Kinetics and isotope effects ort the proton transfer reaction of 4-nitrophenylphenylcyanomethane with tetramethylguanidine in acetonitrile and benzonitrile solvents

1983 ◽  
Vol 61 (9) ◽  
pp. 2029-2032 ◽  
Author(s):  
Arnold Jarczewski ◽  
Przemyslaw Pruszynski ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Significant Contribution ◽  
Transfer Reaction ◽  
Isotope Effects ◽  
Equilibrium Constants ◽  
Proton Transfer Reaction ◽  
Kinetic Measurements ◽  
Enthalpy Of Activation ◽  
Difference Formula ◽  
Good Agreement

The kinetic deuterium isotope effect for the proton transfer reaction between 4-nitrophenylphenylcyanomethane and tetramethylguanidine, kH/kD, at 25 °C, is 10.7 in acetonitrile solvent and 12.5 in benzonitrile. The enthalpy of activation difference, [Formula: see text], in both solvents is large, 2.2 kcal mol−1, and 2.4 kcal mol−1; respectively, indicating a significant contribution from proton tunnelling to the reaction. The equilibrium constants, K, measured spectrophotometrically are large, 6000 dm3 mol−1 in acetonitrile and 2000 dm3 mol−1 in benzonitrile and in good agreement with the values calculated from the kinetic measurements.

Kinetics, isotope effects of the reaction of 1-(4-nitrophenyl)-1-nitroalkanes with DBU in tetrahydrofuran and chlorobenzene solvents

1990 ◽  
Vol 68 (12) ◽  
pp. 2242-2248 ◽  
Author(s):  
Wlodzimierz Galezowski ◽  
Arnold Jarczewski
Keyword(s):  
Proton Transfer ◽  
Isotope Effects ◽  
Equilibrium Constants ◽  
Ion Pairs ◽  
Proton Transfer Reaction ◽  
Kinetic Isotope ◽  
Enthalpy Of Activation ◽  
Deuteron Transfer ◽  
Proton Transfer Reactions ◽  
Kinetics Of

The kinetics of the reaction of[Formula: see text](R = Me, Et, i-Pr; NPNE, NPNP, MNPNP respectively; L is H or D) with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) base in tetrahydrofuran (THF) and chlorobenzene (CB) solvents are reported. The products of these proton transfer reactions are ion pairs absorbing at λmax = 460–480 nm. The equilibrium constants in THF were [Formula: see text]and in CB [Formula: see text]for NPNE, NPNP, MNPNP respectively. The thermodynamic parameters of the reactions are also quoted. The substrate reacts with DBU in both THF and CB solvents in a normal second-order proton transfer reaction. In the case of deuteron transfer, isotopic D/H exchange is much faster than internal return. The reactions show low values of enthalpy of activation ΔH* = 14.3, 18.1, 24.2 and 13.0, 15.1, 18.6 kJmol−1 for NPNE, NPNP, and MNPNP in THF and CB respectively, and large negative entropies of activation −ΔS* = 141, 139, 146; 140, 146, 160 J mol−1 deg−1 for the same sequence of substrates and solvents. The kinetic isotope effects are large, (kH/kD)20°c = 12.2, 13.0, 10.1; 12.9, 12.0, 10.2 for the above sequence of substrates and solvents, and show no difference with changes in either steric hindrance of the C-acids or polarity of the solvents. Keywords: proton transfer, kinetic isotope effect.

Kinetics and isotope effects of the proton transfer reactions between 1-(4-nitrophenyl)-1-nitroethane to phenyltetramethylguanidine in dipolar aprotic solvents

1984 ◽  
Vol 62 (5) ◽  
pp. 954-957 ◽  
Author(s):  
Arnold Jarczewski ◽  
Przemyslaw Pruszynski ◽  
Mohammed Kazi ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Transfer Reaction ◽  
Isotope Effects ◽  
Proton Transfer Reaction ◽  
Transfer Reactions ◽  
Aprotic Solvents ◽  
Enthalpy Of Activation ◽  
Proton Transfer Reactions ◽  
Carbon Acid ◽  
Dipolar Aprotic Solvents

The carbon acid 1-(4-nitrophenyl)-1-nitroethane reacts with phenyltetramethylguanidine in the aprotic solvents acetonitrile, benzonitrile, and chlorobenzene in a bimolecular proton transfer reaction. The primary isotope effects, kH/kD, for these reactions at 25 °C are 8.5 ± 0.4, 6.1 ± 0.4, and 16 in acetonitrile, benzonitrile, and chlorobenzene respectively. The magnitude of the isotope effects on the enthalpy of activation [Formula: see text] are 2.3 ± 0.2, 1.6 ± 0.7, and 4.2 ± 0.6 kcal mol−1, which indicates a contribution from proton tunnelling to the reaction rate of the normal substrate.

Kinetic isotope effect and tunnelling in the proton transfer reaction between 2,4,6-trinitrotoluene and 1,1′,3,3′-tetramethylguanidine in dimethylformamide solvent

1979 ◽  
Vol 57 (6) ◽  
pp. 669-672 ◽  
Author(s):  
Arnold Jarczewski ◽  
Przemyslaw Pruszynski ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Transfer Reaction ◽  
Proton Transfer Reaction ◽  
Deuterium Isotope Effect ◽  
Kinetic Isotope ◽  
Enthalpy Of Activation ◽  
Entropy Of Activation ◽  
Large Primary

The proton transfer reaction between 2,4,6-trinitrotoluene and 1,1′,3,3′-tetramethylguanidine in dimethylformamide solvent shows a large primary deuterium isotope effect, kH/kD = 24.3 at 0 °C and 16.9 at 20 °C. The enthalpy of activation difference (ΔHD≠ − ΔHH≠) = 2.6 ± 0.4 kcal mol−1 and the entropy of activation difference (ΔSD≠ − ΔSH≠) = 3.4 ± 1.3 cal mol−1 K−1. This isotope effect, when fitted to Bell's equation, indicates that there is a considerable contribution to this reaction from tunnelling of the proton through the potential energy barrier.

The kinetics of proton and deuteron transfer from 1-(4-nitrophenyl)-1-nitroethane to1,8-diazabicyclo[5.4.0]undec-7-ene in aprotic solvents

1982 ◽  
Vol 60 (13) ◽  
pp. 1692-1695 ◽  
Author(s):  
Kenneth T. Leffek ◽  
Przemyslaw Pruszynski
Keyword(s):  
Energy Barrier ◽  
Reaction Rate ◽  
Significant Contribution ◽  
Transfer Reaction ◽  
Isotope Effects ◽  
Activation Parameters ◽  
Proton Transfer Reaction ◽  
Potential Energy Barrier ◽  
Deuteron Transfer ◽  
Kinetics Of

1-(4-Nitrophenyl)-1-nitroethane reacts with the base1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in both acetonitrile and toluene solvents in a normal second-order proton-transfer reaction, in contrast to its behaviour with the base 2,7-dimethoxy-1,8-bis(dimethylamino)naphthalene in acetonitrile.The primary isotope effect, kHlkD = 12.0 at 25° in toluene is very similar to that observed by other workers for the reaction of 4-nitrophenylnitromethane with DBU under the same conditions. In acetonitrile solvent a kHlkD ratio of 7.8 was found at 25 °C. The isotope effects on the activation parameters for the reaction in both solvents indicate that tunnelling of the proton through the potential energy barrier makes a significant contribution to the reaction rate.

scholarly journals Gas-to-particle partitioning of major biogenic oxidation products: a study on freshly formed and aged biogenic SOA

2018 ◽  
Vol 18 (17) ◽  
pp. 12969-12989 ◽  
Author(s):  
Georgios I. Gkatzelis ◽  
Thorsten Hohaus ◽  
Ralf Tillmann ◽  
Iulia Gensch ◽  
Markus Müller ◽  
...  
Keyword(s):  
Proton Transfer ◽  
Organic Compounds ◽  
Mass Spectrometer ◽  
Transfer Reaction ◽  
Theoretical Calculations ◽  
Proton Transfer Reaction ◽  
Oxidation Products ◽  
Particle Phase ◽  
Tof Ms ◽  
Good Agreement

Abstract. Secondary organic aerosols (SOAs) play a key role in climate change and air quality. Determining the fundamental parameters that distribute organic compounds between the phases is essential, as atmospheric lifetime and impacts change drastically between the gas and particle phase. In this work, gas-to-particle partitioning of major biogenic oxidation products was investigated using three different aerosol chemical characterization techniques. The aerosol collection module, the collection thermal desorption unit, and the chemical analysis of aerosols online are different aerosol sampling inlets connected to a proton-transfer reaction time-of-flight mass spectrometer (ACM-PTR-ToF-MS, TD-PTR-ToF-MS, and CHARON-PTR-ToF-MS, respectively, referred to hereafter as ACM, TD, and CHARON). These techniques were deployed at the atmosphere simulation chamber SAPHIR to perform experiments on the SOA formation and aging from different monoterpenes (β-pinene, limonene) and real plant emissions (Pinus sylvestris L.). The saturation mass concentration C* and thus the volatility of the individual ions was determined based on the simultaneous measurement of their signal in the gas and particle phase. A method to identify and exclude ions affected by thermal dissociation during desorption and ionic dissociation in the ionization chamber of the proton-transfer reaction mass spectrometer (PTR-MS) was developed and tested for each technique. Narrow volatility distributions with organic compounds in the semi-volatile (SVOCs – semi-volatile organic compounds) to intermediate-volatility (IVOCs – intermediate-volatility organic compounds) regime were found for all systems studied. Despite significant differences in the aerosol collection and desorption methods of the proton-transfer-reaction (PTR)-based techniques, a comparison of the C* values obtained with different techniques was found to be in good agreement (within 1 order of magnitude) with deviations explained by the different operating conditions of the PTR-MS. The C* of the identified organic compounds were mapped onto the two-dimensional volatility basis set (2D-VBS), and results showed a decrease in C* with increasing oxidation state. For all experiments conducted in this study, identified partitioning organic compounds accounted for 20–30 % of the total organic mass measured from an aerosol mass spectrometer (AMS). Further comparison between observations and theoretical calculations was performed for species found in our experiments that were also identified in previous publications. Theoretical calculations based on the molecular structure of the compounds showed, within the uncertainties ranges, good agreement with the experimental C* for most SVOCs, while IVOCs deviated by up to a factor of 300. These latter differences are discussed in relation to two main processes affecting these systems: (i) possible interferences by thermal and ionic fragmentation of higher molecular-weight compounds, produced by accretion and oligomerization reactions, that fragment in the m∕z range detected by the PTR-MS and (ii) kinetic influences in the distribution between the gas and particle phase with gas-phase condensation, diffusion in the particle phase, and irreversible uptake.

Kinetic study of the proton transfer reaction between 1-nitro-1-(4-nitrophenyl)alkanes and TBD and MTBD bases in acetonitrile solvent

2001 ◽  
Vol 79 (7) ◽  
pp. 1128-1134 ◽  
Author(s):  
Iwona Grzeskowiak ◽  
Wtodzimierz Galezowski ◽  
Arnold Jarczewski
Keyword(s):  
Proton Transfer ◽  
Kinetic Study ◽  
Transfer Reaction ◽  
Isotope Effects ◽  
Ion Pairs ◽  
Kinetic Isotope Effects ◽  
Proton Transfer Reaction ◽  
Comparable Amount ◽  
Kinetic Isotope ◽  
Proton Transfer Reactions

The rates of proton transfer reactions between C-acids of the series of nitroalkanes with increasing bulk of R = H, Me, Et, i-Pr substituent as: 4-nitrophenylnitromethane (0), 1-(4-nitrophenyl)-1-nitroethane (1), 1-(4-nitrophenyl)-1-nitropropane (2), 2-methyl-1-(4-nitrophenyl)-1-nitropropane (3) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) have been measured in acetonitrile at pseudo-first-order conditions. The product of the proton transfer reaction with MTBD in acetonitrile is dissociated into free ions while that of the TBD reaction is composed of a comparable amount of ions and ion pairs. The second-order rate constants (k2H) for these bases of almost equal strength in acetonitrile (pKa = 24.70, 24.97 for MTBD and TBD) and C-acids 1, 2, and 3 are: 317, 86, 7.6 dm3 mol–1 s–1; and 15 200, 5300, 1100 dm3 mol–1 s–1, respectively. The appropriate primary deuterium kinetic isotope effects (kH/kD) are 12.5, 10.8, 6.9; and 9.9, 11.2, 12.6. The influence of steric hindrance brought by reacting C-acids and bases is discussed. The different structure of the transition states and the products as mono- and double-hydrogen bonded complexes for these series of C-acids and MTBD and TBD bases is manifested by a distinct reaction mechanism which we attempt to explain.Key words: proton transfer, kinetic study, C-acids, organic bases, acetonitrile, kinetic isotope effects.

The proton transfer reaction between bis(2,4-dinitrophenyl)methane and nitrogen bases in dimethyl sulfoxide and toluene solvents

1991 ◽  
Vol 69 (3) ◽  
pp. 468-473 ◽  
Author(s):  
Arnold Jarczewski ◽  
Grzegorz Schroeder ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Dimethyl Sulfoxide ◽  
Isotope Effects ◽  
Equilibrium Constants ◽  
Activation Parameters ◽  
Kinetic Isotope Effects ◽  
Proton Transfer Reaction ◽  
Kinetic Isotope ◽  
Deuteron Transfer ◽  
Classical Region

Rate constants have been measured for the proton and deuteron transfer reactions of bis(2,4-dinitrophenyl)methane (1) with 1,1,3,3-tetramethylguanidine (TMG) and 1,5-diazabicyclo[5.4.0]undec-7-ene (DBU) in dimethyl sulfoxide (DMSO) and toluene solvents. Equilibrium constants, primary deuterium kinetic isotope effects, and activation parameters are reported. The reaction of 1 with DBU is faster than that with TMG by factors of 5 and 50 in toluene and DMSO respectively. The primary deuterium kinetic isotope effects, kH/kD = 7–9, which are independent of the polarity of the solvent, indicate an uncoupled mechanism of proton transfer and are in the "classical" region with little or no indication of a tunnelling contribution to the enthalpy of activation for these reactions. Key words: proton transfer, bis(2,4-dinitrophenyl)methane, deuterium isotope effects.

Phenyltetramethylguanidines: substituent effect on rates and isotope effects in their reaction with bis(4-nitrophenyl)cyanomethane in acetonitrile

1991 ◽  
Vol 69 (2) ◽  
pp. 205-210 ◽  
Author(s):  
Przemyslaw Pruszynski ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Transfer Reaction ◽  
Isotope Effects ◽  
Proton Transfer Reaction ◽  
Kinetic Isotope ◽  
Reaction Constant ◽  
Base Strength ◽  
Derivatives Of ◽  
Best Fit ◽  
Hammett Relationship

A series of 22 phenyl substituted derivatives of 2-phenyl-1,1′,3,3′-tetramethylguanidine were used as bases in the proton transfer reaction from bis(4-nitrophenyl)cyanomethane in acetonitrile solvent. Brønsted and Hammett type relationships are examined for this family of closely related substrates. The Brønsted relationship constructed from the pKa values determined in acetonitrile shows β = 0.55 ± 0.03. The best fit of the Hammett relationship, with special values for p-NO2 and p-CN groups, gives the reaction constant ρ = −1.39 ± 0.1. The kinetic isotope effect, kH/kD, increases from 9.6 to 12.4 at 25 °C with decreasing base strength, i.e., when the reaction becomes more thermoneutral. Key words: tetramethylguanidine, proton transfer, deuterium isotope effects.

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