High resolution infrared spectrum and molecular structure of dichloroacetylene

The infrared spectrum of dichloroacetylene, prepared by the pyrolysis of dichloromaleic anhydride at 1000°C, has been recorded at both low and high resolution. In the low resolution spectrum a number of combination bands not previously observed have been assigned, the infrared active fundamentals have been reassigned, and a center wavenumber value has been determined for the Raman activev ₁ fundamental. The high resolution spectra of a number of fundamental bands, summation bands, and one difference band for the isotopomers,³⁵CICC³⁵CI and³⁵CICC³⁷CI, have been assigned, while a more limited number of bands has been assigned for the species³⁷CICC³⁷CI and³⁵CI¹³CC³⁵CI. The resultant rotational and vibration-rotation constants have been used to obtainr _o,r _e,r _s, and partial r_s structural parameters. The most reliable bond lengths are obtained from the partialr _s treatment and are 164.105(53) pm for the C-CI bond and 119.203(79) pm for the CC bond.     

The proton spectrum including 13C-satellites of π-benzenechromium tricarbonyl in a nematic solvent

The proton spectrum of π-benzenechromium tricarbonyl with ¹³C-satellites due to ring- and carbonyl-carbons at natural abundance has been investigated in a nematic solvent. The structural data are found to be in agreement with those from electron and neutron diffraction measurements. The proton–proton indirect coupling constants have also been determined.     

High resolution 13C NMR spectroscopy V—structure dependence of the 13C,H coupling constants in aceheptylene,azulene and 5-azaazulene

In order to study the structure dependence of the ¹³C,H coupling constants in polycyclic conjugated π electron systems with 5-and 7-membered rings, the ¹H coupled ¹³C NMR spectra of aceheptylene, azulene and 5-azaazulene have been analysed. The results are discussed, including published data of monocyclic reference compounds, and are compared to theoretical values calculated by the FPT-INDO method. It is shown that, first, the geminal ¹³C,H couplings in the unsaturated 5-membered carbocycles are predominantly dependent on CC bond lengths. Second, the vicinal ¹³C,H coupling constants in 5- as well as in 7-membered unsaturated carbocyclic rings can be linearly related to the lengths of the central CC bonds. Third, the vicinal inter-ring couplings show a large variation and give information on ring junction, thus being of special value in structure determination and are governed mainly by the bond angles. Fourth, the calculated ¹³C,H couplings across one and two bonds are totally useless for practical purposes; those across three bonds, however, at least reflect the experimental trends.     

High resolution 13C and 1H NMR spectral analysis of 1-azafluorene

An analysis of the ¹H and ¹³C spectra of 1-azafluorene has been carried out using computer calculations and homo- and heteronuclear double resonance techniques. The ⁴J, ⁵J and ⁶J long-range coupling constants of the 9-CH₂ group protons with the protons of the pyridine and the phenylene rings have been observed and measured. The long-range J(CH) values in the ¹H coupled ¹³C spectrum have been assigned and measured on a first-order basis.     

Investigation of the structure and 13C NMR spectrum of 5-phenylbarbituric acid

Crystals of 5-phenylbarbituric acid, 2 , are monoclinic, space group C2/c. There are 8 molecules in the unit cell of dimensions a = 20.218(3), b = 7.477(1), c, = 12.443(2), β = 111.54° and V = 1749.6(4) ų. Full-matrix least-squares refinement has reached R = 0.039. This is the first barbiturate reported to exist in the enol form in the solid state. There is extensive hydrogen bonding between adjacent molecules which gives rise to very dense crystals. The ¹³C-nmr spectroscopy shows that 2 exists in both enol and keto forms in DMSO solution.     

13C NMR spectra of iron tricarbonyl complexes of benzolonium ions

Conclusions The¹³C NMR spectroscopy data obtained for the iron tricarbonyl complexes of the benzolonium ions are in agreement with the postulate that the iron tricarbonyl fragment takes an effective part in a delocalization of the positive charge.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 705–707, March, 1973.     

High resolution 13C spectroscopy by Fourier transform NMR. Thiete sulfone

The high resolution ¹³C NMR spectrum of thiete sulfone (obtained without wide-band ¹H decoupling) indicates that ring strain and re-hybridization in this small ring compound are significant. Pulsed-Fourier operation allows rapid determination of spectral parameters. Experimental acquisition time by pulsed NMR without ¹H decoupling is comparable to the experimental time required for swept ¹³C NMR with complete ¹H decoupling.     

The structure of pyrazine determined from its proton magnetic resonance spectrum,including the carbon-13 satellites

The structure of pyrazine partially oriented in a liquid crystal has been determined from its proton magnetic resonance spectrum utilising the ¹³C satellites (at natural abundance). Carbon–carbon, carbon-hydrogen and hydrogen–hydrogen internuclear distance ratios have been determined.     

The 13C NMR spectrum of coumarandione

A re-examination of the ¹³C NMR spectra of coumarandione and isatin with the aid of proton-coupled ¹³C NMR spectra and selective proton decoupling experiments is reported.     

13C NMR spectrum of lagochilin and its derivatives

Summary The¹³C NMR spectra of lagochilin and its derivatives have been studied. A complete assignment has been made of the lines of the spectrum and the values of the chemical shifts of the carbon atoms have been discussed in connection with the spatial structure of the molecules of these compounds.V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 41–43, January–February, 1979.     

High resolution FT-IR spectrum of tricarbon bisulfide,SCCCS

The high resolution Fourier transform infrared spectra of thev ₄-v ₂ andv ₇ band systems of tricarbon disulfide, SCCCS, were measured with a Bomem D A3.002 interferometer and an apodized resolution of 0.004 cm^–1. The rotational structure of the bandsv ₄-v ₂, (v ₄+v ₇)–(v ₂+v ₇), (v ₄+2v ₇)–(v ₂+2v ₇) andv ₇ could be resolved and assigned. The analysis confirmed that SCCCS displays the dynamics of a linear molecule.     

High resolution absorption spectrum of dianilino in the vapor phase

Photophysical and photochemical properties of diradical in the first excited state is recorded for the very first time with the IR, band structure for dianilino molecule at room temperature, in the vapor phase. In this experiment high resolution absorption spectra of anilino free radical, dianilino, aniline in the vapor phase and silicon dioxide in the solid state were recorded by flash photolysis technique photographically. Silicon dioxide absorption band between 250 and 255 nm were also observed for the reaction cell, because the cell and windows of the cell material were spectrosilica grade fused quartz. And this absorption band also used as wavelength calibration for all the photoproducts formed in the reaction cell during optical pumping.     

Interpretation of the 13C NMR spectrum of physostigmine

The 25.1 MHz ¹³C nmr spectrum of physostigmine in deuteriochloroform has been reanalysed with the aid of high resolution proton coupled spectrum and selective proton irradiation experiments. In addition to unambiguous assignment the analysis yielded values for carbon-proton coupling constants.     

Rotational spectrum and carbon-13 hyperfine structure of the C3H, C5H, C6H, and C7H radicals

By means of Fourier transform microwave spectroscopy of a supersonic molecular beam, we have detected the singly substituted carbon-13 isotopic species of C(5)H, C(6)H, and C(7)H. Hyperfine structure in the rotational transitions of the lowest-energy fine structure component ((2)Pi(12) for C(5)H and C(7)H, and (2)Pi(32) for C(6)H) of each species was measured between 6 and 22 GHz, and precise rotational, centrifugal distortion, Lambda-doubling, and (13)C hyperfine coupling constants were determined. In addition, resolved hyperfine structure in the lowest rotational transition (J = 32-->12) of the three (13)C isotopic species of C(3)H was measured by the same technique. By combining the centimeter-wave measurements here with previous millimeter-wave data, a complete set of (13)C hyperfine coupling constants were derived to high precision for each isotopic species. Experimental structures (r(0)) have been determined for C(5)H and the two longer carbon-chain radicals, and these are found to be in good agreement with the predictions of high-level coupled-cluster calculations. C(3)H, C(5)H, and C(7)H exhibit a clear alternation in the magnitude and sign of the (13)C hyperfine coupling constants along the carbon-chain backbone. Because the electron spin density is nominally zero at the central carbon atom of C(3)H, C(5)H, and C(7)H, and at alternating sets of carbon atoms of C(5)H and C(7)H, owing to spin polarization, almost all of the (13)C coupling constants at these atoms are small in magnitude and negative in sign. Spin-polarization effects are known to be important for the Fermi-contact (b(F)) term, but prior to the work here they have generally been neglected for the hyperfine terms a, c, and d.     

High resolution proton magnetic resonance spectra of heterocyclics 1,4-benzodithiin and 1,4-benzodioxin

The proton magnetic resonance spectra of 1,4-benzodithiin and 1,4-benzodioxin have been fully analyzed. The effects of the substituent heteroatoms on the chemical shifts of the various protons in the two molecules have been discussed.     

Molecular structure of α-methylstyreneiron tricarbonyl

Conclusions Breakdown in benzene ring aromaticity occurs in the complex of -methylstyrene with iron tricarbonyl, leading to pronounced alternation of the C-C bond lengths in the ring.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 590–593, March, 1985.