13C NMR Study of the Structure of Vinyl Chloride-1-Vinyl-1,2,4-triazole Copolymer

The structure of the copolymer prepared by radical copolymerization of vinyl chloride with 1-vinyl-1,2,4-triazole was studied by quantitative ¹³C NMR spectroscopy. The structural unit of the copolymer consists of the units of vinyltriazole and quaternized vinyltriazole, vinyl group, and four vinyl chloride units.     

1H and 13C NMR Study of Steric and Electronic Structure of 2-(2-Acylethenyl)-1-vinylpyrroles

According to the ¹H and ¹³C NMR data, the molecule of 2-(2-benzoylethenyl)-1-vinylpyrrole has a nearly planar structure with trans arrangement of the vinyl and oxovinyl groups. The unsaturated fragments give rise to effective conjugation. The vinyl group in 5-substituted 2-(2-acylethenyl)-1-vinylpyrroles strongly deviates from the heteroring plane because of steric effect of the substituent; however, this effect does not change the arrangement of the other unsaturated fragments.     

Kinetic study of the crosslinking reaction of 1,2‐polybutadiene with dicumyl peroxide in the absence and presence of vinyl acetate

The crosslinking reaction of 1,2-polybutadiene (1,2-PB) with dicumyl peroxide (DCPO) in dioxane was kinetically studied by means of Fourier transform near-infrared spectroscopy (FTNIR). The crosslinking reaction was followed in situ by the monitoring of the disappearance of the pendant vinyl group of 1,2-PB with FTNIR. The initial disappearance rate (R₀) of the vinyl group was expressed by R₀ = k[DCPO]^0.8[vinyl group]^−0.2 (120 °C). The overall activation energy of the reaction was estimated to be 38.3 kcal/mol. The unusual rate equation was explained in terms of the polymerization of the pendant vinyl group as an allyl monomer involving degradative chain transfer to the monomer. The reaction mixture involved electron spin resonance (ESR)-observable polymer radicals, of which the concentration rapidly increased with time owing to a progress of crosslinking after an induction period of 200 min. The crosslinking reaction of 1,2-PB with DCPO was also examined in the presence of vinyl acetate (VAc), which was regarded as a copolymerization of the vinyl group with VAc. The vinyl group of 1,2-PB was found to show a reactivity much higher than 1-octene and 3-methyl-1-hexene as model compounds in the copolymerization with VAc. This unexpectedly high reactivity of the vinyl group suggested that an intramolecular polymerization process proceeds between the pendant vinyl groups located on the same polymer chain, possibly leading to the formation of block-like polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4437–4447, 2004     

1H and 13C NMR spectra of N-vinylpyrroles

The position of the substituants in 2, 3-dialkyl-1-vinylpyrroles and 7-methyl-1 vinyl-4,5,6,7-tetrahydroindole was established on the basis of the ¹H and ¹³C NMR spectra. It was found that the S-trans conformation of the N-vinyl group is preferred. It is shown that the condensation of ketoximes with acetylene proceeds through the formation of free pyrroles and that vinyl oximes are not intermediates in the condensation.     

Multinuclear NMR (1H,13C,15N,17O) studies of intramolecular interactions in 1-vinylpyridones and quinolones

¹H and¹³C NMR was used to estimate the dihedral angles between the planes of the vinyl group and the hetero ring for 1-vinylpyridones and quinolones. The¹H,¹³C,¹⁵N, and¹⁷O NMR data showed the existence of a specific intramolecular weak hydrogen bond between the -H atom of the vinyl group and the O atom in 1-vinyl-2-pyridones and 2-vinyl-1-isoquinolone.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1539–1547, July, 1990.     

Reactivities and NMR spectra of vinyl ethers

Copolymerizations of n-butyl vinyl ether (M₁) with other vinyl ethers were carried out in toluene at ?78°C with EtAlCl₂ catalyst and the monomer reactivity ratios were determined. It was found that the relative reactivity of alkyl vinyl ether log 1/r₁ is higher when the alkyl group is more electron-donating and the reactivity correlates linearly with the Taft σ^* of alkyl group in the monomer. The NMR spectra of vinyl ethers and of vinyl ether–trialkylaluminum complexes were investigated. Close correlations were found between the spectral characteristics and the relative reactivity of vinyl ether in the copolymerization. The degree of resonance contribution in alkyl vinyl ether was also discussed on the basis of NMR data.     

Effect of aromatic ring anisotropy on the <Superscript>1</Superscript>H NMR shielding constants and conformational equilibrium of sterically strained aryl vinyl ethers

According to the ¹H and ¹³C NMR data and quantum-chemical calculations, phenyl vinyl ether exists mainly in the s-trans conformation which is characterized by concurrent p-π* interaction of the oxygen atom with both unsaturated fragments. Introduction of two methyl groups into the ortho positions of the benzene ring forces the latter to go out from the vinyloxy group plane, leading to loss of p-π* conjugation with the aromatic ring, enhancement of p-π* conjugation with the vinyl group, and transition of the molecule to s-cis conformation. The ¹H and ¹³C NMR data indicated that replacement of both o-methyl groups by tert-butyl makes the s-cis conformer sterically overcrowded even when the aromatic ring is oriented orthogonally with respect to the vinyl group; as a result, conformational equilibrium is displaced again toward s-trans rotamer.     

C—H···X (X = N,O, S) intramolecular interaction in 1‐vinyl‐2‐(2′‐heteroaryl)pyrroles as monitored by 1H and 13C NMR spectroscopy

¹H and ¹³C NMR spectroscopy of a series of 1‐vinyl‐2‐(2′‐heteroaryl)‐pyrroles were employed for the analysis of their electronic and spatial structure. The C—H···N intramolecular interaction between the α‐hydrogen of the vinyl group and the pyridine nitrogen, a kind of hydrogen bonding, was detected in 1‐vinyl‐2‐(2′‐pyridyl)pyrrole, which disappeared in its iodide methyl derivative. It was shown that this interaction is stronger than the C—H···O and C—H···S interactions in 1‐vinyl‐2‐(2′‐furyl)‐ and ‐2‐(2′‐thienyl)‐pyrroles. Copyright © 2001 John Wiley & Sons, Ltd.     

Structural analysis of 1-vinylbenzazoles by 1H and 13C NMR spectroscopy

Analysis of ¹H and ¹³C NMR spectral parameters for 1-vinylbenzazoles has shown that the vinyl group has a predominantly trans orientation with respect to the condensed benzene ring. Additional evidence is given for a long range effect of the nitrogen lone pair electrons on the one bond ¹³C-¹H and ¹H-¹H spin-spin couplings and on the ¹H chemical shifts.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 499–501, April, 1988.     

Studies on the phase structure of ethylene‐vinyl acetate copolymers by solid‐state 1H and 13C NMR

The phase structure of a series of ethylene‐vinyl acetate copolymers has been investigated by solid‐state wide‐line ¹H NMR and solid‐state high‐resolution ¹³C NMR spectroscopy. Not only the degree of crystallinity but the relative contents of the monoclinic and orthorhombic crystals within the crystalline region varied with the vinyl acetate (VA) content. Biexponential ¹³C NMR spin–lattice relaxation behavior was observed for the crystalline region of all samples. The component with longer ¹³C NMR spin–lattice relaxation time (T₁) was attributed to the internal part of the crystalline region, whereas the component with shorter ¹³C NMR T₁ to the mobile crystalline component was located between the noncrystalline region and the internal part of the crystalline region. The content of the mobile crystalline component relative to the internal part of the crystalline region increased with the VA content, showing that the ¹³C NMR spin–lattice relaxation behavior is closely related to the crystalline structure of the copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2199–2207, 2002     

1,1-Dialkyl-2-acyl-3-hydroxypyrazolidinium and 2,2-dialkyl-5-hydroxyisoxazolidinium salts

Salts of 1,1-dimethyl-2-acylhydrazines and 1,1-dialkylhydroxylamines add quantitatively to the double bond of oxo compounds with an unsubstituted vinyl substituent. The structure of the products depends on the nature of the substituent at the carbonyl group.¹H and¹³C NMR spectroscopy indicated that acrolein derivatives have the cyclic structure of 1,1-dialkyl-2-acyl-3-hydroxypyrazolidinium and 2,2-dialkyl-5-hydroxyisoxazolidinium salts, while derivatives of phenyl vinyl ketone and hydrazide salts are the corresponding linear, hydrazinium salts. Ring-chain tautomerism was found for several derivatives of methyl vinyl ketone in solution.Military Medical Academy, 194175 St. Petersburg. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1199–1203, September, 1998.     

Direct13C-1H coupling constants in the vinyl group of 1-vinylpyrazoles

Conclusions The¹³C-¹H direct coupling constants in the vinyl group of 1-vinylpyrazoles are stereo-specific and vary with change in the conformer ratio.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 202–204, January, 1987.     

Specific intramolecular C-H...O interactions in 1-vinyl-2-formylimidazole and 1-vinyl-2-formylbenzimidazole studied by1H and13C NMR spectral data

According to the¹H and¹³C NMR spectral data, the vinyl group in 1-vinyl-2-formylimidazole and 1-vinyl-2-formylbenzimidazole istrans-oriented with respect to the formyl fragment, while the carbonyl group occupies theanti-position with respect to the N atom of pyridine cycle. A specific intramolecular C—H...O interaction of a weak hydrogen bond type is realized between the -H atom of the vinyl group and O atom of the carbonyl group.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1197–1201, May, 1996.     

Total synthesis of the antiinflammatory and proresolving protectin D1

Stereoselective total synthesis of protectin D1 was completed through construction of the Z,E,E-triene structure by using the Suzuki coupling between the vinyl borane (C13-C22) and the vinyl iodide (C1-C12). The Z-enyne, the acetylene precursor of the vinyl borane was synthesized from optically active γ-TMS allylic alcohol in a straightforward way. On the other hand, the vinyl iodide was prepared by using Wittig reaction between the C8-C12 aldehyde possessing the requisite iodo-olefin moiety and the C1-C7 phosphonium iodide.     

Steric specificity of the direct13C-1H spin-spin coupling constants in the vinyl group in N-vinylpyrroles

Conclusions The direct¹³C-¹H spin-spin coupling constants of the vinyl group -carbon in N-vinyl-pyrroles display steric specificity and change depending on the dihedral angle between the planes of the vinyl group and the heterocycle.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1418–1421, June, 1987.     

Structure of vinyl ethers of a number of azoles according to1H and13C NMR data and quantum-chemical calculations

NMR¹H and¹³C spectra have been used to establish the conformational states of a number of azole vinyl ethers and to study the nature of the conjugation of the unshared pair of electrons of the oxygen atom with the azole and vinyl moieties. The H¹ NMR spectra of the vinyl ethers of indazole, 4,5-diphenylimidazole, benzimidazole, and 1,2,4-triazole revealed anomalous downfield shifts of the signal of the proton of the vinyl group, which are attributed to specific interactions, resembling weak hydrogen bonds, between these hydrogen atoms and the pyridine nitrogen. This conclusion agrees with the results of quantum-chemical calculations for the vinyl ether of indazole.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1031–1036, May, 1990.     

Structure and reactivity in cationic polymerization of butadiene derivatives. IV. 1-alkoxybutadienes

The reactivity of trans-1-alkoxybutadienes in cationic homopolymerization and copolymerizations and structure of the polymers produced were investigated. 1-Ethoxybutadiene is polymerized easily at ?78°C by various acidic catalysis. The reactivity of 1-ethoxybutadiene was similar to that of ethyl vinyl ether. The polymers produced possessed molecular weights of several thousands, and were composed of 70–95% 1,4 structure and 5–30% 3,4 structure. In the copolymerization of ethyl vinyl ether (M₁) with 1-ethoxybutadiene at ?78°C in toluene by boron trifluoride diethyl etherate, r₁ = 1.15, r₂ = 2.62. From the Hammett plot of the relative reactivities of alkoxybutadienes (alkoxy: CH₃O, C₂H₅O, i-C₃H₇O), the reaction constant _p^* was determined to be ?2.9. Results of the present study were compared with those of various butadiene derivatives.     

Studies of reactions with polymers. V. The reaction mechanism and resultant structure of PVA with PAN in DMSO without any catalyst

The reaction of polyacrylonitrile with poly(vinyl alcohol) in dimethyl sulfoxide without any catalyst was studied, and it showed that the adjacent nitrile groups on polyacrylonitrile could be linked up to form conjugated carbon-nitrogen sequence by the presence of poly(vinyl alcohol). However, no such reaction occurred when poly(vinyl alcohol) was replaced by i-propanol or poly(vinyl alcohol) graft copolymers. The structure of the resulting polymers were proposed by means of IR, UV, ¹H, and ¹³C-NMR spectroscopies. On the basis of the results, the effect of polymer feed and polymerization condition on this reaction were discussed. The compositions were determined by elemental analysis. The viscosity and thermal analysis of the products were also determined. At feed weight ratios of poly(vinyl alcohol) to polyacrylonitrile above one-half, gels were obtained.     

NMR Determination of the Microstructure of Polyvinyl Chloride Sulfone). II. 13C-(1H) Spectra

The ¹³C-(¹H) NMR spectra of poly(vinyl chloride sulfone)s with macroscopic compositions corresponding to the ratio vinyl chloride (V):SO₂(S) = n from ca. 1 to 4 have been analyzed in terms of comonomer sequences and configurational placements. In the copolymer with n ? 1, methylene and methine carbons in SVS sequences were resolved and were sensitive to “across SO₂” tacticity. No SVS sequences were observed in the copolymer with n = 2.0, confirming that it had a regular SVVS structure, which also showed a high “internal” stereosequence regularity. It was not possible to discriminate the methylene or methine carbon atoms in S(V)_n S sequences with n ≥ 2.     

Comparison of the electronic and steric structures of 1-vinyl-and 1-(prop-1-en-1-yl)pyrroles according to the <Superscript>1</Superscript>H and <Superscript>13</Superscript>C NMR data

According to the ¹H and ¹³C NMR data, 1-isopropenylpyrroles are characterized by larger dihedral angles between the heteroring and exocyclic double bond planes, as compared to isostructural 1-vinylpyrroles, due to steric effect of the α-methyl group in the propenyl fragment. As a result, p-π conjugation with the propenyl group is weaker than with the vinyl group. The propenyl group in 1-isopropenylpyrrole having no other substituents in the heteroring is forced out from the heteroring plane, while the 1-vinylpyrrole molecule is planar. If substituents are present in positions 2 and 5 of the pyrrole ring, the propenyl group on the nitrogen atom becomes orthogonal with respect to the pyrrole ring plane, so that no p-π conjugation is possible. The steric structures of (E)-1-(prop-1-en-1-yl)pyrrole and (Z)-1-(prop-1-en-1-yl)pyrrole are different: the propenyl group in the former is turned relative to the heteroring plane, while the latter molecule is planar.