共查询到20条相似文献,搜索用时 11 毫秒
1.
Hideaki Tanaka Minoru Tsuda Hiroshi Nakanishi 《Journal of polymer science. Part A, Polymer chemistry》1972,10(6):1729-1743
The photochemistry of the cinnamylideneacetyl group was investigated with respect to a photosensitive polymer, poly(vinyl cinnamylideneacetate). The photochemical reaction of 1,4-butanediol dicinnamylideneacetate was intramolecular cyclobutane formation. The photosensitive polymer underwent dimerization of the cinnamylideneacetyl moiety to form a cyclobutane ring. The reactivity of the double bond adjacent to the carbonyl group was larger than that of the double bond adjacent to the phenyl group in the chromophore. The quantum yield of the reaction was larger in the solid state than in solution: ? > 1.2 in crystalline state, ? = 0.5 in polymer film, ? = 0.1 in solution. The reaction was sensitized by triplet sensitizers (ET > 42 kcal/mole). The thermal reaction of the polymer was completely different from the photochemical reaction. A radical initiator was very ineffective for reaction of the polymer. 相似文献
2.
Lacerda V da Silva GV Constantino MG Tormena CF Williamson RT Marquez BL 《Magnetic resonance in chemistry : MRC》2006,44(1):95-98
Detailed measurements of long-range heteronuclear spin-spin coupling constants, especially (2, 3)J(CH) spin-spin couplings for various cyclopentane derivatives, are reported. The measurements are based on a 2D heteronuclear correlation experiment named G-BIRD(R, X)-CPMG-HSQMBC. 相似文献
3.
4.
Contreras RH Esteban AL Díez E Della EW Lochert IJ Dos Santos FP Tormena CF 《The journal of physical chemistry. A》2006,110(12):4266-4275
Hyperconjugative and electrostatic interactions effects on 1J(CH) spin-spin coupling constants (SSCCs) are critically studied from both theoretical and experimental points of view. A qualitative model is used to predict how the former affect such SSCCs, while electrostatic interactions are modeled with a point charge placed in the vicinity of the corresponding sigma(CH) bond. Hyperconjugative interactions are calculated using the "natural bond orbital" approach, and using the point-charge model, it is shown how intertwined are both types of interactions. Several members of the series 1-X-bicyclo[1.1.1]pentane and 1-X-3-methylbicyclo[1.1.1]pentane are chosen as model compounds for measuring 1J(CH) SSCCs; in some of them were performed also DFT-SSCC calculations. The strained cage substrate in these series defines strong sigma-hyperconjugative interactions, making these compounds excellent examples to verify the qualitative model presented in this work. It is verified that (a) hyperconjugative interactions from the sigma(CH) bond or into the sigma(CH) antibond containing the coupling nuclei yield a decrease of the corresponding 1J(CH) SSCC and (b) hyperconjugative interactions from other bonds involving the coupling C nucleus yield an increase of that 1J(CH) SSCC. 相似文献
5.
E. Taskinen 《Tetrahedron》1978,34(4):429-431
A 13C NMR study of the transmission of substituent effects in m- and p-substituted derivatives of α-MeO-styrene and the E and Z forms of α-MeO-β-Me-styrene has been performed. The CC bond of vinyl ethers is a considerably weaker transmitter of substituent effects than that of ordinary alkenes, especially if p-π conjugation in the vinyloxy system is unhindered. In each series of compounds studied, a fairly good linear correlation exists between the 13C chemical shift of the β carbon and the Hammett σ parameter. The worst linear correlation was obtained for the C-β shifts of α-MeO-styrenes. The shifts concerned, however, were nicely correlated with the Hammett σ+ parameter. 相似文献
6.
Rahimipour S Palivan C Freeman D Barbosa F Fridkin M Weiner L Mazur Y Gescheidt G 《Photochemistry and photobiology》2001,74(2):149-156
The electron-transfer properties of the hypericin derivatives, dibromo-, hexaacetyl-, hexamethyl- and desmethylhypericin, were studied. Cyclovoltammetric measurements revealed that dibromo- and desmethylhypericin have almost the same redox potentials as the parent hypericin. Substitution of the hydroxyl groups by acetoxy leads to less negative E1/2 values, whereas methoxy substitution induces more negative values. Electron paramagnetic resonance (EPR)/electron nuclear double resonance/general TRIPLE spectroscopy and quantum mechanical calculations were used to establish the structure of the one-electron reduced stages of hypericin derivatives. Proton loss in the bay region, already demonstrated for hypericin, was also found for dibromo- and desmethylhypericin. The spin and charge of the radical ions are predominately confined to the central biphenoquinone moiety of the hypericin skeleton. Generation of the radical ions by in situ electrolysis indicates that the redox potentials of hypericin, dibromo- and desmethylhypericin, containing hydroxyls at the 1, 3, 4, 6, 8 and 13 positions, largely depend on the solvent. With phosphate-buffered saline (pH 7.4)/dimethylsulfoxide (DMSO) as the solvent the EPR spectra of the corresponding radical ions appear at markedly lower potentials than in pure DMSO and N,N'-dimethylformamide. However, this effect is not observable for hexaacetyl- and hexamethyl-hypericin-lacking hydroxyl groups. In all cases the EPR data and calculations revealed the presence of 7,14 tautomers. 相似文献
7.
Four new luminescent organoboron complexes have been synthesized and fully characterized. These compounds are four-coordinate boron chelated by either 8-hydroxyquinolato (q) or functionalized 8-hydroxylquinolato ligands, including BPh2(5-(1-naphthyl)-q) (1), BPh2(5-(2-benzothienyl)-q) (2), B(2-benzothienyl)2q (3), and B(2-benzothienyl)2(2-Me-q) (4). All four compounds have a tetrahedral geometry as established by X-ray diffraction analyses. In solution, compounds 1-4 have an emission maximum at 534, 565, 501, and 496 nm, respectively, at room temperature. They emit similar colors in the solid states without red shifts of the emission band due to the lack of significant intermolecular interactions in the crystal lattices. The substituent group at C5 or C2 position of the 8-hydroxyquinolato ligand has been observed to have a significant impact on the emission energy and the emission quantum efficiency of the boron complexes. Molecular orbital calculations (Gaussian 98) showed that the electronic transition of 1 and 2 is a pi-pi* transition centered on the functionalized 8-hydroxyquinolato group and the electronic transition of 3 and 4 is an interligand charge transfer from the 2-benzothienyl ligand to the hydroxyquinolato ring. A double-layer electroluminescent device using 3 as the emitter has been fabricated, which produced a broad emission band with a significant contribution of exciplex emission. 相似文献
8.
Lacerda V da Silva GV Constantino MG Dos Santos RB de Castro EV Silva RC 《Magnetic resonance in chemistry : MRC》2008,46(3):268-273
The (2,3)J(CH) dependence on dihedral angle (theta H--C--C--X) for cyclopentane derivatives was investigated. We observed that the combined use of experimentally obtained (2,3)J(CH) values and the theoretically determined dihedral angles between the corresponding nuclei can be used to infer the relative stereochemistry of the ring substituents in cyclopentane derivatives. There is a good correlation between the magnitude of (3)J(CH) and the dihedral angle between the hydrogen and the coupled carbon (R2 = 0.88). 相似文献
9.
The rate of methoxydefluorination (NaOMe-MeOH, 323.2 K) and the 19F-NMR chemical shifts of some substituted penta- and nona-fluorobiphenyls have been measured. The observed substituent effects parallel those found in the corresponding pentafluorobenzenes and demonstrate proportionate transmission of the total substituent electronic effect across the aromatic system. 相似文献
10.
Examination of several model organophosphorus compounds, bicyclic phosphates ( 1 ), p-substituted phenylphosphonates ( 2 ), and acidic alkylphosphonates ( 3 ) reveals that the polar substituent effect in organophosphorus esters parallels that of carbon compounds. No significant variation in polar effects of different alkyl groups with up to 10 carbon atoms is observed. As demonstrated by us, the commonly used Kabachnik polar constant σΦ for alkyl groups of organophosphorus compounds reflects the steric effect associated with steric hindrance to solvation of acidic anions. Therefore, a set of solvation steric parameters Eps has been calculated from pKa values of organophosphorus acids. This parameter can be applied to describe the structural effect on dissociation of organic acids and, after suitable modification, may reflect the steric effect of alkyl groups in hydrolytic reactions of organophosphorus esters. 相似文献
11.
Substituent effects upon 3J(FF) are demonstrated to be additive, and a previous analysis of 4J(FF) and 5J(FF) in polysubstituted fluorobenzenes is updated. 相似文献
12.
M. Emí lia N.P.R.A. Silva Armando J. L. Pombeiro Jo o J. R. Fraú sto da Silva
Rudolf Herrmann
Norbert DeusRichard E.Bozak
《Journal of organometallic chemistry》1994,480(1-2):81-90The anodic behavior of 31 ferrocene derivatives (FcX) (four of which have been prepared for the first time) of the types shown below has been investigated by cyclic voltammetry (and, in some cases, also by controlled-potential electrolysis and differential pulse polarography) at a Pt electrode, in an aprotic solvent: Fc---C(Y)=Z (class A; Y = R (hydrogen, alkyl or unsaturated-carbon moiety) or Cl; Z = CRR′, derived functionalized groups or {W(CO)5}); Fc---C(Y)=O (class B; Y --- R or OH); other types (class C, including azide, other unsaturated N moieties, acyloxy or phosphino); disubstituted ferrocenes (class D, with alkyl, aminoalkyl, phosphino, B(OH)2 or −HGCl substituents, or the S---S---S bridge). All these substituted ferrocenes exhibit a one-electron reversible oxidation centered at iron and the effect of the substituents on the half-wave oxidation potential is discussed in terms of electronic properties. Using the accepted linear correlations between the half-wave oxidation potential and the Hammett constant σp of the substituent, σp was estimated for the first time for 29 of the substituents in the ferrocenes listed above. The anomalous behavior of complexes with a hydroxy or a carbonyl group is discussed. No correlation was observed between the oxidation potential and either the energy of the electronic absorption bands or the 1H NMR chemical shift of the unsubstituted cyclopentadienyl ring, although there are rough correlations for class A compounds. This behaviour is compared with those of [Fc-CHYZ]. kw]Iron; Redox potentials; Ferrocenes; Electrochemistry; Substituent effects 相似文献
13.
1-(2-Mercaptoethyl)phthalazine (VII) and its analogs such as S-2-(1-phthalazyl)ethyliso-thiuronium bromide (VI), sodium S-2-(1-phthalazyl)ethylthiosulfate (VIII), 1,3-bis-acetylthio-2-(1-phthalazyl)propane (XII), 2-(1-phthalazyl)-1,3-propanedithiol (XIII), disodium 2-(1-phthalazyl)-1,3-propanedithiosulfate (XIV), 3-dimethylamino-2-(1-phthalazyl)-1-propanethiol (XVII) and 3-(4-methyl-1-piperazinyl)-2-(1-phthalazyl)-1-propanethiol (XIX) have been prepared as potential radiation protection agents. 相似文献
14.
Taniyuki Furuyama Daichi Tamura Hajime Maeda Masahito Segi 《Tetrahedron letters》2018,59(30):2913-2916
In this study, indolo-naphthyridine-6,13-diones (5a–d) with four different peripheral substituents were prepared via bay-annulation reactions of indigo. The resulting compounds (5a–d) exhibited fluorescence in the red to near-IR region, while the parent indigo molecule showed no fluorescence. Although the peripheral substituents were oriented to the exterior of the π-conjugated system, the electronic structure affected the absorption and fluorescence spectra. Moreover, calculated molecular orbitals and absorption spectra successfully reproduced the experimental absorption spectra and cyclic voltammograms. 相似文献
15.
Masoud MS Ali AE Shaker MA Ghani MA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(13-14):3102-3107
A series of diazoaminobenzene derivatives (seven) in which the substituents have a wide range of electronic characters are set out to understand the involvement of the substituent identity in controlling the changes in their electronic absorption spectra. The interactions between the diazoamino group and the different groups account for some spectral shifts. The UV-vis spectrum of each compound is measured in several solvents with wide variations of solvent polarity parameters to examine the role of the chemistry of the solvent in these spectroscopical changes. The electronic transitions are assigned and the solvent induced spectral shifts are analyzed in relation to the different solute-solvent interaction mechanisms using computational chemistry. The regression analysis is applied for correlating the different parameters. The results help to assign the solute-solvent interactions and the solvatochromic potential of the investigated compounds. It is concluded that the electronic character of the substituent and the chemical nature of the solvent are the major factors for the observed solvatochromism. 相似文献
16.
H.J. Breunig E. Lork O. Moldovan C.I. Ra? 《Journal of organometallic chemistry》2008,693(15):2527-2534
DmpSbBr2 (Dmp = 2,6-Mes2C6H3) (1) is obtained by the reaction of DmpMgBr with SbCl3. The reaction of 1 with KI in ethanol gives DmpSbI2 (2). Dmp(Ph)SbBr (3) is prepared from DmpMgBr and PhSbCl2. Compound 1 or 3 react with LiAlH4 to form DmpSbH2 (4) or Dmp(Ph)SbH (5). Compound 4 reacts with MeI in presence of DBU to give Dmp(Me)SbH (6). DmpSb(SbMe2)2 (7) is obtained from 4 and Me4Sb2. Elimination of hydrogen from 6 gives [Dmp(Me)Sb]2 (8). Hydrolysis of 3 gives Dmp(Ph)SbOH (9). The molecular structures of 1-3, 5, 8 and 9 were determined by X-ray diffraction on single crystals. 相似文献
17.
Choji Kashima Nobutoshi Yoshiwara Tadakuni Tajima Yoshimori Omote 《Journal of heterocyclic chemistry》1987,24(6):1595-1596
The preparative method of 3-(1-imidazolyl)-2-alkenoic acid derivatives and the related compounds was improved by the use of strong bases such as sodium hydride in DMF. By this improved method, the preparation of 2-substituted 3-(1-imidazolyl)-2-alkenoic acid derivatives was accomplished in good yields. 相似文献
18.
The acid catalysed interaction in dioxan of trialkyl orthoformates with diisophor-2(7)-en-ol-3-one, diisophor-2(7)-en-ol, and their bisnor-homologues, provides the corresponding 1-alkoxy-compounds. Their structure is established by the identity of -methoxydiisophor-2(7)-en-3-one obtained by this method, and by the action of sodium methoxide on 1-chlorodiisophor-2(17)-en-3-one. The latter is regenerated from 1-methoxy(or ethoxy) diisophor-2(7)-en-3-one by the action of stannic chloride-acetyl chloride. Catalytic hydrogenation reduces the 3-keto-function in 1-alkoxydiisophor-2(7)-en-3-ones to a methylene unit; simultaneous removal of the 1-alkoxy-group in the case of the 1-isopropoxy-homologue yields the penultimate parent hydrocarbon of this series, diisophor-2(7)-ene.The combined action of silver sulphate and formic acid in concentrated sulphuric acid on 1-chlorodiisophor-2(7)-en-3-one (and its bisnor-homologue) produces the corresponding 1-carboxylic acids. These are also obtainable by the hydrolysis of the 1-cyano-compound, and are esterifiable by the standard methods. 相似文献
19.
Del Bene JE Alkorta I Elguero J Mó O Yáñez M 《The journal of physical chemistry. A》2010,114(48):12775-12779
Ab initio equation-of-motion coupled cluster (EOM-CCSD) one-bond spin-spin coupling constants (1)J(B-N), (1)J(B-H), and (1)J(B-F) have been evaluated for complexes X:BH(n)F(3-n) with X = N(2), NCH, NCLi, H(2)CNH, NF(3), and NH(3), for n = 0-3. These complexes can be classified as either covalent or van der Waals complexes, on the basis of their binding energies and B-N distances. (1)J(B-N) for covalent complexes varies significantly from -19 to +9 Hz, whereas (1)J(B-N) is less than 2 Hz for van der Waals complexes. An absolute value of (1)J(B-N) of 3 Hz or greater indicates that the complex is covalently bonded, but a small value of this coupling constant does not necessarily mean that it is a van der Waals complex, in view of the variation among these complexes found for (1)J(B-N) as a function of the B-N distance. Deformation of the boron acid upon complex formation and electron donation by the nitrogen base has opposing effects on both (1)J(B-H) and (1)J(B-F). These effects are relatively small in van der Waals complexes. In covalent complexes, electron donation has the dominant effect on (1)J(B-H), and on (1)J(B-F) in complexes with BH(2)F and BHF(2), but acid deformation has the dominant effect on (1)J(B-F) in complexes with BF(3). Values of both (1)J(B-H) and (1)J(B-F) reflect the van der Waals or covalent nature of the B-N bond. 相似文献
20.
N-Mono and N,N-dialkyl/diarylbarbituric acids exist in solution as a single tautomer. The 13C nmr spectroscopy shows that they are present in the triketo form in a number of polar and non-polar solvents. 2-Thiobarbituric acid derivatives, however, show extensive tautomerization. Their 13C chemical shift assignments were achieved by utilizing models 11a , 11c , 12b and 12d and from which relative tautomer distribution ratios were determined. These ratios were correlated with the dielectric constant of the various solvents (?). Thio-barbituric acids also formed adducts with solvents having carbonyl groups, characteristic observed only with barbiturates possessing the thione or thiophenolic group. 6-Amino and 6-methyluracils and thiouracils exist in DMSO solution as stable “ene” forms as do orotic acid, 24 , and its thio analogue 25. Compound 25 undergoes disproportionantion and tautomerization when heated or on prolonged standing in solution. Literature contradictions regarding the structure of “4,6-dihydroxypyrimidine,” 26 , were resolved and its tautomers in solution correctly assigned by 13C nmr. Anions of barbiturics and related systems exist in one of the two possible types A and B, depending on whether ring nitrogens are substituted (type A), or not (type B). Rapid H/D exchange at C5 was evident from C-deuterium coupling. The redistribution of charge through C4(C6) carbonyl groups shown by 13C shifts of carbonyl carbon atoms of up to 10 ppm as compared to the CO carbons of the neutral species was evident. 相似文献