Vladimir D. Kiselev

Compressibility of liquids. Rule of noncrossing V-P curvatures.

Weight analysis of the liquid introduced into the stainless steel bomb under pressures up to 1 kbar in the temperature range of 20-50 degrees C at the interval of 10 degrees C was performed for 1,4-dioxane, acetonitrile, toluene, ethyl acetate, chlorobenzene, and n-hexane. The coefficients of the Tait equation were determined for all of the solvents at each temperature. There was a clear linear relation between the tangent bulk modulus (1/beta T) at atmospheric pressure (1 bar) and the secant bulk modulus at 1 kbar; 1/betaT=0.9865 x (1000 V0/DeltaV(1kbar))-4559 was found at a wide range of temperatures for different liquids, including glycerol and even mercury. This represents the rule of noncrossing P-V curvatures for the liquids. Using the correlation, it is possible to predict the coefficients (C, B) of the Tait equation from the experimental data of betaT at 1 bar or, on the other hand, to calculate the value of betaT from experimental compression at high pressures.

Pressure effect on the rate and equilibrium constants of the Diels-Alder reaction 9-chloroanthracene with tetracyanoethylene

Abstract The pressure effect on the forward and backward rate constants and equilibrium constants of the Diels-Alder reaction of 9-chloroanthracene with tetracyanoethylene has been investigated in 1,2-dichloroethane up to 1000 kgcm−2 at 298.15 K. The reaction volume obtained from the pressure effect on equilibrium (−20.6 ±1.5 cm3mol−1) and as difference of activation volumes of forward (−28.5±1.5) and backward (−6.5 ± 0.5) reaction (−22.0±1.5 cm3mol−1) are in agreement with partial molar volume difference of adduct (255.5±1.5) diene (170.7±0.5) and dienophile (107.8±0.2) giving −23.0 ±2 cm3mol−1.

THE NATURE OF LITHIUM PERCHLORATE AND GALLIUM CHLORIDE SALT EFFECT IN CYCLOADDITION REACTIONS

Abstract Comparing the acceleration effects of (4+2)-, (3+2)- and (2+2)-cycloaddition reactions in the presence of the salts of two types: gallium chloride in inert solvents and lithium perchlorate (LP) in diethyl ether (DE) it was observed that in the presence of GaCl3 the acceleration effect is approximately the same (104 times) for the studied reactions, while in LPDE medium for the same reactions strong increase (up to 104 times), weak increase or even decrease of the rate and equilibrium constants take place even with the common dienophile depending on the nature of the second reagent. It was suggested that the acceleration effect of cycloaddition reactions in the presence of such Lewis acids as aluminum, gallium or boron halides is due to the sharp increase of π-acceptor properties of dienophiles and therefore increasing energy of orbital interaction, whereas LPDE medium demonstrates strong stabilization of static and/or dynamic polar forms and favors reactions with charge control.

Atmospheric and high pressure ene reaction of norbornene with 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione

Thermodynamic and activation parameters (enthalpy, entropy, and volume) have been determined from the pressure and temperature dependences of the rate of the reaction of norbornene with 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione in toluene, which is accompanied by Wagner-Meerwein rearrangement. The enthalpy of the reaction in 1,2-dichloroethane has been determined by calorimetry. The obtained data correspond to a weakly polar transition state.

Diels-Alder reaction between naphthalene and N-phenylmaleimide under mild conditions

The rate and equilibrium constants for the Diels—Alder reactions between benzene or naphthalene and several dienophiles at 25 °C were calculated from the data on the ionization potentials of dienes and electron affinity energies of dienophiles, as well as the reaction enthalpies. The highest yield of the adduct was predicted for the reaction of naphthalene with N-phenylmaleimide. However, the time of its formation in 50% yield exceeds 30 years. The use of gallium chloride as a catalyst affords the endo-adduct for seven days at room temperature in 30% yield. The rate ((2±0.5)·10–6 L mol–1 s–1) and equilibrium constants (5±2 L mol–1) of the reaction were determined.

Ene reaction of 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione with dicyclopentadiene

The kinetics of the ene reaction of endo-dicyclopentadiene with 4-phenyl-3H-1,2,4-triazole-3,5(4H)-dione in benzene, toluene, acetonitrile, 1,2-dichloroetane, and chloroform have been studied. The reaction volumes and enthalpies have been determined, and the activation volume in toluene has been calculated from the pressure kinetic data. The “anomalous” ratio ΔVcorr≠/ΔVr = 1.34 corresponds to a concerted cyclic transition state, though the addition product has acyclic structure.

Features of the Diels-Alder reaction between 9,10-diphenylanthracene and 4-phenyl-1,2,4-triazoline-3,5-dione

The Diels-Alder reaction between substituted anthracenes 1a−1j and 4-phenyl-1,2,4-triazoline-3,5 (2) is studied. In all cases except one, the reaction proceeds on the most active 9,10-atoms of substituted anthracenes. The orthogonality of the two phenyl groups at the 9,10-position of diene 1a is found to shield 9,10-reactive centers. No dienophiles with C=C bonds are shown to participate in the Diels-Alder reaction with 1a; however, the reaction 1a + 2 proceeds with the very active dienophile 2,4-phenyl-1,2,4-triazoline-3,5-dione. It is shown that attachment occurs on the less active but sterically accessible 1,4-reactive center of diene 1a. The structure of adduct 3a is proved by 1H and 13C NMR spectroscopy and X-ray diffraction analysis. The following parameters are obtained for reaction 1a + 2 ⇆ 3a in toluene at 25°C: Keq = 2120 M−1, ΔHf≠ = 58.6 kJ/mol, ΔSf≠ = −97 J/(mol K), ΔVf≠ = −17.2 cm3/mol, ΔHb≠ = 108.8 kJ/mol, ΔSb≠ = 7.3 J/(mol K), ΔVb≠ = −0.8 cm3/mol, ΔHr-n = −50.2 kJ/mol, ΔSr-n = −104.3 J/(mol K), ΔVr-n = −15.6 cm3/mol. It is concluded that the values of equilibrium constants of the reactions 1a−1j + 2 ⇆ 3a−3j vary within 4 × 101−1011 M−1.

Effect of pressure on the rate of the Diels-Alder reaction of diethyl azodicarboxylate with 9,10-dimethylanthracene

The enthalpy, entropy, and volume of activation and volume of the Diels-Alder reaction of diethyl azodicarboxylate with 9,10-dimethylanthracene in 1,2-dichloroethane have been determined. Possible factors responsible for the sharp difference between the volumes of activation and reaction are considered.

Studying the effect of high pressure on the cycloaddition reactions of maleic anhydride and substituted anthracenes

The kinetics (rate, activation, and volume) of the high-pressure (up to 2500 bar) Diels-Alder reactions of maleic anhydride with 9-phenylanthracene and 9,10-dimethylanthracene in toluene is investigated.

Volume, enthalpy and entropy of activation of the Diels-Alder reaction of dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate with 1-hexene

Abstract Pressure and temperature effects on the reaction rate of dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate with 1-hexene were investigated. The activation volume (−26.7 cm3 mol−1, 298.1 K) is in agreement with the conservation of all four nitrogen atoms in transition state. Densitometry, 1H NMR and calorimetric studies of the reaction indicate nitrogen molecule loss by the intermediate just after its formation. Partial molar volumes in acetone of diene (127.2), 1-hexene (127.6) and the resulting adduct (206.9 cm3 mol−1) were determined.