The rate of dimerization of cyclopentadiene and some other cycloaddition reactions is determined by electrophilic solvation of the substrate with some contribution of other solvation factors, primarily nonspecific solvation. The corresponding dependence is described by multiparameter equations.Spontaneous dimerization of cyclopentadiene slows down upon dilution with various solvents; the maximal deceleration (by a factor of 3.5) was observed in strongly polar acetonitrile [1]. However, C1 oster and Pfeil [2] studied the rate of cyclopentadiene dimerization in 16 solvents and found no clear relation betweem the secondorder rate constant k and such solvent parameters as dielectric constant e, dipole moment m, Hildebrand solubility parameter d, and Reichardt electrophilicity parameter E T [3]. A certain relation (with a number of exceptions) was revealed between log k values and enthalpies of vaporization of the solvents: reduction of the latter parameter by a factor of 2 in going from 1-butanol to diethyl ether leads to decrease in k to a comparable extent. The authors concluded that, in the general case, solvent effect on a dissolved substance cannot be described using a single parameter owing to specific interactions.On the other hand, it is known that interactions of a solute with the solvent can be generalized on the basis of the linear Gibbs energy relationship principle by summation of effects produced by various solvation processes via multiparameter equations [4]. Among the latter, one of the most effective is the extended Koppel'3Pal'm equation which takes into account not only specific and nonspecific solvation but also structural features of the medium [5]. In the present work we made an attempt to generalize the data given in [2] on the rate constants for dimerization of cyclopentadiene at 40oC in 0.6 M solutions using Eq. (1): log k = a 0 + a 1 777 + a 2 777 n 2 3 1 n 2 + 2 e 3 1 2e + 1 + a 3 B + a 4 E T + a 5 d 2 + a 6 V M .(1)Here, n and e are, respectively, the refractive index and dielectric constant which determine solvent polarizability and polarity (i.e., factors responsible for nonspecific solvation); B is the basicity according to Pal'm [4], and E T is the Reichardt electrophilicity parameter [3] (these quantities characterize solvent ability for acid3base interactions, i.e., specific solvation); d is the Hildebrand solubility parameter (its squared value is proportional to the cohesion energy density); and V M is the molar volume which takes into account possible effect of structural factors. The solvent parameters were taken from [4] and reviews [6,7], and the calculation procedure conformed to the IUPAC recommendations concerning the application of correlation analysis in chemistry [8]. The corresponding data are collected in Table 1.However, processing of the data for 17 solvents according to Eq. (1) resulted in a too low [8] multiple correlation coefficient (R = 0.925). However, to reach an acceptable correlation quality, it was sufficient to exclude the most deviating data for only one s...

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The structure of synthesized 2,5-dimethyl-3,4-dihydro-2H-pyran-2-carboxylic acid was investigated by the single crystal X-ray diffraction analysis method. It was established that the molecule of the acid exists in the form of the endo isomer while the single crystal exists as a racemate of the two enantiomeric endo stereomers. Quantum-chemical calculations of a model of the macrocell of the acid by means of the semiempirical MOPAC2009 program agree well with the X-ray diffraction data.

Abstract. Kinetic aspects of the reaction of 2-hydroxyethyl-1,3,4-trimethylcyclohex-3-ene-1-carboxylate obtaining have been investigated. On the basis of the obtained results the kinetics of the process has been studied by the MichaelisMenten equation. The limiting stage of the reaction is established and its mechanism is suggested.