Conformational analysis.  I.  Molecular structure, composition, trans-gauche energy and entropy differences, and potential hindering internal rotation of gaseous oxalyl chloride as determined by electron diffraction

Hagen, Kolbjørn; Hedberg, Kenneth

doi:10.1021/ja00785a002

Cited by 154 publications

(44 citation statements)

References 1 publication

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“…These authors also find the trans conformer to be the most stable and the torsional potential energy curve to have the same general shape as that shown in Figure 2. The trans-cis energy difference is 13.4 compared with 24.0 kJ mol-' in this study, and the gauche minimum is at 1 3 1 O (trans 0" convention) with a trans-gauche energy difference of 3.3 kJ mol-', compared with a minimum at 130" and an energy difference of 9.5 kJ mol-'.…”

Section: Appendix Estimation Of the Correlation Energy For 23-diaza-mentioning

confidence: 41%

Rotation about the CN bond in 2‐aza‐1,3‐butadiene and the NN bond in 2,3‐diaza‐1,3 butadiene: A molecular orbital study

Bock¹,

George²,

Trachtman³

1984

J Comput Chem

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The geometry and energy of 2-aza-1,3-butadiene and 2,3-diaza-1,3-butadiene have been calculated using the 6-31G* basis set as a function of the CNCC and CNNC dihedral angles, respectively. With the 2-aza derivative potential minima are located at 0 " (trans) and at about 130 ". for a gauche structure approximately 9.5 kJ mol-' less stable than the trans. Potential maxima are at about 75" giving a gauche barrier height of approximately 19 kJ mol-' relative to the trans structure, and at 180" (cis) giving a barrier height of approximately 14.5 kJ mol-' relative to the 130' gauche structure. With the 2,3-diaza derivative the gauche barrier has disappeared and there are a series of gauche structures in the region 70 O -100 O of almost equal energy, 12.5-15 kJ mol-' less stable than the trans. In addition the cis barrier is much greater, nearly 70 kJ mol-' relative to the trans structure. Inclusion of electron correlation, accounting for about 50% of the correlation energy, produces no significant changes in the shape of the potential energy curves. There are systematic and progressive changes in almost all the geometrical parameters as the =CH-groups in butadiene are replaced by =N-. The outward tilt and compression within the methylene groups show adverse steric interactions to be operative in the cis structures. The values of V,, indicate that gauche structures of both the 2-aza and the 2,3-diaza derivatives near the cis structure are more compact (as with butadiene), and gauche structures of the 2-aza derivative near the trans structure are less compact (as with butadiene). Originating in the changes in bond lengths and bond angles, rotation-independent nuclear-nuclear interactions again play an important role.

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Section: Appendix Estimation Of the Correlation Energy For 23-diaza-mentioning

confidence: 41%

Rotation about the CN bond in 2‐aza‐1,3‐butadiene and the NN bond in 2,3‐diaza‐1,3 butadiene: A molecular orbital study

Bock¹,

George²,

Trachtman³

1984

J Comput Chem

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“…The optical densities were measured with a Joyce Loebl double-beam microdensitometer. The data were reduced in the usual way [27][28][29]. Ranges of data were 2.00 _< s/]k -I <_ 15.00 and4.00 _< silk -I <-30.00 for 1-chlorobutane and 2.00 <_ slY, -~ <_ 15.00 and 4.00 < slY, -I <_ 26.00 for 1-bromobutane and l-iodobutane.…”

Section: Experimental Section and Data Reductionmentioning

confidence: 99%

Molecular structure and conformational composition of 1-Chlorobutane, 1-Bromobutane, and 1-Iodobutane as determined by gas-phase electron diffraction and ab initio calculations

Aarset¹,

Hagen²,

Stølevik³

et al. 1995

Struct Chem

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Gas-phase electron diffraction (ED), together with ab initio molecular orbital calculations, have been used to determine the structure and conformational composition of 1-chlorobutane, 1-bromobutane, and 1-iodobutane. These molecules may in principle exist as mixtures of five different conformers, but only three or four of these were observed in gas phase at temperatures of the ED experiments, 18~ 18~ and 23~ respectively. The observed conformational compositions (1-chlorobutane, 1-bromobutane, and l-iodobutane) were AA (13 + 12%, 21 + 14%, 19 + 17%), GA (60 d-13%, 33 + 32%, 17 + 31%), AG (12 + 16%, 8 + 12%, < 1%), and GG (12 + 16%, 38 5: 34%, 64 5: 31%). A and G denotes anti and gauche positions for the X--CI--C2--C3 (X = C1, Br, I), and the C~--C2--C3--C 4 torsion angles. The results for the most important distances (rs) and angles ( / ~) from the combined ED/ab initio study for the GA conformer of 1-chlorobutane, with estimated 2a uncertainties, are r(C~--C2) = 1.519(3) .~,, r(C2--C3) = 1.530(3) tk, r(C3--C4) = 1.543(3) /~., r(Ci--Cl) -1.800(4) .A.

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“…Six diffraction photographs from the long and four from the short nozzle-to-plate distances were used. Optical densities were measured using a Joyce Loeble dou- ble-beam microdensitometer, and the data were reduced in the usual way [15][16][17]. In order to reduce the noise in the data the short camera photographs were traced twice.…”

Section: Experimental Section and Data Reductionmentioning

confidence: 99%

Structure and conformation of 1-Bromopropane: A gas-phase electron-diffraction investigation using microwave-spectroscopy data and results from ab initio calculations as constraints

Hagen¹,

Stølevik²

1995

Struct Chem

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Conformational analysis. I. Molecular structure, composition, trans-gauche energy and entropy differences, and potential hindering internal rotation of gaseous oxalyl chloride as determined by electron diffraction

Cited by 154 publications

References 1 publication

Rotation about the CN bond in 2‐aza‐1,3‐butadiene and the NN bond in 2,3‐diaza‐1,3 butadiene: A molecular orbital study

Rotation about the CN bond in 2‐aza‐1,3‐butadiene and the NN bond in 2,3‐diaza‐1,3 butadiene: A molecular orbital study

Molecular structure and conformational composition of 1-Chlorobutane, 1-Bromobutane, and 1-Iodobutane as determined by gas-phase electron diffraction and ab initio calculations

Structure and conformation of 1-Bromopropane: A gas-phase electron-diffraction investigation using microwave-spectroscopy data and results from ab initio calculations as constraints

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