a weak intramolecular hydrogen bond between the hydrogen atom of the selenol group and the pi electrons of the triple bond. This hydrogen-bonded conformer is at least 5 kJ/mol more stable than the rotamer having an antiperiplanar conformation for the C-C-Se-H chain. The microwave spectrum clearly shows that the hydrogen atom tunnels between the two mirror-image synclinal forms, but it was not possible to determine the tunneling frequency. The microwave study has been augmented by quantum chemical calculations at the MP2/aug-cc-pVTZ and B3LYP/aug-cc-pVTZ levels of theory. These calculations predict rotational and centrifugal distortion constants that are in good agreement with the experimental counterparts but predict a far too small energy difference of approximately 1.5 kJ/mol for the energy difference between the antiperiplanar and synclinal forms. The conformational properties and internal hydrogen bonding of HC[triple bond]CCH(2)SeH are compared with similar properties of other selenols, which are stabilized by intramolecular hydrogen bonds.The Journal of Physical Chemistry A 04/2010; 114(17):5537-43. · 2.95 Impact Factor -
Article: Microwave and quantum chemical study of propargyl thiocyanate (HC[triple bond]CCH2SC[triple bond]N).
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ABSTRACT: The MW spectrum of propargyl thiocyanate (HC[triple bond]CCH(2)SC[triple bond]N) has been investigated for the first time in the 25-80 GHz spectral region at room temperature or at 0 degrees C. The spectra of the ground vibrational state and of the first excited state of the C-S torsional vibration have been assigned for one conformer. This rotamer, denoted ap, has a symmetry plane (C(s) symmetry) and an antiperiplanar arrangement for the C-C-S-C link of atoms. It has previously been claimed that a conformer that has a synclinal conformation for this chain of atoms is present in the gas in approximately the same concentration as ap (approximately 50% of the gas), but this is not supported by the present experiments, where it is shown that the synclinal rotamer, denoted sc, cannot be present in a concentration exceeding 1/3 of the total. It is therefore concluded that ap must be at least 3.0 kJ/mol more stable than sc. The spectroscopic work has been augmented by quantum chemical calculations at advanced B3LYP/aug-cc-pVQZ, B3LYP/6-311++G(3df,3pd), and MP2/aug-cc-pVTZ levels of theory. These theoretical calculations underestimate the energy difference between ap and sc and predict values for the conformationally important C-C-S-C dihedral angle of the hypothetical synclinal form that deviates by approximately 10 degrees.The Journal of Physical Chemistry A 02/2010; 114(6):2300-5. · 2.95 Impact Factor -
Article: Microwave spectrum of 2-aminooxazole, a compound of potential prebiotic and astrochemical interest.
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ABSTRACT: The microwave spectrum in the 26.6-80 GHz spectral range of 2-aminooxazole, which may have played a potential role in the prebiotic generation of pyrimidine ribonucleotides, is reported. A large number of transitions have been assigned, and accurate values of the rotational and quartic centrifugal distortion constants have been obtained for the four lowest vibrational states. The frequencies of the vibrationally excited states have been determined by relative intensity measurements. The microwave spectra should be useful for the identification of this compound in planetary atmospheres or in interstellar space. 2-Aminooxazole is nonplanar with the amino group bent 35(5) degrees out of the oxazole plane. Inversion of the amino group manifests itself in a characteristic doubling of the microwave transitions and the absence of c-type transitions. The microwave work has been augmented by quantum chemical calculations at the MP2/aug-cc-pVTZ and B3LYP/6-311++G(3df,3pd) levels of theory. The spectroscopic constants obtained by these two methods are in good agreement with one another, as well as with their experimental counterparts. The B3LYP method predicts a more accurate value for the angle between the oxazole ring and the plane formed by the amino group than the MP2 procedure.The Journal of Physical Chemistry A 02/2010; 114(5):2151-6. · 2.95 Impact Factor -
Article: First high resolution spectroscopic studies and ab initio calculations of ethanetellurol.
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ABSTRACT: The millimeter-wave rotational spectrum of ethanetellurol has been recorded and assigned for the first time. The spectroscopic study has been complemented by high level ab initio calculations. Geometries, total electronic energies, and harmonic vibrational frequencies have been determined at the MP2 level. A small-core relativistic pseudopotential basis set (cc-pVTZ-PP) was employed to describe the tellurium atom. Two stable conformers, synclinal and antiperiplanar, have been identified. Both theory and experiment have shown the synclinal form to be more stable by 2 kJ/mol. The doublet structure observed in the rotational spectrum of synclinal conformer is attributed to tunneling motion of tellurol functional group. The energy difference between 0(+) and 0(-) substates split by tunneling has been determined from the observed spectra.The Journal of Physical Chemistry A 02/2010; 114(8):2794-8. · 2.95 Impact Factor
Top co-authors
Top Journals
Institutions
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2002–2012
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University of Oslo
- Department of Chemistry
Oslo, Oslo, Norway
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2011
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Ecole Nationale Supérieure de Chimie de Rennes
Rennes, Brittany, France
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2010
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Université des Sciences et Technologies de Lille 1
Lille, Nord-Pas-de-Calais, France
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2007
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Eötvös Loránd University
Budapest, Budapest fovaros, Hungary
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