Otto Bastiansen

Structure and barrier of internal rotation of biphenyl derivatives in the gaseous state: Part 1. The molecular structure and normal coordinate analysis of normal biphenyl and pedeuterated biphenyl

Abstract The structures of the title compounds have been determined in the gaseous state. Both static and dynamic models have been applied. The structure parameters are found to be: r(C1C1′) = 1.507(4) and 1.489(4). r(C1C2) = 1.404(4) and 1.403(6), r(C2C3)= 1.395(5) and 1.396(8), r(C3C4) = 1.396(5) and 1.398(13), r(CH) = 1.102(2) and r(CD) = 1.095(2), ∠C2C1C6 = 119.4(4) and 117.9(4), ∠/C1C2C3 = 119.4(4) and 121.3(4) respectively for C12H10 and C12D10. Distances, re, are in A and angles, ∠α, in degrees. Both molecules are non planar with a torsional angle equal to 44.4(1.2) and 45.5(1.6) for C12H10 and C12D10 derived from the dynamic model using the potential function V(o) = (V2/2)(1 − cos 2o) + (V4/2)(1 − cos 4o) where V2 = 0,5(1.1) and -0.6(1.9) kJ mol−13 V4 = −6.2(2.3) and −9.5(3.6) kJ mol−1 for C12H10 and C12D10, respectively. The barriers at O° are 6.0(2.1) and 9.9(3.0) kJ mol−1, and at 90° 6.5(2.0) and 9.2 (2.6) kJ mol−1, respectively for C12H10 and C13D13. Uncertainty is one standard deviation from least-squares refinement using a diagonal weight matrix. With the exception of the torsional angles all the geometrical parameters for C12H10 and C12D10 are the same both comparing the two compounds and the results obtained in the gas phase and in the crystal, the experimental errors taken into consideration.

Structure of cyclohexane determined by two independent gas electron-diffraction investigations

Abstract The results of two independent electron-diffraction investigations of cyclohexane are compared. By averaging the results the following parameters and error limits are obtained: r g (CC) = 1.536±0.002 A, r g (CH) = 1.121±0.004 A, and ∠CCC = 111.4±0.2°.

Reinvestigation of the Molecular Structure of 1,3,5,7‐Cyclooctatetraene by Electron Diffraction

The molecular structure of 1,3,5,7‐cyclooctatetraene has been studied by a sector‐microphotometer technique using data extending to very much larger scattering angles than were obtained in earlier investigations. An application of the method of least squares to sector‐microphotometer data in electron diffraction worked out by one of us (KH) has led in three refinement stages to unusually precise values for the parameters. The following are the more interesting parameter values with standard errors. It should be noted these results do not include a possible error of up to 0.2% in the scale of the molecule because of uncertainties in the electron wavelength, nor do they include the effect of correlations among the observations on the standard errors, which we estimate might increase the standard errors by as much as the factor 2½. Molecular symmetry D2d,C=C=1.334±0.001 A,C–C=1.462±0.001 A,C–H=1.090±0.005 A,∠C=C–C=126.46∘±0.23∘,∠C=C–H=118.3∘±5.9∘,aC=C(=〈δl2〉C=C/2)=(103±7)×10−5,aC–C=(147±10)×10−5,aC1···C3=(25...

Molecular Structure of Dicyclopentadienylberyllium (C5H5) 2Be

The molecular structure of gaseous (C5H5) 2Be has been determined from electron‐scattering data. The molecule consists of two planar, symmetrical C5H5 rings. C1–C2 = 1.424±0.002 A and C1–H1 = 1.070±0.005 A. The rings are parallel and staggered with a vertical ring—ring distance h = 3.37±0.03 A. The CH skeleton thus has point group symmetry D5d. The beryllium atom may occupy two alternative positions on the fivefold rotation axis h = 1.485±0.005 A from one ring and h2 = 1.980±0.010 A from the other. The complete molecule thus has point group symmetry C5v.It appears then that the potential energy curve of the beryllium atom has two minima. This is readily understood from an ionic binding model. The discrepancy between the values found for h and h1+h2 is believed to be due to intramolecular motion.

The effect of temperature variatin on the amplitudes of vibration and shrinkage effects in carbon suboxide studied by gas electron diffraction

Abstract C 3 O 2 has been studied in the gas phase by electron diffraction at the nozzle temperature 237°K and 508°K. Preliminary results for the structure parameters are given. The shrinkage effects for three of the non- bonded distances (the O…O-. the longest C…O-. and the C…C distance) are very large and show a significant variation with the temperature. The root-mean-square amplitudes of vibration for the same distances are also very different for the two temperatures. The potential for the CCC bending vibration, and the possibility of determining the “temperature” corresponding to the actual population of the vibrational levels for this vibration are discussed.

Structure and barrier to internal rotation of biphenyl derivatives in the gaseous state: Part 2. Structure of 3,3′-dibromo-, 3,5,4′ -tribronio- and 3,5,3′5′ -tetrabromobiphenyl

Abstract Gas-phase electron diffraction structures of the title compounds have been determined. The structure parameters were found to be: 3,3′-Dibromobiphenyl: r(Br) = 1.892(2), r(CC) ave = 1.398(1), r(ClCl′) = 1.504(5), r(CH)ave = 1.093(5), ∠C6C1C2 = 121.4(4), ∠C2C3Br = 119.4(4). 3,5,4′-Tribromobiphenyl: r(C3Br3) = 1.885(2), r(C4Br4′) = 1.892(2), r(C1C2) = 1.396(1), r(C2C3) = 1.399(1), r(C3C4) = 1.396(1), r(C1′C2′) = 1.394(1), r(C2′C3′) = 1.398(1), r(C3′C4′) = 1.394(1), r(C1C1′)_ = 1.511(9), r(C2H2) = 1.065(6), r(C4H4) = 1.070(6), r(C3′H3′) = 1.066(6), ∠C2C1C6 = 120.5(8), ∠C1C2C3 = 118.9(6), ∠C2′C1′C6′ = 120.4(1.0), ∠C1′C2′C3′ = 120.0(2). 3,5,3′5′ -Tetrabromobiphenyl: r(CBr) = 1.889(1), r(C1C2) = 1.395(5), r(C2C3) = 1.389(7), r(C3C4) = 1.406(9), r(C1C1′) = 1.513(9), r(CH) = 1.062(6), ∠C2C1C6= 120.2(5), ∠C1C2C3 = 119.5(2). Distances ra, are given in Angstroms and angle, ∠α, in degrees referring to the dynamic model. Both static and dynamic models have been applied in investigating the large amplitude motion about the inter-ring CC bond. All title compounds are non-planar. The dynamic model (using potential function V(o) = built1 2 V2 (1 −cos 2o) + built1 2 V4(1 − cos 4o)) gave dihedral angles of 43.8(1,3)°, 42.4(2.6)° and 43.7(0.8)°, and Fourier coefficients V2 and V4 equal to 0.8(0.9) and −5.0(1.8), −1.6(1.2) and 4.5(3.7), 1.3(0.8) and −7.0(1.5) kJ mol−1, respectively for 3,3′ -dibromo-,3,5,4,′-tribromo- and 3.5.3′,5′,-tetrabromo-biphenyl. The numbers in parentheses are one standard deviation as given by least-squares refinements using a diagonal weight matrix.

A theoretical and experimental study of the molecular structure of 1-butyne

Abstract The molecular structure of 1-butyne has been determined by gas electron diffraction (GED) and by theoretical ab initio calculations at the MP2 level and with a 6-311G∗∗ basis set. The vibrational amplitudes and perpendicular amplitude corrections have been calculated based on a force field originating from the ab initio calculations and scaled to observed vibrational frequencies available from the literature. The most important structure parameters obtained from the GED study are the following (standard deviations in parentheses): r a ( C  C ) = 1.217(1) A ; r a ( C  C ) = 1.457(3) A ; r a ( C 3  C 4 ) = 1.544(4) A ; ∠CCC = 111.9(4)°.

The norwegian gas electron-diffraction group

Abstract The present article is an attempt to give some of the historical background for the activities in the Norwegian gas electron-diffraction group. Even professional historians have to base their presentation and their conclusions on limited information and subjective estimates. This is even more the case for an amateur. Facing the challenge of writing this article, it is my intention to try to describe the past, to explain the present and to express some hopes, perhaps dreams, for the future.