1H and 13C endor on phenoxyl biradicals randomly oriented in frozen solution

ENDOR measurements have been performed on ¹³C labelled biradicals, namely Yang's biradical and p-phenylenebisgalvinoxyl, in frozen solutions. Besides intense ENDOR lines at the free nuclear Zeeman frequencies, hyperfine shifted ¹H and ¹³ ENDOR lines could be detected with excellent signal-to-noise ratios. From these spectra not only the magnitudes, but also the signs of the hyperfine splitting components relative to the zero field splitting parameter D could be derived. It is demonstrated that the sign of D in Yang's biradical must be negative. This may be due to a spin-orbit coupling contribution to the zero field splitting parameter.     

ST0 CIDNP from triplet biradicals. Determination of the rate constant for biradical scavenging from magnetic field dependent CIDNP

ST₀ type nuclear spin polarization has been observed in the reaction products of photochemically generated acylalkyl biradicals in the presence of a scavenger. From the magnetic field dependence of biradical CIDNP the rate constant k of proton abstraction from 2-methyl-2-propanethiol by the alkyl site of the biradicals has been determined (k = 5.0 × 10⁷ M^?1 s^?1).     

Structural analysis of alkylated coal by 1H and 13C NMR spectroscopy

Summary A method is presented for derivation of a series of structural parameters describing the average molecule of soluble butylated coal. It is based on ¹H and ¹³C NMR spectral data, molecular mass measurement and ultimate analysis. Average structural models of coals can be constructed in this way.

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Strukturanalyse von alkylierter Kohle mit Hilfe der ¹H- und ¹³C-NMR-Spektroskopie

Zusammenfassung Ein Verfahren wird vorgestellt zur Ableitung einer Reihe von Strukturparametern, die das Durchschnittsmolekül von löslicher butylierter Kohle beschreiben können. Es beruht auf ¹H- und ¹³C-NMR-Spektraldaten, Messungen der Molekülmasse sowie der Elementaranalyse. Durchschnittliche Strukturmodelle von Kohlen können dadurch erstellt werden.

     

NMR study (1H, 13C and 29Si) of the methylallylsilanes

¹H, ¹³C and ²⁹Si NMR data for the compounds (CH₃)_xSi(CH₂CHCH₂)_4-x are reported. The ¹H resonances from the π system are indicative of the electron-supplying inductive effect (+I) of the (CH₃SiCH₂, moiety but the corresponding ¹³C_π chemical shifts seem to be influenced by a sterically induced polarization of the C-H bonds. The ¹³C_All, ¹³C_Me and ²⁹Si chemical shift data reveal an important neighbour anisotropy contribution originating from the π system. Ultraviolet study of the compounds mentioned above gives indication of a σ—π conjugation in accordance with PES and ab initio results [1—5]. The trend observed in the various coupling constants is too small to be Interpreted.     

1H and 13C nmr study of conformational and electronic structure of 1-vinylpyrroles

The ¹H and ¹³C NMR spectra of some 2-alkyl- and 2,3-dialkyl-1-vinylpyrroles as well as model 1-unsubstituted pyrroles were studied. Alkyi substituents affect electronic structures of the compounds through steric inhibition of p,π-conjugation and π-induction. Correlations of the ¹³C chemical shifts of the pyrrole ring carbon atoms with the total charge density (CNDO/2) of these atoms are established.     

The thermal rearrangement of tetra-arylated dihydrosemibullvalene derivatives,and 1H/13C NMR-structure correlations

A systematic study of the thermal cyclisation of isomeric di-p-anisyl-diphenylcyclooctatriene derivatives, and of the facile isomerisation of the resulting dihydrosemibullvalenes, with ¹H/¹³C nmr-structure correlations, supports earlier proposals for rearrangement mechanism.     

1H and13C NMR spectra of biologically active compounds

The¹H and¹³C NMR spectra of diols of the hexachlorobicycloheptene and-heptadiene series, and also of the diacetates and sulfites corresponding to them, have been investigated. Criteria for the stereochemical assignment of the compounds mentioned on the basis of chemical shifts and spin-spin coupling constants have been determined.Institute of Chemistry, Bashkir Branch, USSR Academy of Sciences, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 439–443, May–June, 1988.     

The 1H and 13C nuclear magnetic resonance and IR adsorption spectra of substituted polymethylferrocenes

The NMR and IR spectra of sym-polymethylferrocenes have been studied. The abnormal shifts observed of the ¹³C signals from the adjacent methyl groups are discussed in terms of spatial interactions between these groups, which cause charge redistribution in the vicinity of the ¹³C nuclei.     

四萜Methyl Sartortuoate 的分离和NMR归属

从采自海南岛三亚的扭曲肉芝软珊瑚Sarcophyton tortuosum中分离得到3个新四萜和1个已知四萜methyl sar-tortuoate (1). 利用HMQC, ¹H-¹HCOSY, HMBC等二维NMR方法首次对methyl sartortuoate (1)的所有¹H, ¹³C NMR信号进行了完全的归属.     

1H and 13C NMR spectral analysis of some necines of toxic pyrrolizidine alkaloids

Summary The total assignment of the ¹H and ¹³C NMR spectra of the necines of toxic pyrrolizidine alkaloids (retronecine, heliotridine, crotanecine, otonecine), their hydrochlorides and their N-oxides has been performed. The characteristic chemical shift differences between retronecine and heliotridine, as well as the protonation and N-oxidation shift effects in NMR studies of necines at the corresponding position are proposed to be an additional assignment aid. The assignment of the spectra was achieved by the concerted use of 2D correlation spectroscopy.Dedicated to Prof. Dr. Dr. Dres. h. c. Herbert Oelschläger, Frankfurt/Main, on the occasion of his 70th birthday     

NMR (1H, 13C, 29Si) study of some allylhalogenosilanes

¹H, ¹³C and ²⁹Si NMR spectra of the allylchlorosilanes (CH₂CH-CH₂-)_xSiCl_4?x and of triallylbromosilane have been analysed. Results are discussed in terms of inductive and steric effects and of contributions of diamagnetic anisotropy. There is no conclusive evidence for (p-d)π conjugation.     

Are α-alkoxyalkyl complexes special? 13CH coupling constant evidence.

Comlexes of type L_nMCH₂O₂CCMe₃ exhibit relatively large values of ¹J_CH for the α-carbon; however, unexpectedly large values are also found for the methyl analogs, L_nMCH₃. Thus technique does not provide evidence for any unusual interactions in the former. Cleavage of the ester linkage by MeLi proceeded cleanly only for L_nM = CpMo(Co)₃, leading to CpMo(CO)₃^?; with L_nM = Mn(CO)₅ or CpFe(CO)₂ electron transfer processes predominate. Such reactions are also observed for simple metal alkyls such as CpFe(CO)₂CH₃.     

13C and 1H NMR spectra of monosubstituted ferrocenes containing a chiral centre in the substituent

The ¹³C-{¹H} and ¹H NMR spectra of ferrocenyl chalkones (β-benzoylvinylferrocene add cinnamoylferrocene) and their iron carbonyl complexes were recorded. Splitting of the resonances of both α- and β-substituted cyclopentadienyl ring atoms was found in ¹³C-{¹H} NMR spectra of all complexes. In ¹H NMR spectra splitting of the resonances of the substituted cyclopentadienyl ring α-protons was detected only in the case of (cinnamoylferrocene)iron tricarbonyl. The splitting effect mentioned can be due to thesochsochronism (magnetic nonequivalence) of all carbon and hydrogen nuclei because of the iron carbonyl fragment coordination oauses the substituent to become the chiral group. The coordination of iron carbonyl group results in a reduction of the conjugation in the α,β-unsaturated ketone system. This phenomenon is discussed on the basis of ¹³C-{¹H} and ¹H NMR data.