13C NMR study of propene dimerization on NiO/SiO2 catalysts

¹³C NMR studies of propene adsorbed on NiO/SiO₂ catalysts show -complex formation for propene with Ni²⁺ ions at low temperatures. Via a coordinative mechanism, 4-methylpentenes and, to a lower extent, 1-hexene are formed. No other isomers are formed as primary products but only via isomerization of the primary products.

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¹³C , NiO/SiO₂ - Ni²⁺ . 4- 1- . .

     

Investigation of sesquiterpene lactones by13C NMR spectroscopy. III.13C MNR spectra of artemin and its derivatives

The¹³C NMR spectra obtained under conditions of complete and incomplete decoupling from protons of the sesquiterpene lactone artemin (I), its dihydro derivative (II), and its acetyl derivative (III) have been studied. An assignment has been made of the chemical shifts of all the carbon atoms by comparison of the¹³C NMR spectra of (I), (II), and (III) with one another and also by comparison with literature information.V. L. Komarov Institute of Botany, Academy of Sciences of the AzSSR, Baku, Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 576–578, September–October, 1983.     

13C NMR and SCCCMO studies on substituted benzophenonetricarbonylchromium complexes

¹³C NMR studies on benzophenonetricarbonylchromium and its p-F, p-Cl and p-OCH₃ derivatives, with the substitutents on the uncomplexed rings, show a small substituent effect on the complexed ring and on the carbons of the Cr(CO)₃ group. The SCCCMO calculations show π-electron donation from the ring to the metal but greater σ-electron back-donation which leaves the ring more negatively charged than before complexation. The chromium atom is more positively charged than it is in benzenetricarbonylchromium. The trends is calculated CO bond orders are in agreement with the trends in CO infrared stretching frequencies.     

13C NMR studies on tricarbonylchromium complexes of dimethylaminofulvene and diphenylfulvene

The ¹³C NMR spectra of tricarbonylchromium complexes of dimethylaminofulvene diphenylfulvene have been studied. Comparison of the ¹³C NMR spectra of these complexes with those of the corresponding non-coordinated fulvenes shows that the contribution from the ylidic structure of the π-ligand in the first complex increases when the Cr atom becomes coordinated, while in the second complex this coordination does not favour a formation of the ylidic structure of the π-ligand.     

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.     

13C NMR of pterocarpans

¹³CNMR spectra of eight pterocarpans are reported Assignments are based on multiplicities and second-order features in off-resonance decoupled spectra and on chemical shifts in model compounds. Comparison of the degree of long-range (C, H) coupling in ¹H-coupled spectra is found useful     

13C NMR spectra of some methylplatinum(IV) complexes

The ¹³C NMR spectra of some methylplatinum(IV) Schiff-base and related complexes have been recorded. The results are interpreted in terms of the differing effects of various donor atoms on a platinumcarbon bond in the trans position.     

13C NMR studies of the interaction of CO with H2 over Rh/La2O3 catalyst

¹³C NMR studies have revealed that the interaction of CO with H₂ over a Rh/La₂O₃ catalyst yields surface particles containing carbonyl groups. Depending on the CO/H₂ ratio, carbonyl groups transform to various products: either alcohols and ethers or acids and esters.

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¹³C , CO H₂ Rh/La₂O₃ , . CO H₂ : .

     

13C NMR spectrum of coumarin

Summary The positions of the signals from the C₃, C₅, C₆, and C₇ carbon atoms in the¹³C NMR spectrum of coumarin have been established with the aid of information obtained from the¹³C NMR spectra of [3-D]-, [4-D]-, and 7-methoxycoumarins and by the use of an additive calculation based on the increments of the methoxy group in the¹³C NMR spectrum of anisole.M. V. Lomonosov Moscow State University Scientific-Research Institute of Pharmacology, Academy of Medical Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 458–462, July–August, 1975.     

13C NMR spectroscopy of cyclopentenpoliols

The ¹³C NMR spectral parameters of eleven cyclopentenpoliols are discussed. Chemical shift criteria to distinguish isomeric 3' and 4' monodeoxy eucommiols have been clearly established.     

Acid-base and redox properties of the TiO2/SiO2 surface

Acid-base and redox properties of TiO₂/SiO₂ surface go through a minimum as a function of temperature. Practical applications of this phenomenon are discussed.     

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.     

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.     

Electronic effects in octahedral π-allyliron complexes: 13C NMR spectra

¹³C NMR spectra have been studied for the three series of allyliron derivatives: (i) C₃HP₅Fe(CO)₃X (X = I, Br, Cl, ONO₂, OCOCH₃, OCOCF₃); (ii) 2-RC₃H₄Fe(CO)₃X (R = CH₃, Br; X = I, Br, Cl, ONO₂, OCOCF₃), and (iii) 1-RC₃H₄Fe(CO)₃X (R = CH₃, C₆H₅; X = Br, Cl, OCOCF₃). The spectra reveal the effect of the nature of the ligand X and substituent R on the chemical shifts of the allyl and carbonyl carbon atoms.     

Influence of fluorine-modified SiO2-surfaces on the properties of V2O5/SiO2 catalysts

The preparation of vanadium catalysts is described using fluorine modified Aerosil as support. It is shown that modification with fluorine changes the concentration and topology of the surface silanol groups and, as a consequence, the catalytic properties.

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, , . , , , .

     

NMR 13C study of the structure of polyethyleneimine

The NMR ¹³C (CMR) spectrum of high molecular weight (M = 20,000) branched polyethyleneimine (PEI) obtained by polymerization of ethyleneimine (EI) in aqueous and alcoholic solutions at 50° with 1,3-dichloropropanol as initiator, contains 8 lines. The lines were identified using CMR spectra of model compounds, i.e. linear PEI, regularly branched PEI, diethylenetriamine and ethyleneimine pentamer. It has been shown that the deshielding effect of the nitrogen atoms on the α-atoms of carbon decreases in the folowing order: N_tert > N_sec > N_prim; with the atoms of carbon in the β-position, the effect increases in the opposite order.A quantitative estimation has been made of the distribution of the diads of elementary units containing the same and different nitrogen atoms. The data have been used to draw some conclusions about the structure of the PEI macromolecule.