V. V. Zaitseva

Isomers of some vinyl and allyl compounds

The structures of two rotational isomers of styrene, methyl methacrylate, N-vinylpyrrolidone, and allyl benzoate found by AM1 calculations are discussed. Their formation is indicated by the presence of two minima on the curves of the rotation barriers around the C1-C2, C2-N3 and C(=O)-O, O-C(H2) bonds. The structures of the isomers of allyl compounds were detected capable of providing the cyclization reaction and hydrogen atom elimination. It was found that both double bonds were of similar reactivity. The suggested structures of the isomers can participate in intermolecular interactions with the formation of self-associates and heteroassociates (molecular complexes) due to the presence of C=C and C=O groups with different degree of conjugation.

Formation and decomposition of molecular complexes of N-vinylpyrrolidone, methyl methacrylate, and maleic anhydride

Schemes of complex formation and decomposition in monomers copolymerization in the absence of initiator (313 K) are suggested. The energy of formation of π-H- and H-complexes of N-vinylpyrrolidone with maleic anhydride, methyl methacrylate, or two latter with each other is 9.9–18.0 kJ mol–1, the equilibrium constant is 0.58–0.19 L mol–1 (CCl4). In the case of N-vinylpyrrolidone complexes with maleic anhydride we found the proceeding of a parallel radical process of formation of dimers, oligomers, and copolymers till ~10 wt % conversion. The copolymerization rate of these monomers is higher than the rate of their homopolymerization.

Structure of associates of vinyl molecules and maleic anhydride in CCl4 solution

The self-association of styrene, acrylonitrile, methylmethacrylate, N-vinylpyrrolidone, and maleic anhydride molecules is considered in dependence on the nature of the monomer, i.e., on the conjugation between functional groups. The AM1, Hartree-Fock (RHF), and density functional theory (DFT) methods of calculation are used in our investigations. Charge distributions on the atoms of interacting groups and contributions from overlapping molecular orbitals to the energy of formation of self-associates are found. The calculated parameters are compared with experimental data on absorption band shifts in IR spectra and on chemical shifts ΔH and ΔC for the hydrogen and carbon atoms of =CH, =CH2, C=O groups of bound molecules in 1H and 13C NMR spectra. The formation of π-H, CH…O, and CH…N bonds is proved. Analysis of CCl4/monomer dependences shows that dimers are present in dilute solutions, while the presence of trimers in concentrated solutions cannot be excluded. Self-association constants are determined along with the degree of self-association, which lies within the range of 40–60% for 50 mol% of a monomer in solution.

The physicochemical properties of cis-trans isomers of substituted epoxycyclohexanes and their molecular complexes with maleic anhydride

AM1, IR, and NMR studies of 1-methoxycarbonyl- and 1-acryloyloxymethyl-3,4-epoxycyclohexanes showed that the ratios between their trans and cis isomers were of 0.60: 0.40 and 0.45: 0.55, respectively. The equatorial forms were most favorable energetically (0.86 and 0.67 mole fractions). The trans-e and cis-e H-complexes of the epoxycyclohexanes with maleic anhydride were obtained; their heats of formation ranged from 0.8 to 3.3 kcal/mol according to AM1 calculations. The participation of the epoxide, carbonyl, and methyl or vinyl group in complex formation gave structures I, III, IIa or IIb, and IV with C-H⋯O (I–III) and C-H⋯π (IV) interactions. The vinyl group was a proton donor in complex II and a proton acceptor in complex IV. The presence of H-bonds in the structures caused the polarization of C=C bonds in 1-acryloyloxymethyl-3,4-epoxycyclohexane and maleic anhydride, which increased their reactivities. Structures IIIb and IV should exhibit the highest reactivity in copolymerization, and complex Ib should exhibit that in oxirane ring opening.

Quantum-chemical study of the reaction of N-vinylpyrrolidone with maleic anhydride

Energy profiles are calculated for the reaction of the structural isomer of N-vinylpyrrolidone with maleic anhydride in the gas phase. One of the reaction pathways leads to the formation and regeneration of maleic anhydride, acting as an activator of the process of (co)polymerization and dimerization of N-vinylpyrrolidone. According to calculations, the intermediate, isomer of N-vintlpyrrolidone, is a hybride of the singlet biradical and zwitter-ionic form.

Interaction between N-vinylpyrrolidone and methyl methacrylate

It is established that the interaction of the isomers of N-vinylpyrrolidone (NVP) and methyl methacrylate (MMA) leads to the formation of molecular π-H- and H-complexes with energies within the limits of 10.2–13.6 (AM1) or 18.2–24.0 (B3LYP/6-311++G(d)) kJ/mol. The structures of complex-bound molecules are examined with respect to changes in the charges on terminal -C1=C2- groups, the distance between them and atoms in an H-bond, and the presence of combined overlapping molecular orbitals (MOs). The presence of an averaged complex that includes presumably all possible structures and allows us to perform the copolymerization of specified monomers in the absence of an initiator is confirmed by means of UV and NMR spectroscopy.

Copolymerization of styrene with acrylonitrile and maleic anhydride

The complex formation constants for styrene (donor)-acrylonitrile (acceptor) and styrene-maleic anhydride (acceptor) systems are found to be 0.19 ± 0.01 and 0.28 ± 0.01 l/mol (1H NMR, CCl4, 298 K); the same values are characteristic for three-component systems of these monomers. The calculated ΔH 0 values (the AM1 method) for styrene-acrylonitrile (C1) and styrene-maleic anhydride (C2) complexes comprise −1.24 and −2.30 kJ/mol. Changes in charges on double bonds of complex-bonded molecules are in the range from 0.001 to 0.006 au. These values are typical of π-π complexes. By analyzing the composition and rate of bulk copolymerization (333 K, 0.03 mol/l AIBN), we have shown that two complexes are involved in chain propagation: r 1 =

Copolymerization of 3,4-epoxyhexahydrobenzyl acrylate with vinyl monomers☆

k_{2C_1 } /k_{2C_2 }