Publications by authors named "Kirsten Aarset"

6 Publications

  • Page 1 of 1

Hydrogen bonding in the gas-phase: the molecular structures of 2-hydroxybenzamide (C7H7NO2) and 2-methoxybenzamide (C8H9NO2), obtained by gas-phase electron diffraction and theoretical calculations.

J Phys Chem A 2013 Apr 2;117(14):3034-40. Epub 2013 Apr 2.

Faculty of Technology, Art and Design, Oslo and Akershus University College of Applied Sciences, PO Box 4, St. Olavs Plass N-0130 Oslo, Norway.

The structures of 2-hydroxybenzamide (C7H7NO2) and 2-methoxybenzamide (C8H9NO2) have been determined in the gas-phase by electron diffraction using results from quantum chemical calculations to inform restraints used on the structural parameters. Theoretical methods (HF and MP2/6-311+G(d,p)) predict four stable conformers for both 2-hydroxybenzamide and 2-methoxybenzamide. For both compounds, evidence for intramolecular hydrogen bonding is presented. In 2-hydroxybenzamide, the observed hydrogen bonded fragment is between the hydroxyl and carbonyl groups, while in 2-methoxybenzamide, the hydrogen bonded fragment is between one of the hydrogen atoms of the amide group and the methoxy oxygen atom.
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http://dx.doi.org/10.1021/jp311003dDOI Listing
April 2013

The molecular structure of hexamethyldigermane determined by gas-phase electron diffraction with theoretical calculations for (CH3)3M-M(CH3)3 where M = C, Si, and Ge.

J Phys Chem A 2010 Jul;114(26):7187-90

Oslo University College, Faculty of Engineering, PO Box 4, St. Olavs Plass N-0130 Oslo, Norway.

Gas-phase electron diffraction (GED) data together with results from ab initio molecular orbital calculations (HF and MP2/6-311+G(d,p)) have been used to determine the structure of hexamethyldigermane ((CH(3))(3)Ge-Ge(CH(3))(3)). The equilibrium symmetry is D(3d), but the molecule has a very low-frequency, large-amplitude, torsional mode (phiCGeGeC) that lowers the thermal average symmetry. The effect of this large-amplitude mode on the interatomic distances was described by a dynamic model which consisted of a set of pseudoconformers spaced at even intervals. The amount of each pseudoconformer was obtained from the ab initio calculations (HF/6-311+G(d,p)). The results for the principal distances (r(a)) and angles (angle(h1)) obtained from the combined GED/ab initio (with estimated 1sigma uncertainties) are r(Ge-Ge) = 2.417(2) A, r(Ge-C) = 1.956(1) A, r(C-H) = 1.097(5) A, angleGeGeC = 110.5(2) degrees, and angleGeCH = 108.8(6) degrees. Theoretical calculations were performed for the related molecules ((CH(3))(3)Si-Si(CH(3))(3) and (CH(3))(3)C-C(CH(3))(3)).
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http://dx.doi.org/10.1021/jp1026042DOI Listing
July 2010

Molecular structures of 3-hydroxybenzoic acid and 4-hydroxybenzoic acid, obtained by gas-phase electron diffraction and theoretical calculations.

J Phys Chem A 2008 Oct 18;112(40):10040-5. Epub 2008 Sep 18.

Faculty of Engineering, Oslo University College, P.O. Box 4, St. Olavs Plass, N-0130 Oslo, Norway.

The structures of 3-hydroxybenzoic acid and 4-hydroxybenzoic acid have been determined by gas-phase electron diffraction using results from quantum chemical calculations to inform the choice of restraints applied to some of the structural parameters. The results from the study presented here demonstrate that resonance hybrids are not as helpful in rationalizing the structures of 2-, 3-, and 4-hydroxybenzoic acids as are models based upon electrostatic effects.
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http://dx.doi.org/10.1021/jp804539uDOI Listing
October 2008

Molecular structures of benzoic acid and 2-hydroxybenzoic acid, obtained by gas-phase electron diffraction and theoretical calculations.

J Phys Chem A 2006 Jul;110(28):9014-9

Oslo University College, Faculty of Engineering, P.O. Box 4, St. Olavs Plass, N-0130 Oslo, Norway.

The structures of benzoic acid (C6H5COOH) and 2-hydroxybenzoic acid (C6H4OHCOOH) have been determined in the gas phase by electron diffraction using results from quantum chemical calculations to inform restraints used on the structural parameters. Theoretical methods (HF and MP2/6-311+G(d,p)) predict two conformers for benzoic acid, one which is 25.0 kJ mol(-1) (MP2) lower in energy than the other. In the low-energy form, the carboxyl group is coplanar with the phenyl ring and the O-H group eclipses the C=O bond. Theoretical calculations (HF and MP2/6-311+G(d,p)) carried out for 2-hydroxybenzoic acid gave evidence for seven stable conformers but one low-energy form (11.7 kJ mol(-1) lower in energy (MP2)) which again has the carboxyl group coplanar with the phenyl ring, the O-H of the carboxyl group eclipsing the C=O bond and the C=O of the carboxyl group oriented toward the O-H group of the phenyl ring. The effects of internal hydrogen bonding in 2-hydroxybenzoic acid can be clearly observed by comparison of pertinent structural parameters between the two compounds. These differences for 2-hydroxybenzoic acid include a shorter exocyclic C-C bond, a lengthening of the ring C-C bond between the substituents, and a shortening of the carboxylic single C-O bond.
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http://dx.doi.org/10.1021/jp0620825DOI Listing
July 2006

Molecular structure of 2,5-dihydropyrrole (C4NH7), obtained by gas-phase electron diffraction and theoretical calculations.

J Phys Chem A 2005 Jun;109(22):4961-5

Faculty of Engineering, Oslo University College, Postboks 4 St. Olavs plass N-0130 Oslo, Norway.

The structure of 2,5-dihydropyrrole (C4NH7) has been determined by gas-phase electron diffraction (GED), augmented by the results from ab initio calculations employing third-order Møller-Plesset (MP3) level of theory and the 6-311+G(d,p) basis set. Several theoretical calculations were performed. From theoretical calculations using MP3/6-311+G(d,p) evidence was obtained for the presence of an axial (63%) (N-H bond axial to the CNC plane) and an equatorial conformer (37%) (N-H bond equatorial to the CNC plane). The five-membered ring was found to be puckered with the CNC plane inclined at 21.8 (38) degrees to the plane of the four carbon atoms.
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http://dx.doi.org/10.1021/jp0407472DOI Listing
June 2005

Molecular structure and conformational composition of 2-chloro-1-phenylethanone, ClH2C-C(=O)Ph, obtained using gas-phase electron-diffraction data and results from theoretical calculations.

J Phys Chem A 2005 Mar;109(9):1897-902

Oslo University College, Faculty of Engineering, P.O. Box 4 St. Olavs plass N-0130 Oslo, Norway.

The structure and conformation of 2-chloro-1-phenylethanone, ClH(2)C-C(=O)Ph (phenacyl chloride), have been determined by gas-phase electron diffraction (GED), augmented by results from ab initio molecular orbital calculations, employing the second-order Møller-Plesset (MP2) level of theory and the 6-311+G(d) basis set. The molecules may exist as a mixture of different conformers with the C-Cl bond either syn (torsion angle phi = 0 degrees ) or gauche to the carbonyl bond. At 179 degrees C, the majority of the molecules (90 +/- 11%) have the gauche conformation (phi = 112(3) degrees). Torsion is also possible about the C-Ph single bond. Both experimental and theoretical data indicated, however, that the phenyl ring is coplanar or nearly coplanar with the carbonyl group. The results for the principal distances (r(g)) and angles (angle(alpha)) for the gauche conformer from a combined GED/ab initio study (with estimated 2sigma uncertainties) are the following: r(C-C)(phenyl) = 1.394(2) (average value) A, r(C(phenyl)-C(carbonyl)) = 1.484(5) A, r(C(carbonyl)-C(alkyl)) = 1.513(5) A, r(C-Cl) = 1.790(5) A, r(C=O) = 1.218(6) A, r(C-H)(phenyl) = 1.087(9) (average value) A, r(C-H)(alkyl) = 1.090(9) A (average value), angle C(phenyl)-C=O = 119.5(9) degrees, angle C(phenyl)-C(carbonyl)-C(alkyl) = 119.2(10) degrees, angle C-C-Cl = 109.8(12) degrees, angle C(2)-C(1)-C(carbonyl) = 122.8(15) degrees, angle C-C(alkyl)-H = 111.2 degrees (ab initio value).
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http://dx.doi.org/10.1021/jp0404192DOI Listing
March 2005
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