E. Vajda

On the molecular structure of (CH3)2NSO2N(CH3)2 as studied by gas electron diffraction

Abstract The following bond lengths and bond angles have been deduced from a vapour phase electron diffraction study of (CH 3 ) 2 NSO 2 N(CH 3 ) 2 : r (C-H) 1.114 ± 0.005 A, r (S-O) 1.432 ± 0.010 A, r (N-C) 1.475 ± 0.013 A, r (S-N) 1.651 ± 0.003 A, ∠N-C-H 109.3 ± 2.0°, ∠C-N-C 118.0 ± 302°, ∠S-N-C 115.2 ± 1.1°, ∠N-S-N 110.5±1.3° and ∠O-S-O 114.7±2.5°. The sulphur bond configuration and the prevailing conformation, which was identical to that in the crystal, are discussed in relation to analogous sulphide and sulphoxide derivatives.

The molecular structure of maleimide: an electron diffraction study

Abstract The molecular structure of maleimide has been investigated by electron diffraction. The experimental data are consistent with a C 2v symmetry model. The following bond lengths ( r g ) and bond angles ( r c ) were determined:NC 1.409 = 0.003, CC 1.508 ± 0.003, C=C 1.344 ± 0.004, and C=O 1.206 ± 0.002 A; CNC 112.0 = 0.2, NCC 106.8 ± 0.2, NC=O 123.9 ± 0.3, and CCH 114.7 ± 1.3°. The electron diffraction structure is in agreement with the results of quantum chemical calculations. The bond lengths indicate a somewhat greater delocalization about the N atom than in the OCCCCO skeleton.

Two independent gas electron diffraction investigations of the structure of plumbous chloride

Abstract The results of two independent electron diffraction analyses of PbCl 2 are compared. The bond lengths ( r g ) and angles ( r α ) were found to be 2.447 ± 0.005 A and 98.7 ± 1.0° (nozzle temperature 853 K, Budapest), and 2.444 ± 0.005 A and 98.0 ± 1.4° (nozzle temperature 963 K, Moscow), respectively.

Molecular structure of (E)- and (Z)-methylcyanovinyl sulphone in the gas phase and in crystal☆

Abstract The structure of (E)- and (Z)-methylcyanovinyl sulphone has been determined by gas electron diffraction and by X-ray crystallography. Considerably widened bond angles in the Z-isomer indicate steric repulsions across the CC bond. The conformer occurring in the crystal and prevailing in the gas phase has nearly eclipsed CC and SO bonds and is stabilized by an intramolecular hydrogen bond in the E-isomer, and by an attractive interaction, O···C(N) 2.78–2.81 A, in the Z-isomer. Parameters (rg with estimated total errors) SO, SCmean, CC, CN and OSCvinyl, OSCmethyl, CSC, SCC, CCC, OSO in the free E-isomer: 1.437(3), 1.781(4), 1.344(5). 1.165(3) A and 105.2(5), 110.2(2), 102.3(9), 114.9(6), 121.5(7), 121.4(7)°; in the free Z-isomer: 1.437(3), 1.780(4), 1.344(5), 1.168(3) A and 109.6(3), 104.3(3), 108.4(5), 124.7(4), 127.3(7), 119.8(0)°. Crystal data: E-isomer: P1, a=5.798(1), b=6.185(1), c=8.959(2) A, α=102.83(2), β=108.74(2), γ=92.18(2)°, Z=2,ϱm=1.476(7),ϱc=1.480 g cm−3; Z-isomer; P21/c, a=10.613(4), b=16.066(4), c=8.630(2) A, α=90, β=122.14(2), γ=90°, Z=8, ϱm=1.395(4), ϱc=1.398 g cm−3. There is an O⋯H contact of 2.26 A between the two independent molecules in the asymmetric unit of the Z-isomer.

Molecular structure of trans- and cis-methylchlorovinyl sulphone

Abstract An electron diffraction analysis of trans and cis isomers of methylchlorovinyl sulphone is described. The bond lengths ( r g ) and bond angles with estimated total errors in parentheses in units of the last digit are as follows: trans isomer SO 1.437(3), SC mean 1.769(9), CCl 1.721(7), CH mean 1.136(6) A, OSO 119.5(8), OSC vinyl 109.2(6), SCC 117.8(7), CSC 102.4(12), CCCl 123.0(13), CCH 121(2), SCH 109.1(10)°; cis isomer: SO 1.437(3), SC mean 1.766(10), CH mean 1.116(5) A, OSO 120.3(10), OSC vinyl 111.1(7), SCC 127.6(10), CSC 101.2(15), CCCl 124.3(10), CCH 120(2), SCH 108(2)°. Two conformers are detected for each geometrical isomer. The CC bond tends to eclipse other bonds in the trans isomer. The absence of eclipsed conformers in the cis isomer may be ascribed to steric hindrance. This is consistent with the opening of the SCC, CCCl and OSC vinyl angles in this isomer as compared with the trans isomer.

Electron diffraction and vibrational spectroscopic investigation of the molecular structure of (chloromethyl)trichlorosilane

Abstract An electron diffraction analysis of the molecular structure of the title compound has been carried out, and related vibrational spectroscopic measurements and calculations have been made. The main bond lengths ( r g and bond angles r α ) are as follows: SiCl, 202.8(2); SiC, 185.1(10); CCl, 179.4(11); CH, 111.2(18) pm; SiCCl, 111.7(4);l ClSiC, 109.95(21)°. The conformation of the molecule is staggered. The barrier to internal rotation is estimated to be around 10 kJ mol −1 .

The preparation and electron diffraction study of dichlorogermylene in the vapour phase

Abstract A preparative technique for dichlorogermylene for vapour phase investigation is described. An electron diffraction study on a mixture of GeCI 2 and GeCl 4 in the vapour phase reproduced earlier results for the tetrachloride structure and showed the bond angle to be 107 ± 5° in GeCl 2 . This result, with its large error limit, is in conformity with structural variations observed for other dihalide molecules.

Molecular structures of (SiCl3)2CH2 and (SiCl3)2CCl2 as studied by electron diffraction

Abstract An electron diffraction analysis of the molecular structures of 1,1,1,3,3,3-hexachloro-1,3-disilapropane and octachloro-1,3-disilapropane has been carried out. Deviations from the staggered conformation are indicated. The data may be approximated by models with C 2 symmetry and a small tilt of the SiCl 3 groups. The main bond lengths ( r g ) and bond angles obtained for (SiCl 3 ) 2 CH 2 are: SiCl, 202.7(4); SiC, 186.6(6); CH, 109.8(24) pm, ClSiCl, 107.9(1); SiCSi, 118.3(7)°; and for (SiCl 3 ) 2 CCl 2 : SiCl, 202.0(4); SiC, 190.2(9); CCl, 179.6(9) pm; ClSiCl, 109.5(1); SiCSi, 120.6(9); ClCCl, 110.9(16); SiCCl, 106.3(3)°.

Electron diffraction investigation of the molecular structure of chloromethyl phosphonic dichloride CH2ClPOCl2

Abstract According to the electron diffraction data on chloromethyl phosphonic dichloride, CH 2 ClPOCl 2 , two conformers with C s and C 1 , symmetry, respectively, are present in approximately equal amounts in the vapour phase. The molecular parameters determined include: r a (PO) 1.457 ± 0.003 A, r a (P—Cl) 2.008 ± 0.004 A, r a (P-C) 1.862 ± 0.019 A, r a (C-Cl) 1.769 ± 0.006 A, ∠Cl-P-Cl 101.3 ± 1.0°, ∠OP-Cl 113.7 ± 2.6°, ∠Cl-P-C 100.8 ± 1.7°, ∠P-C-Cl 113.4 ± 2.5°.

Electron diffraction study of the trichloromethyltrichlorogermane molecular structure and estimation for torsional barrier

Abstract The molecular geometry (in terms of r a and r g internuclear distances) and mean amplitudes of vibration of CCl 3 GeCl 3 have been determined by electron diffraction. The bond lengths are similar to those found in analogous molecules. Although bond angles of unambiguous physical definition have not been determined it is established that the carbon and germanium bond configurations deviate little from the regular tetrahedral arrangement. The molecule performs large amplitude motion around the carbon-germanium bond. The torsional barrier was estimated to be 1.1 kcal mole −1 using J. Karles method [8].