Association of thiopivalic acid in solutions, as investigated by IR spectra and NMR spectra at low temperatures

1983 ◽  
Vol 39 (2) ◽  
pp. 938-941
Author(s):  
N. S. Golubev ◽  
L. L. Kimtis ◽  
R. A. Shimkus
Keyword(s):  
Ir Spectra ◽  
Low Temperatures ◽  
Nmr Spectra

Dioxobis(Carboxylato)Chromium(VI) and Oxo(Carboxylato)Chromium(III): Reactions of CrO3 with Carboxylic Acid Anhydrides

1984 ◽  
Vol 39 (12) ◽  
pp. 1702-1705 ◽  
Author(s):  
Ramesh Kapoor ◽  
Ramneek Sharma ◽  
Pratibha Kapoor
Keyword(s):  
Carboxylic Acid ◽  
Ir Spectra ◽  
Low Temperatures ◽  
Nmr Spectra ◽  
Room Temperature ◽  
Equimolar Ratio ◽  
H Nmr ◽  
Chromium Vi ◽  
Polar Organic Solvents ◽  
Acid Anhydrides

Reactions of carboxylic acid anhydrides [(RCO)2O where R = CH3, C2H5, n-C3H7 and CHCl2] with excess of chromium (VI) oxide at low temperatures yield chromyl carboxylates, CrO2(OOCR)2. These compounds are non-conducting in polar organic solvents. IR spectra suggest the presence of both unidentate and bidentate carboxylato groups and discrete Cr = 0 units. The 1H NMR spectra show the presence of only one type of carboxylato group.Reactions of carboxylic acid anhydrides with CrO3 in equimolar ratio yield reduced chromium(III) com pounds o f the type CrO(OOCR) at room temperature. Their millimolar solutions in C6H5NO2, CH3NO2 and CH3CN are non-conducting. IR spectra, magnetic susceptibility and some other properties have been investigated. Both types of compounds are polymeric in nature having covalent structures.

Constant Temperature Dewar for NMR Spectra at Low Temperatures

1966 ◽  
Vol 37 (2) ◽  
pp. 238-239 ◽  
Author(s):  
W. B. Rose ◽  
J. W. Nebgen ◽  
F. I. Metz
Keyword(s):  
Constant Temperature ◽  
Low Temperatures ◽  
Nmr Spectra

scholarly journals New Perfluorophtalate Complexes of Platinum(II) With Chemotherapeutic Potential

1996 ◽  
Vol 3 (3) ◽  
pp. 117-122
Author(s):  
M. B. de Oliveira ◽  
J. Miller ◽  
R. E. Banks ◽  
L. R. Kelland ◽  
C. A. McAuliffe ◽  
...  
Keyword(s):  
Ir Spectra ◽  
Ovarian Carcinoma ◽  
Elemental Analysis ◽  
Nmr Spectra ◽  
Carcinoma Cell ◽  
Acquired Resistance ◽  
Cross Resistance ◽  
Carcinoma Cell Lines ◽  
Human Ovarian Carcinoma ◽  
Anti Hiv

Two new platinum(II) complexes have been synthesized and their anti-tumour and anti-HIV activities have been evaluated.The new complexes are: (i) cis-tetrafluorophthalate-ammine-morpholine-platinum(II) or MMF3 and (ii) cis-tetrafluorophthalate- ammine-piperidine-platinum(II) or MPF4. They were characterized by elemental analysis, IR spectra and H1 and C13 NMR spectra.They were tested against five human ovarian carcinoma cell lines, viz., CH1, CH1cisR, A2780, A2780cisR and SKOV-3. They were less active than cis-platin and showed cross-resistance with cis-platin in the CH1cisR and A2780cisR acquired resistance lines.They were also tested for possible anti-HIV activity using the HIV-I IIIB virus and C8166 cells, but they were inactive compared with AZT.

Rotational Tunnelling of CD3Groups in Molecular Crystals as Studied by NMR Spectra

1988 ◽  
Vol 43 (3) ◽  
pp. 219-227 ◽  
Author(s):  
Z. T. Lalowicz ◽  
Ulrike Werner ◽  
W. Müller-Warmuth
Keyword(s):  
Low Temperatures ◽  
Nmr Spectra ◽  
Spectral Response ◽  
Molecular Crystals ◽  
Numerical Calculations ◽  
Methyl Groups ◽  
H Nmr ◽  
Dipole Interactions ◽  
Large Tunnel

Abstract Tunnelling frequencies of rotating CD3 groups in solids between about 20 kHz and 2 MHz may be obtained from the 2H NMR spectra. The theory of the spectral response is developed where quadrupole and dipole-dipole interactions as well as rotational tunnelling are taken into account. Features characteristic of tunnelling, which distinguish the spectra from those of rapidly reorienting deuterated methyl groups, are found from analytically calculated spectra even for the case of very large tunnel splittings. Numerical calculations have been performed for various conditions to deter­ mine the tunnel frequency. Experimental spectra measured at 45 MHz and low temperatures have revealed the appearance of rotational tunnelling in CD3I, CD3COONa, and (CD3COO)2Cu • H2O. In the latter case, a tunnelling frequency of 608 kHz has been extracted from the spectrum at 27 K.

Konformative Beweglichkeit flexibler Ringsysteme. Untersuchungen mit Hilfe der Protonenresonanz-Spektroskopie

1966 ◽  
Vol 21 (4) ◽  
pp. 320-324 ◽  
Author(s):  
S. Kabuss ◽  
A. Lüttringhaus ◽  
H. Friebolin ◽  
R. Mecke
Keyword(s):  
Nmr Spectroscopy ◽  
Low Temperatures ◽  
Nmr Spectra ◽  
Ring Inversion ◽  
Conformational Isomers

The rates of ring-inversion of six- and seven-membered cyclic trisulfides were investigated by nmr-spectroscopy. The JG#-values are higher than those of the corresponding disulfides. but are not high enough for separation of conformational isomers.At low temperatures the nmr-spectra in some cases show the signals of two different conformers.For certain examples simple symmetry-considerations allow the identification of the actual conformation.

FT-IR spectra of proteins at low temperatures

1988 ◽  
Vol 94 (1-6) ◽  
pp. 195-197 ◽  
Author(s):  
Hector L. Casal ◽  
Ulrich K�hler ◽  
Henry H. Mantsch ◽  
Jose L. R. Arrondo
Keyword(s):  
Ir Spectra ◽  
Low Temperatures ◽  
Ft Ir

Direct observation of dienols produced by photochemical enolisation of α,β-unsaturated ketones: rates and activation parameters for dienol reketonisation via a 1,5-hydrogen shift

1987 ◽  
Vol 65 (8) ◽  
pp. 1867-1872 ◽  
Author(s):  
Randy M. Duhaime ◽  
Alan C. Weedon
Keyword(s):  
Activation Energy ◽  
Low Temperatures ◽  
Nmr Spectra ◽  
Arrhenius Plot ◽  
Activation Parameters ◽  
Activation Entropy ◽  
Hydrogen Shift ◽  
Unsaturated Ketones ◽  
Ultraviolet Light Irradiation ◽  
Stable Solutions

The production of stable solutions of Z-dienols by ultraviolet light irradiation of α,β-unsaturated ketones at low temperatures (ca. −76 °C) in d4-methanol is reported. The rates of reketonisation of the dienols via a 1,5-sigmatropic hydrogen shift were determined at various temperatures between −43 °C and + 2 °C by monitoring the proton nmr spectra of the dienols. From the data the activation parameters for the reaction were calculated. For the dienol Z-2-hydroxy-4-methyl-2,4-pentadiene, 2, derived from photoenolisation of 4-methyl-3-penten-2-one, 1, the activation energy from the Arrhenius plot is 62 ± 4 kJ/mol, and the activation entropy and enthalpy from the Eyring plot are −87 ± 15 J/mol K and 60 ± 4 kJ/mol, respectively. For the dienol Z-4-tert-butyl-2-hydroxy-2,4-pentadiene, 4, obtained from photoenolisation of 4,5,5-trimethyl-3-hexen-2-one, 3, the activation energy, entropy, and enthalpy were found to be 47 ± 5 kJ/mol, −135 ± 19 J/mol K, and 45 ± 5 kJ/mol, respectively.

Mechanism of the lithium–iodine exchange in an iodothiophene

2005 ◽  
Vol 83 (9) ◽  
pp. 1577-1587 ◽  
Author(s):  
Hans J Reich ◽  
Wesley L Whipple
Keyword(s):  
Nmr Spectroscopy ◽  
Exchange Reaction ◽  
Low Temperatures ◽  
Nmr Spectra ◽  
Variable Temperature ◽  
Activation Parameters ◽  
Kinetic Scheme ◽  
Hypervalent Iodine ◽  
Metal Exchange ◽  
Complex Lithium

Solutions of 2-lithio-5-methylthiophene (4) were characterized using DNMR techniques and shown to be a mixture of monomer and dimer in THF–Et2O (3:2). The hypervalent iodine ate complex 5 (Ar2I–Li+), a presumed intermediate in the Li–I exchange with 2-iodo-5-methylthiophene, was observed by 13C and 7Li NMR spectroscopy at low temperatures (–130 °C). At higher temperatures, the ate complex coalesced with 2-lithio-5-methylthiophene. A kinetic scheme was developed, which accounts for the exchange of the monomer 4M, dimer 4D, and 2-iodo-5-methylthiophene (6) with the ate complex 5. The rates of the various exchanges were obtained through a DNMR analysis of the variable temperature 13C and 7Li NMR spectra, and the thermodynamic and activation parameters were calculated. The monomer 4M and the ate complex 5 have similar reactivity as aryl donors in the Li–I exchange reaction, but 4M is at least 1000 times as reactive as the dimer 4D towards the iodide.Key words: halogen–metal exchange, lithium iodinate, iodine ate complex, lithium reagent, aggregate reactivity.

N-Tribromphosphazo-Verbindungen / N-Tribromophosphaza-compounds

1971 ◽  
Vol 26 (2) ◽  
pp. 75-78 ◽  
Author(s):  
Herbert W. Roesky ◽  
Graalf Remmers
Keyword(s):  
Ir Spectra ◽  
Elemental Analysis ◽  
Nmr Spectra ◽  
Chemical Behavior ◽  
H Nmr

By reaction of N-sulfuroxideimides with phosphorus-pentabromide the compounds R-SO2NPBr3 (R = CH3 , CF3 , C6H5, p-Cl-C6H4, and p-CH3C6H4) were prepared. Reactions of hexamethyldisilazane and N- (dimethyl) -trimethylsilylamide resulted in the formation of R-SO2NPBr2N (CH3)2, (R = CH3, C6H5), and R-SO2NPBr2NHSi(CH3)3 (R = CF3, p-CH3-C6H4). The properties and the chemical behavior of these compounds are described. Results of IR-spectra, as well as 31P-, 19F-, and 1H-NMR-spectra and elemental analysis characterize the compounds.

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