乙烯-甲基丙烯酸甲酯共聚物结构的~1H NMR和~(13)C NMR表征

采用核磁共振(1H NMR、13C NMR)技术对由双[N-(2,6-二异丙基苯基)-3-异丙基水杨醛亚胺]镍(Ⅱ)配合物/甲基铝氧烷(Methylaluminoxane,MAO)催化乙烯-甲基丙烯酸甲酯共聚得到的共聚物(EMMA-a)的微观结构和组成进行了详细的分析与表征,同时对自由基聚合制得的乙烯-甲基丙烯酸甲酯共聚物(EMMA-b)作了相应的分析与表征。通过1H NMR数据,计算得到两种共聚物样品中共聚单体甲基丙烯酸甲酯(MMA)的插入率分别为14.10%和10.26%(摩尔百分数)。基于13C NMR数据,分析比较了由配位共聚与自由基共聚所得共聚物样品在微观结构上的区别,结果发现,在共聚物的乙烯链段部分,由配位共聚得到的共聚物样品EMMA-a主要含有甲基型支链,而由自由基共聚所得共聚物样品EMMA-b具有长链型支链。另外,在共聚物的MMA链节部分,EMMA-a中的MMA单元的羰基(C‖O)碳的化学位移为177.27,而EMMA-b中的MMA单元的羰基(C‖O)碳的化学位移为175.96。     

1H and 13C NMR spectra of C-6 and C-9 substituted 3-azabicyclco[3.3.1]nonanes

The 1H and 13C NMR data for 3-azabicyclo[3.3.1]nonanes with OH and OMe substituents at C-6 and C-9 were measured using 1D (DEPT) and 2D (COSY, HSQC, HMBC, NOESY) experiments. Comparison of this NMR data illustrates the effects of stereochemistry and substitution at these positions.     

1H and 13C NMR data for C-6 substituted 3-azabicyclo[3.3.1]nonane-1-carboxylates

The 1H and 13C NMR spectra of 3-azabicyclo[3.3.1]nonanes with various oxygenated substituents at C-6 were assigned using 1D (DEPT) and 2D (COSY, HSQC, HMBC, NOESY) experiments. Close examination of this NMR data details the effects of substitution and stereochemistry at C-6 in these compounds.     

Radical Copolymerization of Acrylic Monomers. I. Effect of Solvent on the Copolymerization of Methyl Methacrylate and 1-Naphthyl Methacrylate

A study of the radical copolymerization of methyl methacrylate and 1-naphthyl methacrylate in benzene, chlorobenzene, and o-dichlorobenzene was made at 50°C. There is a marked effect of solvent on both r₁ and r₂ in all these systems, which can be correlated with the variation in the polarity of solvents. The glass transition temperatures of copolymers were discussed taking into consideration the sequence distribution of the copolymers and the homopolymers tg - values.     

Radical Copolymerization of Acrylic Monomers. II Effect of Solvent on Radical Copolymerization of Methyl Methacrylate and Styrene

The influence of various solvents on the copolymerization behavior of methyl methacrylate with styrene has been investigated. In these systems there is a significant solvent effect on both r_S and r_M which may be attributed to changes in the dielectric constant of the solvents used. The calculated relative reactivity of the polystyryl radical towards the methyl methacrylate monomer increases with increasing solvent polarity, whereas the reactivity of poly(methyl methacrylate) radical towards styrene monomer decreases. The results obtained are discussed taking into account the behavior of both monomers in homopolymerization with the same experimental conditions as in copolymerization.     

1H and13C NMR spectra of C- and N-substituted oxazolidines

An interrelationship between the structure of oxazolidines and the character of their¹H and¹³C NMR spectra was ascertained, and the most characteristic signals of the individual groups, which make it possible to establish the structure of the investigated compounds, were found.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 900–903, July, 1982.     

甲基丙烯酸甲酯和长链烷基酯的嵌段共聚

甲基丙烯酸甲酯和长链烷基酯的嵌段共聚戴李宗＊邹友思郭金泉潘容华（厦门大学化学系厦门３６１００５）关键词阴离子聚合，甲基丙烯酸酯，嵌段共聚合，表征１９９６－０８－０７收稿，１９９６－１１－１８修回国家自然科学基金资助项目嵌段共聚合能得到具微相体系的共聚...     

膦腈碱催化甲基丙烯酸烯丙酯与甲基丙烯酸甲酯的负离子共聚反应

室温下以膦腈碱(t-Bu P4)为催化剂,催化甲基丙烯酸烯丙酯(AMA)和甲基丙烯酸甲酯(MMA)进行负离子共聚反应.用核磁(1H-NMR、13C-NMR)、红外光谱(FTIR)、凝胶渗透色谱(GPC)、示差扫描量热仪(DSC)和热失重分析仪(TGA)等对聚合物结构和性能进行表征.结果发现,t-Bu P4能在室温下成功催化AMA与MMA的共聚反应,一步法合成结构可控的含悬垂双键共聚物.共聚反应中单体AMA和MMA的转化率均高于90%,且无交联或凝胶生成.通过NMR和FTIR对聚合物进行结构分析表明,AMA单体仅甲基丙烯酸酯双键参与聚合反应,烯丙基双键不参与聚合反应、无交联反应、环化反应等.聚合物中烯丙基结构单元的含量可通过体系中AMA/MMA的投料比调节.GPC结果表明所得共聚物分子量可控且分子量分布较窄.TGA和DSC结果表明,共聚物的热分解温度升高,玻璃化温度降低.     

Copolymerization and Copolymers of 2,4,5-Tribromostyrene with Methyl Acrylate and Methyl Methacrylate

Abstract

2,4,5-Tribromostyrene (TBSt) was copolymerized with methyl acrylate (MA) or methyl methacrylate (MMA) in a toluene solution using 2,2′-azobisisobutyronitrile as free radical initiator. The copolymerization reactivity ratios were found to be for the system TBSt / MA r₁= 7.4 ± 1.2 (TBSt) and r₂= 0.1 ± 1.4 (MA) and for the system TBSt / MMA r₁ = 1.8 ± 0.2 (TBSt) and r₂ = 0.1 ± 0.2 (MMA). The e and Q values were also calculated. The initial rate of copolymerization, as well as molecular weight of the obtained copolymers for both system linearly increase as the content of TBSt in the monomer mixture increases. Similar behavior has also been established for the course of the copolymerization reactions to high conversions. The resulting copolymers rapidly decompose at temperatures 20–800°C above the decomposition of corresponding (metha)crylate hompolymers. However, the glass transition temperature increases markedly with increasing TBS content.     

1H and 13C NMR studies of two monosubstituted [2.2]paracyclophanes

250 MHz ¹H NMR of two monosubstituted [2.2]paracyclophanes shows that whether the substituent is an electron releasing group, OMe, or a withdrawing group, CO₂Me, the transannular effect is deshielding. 62.86 MHz ¹³C NMR shows that among the six transannular effects, only one has a sign which changes with the nature of the substituent (–4.6 ppm for OMe but +3.3 ppm for CO₂Me).     

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.     

1H and 13C NMR chemical shifts of methyl-substituted benz[a]anthracenes

High-resolution ¹H NMR spectra are described for 1-, 2-, 3-, 4-, 5-, 6-, 8-, 11-, and 12-methyl-and 1,12-, 3,9-, and 3,10-dimethylbenz[a]anthracenes recorded at 220 MHz in carbon disulphide solution. ¹H shifts reflect ortho and para substituent effects as well as molecular distortions, especially in the bay regions of the 1-, 12-, and 1,12- compounds. ¹³C NMR resonances are reported for 4-,5-, and 12-methyl-, and 1,12-, 3,9-, and 3,10-dimethylbenz[a]lanthracenes. The protonated aromatic ¹³C shifts show γ- and δ-steric effects; γ shieldings also cause higher field (20 ppm) CH₃-resonances in 4- and 5-methylbenz[a]anthracenes than for unhindered methyl groups (∼ 21.6 ppm) in 3,9- and 3,10-dimethylbenz[a]anthracenes.     

1H and 13C NMR Spectra of 9H-Pyrimido[4,5-b]indoles

Based on analysis of ¹H and ¹³C NMR spectra of 9H-pyrimido[4,5-b]indole and its 4-phenyl-2-substituted derivatives, we have made assignments for the signals from the ¹H and ¹³C atoms of these compounds.     

Bulk Copolymerization of Styrene and Methyl Methacrylate at Elevated Temperatures

Reactivity ratios and full conversion range data (conversion, copolymer composition, molecular weight averages, glass transition temperature) are presented for styrene (STY)/methyl methacrylate (MMA)/copolymerization at elevated temperatures (130 and 150°C), a region where polymerization studies are scarce for the system, both for purely thermal polymerization and for peroxide‐initiated ones.     

Rapid 1H[13C]-resolved diffusion and spin-relaxation measurements by NMR spectroscopy

Hadamard-encoded heteronuclear-resolved NMR diffusion and relaxation measurements allow overlapping signal decays to be resolved with substantially shorter measuring times than are generally associated with 2D heteronuclear cross-correlation experiments. Overall measuring time requirements can be reduced by approximately an order of magnitude, compared to typical 2D heteronuclear single-quantum correlation-resolved diffusion or relaxation measurements. Specifically, in cases where chemical shift correlation information provides enhanced spectral resolution, the use of Hadamard encoding can be used to overcome uniqueness challenges that are associated with the analysis of concurrent dynamic processes and the extraction of time constants from overlapping exponential signal decays. This leads to substantially improved resolution of similar time constants than can be achieved solely through the use of post-acquisition processing techniques. In the ideal case of complete spectral separation of the signal decays, the usual constraint that time constants must be sufficiently different to resolve by exponential analysis can be circumvented entirely. Hadamard-based pulse sequences have been used to determine 1H[13C]-resolved diffusion coefficients and spin-relaxation time constants for the chemically similar components of an aqueous solution of ethanol, glycerol, and poly(ethylene glycol), and a dye-containing block-copolymer solution, which exhibit significant spectral overlap in their 1H NMR spectra.     

The conformations of bicyclo[3.1.0]hexane derivatives by 1H and 13C NMR

The ¹H and ¹³C spectra of bicyclo[3.1.0]hexanes and thujanes have been recorded and assigned. Application of the Karplus equation has yielded dihedral angles, and a computer calculation of the angle of ring buckle as a function of the main dihedral angles has been carried out. The calculated angles of ring buckle agree well with known values in the bicyclo[3.1.0]hexanes, but for 1-methylbicyclo[3.1.0]hexanes and thujanes the results are not self consistent. It is suggested that the bridgehead substituent causes the boat to twist, although the twist can be reduced by an axial methyl substituent on C-4.     

Correlated C-C and C-O bond conformations in saccharide hydroxymethyl groups: parametrization and application of redundant 1H-1H, 13C-1H, and 13C-13C NMR J-couplings

Methyl alpha- and beta-pyranosides of d-glucose and d-galactose 1-4 were prepared containing single sites of (13)C-enrichment at C4, C5, and C6 (12 compounds), and (1)H and (13)C[(1)H] NMR spectra were obtained to determine a complete set of J-couplings ((1)J, (2)J, and (3)J) involving the labeled carbon and nearby protons and carbons within the exocyclic hydroxymethyl group (CH(2)OH) of each compound. In parallel theoretical studies, the dependencies of (1)J, (2)J, and (3)J involving (1)H and (13)C on the C5-C6 (omega) and C6-O6 (theta;) torsion angles in aldohexopyranoside model compounds were computed using density functional theory (DFT) and a special basis set designed to reliably recover the Fermi contact contribution to the coupling. Complete hypersurfaces for (1)J(C5,C6), (2)J(C5,H6)(R), (2)J(C5,H6)(S), (2)J(C6,H5), (2)J(C4,C6), (3)J(C4,H6)(R), (3)J(C4,H6)(S), and (3)J(C6,H4), as well as (2)J(H6)(R)(,H6)(S), (3)J(H5,H6)(R), and (3)J(H5,H6)(S), were obtained and used to parametrize new equations correlating these couplings to omega and/or theta;. DFT-computed couplings were also tested for accuracy by measuring J-couplings in (13)C-labeled 4,6-O-ethylidene derivatives of d-glucose and d-galactose in which values of omega and theta; were constrained. Using a new computer program, Chymesa, designed to utilize multiple J-couplings sensitive to exocyclic CH(2)OH conformation, the ensemble of experimental couplings observed in 1-4 were analyzed to yield preferred rotamer populations about omega and theta;. Importantly, due to the sensitivity of some couplings, most notably (2)J(H6)(R)(,H6)(S), (2)J(C5,H6)(R), and (2)J(C5,H6)(S), to both omega and theta;, unique information on correlated conformation about both torsion angles was obtained. The latter treatment represents a means of evaluating correlated conformation in 1,6-linked oligosaccharides, since psi and theta; are redundant in these linkages. In the latter regard, multiple, redundant scalar couplings originating from both sides of the glycosidic linkage can be used collectively to evaluate conformational correlations between psi/theta; and C5-C6 bond rotamers.     

Mechanism of the Radical Copolymerization of Methyl Methacrylate and Maleic Anhydride

The kinetics of the copolymerization of methyl methacrylate and maleic anhydride was investigated in benzenic solutions at 60 and 70° C and in bulk at 60°C. The microstructure of the copolymers was determined by ¹H-NMR and IR spectrophotometry. In benzene solutions the mechanism of copolymerization involves the participation of an associative species between both comonomers. In bulk a terminal model is sufficient to explain all the results.