Hydrolysis kinetics of ATBS polymers at elevated temperature, via 13 C NMR spectroscopy, as basis for accelerated aging tests

2,7-Dimethyl-2,6-octadiene is formed in the catalytic solution for the dimerization of 2-methyl-1,3-butadiene to β-myrcene (3-methylene-7-methyl-1,6-octadiene), as revealed by mass spectrometry and 13C NMR spectroscopy. Visual observations together with the results of gas chromatographic analysis of the catalytic solution suggest that the formation of 2,7-dimethyl-2,6-octadiene is associated with the transition of the alkali metal (sodium) from the solid phase into the solution. A reaction pathway is suggested accounting for the formation of 2,7-dimethyl-2,6-octadiene in the system.

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Catalytic activity of rhodium(I) complexes containing (ω-trimethylsilylalkyl)diphenylphosphines

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19802219 ◽

1980 ◽

Vol 45 (8) ◽

pp. 2219-2223 ◽

Cited By ~ 6

Author(s):

Marie Jakoubková ◽

Martin Čapka

Keyword(s):

Catalytic Activity ◽

Nmr Spectroscopy ◽

Ir Spectroscopy ◽

Electron Density ◽

Phosphorus Atom ◽

Proton Acceptor ◽

Trimethylsilyl Group ◽

Kinetics Of

Kinetics of homogenous hydrogenation of 1-heptene catalysed by rhodium(I) complexes prepared in situ from μ,μ'-dichloro-bis(cyclooctenerhodium) and phosphines of the type RP(C6H5)2 (R = -CH3, -(CH2)nSi(CH3)3; n = 1-4) have been studied. The substitution of the ligands by the trimethylsilyl group was found to increase significantly the catalytic activity of the complexes. The results are discussed in relation to the electron density on the phosphorus atom determined by 31P NMR spectroscopy and to its proton acceptor ability determined by IR spectroscopy.

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Non-cyclol (lactame) ergot alkaloids

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19823312 ◽

1982 ◽

Vol 47 (12) ◽

pp. 3312-3317 ◽

Cited By ~ 6

Author(s):

Josef Stuchlík ◽

Alois Krajíček ◽

Ladislav Cvak ◽

Jiří Spáčil ◽

Petr Sedmera ◽

...

Keyword(s):

Nmr Spectroscopy ◽

Ergot Alkaloids ◽

C Nmr

Two new alkaloids were isolated from the field ergot. Their structures, N-(D-lysergyl-L-valyl)cyclo(L-valyl-D-prolyl) (IV) and N-(D-lysergyl-L-valyl)cyclo(L-leucyl-D-prolyl) (V), were assigned by mass, 1H and 13C NMR spectroscopy.

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An unusual reaction of a bridged triterpenoid α-diketone with acetic anhydride

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19912917 ◽

1991 ◽

Vol 56 (12) ◽

pp. 2917-2935 ◽

Cited By ~ 1

Author(s):

Eva Klinotová ◽

Václav Křeček ◽

Jiří Klinot ◽

Miloš Buděšínský ◽

Jaroslav Podlaha ◽

...

Keyword(s):

Acetic Acid ◽

Nmr Spectroscopy ◽

Acetic Anhydride ◽

Spectral Methods ◽

X Ray Diffraction ◽

X Ray ◽

Mild Conditions ◽

Condensation Products ◽

Unsaturated Lactones ◽

C Nmr

3β-Acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (IIIa) reacts with acetic anhydride in pyridine under very mild conditions affording β-lactone IVa and γ-lactones Va and VIIa as condensation products. On reaction with pyridine, lactones Va and VIIa undergo elimination of acetic acid to give unsaturated lactones VIIIa and IXa, respectively. Similarly, the condensation of 20β,28-epoxy-21,22-dioxo-18α,19βH-ursan-3β-yl acetate (IIIb) with acetic anhydride leads to β-lactone IVb and γ-lactone Vb; the latter on heating with pyridine affords unsaturated lactone VIIIb and 21-methylene-22-ketone Xb. The structure of the obtained compounds was derived using spectral methods, particularly 1H and 13C NMR spectroscopy; structure of lactone IVa was confirmed by X-ray diffraction.

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A New Dimeric Derivative of Ethoxyquin from Its Reaction with Alkylperoxy Radicals

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19931914 ◽

1993 ◽

Vol 58 (8) ◽

pp. 1914-1918 ◽

Cited By ~ 3

Author(s):

Jaroslav Kříž ◽

Luděk Taimr

Keyword(s):

Mass Spectrometry ◽

Nmr Spectroscopy ◽

Peroxy Radicals ◽

Methyl Group ◽

Alkylperoxy Radicals ◽

C Nmr

The structure of a new compound formed in the reaction of ethoxyquin with alkylperoxy radicals was resolved by 1H and 13C NMR spectroscopy (including COSY, NOESY, HHC RCT and SSLR INEPT techniques) and confirmed by mass spectrometry. The structure suggest participation of 4-methyl group of ethoxyquin in the deactivation of peroxy radicals. A mechanism of this reaction is proposed.

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Reactivity of Sodium Hexaethyl-2,4-dicarba-nido-hexaborate(1-)

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19990977 ◽

1999 ◽

Vol 64 (6) ◽

pp. 977-985 ◽

Cited By ~ 17

Author(s):

Bernd Wrackmeyer ◽

Hans-Jörg Schanz ◽

Wolfgang Milius ◽

Catherine McCammon

Keyword(s):

Mössbauer Spectroscopy ◽

Nmr Spectroscopy ◽

Structural Analysis ◽

Hydrogen Atom ◽

Mossbauer Spectroscopy ◽

Sandwich Complex ◽

X Ray ◽

Bromo Derivative ◽

Boron Tribromide ◽

C Nmr

Sodium hexaethyl-2,4-dicarba-nido-hexaborate(1-) (6), available from hexaethyl-2,4-dicarba- nido-hexaborane(8) (4) by deprotonation, reacts with deuterated methanol, CD3OD, to give back 4 without H/D exchange of the B-H-B hydrogen atom. The reaction of 6 with diethylboron chloride, Et2BCl, affords hexaethyl-2,4-dicarba-closo-hexaborane(6) (7), the first example of a peralkylated carborane of this type. In contrast, the reaction of 6 with boron tribromide, BBr3, leads mainly to 2,3,4,5,6,7-hexaethyl-2,4-dicarba-closo-heptaborane(7) (8), together with the corresponding 1-bromo derivative (9) and the closo-carborane 7 as side products. The reaction of two equivalents of 6 with FeCl2 gives the air-stable sandwich complex bis[hexaethyl-2,4-dicarba-nido-hexaborate(1-)]iron 10 which was characterised by X-ray structural analysis. All products were characterised by 1H, 11B and 13C NMR spectroscopy, and 57Fe Mössbauer spectroscopy was used to study 10.

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Trypsin entrapped within liposomes. Partition of a low-molecular-mass substrate as the main factor in kinetic control of hydrolysis

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19910712 ◽

1991 ◽

Vol 56 (3) ◽

pp. 712-717 ◽

Cited By ~ 2

Author(s):

Jana Formelová ◽

Albert Breier ◽

Peter Gemeiner ◽

Lubica Kurillová

Keyword(s):

Molecular Mass ◽

Egg Yolk ◽

Kinetic Control ◽

Hydrolysis Kinetics ◽

Liposomal Membrane ◽

Kinetics Of ◽

Main Factor

Trypsin has been entrapped within liposomes prepared from egg yolk phospholipides by the method of controlled dialysis, and the hydrolysis kinetics of Nα-benzoyl-DL-arginine p-nitroaniline catalyzed by the liposome-entrapped trypsin has been studied by monitoring the flux of substrate and product across the liposomal membrane. The partitioning of the substrate and product between liposomal and extraliposomal environment has been found to represent the main factor in the kinetic control of the hydrolysis.

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Formation of spiro adduct from N-methyl-N-(2,4,6-trinitrophenyl)glycine anion

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19890440 ◽

1989 ◽

Vol 54 (2) ◽

pp. 440-445 ◽

Cited By ~ 1

Author(s):

Vladimír Macháček ◽

Alexandr Čegan ◽

Miloš Sedlák ◽

Vojeslav Štěrba

Keyword(s):

Nmr Spectroscopy ◽

Dimethyl Sulfoxide ◽

Equilibrium Constant ◽

Mole Fraction ◽

Nucleophilic Addition ◽

Adduct Formation ◽

First Case ◽

C Nmr

The intramolecular nucleophilic addition of N-methyl-N-(2,4,6-trinitrophenyl)glycine anion in methanol-dimethyl sulfoxide mixtures produces spiro[(3-methyl-5-oxazolidinone)-2,1'-(2',4',6'-trinitrobenzenide)]. The spiro adduct has been identified by means of 1H and 13C NMR spectroscopy. This is the first case when the formation of a Meisenheimer adduct with carboxylate ion is observed. Logarithm of the equilibrium constant of adduct formation increases linearly with the mole fraction of dimethyl sulfoxide in its mixture with methanol.

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