13C NMR spectra of substituted thiacyclohexanes

Conclusions The use of the¹J_CH values permits making an unequivocal assignment of the¹³C signals in the spectra of substituted thiacyclohexanes. The steric arrangement of the substituants in 2,4-disubstituted thianes can be established on the basis of the chemical shift values of the C⁶ nuclei. The obtained data can be used to identify the cyclic organosulfur compounds that are isolated from crude petroleum.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 452–454, February, 1982.     

13C NMR spectra of cyclopropane derivatives. Stereoisomeric substituted 2-phenylcyclopropanes

Proton-decoupled carbon-13 magnetic resonance spectra of a series of cyclopropane derivatives have been studied. For stereoisomeric substituted 2-phenylcyclopropanes a difference between the isomers has been found in the shieldings of the three-membered cyclic carbons as well as in the shieldings of the carbons of the substituents. The chemical shifts have been interpreted on the basis of an additive approach worked out in a study of the spectra of monosubstituted cyclopropanes and substituted 2,2-diphenylcyclopropanes. Some simple rules have been proposed, which are useful in distinguishing stereoisomeric 1,2-disubstiuted cyclopropanes.     

13C NMR spectral study of polyacetoxyxanthones. IV—13C NMR spectroscopy of substituted xanthones

The ¹³C NMR chemical shifts of nine acetoxyxanthones are reported and identified. The acetoxy substituent effects have been evaluated and the corresponding shift increments proposed.     

13C-NMR spectra of substituted 1,4-dihydropyridines

It has been found that the electron shift in the C₍₂₎=C₍₃₎ bond, under the influence of the substituent attached to the nitrogen atom and the substituents in the 3- and 5-positions, occurs via a -inductive mechanism. 4-(1,4-Dihydropyridyl) functional groups behave as electron donating substituents via an inductive mechanism.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1232–1238, September, 1989.     

A study of sesquiterpene lactones by13C NMR spectroscopy. I.13C NMR spectra of badkhyzin and its derivatives

The¹³C NMR spectra of badkhyzin and its derivatives have been studied.     

Studies in mass spectroscopy—II Mass spectra of substituted furans

The mass spectra of 29 furans, variously substituted with alkyl, aldehyde, ketone, ester, nitrile and nitro groups are reported and discussed. The spectra are generally quite simple and amenable to analysis. Not only do the characteristic m/e values give information as to the type of substituents, but also the operation of certain ortho-effects permits conclusions as to the relative location of functional groups. A number of rearrangement process have been investigated by high resolution measurements and deuterium labelling.     

1H, 13C and 77Se NMR spectra of substituted selenoanisoles

The ¹H, ¹³C and ⁷⁷Se chemical shifts and the ¹J[C(Me)H(Me)], ^1.2J(SeC) and ²J(SeH) coupling constants in 14 para- or meta-substituted selenoanisoles, R? C₆H₄? Se? CH₃, have been measured and the dependence of these parameters on the electronic effects of the substituent R is discussed. A significant (up to 6 ppm) deviation from additivity of the substituent influence on the shielding of the ¹³C ring carbons has been found.     

13C NMR spectra of some N-aryl substituted sulphur–nitrogen compounds

The ¹³C n.m.r. spectra of four classes of N-aryl sulphur–nitrogen compounds are discussed. The para carbon shieldings of the N-phenyl derivatives reflect the substituents effects of the various nitrogen groups. These show large differences for the four classes of compounds due to differences in the electronic structure of the sulphur–nitrogen bond.     

A study of substituent effect on 1H and 13C NMR spectra of mono,di and poly substituted carbazoles

¹H and ¹³C NMR spectra of several substituted carbazoles (Series 1, 2, 3, 4 and 5) were measured. Substituent chemical shifts (SCS's) and Lynch correlations of ¹H and ¹³C nuclei were calculated and the substituent effect on the NMR phenomena was determined. Atomic charge densities for carbazoles of Series 1, 2, 3, 4 and 5 were calculated by using the semi empirical PM3 method. These values also show a linear correlation with the ¹³C chemical shifts.     

A study of sesquiterpene lactones by13C NMR spectroscopy. II.13C NMR spectra of alkhanin,acetylartemisin, and tauremisin

The¹³C NMR spectra of alkhanin, acetylartemisin, and tauremisin have been studied.     

The13C NMR spectra of some polychlorinated dibenzo-p-dioxins. A calculation of13C chemical shifts

The¹³C NMR spectra of a number of polychiorinated dibenzo-p-dioxins (PCDD) were measured. These and previously known spectra were used for the development of a method for calculation of¹³C NMR spectra of chloroaromatics in the framework of a two-particle increment scheme for carbon chemical shifts. The scheme one allows to calculate¹³C chemical shifts for all 75 PCDD.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 760–761, April, 1994.     

The ring opening of substituted cyclopropylidenes to substituted allenes: the effects of steric and long-range electrostatic interactions

Summary It is shown that all stereospecific preferences found experimentally for the ring opening of substituted cyclopropylidenes are satisfactorily reproduced by adding steric and long-range electrostatic interactions to the cyclopropylidene reaction surface. The corresponding surface for dimethyl cyclopropylidene is mapped out in detail. The surface for 3-methyl- and 2-bromo-3-methyl-cyclopropylidene is explored around the transition region. From the success of this approach it is inferred that short-range covalent interactions are unlikely to be responsible for sterospecific preferences found in these systems.Operated for the U.S. Department of Energy by Iowa State University under Contract No. 7405-ENG-82. This work was supported by the office of Basic Energy Sciences     

A study of substituent effect on 1H and 13C nmr spectra of N‐ and C‐substituted carbazoles

¹H and ¹³C nmr spectra of several N‐ and C‐substituted carbazoles (Series 1, 2, 3 and 4) were measured. Correlations between chemical shifts and substituent constants show that these parameters describe properly the substituent effect on the nmr phenomena. Atomic charge densities for carbazoles of Series 1, 2, 3 and 4 were calculated by using the semi empirical PM3 method. These values also show a linear correlation with the ¹³C chemical shifts. The synthesis of several carbazole derivatives 1a – 1g, 2a – 2g, 3a – 3j and 4a – 4g have been carried out according to literature procedures. The carbazoles 3i, 3j and 4c have been synthesized and fully characterized for the first time.     

Proton and 13C NMR spectra of substituted methyl cyanopropionates: Effects of molecular asymmetry

The proton NMR spectra at 220 MHz of two series of substituted cyanopropionates, have been investigated. In addition the ¹³C spectra at 15 MHz of the series I were also studied. In I, where the R groups are diastereotopic, differences are observed in the proton chemical shifts of the CH₃ groups in R for R = CH₃, C₂H₅, n-C₃H₇, i-C₃H₇, n-C₄H₉, n-C₅H₁₁ and n-C₆H₁₃. In II [R′ = n-C₃H₇, CH(CH₃)₂, CH₂CH(CH₃)₂ and C(CH₃)₃] diastereoisomers are found with substantial differences in chemical shifts between corresponding protons. Coupling constants are interpreted in terms of conformational preferences for certain molecules in both series.     

A comparative study of some oxygen and sulphur substituted alkyl radicals

Several sulphur containing alkyl radicals have been generated and their ESR spectra and hyperfine coupling constants compared with those of the oxygen analogues. Deviations from planarity are smaller when a tervalent carbon atom is bonded to sulphur than when bonded to oxygen. Moreover greater delocalization of the unpaired electron is apparent in the sulphur radicals and this leads to higher barriers to internal rotation in radicals of the form H₂SR compared with H₂OR.     

NMR-spectroscopic study of conjugation effects. 9.13C NMR spectra of alkyl vinyl sulfoxides and sulfones

Conclusions Polarization and steric effects of the alkylhetero groups have the main influence on the C^1,2 chemical shifts of the vinyl fragment in alkyl vinyl sulfoxides and sulfones. In sulfones, an appreciable role can be played by a -acceptor interaction between the sulfur atom and the double bond.For the previous communication, see [I].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1007–1011, May, 1980.     

Withasteroids ofPhysalis. V. A study of the1H and13C NMR spectra of the withasteroids visconolide and 28-hydroxywithaperuvin C

The PMR and¹³C NMR spectra of new withasteroids — visconolide and 28-hydroxywithaperuvin C, isolated fromPhysalis viscosa L. — have been investigated. A detailed analysis of the spectral characteristics obtained is given. For visconolide is proposed the structure of 4β,12α,17β,28-pentahydroxy-1-oxo-5β, 6β-epoxy-22R-witha-2,24-dienolide, and for 28-hydroxywithaperuvin C that of 6β,14α,17β,20R, 28-pentahydroxy-l-oxo-22R-witha-2, 4, 24-trienolide.