Studies in cyclocopolymerization. V. Further evidence for charge-transfer complexes in cyclocopolymerization

Previous work from this laboratory has shown that certain 1,4-dienes which readily undergo cyclocopolymerization with certain alkenes also form charge-transfer complexes with the same alkenes. The results observed and the proposed cyclocopolymerization mechanism are consistent with participation of the charge-transfer complex as a distinct species in the copolymerization. It was the purpose of this investigation to determine whether there was a dilution effect on the relative reactivities of the monomers in support of the charge-transfer participation concept, and whether the results of a suitable terpolymerization study would also support this postulate. In the divinyl ether–fumaronitrile system, the maximum rate of copolymerization occurred at a monomer feed ratio of 1:2 and the composition of the copolymer was also 1:2 at a total monomer concentration of 3 mole/l. However, when the concentration was progressively lowered to 0.5 mole/l. at the same monomer feed ratio, the fumaronitrile content of the copolymer decreased in a linear manner. In a series of terpolymerization experiments with the divinyl ether–maleic anhydride–acrylonitrile system, it was shown that the divinyl ether–maleic anhydride ratio in the terpolymer was always less than 1:1 and had an upper limit of 1:2, regardless of the feed ratio of the termonomers. These results are consistent with the participation of the charge-transfer complex of divinyl ether and maleic anhydride in a copolymerization process with either maleic anhydride or acrylonitrile as the comonomer.     

Studies on the copolymerization of unsaturated 1,3-dioxane derivatives—IV. Radical copolymerization of 2-furyl-5,5-dimethyl-1,3-dioxane with maleic anhydride

The copolymerization of 2-furyl-5,5-dimethyl-1,3-dioxane with maleic anhydride in the presence of a radical catalyst yields equimolar, alternating copolymers in which the furyl units have 2,5-linkage. It has been shown that 2-furyl-5,5-dimethyl-1,3-dioxane forms a charge transfer complex with maleic anhydride. The equilibrium constant for the complex was determined by NMR spectroscopy.     

Note Copolymerization of Styrene with Maleic Anhydride Initiated by L-Ascorbic Acid

It is well known that maleic anhydride (MAH) behaves as an electron acceptor and forms charge-transfer complexes with donor monomers such as styrene (ST) [1,2], divinyl ether [3], and some of other olefms [4–61. The charge-transfer polymerization of ST with MAH has been extensively studied [1,7–11]. On the other hand, L-ascorbic acid (L-Asc) in combination with a suitable oxidants proved to be an efficient redox initiator for various vinyl polymerizations. Misra et al. [12] showed that the reduction of peroxides by ascorbic acid follows a chain mechanism with ascorbate and other free radicals as intermediates. Thus, we can expect that such an electron donor might initiate the copolymerization of MAH with ST.     

CHARGE-TRANSFER AND ENERGY-TRANSFER IN THE PHOTO-INDUCED COPOLYMERIZATION OF 2-VINYLNAPHTHALENE WITH MALEIC ANHYDRIDE

The initiation mechanism of the copolymerization of 2-vinylnaphthalene with maleic anhydride was studied under irradiation of 365 nm. The excited complex was formed from (1) the local excitation of 2-vinylnaphthalene followed by the charge-transfer interaction with maleic anhydride and (2) the excitation of the ground state charge-transfer complex, and then it collapsed to 1,4-tetramethylene biradical for initiation. A1: 1 alternating copolymer was formed in different monomer feeds. Addition of benzophenone could greatly enhance the rate of copolymerization through energy-transfer mechanism.     

Copolymer of maleic anhydride with 1,3-dichlorobuten: 2. Synthesis, characterization, and charge-transfer interaction with dimethyl sulfoxide

A new type of copolymer with strong electron accepting ability on the basis of maleic anhydride and 1,3-dichlorobutene-2 has been synthesized. Both solutions and solids have been investigated. It was found that the dissolution of copolymer in dimethyl sulfoxide (DMSO) leads to its transformation: charge-transfer interaction with DMSO and subsequent Pummerer rearrangement.     

The Fundamental Basis for Cyclopolymerization. I. Unconjugated Chromophoric Interactions Related to Cyclopolymerization

Abstract

A far ultraviolet study showed progressive bathochromic wavelength shifts within the following series of compounds: (i) allyltrimethylsilane, diallyldimethylsilane, triallylmethylsilane, tetraallylsilane; (ii) allyltripropylsilane, diallyldipropylsilane, triallylpropylsilane; (iii) 4,4-dimethyl-1-pentene, 4,4-dimethyl-1,6-heptadiene, 4-allyl-4-methyl-1,6-heptadiene. In the series tri-methylvinylsilane, dimethyldivinylsilane, methyltrivinylsilane, and tetravinylsilane, trimethylvinylsilane was shifted bathochromically from the rest of the vinylsilanes, which were grouped together. Allyldimethylvinylsilane showed two independent absorptions.     

Kinetic Features and Mechanism of Alternating Copolymerization of lndene with Maleic Anhydride

The radical copolymerization of indene (IN) with maleic anhydride (MA) was investigated. The charge-transfer complexes (CT complexes) between comonomers were studied by means of spectrophotometric measurements. It was found that the maximum copolymerization rate occurred at a comonomer feed ratio that did not correspond to the composition of the CT complex and the composition of copolymer. It was shown that rate maximum was displaced towards an excess of IN in the solvents with strong donicity. The Acceptor Number of solvent influences neither the initial rate nor the position of the rate maximum. Some kinetic calculations were made to assess values of the cross-propagation rate constants and to elucidate the mechanism of propagation of macromolecular chains.     

Über die reaktion von pyridin mit maleinsäureanhydrid-I

The reaction between pyridine and maleic anhydride was studied thermoanalytically. With reagents of high purity, the reaction proceeds very slowly with formation of oligomeric and polymeric products. Protic reagents (such as water, maleic acid, acetic acid or pyridinium hydrochloride) catalyse the reaction during which polymerization occurs at a later stage.Radical inhibitors (such as sulphur, 2,2-diphenyl-1-picryl hydrazyl or anthracene) have no influence on the reaction rate.Ultra-violet spectroscopic studies on solutions of maleic anhydride and some derivatives in pyridine and dimethyl sulphoxide show a charge-transfer absorption for the maleic anhydride/pyridine system at 303 nm.     

On the origin of long-lived emission in some charge-transfer crystals

Temperature dependence of emission spectra, decay times and intensity of emission, for molecular (1:1) crystals of charge-transfer (CT) complexes of tetrachloro- and tetrabromophthalic anhydride with penta- and hexamethylbenzene, have been investigated over a wide temperature range (1.7–300 K). A long-lived emission, observed in those crystals, has been identified as CT phosphorescence from CT triplet traps. No delayed emission, controlled by triplet—triplet annihilation (P-type), has been found. An explanation of observations connected with the fact that these complexes belong to the class where the lowest triplet state is of charge-transfer character is offered.     

Copolymerization and Charge-Transfer Interaction of Methyl Isopropenyl Ketone Cyclodimer with Maleic Anhydride and Maleimide

The copolymerizations of methyl isopropenyl ketone cyclodimer(MIPKD: 2-acetyl-2,5,6-trimethyl-2,3-dihydropyran) with maleic anhydride (MAn) and with maleimide (MI) in the presence of α,α′-azobisisobutyronitrile were investigated at 60 and 80°C. It was found that the copolymerizations were performed in both systems to give rather low molecular weight copolymers consisting of less than 50% MIPKD units. It was also observed from IR and NMR spectral determinations of the systems of MIPKD with MAn and with MI that 1:1 charge-transfer complexes with a small equilibrium constant were formed. Formation of these complexes seemed to affect the copolymerizations. Finally, the copolymerization of MIPKD with MAn was studied kinetically. The mechanism of copolymerization is discussed.     

Synthesis of a new chiral bisphospholane ligand for the Rh(I)-catalyzed enantioselective hydrogenation of isomeric beta-acylamido acrylates

The highly stereoselective synthesis of a chiral silylphospholane has been described, which can be advantageously used as a building block under base-free conditions for the construction of diphosphines related to DuPHOS. The utility of silylphospholane is shown in the synthesis of a new bisphospholane ligand 1 (MalPHOS), which is characterized by a maleic anhydride backbone. The ligand forms with Rh(I) a complex with a larger bite angle P-Rh-P than the analogue Me-DuPHOS complex. Both complexes have been tested in the asymmetric hydrogenation of unsaturated alpha- and beta-amino acid precursors of pharmaceutical relevance. In several cases, the new catalyst was superior in comparison to the Me-DuPHOS complex, in particular when (Z)-configured beta-acylamido acrylates were used as substrates.     

Investigation of the stereochemistry of adducts of aryloxyfurans with maleic acid derivatives by PMR spectroscopy

The stereochemistry of adducts of aryloxyfurans with maleic acid derivatives was studied by PMR spectroscopy. It was shown that adducts with maleic anhydride are produced only in the form of exo isomers, whereas adducts with N-phenyl-maleinimide are isolated from the reaction in the form of mixtures of endo and exo forms. Bromination of the adducts was realized. The orientation of the bromine atoms in the bromination products was established by PMR spectroscopy: The bromine atoms in the dibromo derivative of the adduct with maleic anhydride are cis-oriented (endo-4-Br, endo-5-Br), whereas the bromine atoms have a trans configuration (endo-4-Br, exo-5-Br) in the dibromo derivative of the adduct with N-phenylmaleinimide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 613–615, May, 1984.     

Molecular complexes of antipsychotic pharmaceutical parent molecule phenothiazine and unsaturated acid anhydrides

The charge-transfer complexes (CTC) between a parent molecule of antipsychotic pharmaceuticals, phenothiazine, and seven unsaturated acid anhydrides, 1,4,5,8-naphtalenetetracarboxylic dianhydride, diphenic anhydride, maleic anhydride (MA), 3,4,5,6-tetrahydrophthalic anhydride (THPA), 3-hydroxy-1,8-naphthalic anhydride (HONA), 4-chloro-1,8-naphthalic anhydride (ClNA), and 1,8-naphthalic anhydride (NA) were studied using IR and UV spectroscopy. Stability constants (K) at different temperatures were measured, and based on the K's DeltaH and DeltaS were calculated. The values of electron affinity (E(A)) of anhydrides were obtained according to Mulliken's theory. The results show that phenothiazine is an excellent donor and has strong ability to complex with the carbonyl group, and the E(A) values have good linear relationships with DeltaH and K, respectively. The solvent effect on CTCs was also determined and explained. The CTC of phenothiazine-succinic anhydride (SA) was studied under the same conditions. It was deduced from the results obtained that there were two charge-accepting centers in the unsaturated acid anhydrides when they formed CTCs with phenothiazine. The first one was carbon atom of the two carbonyl groups and the second one was their -C=C- in the molecules.     

马来酸酐均聚反应机理的理论研究Ⅰ: 马来酸酐的基态和激发态电子结构

用AM1方法计算了马来酸酐的基态和激发态电子结构、电荷分布和键级。马来酸酐基态分子的HOMO和LUMO分别是双键C=C的成键π-MO和反键π*-MO。从微观电子结构层次探讨了马来酸酐在不同条件下的均聚反应机理。计算结果能很好地阐明实验事实。     

Polymerization of cyclic ethers in the presence of maleic anhydride. Part II. Investigation of the polymerization mechanism

In order to elucidate the reaction mechanism of both the radiation-induced and benzoyl peroxide-catalyzed polymerizations of cyclic ethers in the presence of maleic anhydride, the development of color during reaction and copolymerization of oxetane derivatives were investigated. Upon addition of a small amount of the γ-ray or ultraviolet-irradiated equimolar solution of a cyclic ether and maleic anhydride to isobutyl vinyl ether, a rapid polymerization took place, and the resulting polymer was confirmed to be a homopolymer of isobutyl vinyl ether. A heated solution of dioxane, maleic anhydride, and a small amount of benzoyl peroxide can initiate the polymerization of isobutyl vinyl ether in the same manner. The electrical conductivity of a 1:1 mixture of maleic anhydride and dioxane is increased by about a factor of ten after ultraviolet irradiation. These results indicate that some cationic species are actually formed in the system by irradiation or the decomposition of added benzoyl peroxide. The mechanism of formation of the cationic species responsible for the initiation may be explained as follows. A free radical of an ether is formed by abstraction of a hydrogen atom attached to the carbon adjacent to oxygen atom, followed by a one-electron transfer from the resulting radical to maleic anhydride, an electron acceptor, to yield the cationic species of the ether and the anion-radical of maleic anhydride, respectively. The resulting cationic species as well as the counteranion-radical are resonance-stabilized. Therefore, the present polymerization may be designated a radical-induced cationic polymerization.     

Charge-transfer complex formation and copolymerization of maleic anhydride with benzoselenophene

Under the influence of azobisisobutyronitrile, benzoselenophene and maleic anhydride slowly polymerize to form an alternating copolymer. The two comonomers form a charge-transfer complex (K^AD_c at 30° in chloroform: 0·22 l mol^?1). These properties of benzoselenophene are similar to those of benzothiophene and indole but are different from those of benzofuran. It is possible that the charge-transfer complex plays a role in the copolymerization.     

On the role of monomer—monomer donor—acceptor complexes in the free-radical copolymerisation of styrene and maleic anhydride

The kinetics of the free-radical copolymerisation of styrene and maleic anhydride at 60° in bulk and in several solvents have been studied. Copolymer compositions may be interpreted either in terms of a mechanism involving a penultimate group effect or in terms of a mechanism involving some propagation via styrene—maleic anhydride donor—acceptor complexes. However, experiments at various overall monomer concentrations and in which zinc chloride and phthalic anhydride have been added indicate that the penultimate group effect mechanism is to be preferred.     

Radiation-induced solid-state copolymerization of maleic anhydride and acenaphthylene

Radiation-induced solid-state copolymerization of the maleic anhydride–acenaphthylene system was carried out for the purpose of studying the solid-state polymerization of vinyl compounds in a binary system. Melting point measurement confirmed that this binary monomer system forms a eutectic mixture in the solid state. The solid-state polymerization of these monomers proceeds at maximum rate at the eutectic composition, and the polymerization products consist of a mixture of polyacenaphthylene and 1:1 maleic anhydride–acenaphthylene alternating copolymer. Since the 1:1 copolymer was obtained in solution polymerization also and maleic anhydride did not homopolymerize in solid state, it is considered that the solid-state copolymerization of maleic anhydride and acenaphthylene occurs in a liquidlike state at the boundary of the two monomer crystals.     

PHOTOCOPOLYMERIZATION OF MALEIC ANHYDRIDE AND VINYL ACETATE

The charge-transfer complex of maleic anhydride and vinyl acetate was copolymerized under UV light. The chain composition and structure of the copolymer were analyzed with conductometry and NMR, and the chain sequence was determined as alternating. The copolymerization rates at different feed ratios, temperatures and in different solvents were investigated, giving evidence to the very active involvement of the CT complexes in the copolymerization. Terpolymerization with acrylonitrile also showed that the complex mechanism was a proper one for this system.     

Donor-Acceptor Complexes in Copolymerization. XXXVII. Alternating Diene-Dienophile Copolymers. 5. Formation of Conjugated Diene-Maleic Anhydride Copolymers through Retrograde Dissociation of Furan-Maleic Anhydride Diels-Alder Adduct

Abstract

The equimolar, alternating copolymer of isoprene, as well as other conjugated dienes, and maleic anhydride is formed by the radical catalyzed reaction of the conjugated diene with maleic anhydride in the presence of furan as well as with the furan-maleic anhydride Diels-Alder adduct. The retrograde dissociation of the cyclic adduct above 60°C regenerates furan and maleic anhydride which in the presence of isoprene forms the isoprene-maleic anhydride ground state complex. The latter yields the corresponding cyclic adduct in the absence of a radical catalyst and undergoes excitation and homopolymerization in the presence of a catalyst.