E. A. Kashaeva

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.

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.

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.

Dramatic solvent effect on the volume of the Diels-Alder reaction between tetracyanoethylene and cyclopentadiene

The partial molar volumes (V) and the enthalpies of dissolution (ΔdisH) for tetracyanoethylene, cyclopentadiene, and their Diels—Alder adduct were determined at 25°C. Eleven solvents of the π- and n-donor type were used. The use of alkylbenzenes as solvents for tetracyanoethylene induces pronounced changes in the enthalpy of dissolution (up to 26 kJ mol−1) and in the partial molar volume (up to 11 cm3 mol−1), whereas these parameters for the adduct change slightly. TheV and ΔdisH values for cyclopentadiene virtually do not depend on the nature of the solvent. In the case of tetracyanoethylene and the adduct in n-donor solvents, considerable variations of theV and ΔdisH values are observed; they are not linear functions of the change in the partial molar volume of the adduct. Therefore, the reaction volumes in acetonitrile (−40.69) and ethyl acetate (−45.56) differ sharply from those ino-xylene (−24.28) and mesitylene (−21.76 cm3 mol−1).

Enthalpies of the Diels–Alder reactions of a series of dienes with tetracyanoethylene and 4-phenyl-1,2,4-triazoline-3,5-dione

The enthalpies of the Diels–Alder reactions of twenty dienes with two active dienophiles, tetracyanoethylene and 4-phenyl-1,2,4-triazoline-3,5-dione, are compared, and the corresponding relationship between them was obtained. The values of enthalpies of very slow and/or equilibrium reactions were calculated from the obtained relationship. These data obtained make it possible to optimize the conditions for such reactions.

Kinetic and equilibrium parameters of [4+2] cycloaddition reaction of 2,6-dimethylnaphthalene with 4-phenyl-1,2,4-triazoline-3,5-dione

Kinetic parameters of forward and retro Diels-Alder reactions between 2,6-dimethylnaphthalene and 4-phenyl-1,2,4-triazolinedione were determined, as well as the equilibrium parameters of the reaction in 1,2-dichloroethane.