Styrene Forming Elimination Reaction from β-Phenylethylphosphonium Salts+

1983 ◽  
Vol 38 (1) ◽  
pp. 115-116 ◽  
Author(s):  
S. Alunni ◽  
G. Giulietti
Keyword(s):  
Rate Constants ◽  
Second Order ◽  
Elimination Reaction ◽  
Order Rate ◽  
Leaving Group

β-Phenylethylphosphonium salts in RO-/ROH give styrene in amount depending on the steric requirements of the nucleophile and of the salt. The % of styrene formed increases from 22.9 with leaving group PPH3 to 85.0 with leaving group P(<-BU)3 in t-BuOK/t-BuOH. Second order rate constants at 30 °C in t-BuOK/t-BuOH are 1.1 · 10-2lm-1s-1 with leaving group P(n-Bu)3 and 0.96- 10-2 lm-1s-1 with leaving group P (cyclohexyl)3. The data are consistent with a mechanism of β-elimination.

A Study on the β-Elimination Reaction from N-[2-(p-nitrophenyl)ethyl]quinuclidinium and 2-(p-nitrophenyl)ethyl bromide induced by amines in dimethylsulfoxide with formation of p-nitrostyrene

2000 ◽  
Vol 2000 (2) ◽  
pp. 62-63
Author(s):  
Sergio Alunni ◽  
Arianna Rocchi
Keyword(s):  
Rate Constants ◽  
Second Order ◽  
Ethyl Bromide ◽  
Elimination Reaction ◽  
Order Rate

Second order rate constants kE M−1 s−1 for the β-elimination reaction from N-[2-( p-nitrophenyl)ethyl]quinuclidinium and 2-( p-nitrophenyl)ethyl bromide induced by amines of different structure in dimethylsulfoxide at 50 °C have been measured. Application of the Brønsted equation shows a similar behaviour of the two substrates, with values of β = 0.649 and 0.584 respectively.

Octahedral cobalt(III) complexes of the chloropentanimine type. XXX. The thallium(III)-induced aquation of some cis-Halogeno(amine)bis(ethylenediamine)cobalt(III) cations in aqueous solution

1973 ◽  
Vol 26 (6) ◽  
pp. 1235 ◽  
Author(s):  
SC Chan ◽  
SF Chan
Keyword(s):  
Aqueous Solution ◽  
Rate Constants ◽  
Activation Parameters ◽  
Second Order ◽  
Alternative Possibility ◽  
Order Rate ◽  
Leaving Group ◽  
Activated Complex

The second-order rate constants for the thallium(III)-induced aquation of cis-[Co(en)2(RNH2)Cl]2+ cations, where R is H, Me, Et, Prn, and Pri, have been measured in aqueous solution over a range of temperatures, and the activation parameters calculated. The kinetic results are discussed in terms of a rapid pre-equilibrium formation of an activated complex Co-Cl-Tl, followed by a simple rate-determining aquation in which TlCl2+ acts as the leaving group, although the alternative possibility of a rate-determining attack by Tl3+ cannot be excluded. In the case of R = H, the investigations have been extended to the corresponding bromo cation which reacts some 50 times faster than its chloro analogue.

Octahedral cobalt(III) complexes of the chloropentammine type. XXIII. The mercury(II)-induced aquation of some cis-Chloropyridinebis(ethylenediamine) cobalt(III) complexes

1971 ◽  
Vol 24 (10) ◽  
pp. 2071 ◽  
Author(s):  
SC Chan ◽  
SF Chan
Keyword(s):  
Aqueous Solution ◽  
Rate Constants ◽  
Second Order ◽  
Order Rate ◽  
Leaving Group ◽  
Inductive Effects ◽  
Activated Complex

The second-order rate constants for the mercury(II)-induced aquation of some cis-chloropyridinebis(ethylenediamine)cobalt(III) cations have been measured in aqueous solution over a range of temperatures. The results are interpreted in terms of the formation of an activated complex Co-Cl-Hg, which yields the aquo product by a unimolecular aquation with HgCl+ as the leaving group. The competitive influences of the steric and inductive effects of alkyl substituents are discussed.

Inhibition in Purified Systems and in Human Plasma of Chimaeric Plasminogen Activators Consisting of the NH2-Terminal Region of Tissue-Type Plasminogen Activator and the COOH-Terminal Region of UrokinaseType Plasminogen Activator

1988 ◽  
Vol 60 (02) ◽  
pp. 247-250 ◽  
Author(s):  
H R Lijnen ◽  
L Nelles ◽  
B Van Hoef ◽  
F De Cock ◽  
D Collen
Keyword(s):  
Plasminogen Activator ◽  
Rate Constants ◽  
Plasminogen Activators ◽  
Second Order ◽  
Tissue Type ◽  
Single Chain ◽  
Chain Molecules ◽  
Order Rate ◽  
Type Plasminogen Activator ◽  
Urokinase Type Plasminogen Activator

SummaryRecombinant chimaeric molecules between tissue-type plasminogen activator (t-PA) and single chain urokinase-type plasminogen activator (scu-PA) or two chain urokinase-type plasminogen activator (tcu-PA) have intact enzymatic properties of scu-PA or tcu-PA towards natural and synthetic substrates (Nelles et al., J Biol Chem 1987; 262: 10855-10862). In the present study, we have compared the reactivity with inhibitors of both the single chain and two chain variants of recombinant u-PA and two recombinant chimaeric molecules between t-PA and scu-PA (t-PA/u-PA-s: amino acids 1-263 of t-PA and 144-411 of u-PA; t-PA/u-PA-e: amino acids 1-274 of t-PA and 138-411 of u-PA). Incubation with human plasma in the absence of a fibrin clot for 3 h at 37° C at equipotent concentrations (50% clot lysis in 2 h), resulted in significant fibrinogen breakdown (to about 40% of the normal value) for all two chain molecules, but not for their single chain counterparts. Preincubation of the plasminogen activators with plasma for 3 h at 37° C, resulted in complete inhibition of the fibrinolytic potency of the two chain molecules but did not alter the potency of the single chain molecules. Inhibition of the two chain molecules occurred with a t½ of approximately 45 min. The two chain variants were inhibited by the synthetic urokinase inhibitor Glu-Gly-Arg-CH2CCl with apparent second-order rate constants of 8,000-10,000 M−1s−1, by purified α2-antiplasmin with second-order rate constants of about 300 M−1s−1, and by plasminogen activator inhibitor-1 (PAI-1) with second-order rate constants of approximately 2 × 107 M−1s−1.It is concluded that the reactivity of single chain and two chain forms of t-PA/u-PA chimaers with inhibitors is very similar to that of the single and two chain forms of intact u-PA.

Determination of the Nucleophilicity of Tricarbonyliron Coordinated Cyclohepta-1,3,5-triene

1999 ◽  
Vol 64 (11) ◽  
pp. 1770-1779 ◽  
Author(s):  
Herbert Mayr ◽  
Karl-Heinz Müller
Keyword(s):  
Gibbs Energy ◽  
Ambient Temperature ◽  
Rate Constants ◽  
Second Order ◽  
Order Rate ◽  
Electrophilic Additions ◽  
Kinetics Of

The kinetics of the electrophilic additions of four diarylcarbenium ions (4a-4d) to tricarbonyl(η4-cyclohepta-1,3,5-triene)iron (1) have been studied photometrically. The second-order rate constants match the linear Gibbs energy relationship log k20 °C = s(E + N) and yield the nucleophilicity parameter N(1) = 3.69. It is concluded that electrophiles with E ≥ -9 will react with complex 1 at ambient temperature.

Luminescence Quenching of Rhodamines by Cyclooctatetraene

1987 ◽  
Vol 42 (9) ◽  
pp. 1009-1013 ◽  
Author(s):  
P. Targowski ◽  
B. Ziętek ◽  
A. Bączyński
Keyword(s):  
Rhodamine B ◽  
Rate Constants ◽  
Internal Conversion ◽  
Rhodamine 6G ◽  
Second Order ◽  
Luminescence Quenching ◽  
Intersystem Crossing ◽  
Order Rate ◽  
Quenching Process

Cyclooctatetraene (COT) as a quencher of fluorescence of a series of Rhodamine solutions was studied. The second order rate constants for the quenching process of Rhodamine 110, Rhodamine 19 pchl., Rhodamine 6G pchl., Rhodamine 6G, Tetramethylrhodamine, Rhodamine B and Rhodamine 3B pchl. are given. It was found that COT enhances rather intersystem crossing than internal conversion.

The mercury(II)-induced aquation of trans-Chloroamminebis(dimethylglyoximato)cobalt(III) complex

1975 ◽  
Vol 28 (5) ◽  
pp. 1133 ◽  
Author(s):  
S Chan ◽  
S Tan
Keyword(s):  
Rate Constants ◽  
Aqueous Ethanol ◽  
Association Constants ◽  
First Order ◽  
Order Rate ◽  
Leaving Group ◽  
Pseudo First Order ◽  
Activated Complex

The pseudo first-order rate constants for the mercury(II)-induced aquation of trans-[Co(Hdmg)2(NH3)Cl] (Hdmg = dimethylglyoximate ion) have been measured in aqueous and aqueous ethanol solutions (ethanol- water mole ratio 1 : 5.1) containing various excess amounts of mercury(II)ion at 273.2 K. Association constants of the complex formed with mercury(II) ion and rate constants for dissociation of the activated complex in both solutions have been calculated. The kinetic results are discussed in terms of formation of an activated complex Co-C1-Hg, followed by a simple rate-determining aquation in which HgCl+ acts as the leaving group.

KINETICS OF THE AQUEOUS ALKALINE HOMOGENOUS HYDROLYSIS OF HIGH EXPLOSIVE 1, 3,5,7-TETRAAZA- 1, 3,5,7-TETRANITROCYCLOOCTANE (HMX)

1994 ◽  
Vol 30 (3) ◽  
pp. 53-61 ◽  
Author(s):  
Harro M. Heilmann ◽  
Michael K. Stenstrom ◽  
Rolf P. X. Hesselmann ◽  
Udo Wiesmann
Keyword(s):  
Temperature Dependence ◽  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Elevated Temperatures ◽  
Second Order ◽  
Order Rate ◽  
Subsequent Calculation ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Order Rate Equation

In order to get basic data for the design of a novel treatment scheme for high explosives we investigated the kinetics for the aqueous alkaline hydrolysis of 1,3,5,7-tetraaza-1,3,5,7-tetranitrocyclooctane (HMX) and the temperature dependence of the rate constants. We used an HPLC procedure for the analysis of HMX. All experimental data could be fit accurately to a pseudo first-order rate equation and subsequent calculation of second-order rate constants was also precise. Temperature dependence could be modeled with the Arrhenius equation. An increase of 10°C led to an average increase in the second-order rate constants by the 3.16 fold. The activation energy of the second-order reaction was determined to be 111.9 ±0.76 kJ·moJ‒1. We found the alkaline hydrolysis to be rapid (less than 2.5% of the initial HMX-concentration left after 100 minutes) at base concentrations of 23 mmol oH‒/L and elevated temperatures between 60 and 80°C.

scholarly journals The accessibility of protein-bound dinitrophenyl groups to univalent fragments of anti-dinitrophenyl antibody

1976 ◽  
Vol 159 (2) ◽  
pp. 323-333 ◽  
Author(s):  
C G Knight ◽  
N M Green
Keyword(s):  
Dissociation Constant ◽  
Rate Constants ◽  
Alkyl Chain ◽  
Dissociation Constants ◽  
Tryptophan Fluorescence ◽  
Thiol Group ◽  
Second Order ◽  
Thiol Compounds ◽  
Order Rate ◽  
Chain Lengths

A series of N-(N-dinitrophenylaminoalkyl)maleimides were sythesized with alkyl-chain lengths of two, four and six carbon atoms. When these compounds reacted with the thiol group of mercaptalbumin, the tryptophan fluorescence of the protein was quenched. This change in fluorescence was used to determine the rate of reaction of the Dnp (dinitrophenyl)-maleimides with mercaptalbumin. The second-order rate constants were similar to those observed in reactions between low-molecular-weight thiol compounds and maleimides. When N-(N-Dnp-aminoalkyl)succinimidomercaptalbumins were added to univalent fragments of anti-Dnp antibody the antibody fluorescence was quenched. Florescence-quenching titrations showed that the protein-bound Dnp groups were fully available to the antibody even when the alkyl chain was short. The apparent dissociation constants were significantly > that of the interaction between anti-Dnp antibody and the free hapten, 6-(N-Dnp)-aminohexanoate. The antibody fluorescence was quenched efficienty by [dnp-Lys41]ribonuclease A, also with an increased dissociation constant. It could be concluded from the increase in dissociation constant that the Dnp group spent no more than 0.1% of its time in the dissociated state, available to antibody. The second-order rate constants for the association between the Dnp-mercaptablumins and the antibody were determined and were similar in magnitude to those observed in other interactions between protein and anti-protein antibody.

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