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1.
The molecular structure of gaseous epichlorohydrin has been investigated using electron diffraction data obtained at 67°C. The conformational composition at this temperature is such that the molecules exist predominantly in a gauche-2 conformer (where the C---Cl bond is 160° away from the C---O) bond). Refinements showed that 33% (σ = 4) of the molecule exist in the gauche-1 form. The important distances ( rg) and angle () with the associated uncertainties are r(C---H) = 1.095(5) Å, r(C---O) = 1.442(3) Å, r(C---C) = 1.475(8) Å, r(C---C M) = 1.523(7) Å, r(C---Cl) = 1.788(2) Å, CCO = 114° (1), CCC M = 119°(1), ClCC = 108.9° (7), and Tau(ClCCO) = −150°(10) ( gauche-2) and Tau(ClCCO) = 78° (10) ( gauche-1). 相似文献
2.
Dichlorotetramethyldisiloxane is studied by gas-phase electron diffraction at room temperature. The least-squares values of the bond distances ( rg) and bond angles ( ) are: r(C---H)=1.084(5) Å, r(Si---O) = 1.624(2) Å, r(Si---C) = 1.852(2) Å, r(Si---Cl) = 2.067(2) Å, SiOSi = 154.0° (1.5), ClSiO = 110.2° (0.8), ClSiC = 109.6°(0.7), HCSi = 111.7°(1.5), OSiC = 110.0°(0.8), τ 1 (zero corresponds to the Si---Cl bond trans to the Si---O---Si linkage) = 78°(6) and τ 2 = 141°(19). A two-conformer model cannot be ruled out. 相似文献
3.
The molecular structure of 2-furoyl chloride has been investigated by gas-phase electron diffraction at 86°C. Two distinct conformers were identified, a more stable planar form with the furan oxygen and the carbonyl oxygen syn and a less stable planar (or nearly planar) anti form. Assuming that the two forms differ in their geometries only in the O=C---C---O torsion angles and assuming the furan ring to have C 2v symmetry, the results for some of the distances ( ra) and angles ( a) are: r(C---H) = 1.110(20) Å, r(C=O) = 1.207(6) Å, r(C---O) = 1.378(10) Å, r(C??? = 1.465(13) A, ( r(C---C)) (average carbon—carbon distance in the furan ring) = 1.392(8) A Δ r(C---C) (difference between single and double carbon—carbon distances in the furan ring) = 0.069 A (assumed), r(C---Cl) = 1.787(6) A, C=C---COCl = 131.6(9)°, C=C---O = 110.9(4)°, C=C---H = 127.7(13.4)°, C---C=O = 125.8(8)° and C---C---Cl = 111.8(6)°. At 359 K the observed amount of the conformer with the oxygen atoms syn was 69.8(14.2)%. 相似文献
4.
Gaseous 3-chloro-1-butene has been studied experimentally by electron diffraction (ED) at 20 and 180°C, and at these temperatures, 76(10)% and 62(10)%, respectively, of the most stable conformer i.e. the one having a hydrogen atom eclipsing the double bond, were found. The conformer with the chlorine atom eclipsing the C=C bond was also present. However, from the experimental data it was not possible to establish conclusive evidence for the conformer with an eclipsed CH 3 group. Molecular mechanics (MM) calculations and ab initio calculations using a 4-21 basis set were carried out with complete geometry optimization, and calculated parameters from each of the methods were used in combination with the ED data. Such calculations indicated the existence of all three conformers mentioned above. Least-squares analysis including constraints from the ab initio calculation gave as a result the following molecular structure ( ra distances and ??? angles) for the predominant conformer: r(C=C) = 1.337(6) Å, r(=C---C) = 1.503(4) Å, r(C---CH 3) = 1.522 Å, R(C---Cl) = 1.813(4) Å, < r(C---H)> = 1.089(18) Å, ???C=C---C = 122.9(2.1)°, ???C---C---C = 112.6(2.2)°, ???=C---C---Cl = 109.9(0.2)°, ???Cl---C---CH 3 = 109.3°. ?? C=C---H> = 121.9° and ?? C---C---H> = 110.0(1.3)°. The torsional angles were then τ(C=C---C---Cl> = −119.4° and τ(C=C---C---CH 3) = 120.3(2.1)°. Error limits are 2σ (σ includes estimates of systematic errors and correlations), parameters without quoted uncertainties are dependent or were constrained relative to another parameter. Combining the ED data with MM results yielded parameters consistent with those given above. 相似文献
5.
The structure of 1,1-difluorosilacyclopentane has been studied by gas-phase electron diffraction. The molecule is found to have a barrier of pseudorotion of 2.25(90) kcal mol −1. The potential function has minimum at the twist form ( C2) symmetry and maxima at the envelope forms. The major bond distances (itr) g) and valence angles obtained from the least-squares refinements with error estimates are as follow: r(C---H) = 1.128(7) A, r(C---C) av = 1.553(15) A, r(Si---F) = 1.582(6) A, r(Si---C) = 1.853(3) A, (CSiF) = 113.4′(3), CCC = 106°(1), and Tau(C1C2C3C4) = 56.0°(32). 相似文献
6.
The structure of acetyl cyanide has been determined by making joint use of the electron diffraction intensities measured in the present study and the rotational constants reported by Krisher and Wilson. The thermal average bond distances are: rg(C-H) = 1.116±0.011 Å, rg(CN) = 1.167±0.010 Å, rg(C=O) = 1.208±0.009 Å, rg(=C-C) = 1.477±0.008 Å and rg(C-C methyl) = 1.518±0.009 Å. The bond angles in the zero-point average structure ( rav) are: (C methyl-C=O) = 124.6±0.7°, (C-C-C) = 114.2±0.9°, (C-CN) = 179.2±2.2° and (H-C-H) = 109.2±0.7°. The uncertainties represent the estimated limits of experimental error. The C-C single bond placed between the double and triple bonds is longer than those in vinylacetylene, acrylonitrile and propynal. Other structural parameters are also compared with those in related molecules. The infrared and Raman spectra of this molecule have been measured, and Urey-Bradley force constants have been determined. 相似文献
7.
Gaseous di-t-butylamine, NHBu t2, has been studied by electron diffraction at a nozzle temperature of ca. 293 K. The diffraction data reveal that this amine is exceedingly hindered. Repulsive steric interactions between the Bu t groups are mainly relieved by an opening of the CNC valence angle to 135(3)°. Evidence of steric strain may also be found in the non-zero tilts (2–3°) of the Bu t groups, defining the angle of rotation of these groups about axes through the N-bonded carbon atoms orthogonal to the NC 2 plane. The N---C and C---C bonds, 1.467(13) and 1.561(6) Å, respectively, are on the other hand relatively unstrained. Other principal geometrical parameters are unexceptional: C---H = 1.103(10) Å, NCC = 111.3(1.5)° (mean value) and CCH = 106(2)°. The position of the N-bonded hydrogen atom relative to the NC 2 plane could not be determined. The torsional positions of the Bu t groups, with respect to the N---C bonds, could not be derived from least-squares refinements. A large number of models with Bu t groups in various fixed positions were considered; the best fit between the observed and theoretical intensity data was obtained with one Bu t group being twisted 19° away from the position typified by one C---C bond of this group being anti to the remote N---C bond, and the other Bu t group similarly twisted by 30°. When viewed along the N---C bonds, the Bu t groups are twisted in the same direction. Viewed along the C(N)C axis, these groups come close to being staggered with respect to each other. The values of the above bond distances are those of ra parameters. Parenthesized values denote error limits, being least-squares standard deviations multiplied by a factor of three. 相似文献
8.
A gas phase electron diffraction study of 3-bromo-2-methyl-1-propene shows that there is predominantly a gauche conformer present. Data recorded at 20 and 180°C show 4(8) and 5(4)% respectively of a second confomer with a planar heavy atom skeleton. The gauche structural results in terms of ra distances and angles at 20°C were found to be: r(C---C) = 1.331(9) Å, r(C---CH 2Br) = 1.484(6) Å, r(C---CH 3) — r(C---CH 2Br) = 0.017 Å, (assumed), r(C---Br) = 1.965(6) Å, C=C---CH 2Br = 121.5(0.7)°, C=C---CH 2Br — C=C---CH 3 = 0.7° (constraint from molecular mechanics calculation), C---C---Br = 112.2(0.5)°, torsional ANGLE = 112.5(2.2)°. Uncertainties are given as 2σ, where σ includes uncertainties due to correlation among observations, electron wavelength and other parameters used in the data reduction. The results obtained from the 180°C data agree very well with those given above. The molecular mechanics calculations yield information consistent with the experimental results. 相似文献
9.
Microwave spectra of allylsilane and its 13C and deuterium substituted species have been measured and assigned for the skew isomer. The rs structure was determined with the aid of several assumptions. Some of the parameters determined are; r(C=C) = 1.328 ± 0.007 Å, r(C---C) = 1.492 ± 0.008 Å, (CCC) = 126.7 ± 0.8°, (CCSi) = 111.6 ± 0.5° and τ(CCCSi) = 106.8 ± 1.1°. Dipole moments and their components were also determined for the CH 2 = CHCH 2SiH 3 and CH 2=CHCH 2SiD 3 species. Hyperconjugation between the C=C π bond and the C---Si σ bond is discussed. 相似文献
10.
The molecular structure of 1,1,2,2-tetrabromodisilane has been investigated using gas-phase electron diffraction data obtained at 110°C. At this temperature the molecules exist as a mixture of about equal parts ( X = 0.5 ±0.2) of the two conformers with the H---Si---Si---H torsion angle equal to 180° ( anti) or 60° ( gauche). Assuming that the two conformers differ in their geometries only in the torsion angle φ, some of the important distance ( ra) and angle ( ) parameters are: r(Si---Si) = 2.349(19) Å, r(Si---Br) = 2.205(5) Å, r(Si---H) = 1.485 Å (assumed), Br---Si---Br = 110.1(1.6)°, Si---Si---Br = 107.1(1.2)° Si---Si---H = 108.6° (assumed). The error limits are 2σ. The observed conformational composition ( Xanti = 0.5(0.2)) corresponds to an energy difference between the conformers of Δ E = E( gauche) — E( anti) = 0.5 ± 0.6 kcal mol −1, assuming Δ S = Rln2. 相似文献
11.
The geometric structure of (CH 3) 3Si---NSO in the vapour phase has been determined by gas electron diffraction. The molecule possesses a planar Si---N=S=O skeleton with syn conformation. The Si(CH 3) 3 group staggers the N=S double bond. The following skeletal parameters ( ra distances and angles with 3σ errors limits) were obtained: Si---N 1.750(6)Å, N=S 1.508(5)Å, S=O 1.444(4)Å, Si---N=S 133.9(9)°, N=S=O 122.5(10)°. Ab initio calculations (HF/3−21G*) were performed for H 3Si---NSO and confirm the planar syn structure for sulfinyl silanamines. 相似文献
12.
The molecular structure of 3-methylthiophene
has been determined by gas electron diffraction (GED) combined with microwave (MW) spectroscopic data. Ab initio calculations at the HF/3–21G* level were carried out and used as structural constraints in the data analysis. The torsional vibration of the methyl group was treated as a large-amplitude motion. The structural parameters were determined to be: rg(S---C2) = 1.719(2) Å, rg(C2=C3) = 1.370(3) Å, rg(C3---C6) = 1.497(6) Å, rg(C2---H) = 1.101(5) Å, CSC = 91.6(2)°, SC2C3 = 113.3(5)°, SC5C4 = 111.3(3)°, C2C3C6 = 123.2(11)° and C3C6H = 112(2)°. The values of r(S---C2) − r(S---C5) and r(C2=C3) − r(C4=C5) were fixed at the 3–21G* value of 0.002Å. Parenthesized values are the estimated limits of error (3σ) referring to the last significant digit. 相似文献
13.
The molecular structure of 3-methylthiophene
has been determined by gas electron diffraction (GED) combined with microwave (MW) spectroscopic data. Ab initio calculations at the HF/3–21G* level were carried out and used as structural constraints in the data analysis. The torsional vibration of the methyl group was treated as a large-amplitude motion. The structural parameters were determined to be: rg(S---C2) = 1.719(2) Å, rg(C2=C3) = 1.370(3) Å, rg(C3---C6) = 1.497(6) Å, rg(C2---H) = 1.101(5) Å, CSC = 91.6(2)°, SC 2C 3 = 113.3(5)°, SC 5C 4 = 111.3(3)°, C 2C 3C 6 = 123.2(11)° and C 3C 6H = 112(2)°. The values of r(S---C 2) - r(S=C 5) and r(C 2=C 3)- r(C 4 =C 5) were fixed at the 3–21G* value of 0.002 Å. Parenthesized values are the estimated limits of error (3σ) referring to the last significant digit. 相似文献
14.
The geometric structure of (CF 3S) 2C=C(SCF 3) 2 in the vapour phase was determined by electron diffraction. The molecule possesses D2 symmetry with the S---CF 3 bonds oriented perpendicular to the ethene plane, in alternating directions up-down-up-down. The following skeletal geometric parameters were obtained ( ra distances and angles, experimental uncertainties are 3σ values): C=C = 1.34Å (ass.), C(sp 2---S = 1.761(5)Å, S---C(sp 3) = 1.832(5)Å, S---C---C = 119.6(4)°, C---S---C = 100.6(13)°, and ø(C=C---S---C) = 90.9(11)°. The gas phase conformation differs considerably from the crystal structure, where the molecule possesses Ci symmetry and the CF 3 groups, which are bonded to cis-standing sulfur atoms, lie on the same side of the ethene plane with dihedral angles ø(C=C---S---C) of 117° and 127°. 相似文献
15.
The molecular structure of 4,4′-sulfanidyl-bis-thiophenol (C 12H 10S 3) has been determined by gas electron diffraction. Assuming identical geometry and D2h local symmetry for ---SC 6H 4S--- moieties, the following bond lengths ( rg) and bond angles were obtained: C---H = 1.101 ± 0.005, S---H = 1.388 ± 0.019, (C---C) mean = 1.400 ± 0.003, (S---C) mean = 1.778 ± 0.004 Å, C ar---S---C ar = 103.5 ± 1.3, C---C(S)---C = 120.4 ± 0.3, C(H)---C(H)---H = 119.1 ± 0.9 and C---S---H = 94.6 ± 3.1°. Two ratational forms were found to reproduce the experimental data, characterized by dihedral angles of the benzene rings with respect to the C arSC ar plane; 1 = 67.8 ± 2.0°, 2 = 4.5 ± 7.2°, and 1 = 69.4 ± 2.0δ, 2 = −26.6 ± 7.1°. Identical signs of 1 and 2 indicate that the two benzene rings are rotated in the same direction about the respective S central---C axes. 相似文献
16.
The pentaamminecobalt(III) complex with the 3-cyano-2,4-pentanedionate anion coordinated through the nitrile nitrogen has been characterized by X-ray crystallography. The crystals of [(NH 3) 5CoNCacac](Cl)(ClO 4)·2H 2O are triclinic, space group P
, a = 10.245(2) Å, b = 14.071(4) Å, c = 6.971(2) Å, = 90.03(3)°, β = 109.86(2)°, γ = 108.91(2)°, V= 887.1 Å 3, Z = 2, Dc = 1.64 g cm −3, F(000) = 456, Mo- K radiation, λ = 0.71069 Å, μ(Mo- K) = 12.7 cm −1. The structure was determined by the heavy-atom method, and refined by block-diagonal least-squares calculations, R = 0.0537, Rw = 0.0607, for 2499 observed reflections. Principal dimensions are: Co---N(NH 3) trans to NCacac − 1.940(5), other Co---N(NH 3) 1.967(2), Co---N(NCacac −) 1.911(5) Å. The pendant acac moiety is best described in terms of a delocalized bond network with, for example, C---C distances in the range 1.44–1.52(1) Å. Several reactions involving this free acac group are also described including the preparation and characterization of the dimeric species pentaamminecobalt(III) - μ - (3 - cyano - 2,4 - pentanedionato) - bis(propylenediamine) cobalt(III) perchlorate. 相似文献
17.
The geometric structure of c-C 4F 8SF 4 has been determined by gas-phase electron diffraction. The five-membered ring has the twist form ( C2 symmetry) with a puckering amplitude q = 0.42 (2) Å. The following principle geometric parameters ( ra values) with estimated uncertainties have been derived: (C---C) av = 1.541(10), S---C = 1.896(7), S---F e = 1.558(6), S---F a = 1.594(6) Å, CSC = 90.0(9)°, SCC = 109.1(8)°, CCC = 106.5(12)°, F aSF e = 90.5(15)° and F eSF e = 87.7(29)°. Vibrational amplitudes for long non-bonded CF and FF distances indicate a high barrier to pseudorotation of the ring. 相似文献
18.
Structures of the following compounds have been obtained: N-(2-pyridyl)- N′-2-thiomethoxyphenylthiourea, PyTu2SMe, monoclinic, P2 1/ c, a=11.905(3), b=4.7660(8), c=23,532(6) Å, β=95.993(8)°, V=1327.9(5) Å 3 and Z=4; N-2-(3-picolyl)- N′-2-thiomethoxyphenyl-thiourea, 3PicTu2SeMe, monoclinic, C2/ c, a=22.870(5), b=7.564(1), c=16.941(4) Å, β=98.300(6)°, V=2899.9(9) Å 3 and Z=8; N-2-(4-picolyl)- N′-2-thiomethoxyphenylthiourea, 4PicTu2SMe, monoclinic P2 1/ a, a=9.44(5), b=18.18(7), c=8.376(12) Å, β=91.62(5)°, V=1437(1) Å 3 and Z=4; N-2-(5-picolyl)- N′-2-thiomethoxyphenylthiourea, 5PicTu2SMe, monoclinic, C2/ c, a=21.807(2), b=7.5940(9), c=17.500(2) Å, β=93.267(6)°, V=2893.3(5) Å 3 and Z=8; N-2-(6-picolyl)- N′-2-thiomethoxyphenylthiourea, 6PicTu2SMe, monoclinic, P2 1/ c, a=8.499(4), b=7.819(2), c=22.291(8) Å, β=90.73(3)°, V=1481.2(9) Å 3 and Z=4 and N-2-(4,6-lutidyl)- N′-2-thiomethoxyphenyl-thiourea, 4,6LutTu2SMe, monoclinic, P2 1/ c, a=11.621(1), b=9.324(1), c=14.604(1) Å, β=96.378(4)°, V=1572.4(2) Å 3 and Z=4. Comparisons with other N-2-pyridyl- N′-arylthioureas having substituents in the 2-position of the aryl ring are included. 相似文献
19.
The crystal structure of N-(2-hydroxy-5-chlorophenyl) salicylaldimine (C 13H 10NO 2Cl) was determined by X-ray analysis. It crystallizes orthorhombic space group P2 12 12 1 with a=12.967(2) Å, b=14.438(3) Å, c=6.231(3) Å, V=1166.5(6) Å 3, Z=4, Dc=1.41 g cm −3 and μ(MoK )=0.315 mm −1. The title compound is thermochromic and the molecule is nearly planar. Both tautomeric forms (keto and enol forms in 68(3) and 32(3)%, respectively) are present in the solid state. The molecules contain strong intramolecular hydrogen bonds, N1–H1O1/O2 (2.515(1) and 2.581(2) Å) for the keto form and O1–H01N1 for the enol one. There is also strong intermolecular O2–HO1 hydrogen bonding (2.599(2) Å) between neighbouring molecules. Minimum energy conformations AM1 were calculated as a function of the three torsion angles, θ1(N1–C7–C6–C5), θ2(C8–N1–C7–C6) and θ3(C9–C8–N1–C7), varied every 10°. Although the molecule is nearly planar, the AM1 optimized geometry of the title compound is not planar. The non-planar conformation of the title compound corresponding to the optimized X-ray structure is the most stable conformation in all calculations. 相似文献
20.
The molecular structure of CF 3SiH 3 in the gas phase has been determined by electron diffraction analysis. Combined with a B0 value derived from high resolution infrared spectra, this yielded r(SiC), 1.923(3) Å, r(SiH) 1.482(5) Å, r(CF) 1.348(1) Å, FCF 106.7(5)° and HSiH 110.3(10)° ( r° values). The gas phase infrared and liquid phase Raman spectra of CF 3SiH 3, CF 3SiH 2D, CF 3SiD 3 have been measured and assigned, and force constants have been calculated by means of a normal coordinate analysis based on 52 experimental frequencies. The weakness of the SiC bond is confirmed by the low f(SiC) value of 2.54 N cm −1. Infrared spectra recorded with a resolution of 0.04 cm −1 at 240 K revealed rotational structure of vibrational bands. Rotational analyses of most parallel and a few perpendicular bands of CF 3SiH 3 and CF 3SiD 3 have been performed. Ground and excited state vibrational parameters have been obtained and used as supplementary data for the determination of the harmonic force field. Strong blending of all bands due to hot band cascades was noted. 相似文献
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