Syntheses and 13C NMR spectra of fluorinated adamantane derivatives

The syntheses of a variety of fluorine-containing adamantane derivatives are described. The ¹³C NMR spectra of those compounds with different configurations are interpreted in terms of through-bond and through-space substituent interactions.     

The solid state 13C-NMR and 19F-NMR spectra of some graphite fluorides

The solid state ¹³C nuclear magnetic resonance spectra of fluorinated graphites show two resonances, one of which is assigned to aromatic carbon and the other to aliphatic carbon. The resonances are very broad with the high-field resonance centered at about 35 ppm below tetramethylsilane (TMS) and a low-field resonance centered at about 160 ppm below tetramethylsilane. The high-field resonance is typical of an sp³-like carbon and the low-field resonance is assigned to sp²-like carbons. It is found that the aromatic resonance in graphite decreases with an increase in fluorination of the graphite fluorides examined in this study. The ¹⁹F nuclear magnetic resonance spectra of C₄F and CF₁ each show one resonance. The fluorine resonance in C₄F is 180 ppm above CFCI₃ whereas the fluorine resonance in CF₁ is 55 ppm above CFCI₃. These peaks are in the range for fluorine bonded to aromatic and aliphatic carbons, respectively.     

13C NMR spectroscopy in diamonds using dynamic nuclear polarization

In diamonds unpaired electrons associated with nitrogen impurities can be used to enhance the ¹³C NMR signal via the solid-state effect. ¹³C spectra of three natural and two synthetic diamonds are shown that were obtained in this manner in 10–30 min.     

13C NMR spectra of some furocoumarins

¹³C NMR spectra of some naturally occurring furocoumarins and derivatives have been examined. The assignment of chemical shifts for all the C atoms has been achieved by using techniques recently reported by Bose et al.     

29Si and 13C NMR spectra of permethylpolysilanes

²⁹Si, ¹³C and ¹H NMR spectra are reported for the series of linear permethylpolysilanes Me(SiMe₂)_nMe where n = 1 to 6, for the cyclic permethylpolysilanes (Me₂Si)_n where n = 5 to 8, and for a few related compounds. For linear polysilanes the ²⁹Si and ¹³C chemical shifts can be accurately calculated from simple additivity relationships based on the number of silicon atoms in α, β, γ and δ positions. Adjacent (α) silicon atoms lead to upfield shifts in the ²⁹Si and ¹³C resonances, whereas more remote silicon atoms lead to downfield shifts. The ²⁹Si chemical shifts of the polysilane chains are linearly related to the ¹³C shifts of the carbon atoms attached to the silicon. The ²⁹Si and ¹³C resonances of the cyclic silanes deviate from this relationship. Ring current effects arising from σ delocalization are suggested as an explanation for the deviations. Proton-coupled ²⁹Si NMR spectra are reported for Me₃SiSiMe₃ and for (Me₂Si)_n, n = 5 to 7.     

1H- and 13C-NMR spectra of palladium and platinum meso-tetraphenylporphyrins

The ¹H- and ¹³C-NMR spectra of palladium and platinum mesotetraphenylporphyrins (TPP) are reported. PtTPP demonstrates spin-spin coupling between platinum and the pyrrole·β-protons and carbons. There is some evidence for spin-spin coupling between platinum and the pyrrole α-carbons. PdTPP and PtTPP also demonstrate upfield shifting of their pyrrole α-carbon ¹³C-resonances. Structural and electronic arguments are advanced to explain this behaviour.     

Microwave spectra of tetrahydroselenophene-α13C, -β13C and molecular ring structure

Microwave spectra of isotopic species α-¹³C and β-¹³C of tetrahydroselenophene molecules have been investigated and rotational constants determined: A = 5608.98 Mc, B = 2819.532 Mc, C = 2022.624 Mc forα-¹³C isotopic species and A = 5695.94 Mc, B = 2770.714 Mc, C = 2009.166 Mc for β-¹³C isotopic species. The r_s-ring structure was found to be Se-C₂ = 1.963 Å, C₂-C₃ = 1.549 Å, C₃-C₄ = 1.527 Å, ∠C₅SeC₂ = 90° 44', ∠SeC₂C₃ = 104° 58', ∠C₂C₃C₄ = 106° 52', the angle of twist = 29° 44'.     

Optimized prediction of 13C-NMR spectra using increments. Comparison with other methods

Summary A detailed comparison of one approach for Optimized P2re diction of ¹³C-NMR Spectra using Increments (OPSI) with a parameter-derived and the HOSE-code method is discussed. The results reveal that the OPSI-approach has several advantages over the methods described in the literature.On leave from: University of Science and Technology of China Hefei, Anhui 230026, The People's Republic of China     

The solid state 13C-NMR spectra of some intercalation compounds

The ¹³C-nuclear magnetic resonance spectra of graphite bromine (C₈Br) and two graphite potassium compounds (C₈K and C₂₄K) have been obtained in the solid state. A similar spectrum is observed for all three compounds. The major feature in all three compounds is a very broad upfield resonance. These spectra are interpreted as indicative of an interaction of the intercalate with the graphite π system leading to more aliphatic-like carbon atoms.     

Quantitative 13C-NMR spectroscopy of coals using 200 MHz-spectrometers

Summary A technique is described for recording all carbons in coals almost quantitatively using 200 MHz NMR-spectrometers. A spinning rate of 8 kHz and single pulse excitation are employed to achieve this aim. The determined aromaticities obtained by means of single-pulse excitation and cross-polarisation experiments are compared. Furthermore, dipolar dephasing experiments are applied to illustrate that a great part of Cq-carbon cannot be observed using the cross-polarisation technique.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday     

13C-NMR of some ajmalane alkaloids

The ¹³C-NMR spectra of the alkaloid ajmaline ($\text{1}$) and its stereoisomers isoajmaline ($\text{2}$), sandwichine ($\text{3}$) and isosandwichine ($\text{4}$) are reported. The different stereochemistry at C (17), C(20) and C(21) of the four isomers can be directly ascertained by chemical shifts data.     

13C NMR spectra of some coumarins of Haplophyllum obtusifolium

Coumaris ofHaplophyllum obtusifolium Ledeb. — obtusinin, capensin, and fraxetin 7-O--D-glucopyranoside — have been investigated by¹³C NMR spectroscopy. Several distinctive features of their NMR spectra have been observed. A complete assignment of the¹³C NMR spectra of these coumarins has been made and their structures have been confirmed.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 796–799, November–December, 1987.     

Fourier 13C NMR and PMR including 13C satellites of oriented cyanopropyne

Fourier ¹³C and proton NMR spectra of cyanopropyne partially oriented by a nematic phase have been recorded and interpreted. It is shown that more accurate measurements are obtained much more rapidly by observing ¹³C satellites by Fourier PMR than by direct observation of the ¹³C spectrum. The geometry has been extracted from direct couplings; a small but systematic discrepancy with microwave spectroscopy is observed for the carboncarbon bond lengths.     

29Si and 13C NMR spectra of chloro- and fluoro-substituted linear permethylpolysilanes

²⁹Si and ¹³C NMR spectra are reported for the three halopolysilane series Me(SiMe₂)_nCl, Cl(SiMe₂)_nCl and F(SiMe₂)_nF, where n = 2 to 6. Except for the dihalodisilanes (XSiMe₂)₂, data for all of the compounds fit linear relationships based on substituent constants for chlorine or fluorine atoms in the α, β and γ positions. The effects of halogen substitution on ²⁹Si and ¹³C chemical shifts are rapidly attenuated along the polysilane chain, becoming negligible four atoms away from the halogen. The NMR data provide no evidence for long-range electronic transmission from chlorine or fluorine in halopermethylpolysilanes of the type suggested by other workers [1].     

13C nuclear magnetic resonance spectra of ethers and glycols

The ¹³C NMR spectra of 21 linear and branched ethers together with the corresponding alcohols have been determined in an attempt to correlate the shieldings in both series. It has been found that the shielding of a carbon in an acyclic ether can be given by the summation of additive shift parameters for substituents and correction parameters for the substitution patterns based on the shielding of the parent alcohol. On examination of solvent-induced shifts for α- and β-carbons in ethers and alcohols, significant ones have been noted in carbon tetrachloride→dimethylsulfoxide and carbon tetrachloride→trifluoroacetic acid. No appreciable concentration-dependent shifts of the shieldings have been observed in both ethers and alcohols. For the shieldings of α-carbons in acyclic glycols, it has been noticed that the observed and predicted values are in accord in 1,3-, 1,4- and 1,5-glycols but deviate in 1,2-glycols. The latter has been examined in a polycyclic system, where the deviations ( > 3·5ppm) in a cis (gauche) 1,2-glycol are larger than those (<2·5 ppm) in a trans (anti-parallel) 1,2-glycol.     

13C NMR spectra and structure of some coumarin derivatives

The results are given of a study of the¹³C NMR spectra of (–)-3(R)-decursinol, obtusifol, bergapten, isoimperatorin, and oxypeucedanin and its hydrate. The possibility has been shown of using the principle of additive contributions in the assignment of the signals of the carbon atoms in the compounds under investigation.Institute of Toxicology, Ministry of Health of the USSR, Leningrad. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 301–307, May–June, 1982.     

The 13C NMR spectra of π-arenechromium carbonyl complexes

The ¹³C NMR spectra of π-arenechromium complexes XC₆H₅Cr(CO)₂L (where I, L  CO; II, L  PPh₃; X  aliphatic and aromatic substituents) were investigated. The effect of the nature of the substituent X on the chemical shifts of the carbon atoms of the aromatic ring in these complexes was analyzed.It was established that a correlation exists between δ(¹³C) and σ_R (Taft's constant) in complexes I, not only for C(4) nuclei but also for C(3) metal atoms, the difference being that the slopes of the corresponding curves are opposite.