The role of added pyridine in substitution reactions of triphenylmethyl chloride in benzene solution

1967 ◽  
Vol 45 (13) ◽  
pp. 1497-1503
Author(s):  
K. T. Leffek ◽  
R. G. Waterfield
Keyword(s):  
Quaternary Ammonium ◽  
Benzene Solution ◽  
Alkyl Halide ◽  
Covalent Bonding ◽  
Kinetic Investigation ◽  
Exchange Reactions ◽  
Substitution Reactions ◽  
Kinetics Of ◽  
Strong Covalent Bonding

A detailed kinetic investigation has been made of the specific role of pyridine when added to the methanolysis and radiochloride exchange reactions of triphenylmethyl chloride in benzene. It is concluded that neither of the two proposals in the literature, i.e. that it reacts with the alkyl halide to form a quaternary ammonium salt or that it has no effect whatever except to take up the hydrogen chloride product, is correct. The present results indicate that pyridine forms a complex with the triphenylmethyl chloride, without strong covalent bonding, which has a distinctive effect on the kinetics of the reactions.

Solvent-free Substitution Reactions of Solid Phosphines with (η5-RC5H4)Fe(CO)2I (R = H, Me) Complexes

2007 ◽  
Vol 62 (3) ◽  
pp. 453-459 ◽  
Author(s):  
Apollinaire Munyaneza ◽  
Muhammad D. Bala ◽  
Neil J. Coville
Keyword(s):  
Benzene Solution ◽  
Phosphine Ligands ◽  
Solvent Free ◽  
Substitution Reactions ◽  
Ionic Complex ◽  
Solvent Free Conditions ◽  
Mechanism Of The Reaction ◽  
Solvent Free Reaction ◽  
Melt Phase

Reactions of (η5-RC5H4)Fe(CO)2I (R = H, Me) complexes with phosphine ligands PR′3 (R′ = Ph, m-Tol, p-C6H4OMe, p-C6H4Cl, p-C6H4F) have been performed under solvent-free conditions in the melt phase and generally yielded the ionic products [(η5-RC5H4)Fe(CO)2PR′3]I rather than the CO substituted products (η5-RC5H4)Fe(CO)(PR′3)I. The complexes have been characterised by IR, NMR and MS techniques. By contrast, the same reactions studied in benzene solution have yielded mainly the CO substitution products. Factors that affect the solvent-free reaction include variation in R and R′ , reaction temperature and the addition of [CpFe(CO)2]2 as a catalyst. The mechanism of the reaction for the formation of the ionic complex is proposed to go via a 19 electron intermediate. This is in contrast to the reaction in bezene that occurs via a 17 electron intermediate, clearly indicating the role of the melt phase in the reaction.

Chemische Wirkungen des 80 mBr-Kernisomeren-Überganges in kristallinen Co-, Rh- und Ir-Pentamminbromokomplexsalzen*

1963 ◽  
Vol 18 (4) ◽  
pp. 505-509
Author(s):  
G. B. Schmidt ◽  
W. Herr
Keyword(s):  
Room Temperature ◽  
Chemical Nature ◽  
Exchange Reactions ◽  
Substitution Reactions ◽  
Fast Reaction ◽  
Isomeric Transition ◽  
Yield Values ◽  
Kinetics Of ◽  
Limiting Values ◽  
Reducing Properties

The percentage of separable 80gBr--ions, following the 80mBr→80gBr isomeric transition, was determined in labelled pentamminebromo complexes of Co, Rh and Ir at various temperatures. In [Me(NH3)5Br] (NO3)2 crystals the 80gBr--yields are constant (90, 80 and 77% resp.) over a certain range of temperature, but above 50°, 75°, and 110°C for the Co, Rh, and Ir-complex, respectively, the 80gBr--yields decrease lineary with temperature. The annealing of the metastable fragments is rapid and reaches characteristic equilibrium values. The kinetics of this fast reaction was studied and an activation energy of 6,7 kcal/mol was calculated for [Rh (NH3) 5Br] (NO3)2. In contrast to the bromo nitrates, the 80gBr--yields increase with temperature in the Rh- and Irpentamminebromo-halogenid complexes and reach limiting values of ∼66% at 210—250°C. In this case the excitation energy of the isomeric transition seems to effect activated exchange reactions between complex bound bromide and anionic bromide or chloride. In the Co-, Rh- and Ir-pentamminebromocomplexes investivated, the 80gBr--yield is strongly influenced by the chemical nature of the anion and/or the physical properties of the crystals. 12 different [Ir (NH3) 5Br] X2 complexes yield values of 80gBr— between 77% (X= ΝΟ3—) and 41% (X2 = C2O4— —) at room temperature. Anions with oxidizing properties show higher values than those with reducing properties. The latter may favour intermolecular charge neutralisation.In an inversion of the above experiments, we found that in anionic 80mBr-labelled Rh-hexamminebromide and also in different Rh- and Ir-pentammine acido bromides, 9 — 18% of the 80gBr daughter atoms were complex bound. These yields are independent of temperature, indicating that substitution reactions of ligand groups occur only by “hot atom” processes. The results are compared with those of the (n,γ) nuclear reaction.

THE ROLE OF REACTION PRODUCTS IN THE SILVER-CATALYZED OXIDATION OF ETHYLENE

1960 ◽  
Vol 38 (11) ◽  
pp. 2256-2268 ◽  
Author(s):  
Kenneth E. Hayes
Keyword(s):  
Carbon Dioxide ◽  
Ethylene Oxide ◽  
Initial Rate ◽  
Flow System ◽  
Oxygen Exchange ◽  
Reaction Products ◽  
Exchange Reactions ◽  
Kinetics Of ◽  
Catalyzed Oxidation

Initial-rate studies of the kinetics of the silver-catalyzed oxidation of ethylene oxide and carbon dioxide in a flow system have been made. It was found that, using carefully purified reactants, the effect of added carbon dioxide was to suppress the formation of ethylene oxide only. The initial rate of the formation of ethylene oxide is given by the equation[Formula: see text]where r0 is the initial rate in the absence of CO2; m, n, and k are constants with m + n = 1.These results together with the results of oxygen exchange reactions between O18 and C2H4O16, CO216 and H2O16 are interpreted mechanistically.

Thermodynamic and Kinetic Investigation of the Solvent Effect on the Oxidation of [Co(en)2SCH2COO]+ with S2O82- In Water-Methanol and Water-tert-Butyl Alcohol Mixtures

1993 ◽  
Vol 58 (5) ◽  
pp. 1001-1006 ◽  
Author(s):  
Oľga Vollárová ◽  
Ján Benko
Keyword(s):  
Transfer Functions ◽  
Activation Parameters ◽  
Butyl Alcohol ◽  
Oxidation Of Co ◽  
Kinetics Of Oxidation ◽  
Tert Butyl ◽  
Tert Butyl Alcohol ◽  
Alcohol Mixtures ◽  
Kinetics Of

The kinetics of oxidation of [Co(en)2SCH2COO]+ with S2O82- was studied in water-methanol and water-tert-butyl alcohol mixtures. Changes in the reaction activation parameters ∆H≠ and ∆S≠ with varying concentration of the co-solvent depend on the kind of the latter, which points to a significant role of salvation effects. The solvation effect on the reaction is discussed based on a comparison of the transfer functions ∆Ht0, ∆St0 and ∆Gt0 for the initial and transition states with the changes in the activation parameters accompanying changes in the CO-solvent concentration. The transfer enthalpies of the reactant were obtained from calorimetric measurements.

Evidence for general base catalysis by protic solvents in a kinetic study of alcoholyses and hydrolyses of 1-(phenoxycarbonyl)pyridinium ions under both solvolytic and non-solvolytic conditions

2009 ◽  
Vol 74 (1) ◽  
pp. 43-55 ◽  
Author(s):  
Dennis N. Kevill ◽  
Byoung-Chun Park ◽  
Jin Burm Kyong
Keyword(s):  
Second Order ◽  
Base Catalysis ◽  
Substitution Reactions ◽  
Third Order ◽  
Methoxy Derivative ◽  
First Order ◽  
General Base ◽  
Protic Solvents ◽  
Kinetics Of ◽  
Pyridinium Ions

The kinetics of nucleophilic substitution reactions of 1-(phenoxycarbonyl)pyridinium ions, prepared with the essentially non-nucleophilic/non-basic fluoroborate as the counterion, have been studied using up to 1.60 M methanol in acetonitrile as solvent and under solvolytic conditions in 2,2,2-trifluoroethan-1-ol (TFE) and its mixtures with water. Under the non- solvolytic conditions, the parent and three pyridine-ring-substituted derivatives were studied. Both second-order (first-order in methanol) and third-order (second-order in methanol) kinetic contributions were observed. In the solvolysis studies, since solvent ionizing power values were almost constant over the range of aqueous TFE studied, a Grunwald–Winstein equation treatment of the specific rates of solvolysis for the parent and the 4-methoxy derivative could be carried out in terms of variations in solvent nucleophilicity, and an appreciable sensitivity to changes in solvent nucleophilicity was found.

scholarly journals Association between perinatal factors, genetic susceptibility to obesity and age at adiposity rebound in children of the EDEN mother–child cohort

2021 ◽  
Author(s):  
Aminata Hallimat Cissé ◽  
Sandrine Lioret ◽  
Blandine de Lauzon-Guillain ◽  
Anne Forhan ◽  
Ken K. Ong ◽  
...  
Keyword(s):  
Weight Gain ◽  
Genetic Susceptibility ◽  
Gestational Weight Gain ◽  
Gestational Age ◽  
Obesity Risk ◽  
Perinatal Factors ◽  
Gestational Weight ◽  
Adiposity Rebound ◽  
Kinetics Of

Abstract Background Early adiposity rebound (AR) has been associated with increased risk of overweight or obesity in adulthood. However, little is known about early predictors of age at AR. We aimed to study the role of perinatal factors and genetic susceptibility to obesity in the kinetics of AR. Methods Body mass index (BMI) curves were modelled by using mixed-effects cubic models, and age at AR was estimated for 1415 children of the EDEN mother–child cohort study. A combined obesity risk-allele score was calculated from genotypes for 27 variants identified by genome-wide association studies of adult BMI. Perinatal factors of interest were maternal age at delivery, parental education, parental BMI, gestational weight gain, maternal smoking during pregnancy, and newborn characteristics (sex, prematurity, and birth weight). We used a hierarchical level approach with multivariable linear regression model to investigate the association between these factors, obesity risk-allele score, and age at AR. Results A higher genetic susceptibility to obesity score was associated with an earlier age at AR. At the most distal level of the hierarchical model, maternal and paternal educational levels were positively associated with age at AR. Children born to parents with higher BMI were more likely to exhibit earlier age at AR. In addition, higher gestational weight gain was related to earlier age at AR. For children born small for gestational age, the average age at AR was 88 [±39] days lower than for children born appropriate for gestational age and 91 [±56] days lower than for children born large for gestational age. Conclusion The timing of AR seems to be an early childhood manifestation of the genetic susceptibility to adult obesity. We further identified low birth weight and gestational weight gain as novel predictors of early AR, highlighting the role of the intrauterine environment in the kinetics of adiposity.

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