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1.
Chemically induced degradation of polystyrene (PSt) in the presence of 2,4,6-tri-chloronitrosobenzene (TCNB) as radical generator was investigated in benzene solution by means of the electron spin resonance (ESR) method. The ESR spectra observed after the addition of TCNB to PSt in benzene solution were assigned to the nitroxide radicals (spin adducts) of the PSt radicals, , and . These assignments were deduced from comparisons between observed and computer simulated spectra and were supported by experiments using α-deuterated PSt. It was found by analyses of ESR spectra that two kinds of type (B) radicals were produced, which were different in local conformation. The radicals (A) and (B) were thought to be produced by hydrogen abstraction by the chlorinated phenyl radical which results from homolytic scission of the CN bond of TCNB on slight warming. On the other hand, it was concluded that β-scission of radical (A) results in the formation of the chain scission radical (C). The mechanism of degradation of PSt induced by TCNB as radical initiator is discussed, together with the decrease in molecular weight observed after the addition of TCNB to a PSt-benzene solution. From the decrease of molecular weight it is concluded that TCNB acts as a scission inducer. 相似文献
2.
It was found that free radicals of poly(methyl methacrylate) (PMMA) were formed by addition of the spin trapping agent, 2,6,-di-chloro-nitrosobenzene (DCNB), to a PMMA-benzene solution. This PMMA radical was detected by the spin adduct with DCNB. It was identified as a chain scission radical by the analysis of the ESR spectrum and experiments using samples of PMMA deuterated either in the α-methyl or in the ester methyl group. Since DCNB is known to abstract hydrogen from other molecules, the main chain scission of PMMA caused by the action of DCNB is an indirect process resulting from a ß-scission of the PMMA radical after a methylene hydrogen has been abstracted. 相似文献
3.
Results of ESR studies are presented for a number of radical ions selected from several classes of compounds of current interest. The strikingly different hyperfine data for the radical cations of 1,6:8,13-propane-1,3- and 1,6:8,13-ethane-diylidene-[14]annulene demonstrate the effect of an interplay of homoconjugative, inductive and hyperconjugative perturbations. The unusually stable radical cations of N,N′-dimethyl- and N,N′-trimethylene-1,6:8,13-bisimino[14]annulene should be regarded as N-centered radicals with an N-N 3-electron σ-bond. Despite similar geometries of [2.2]paracyclophane , its 1,1,2,2,9,9,10,10-octa-fluoro-derivative and its 1,9,-diene , the corresponding radical anions strongly differ in their electronic structure. An unexpected conformatinal interconversion is observed for the radical anion of . Electron acceptors, such as tetracyanoquinodimethane (TCNQ;) and its areno analogues, and electron donors, represented by tetrathiafulvalene (TTF;) and compounds containing the TTF system, form salts exhibiting high electronic conductivity (“organic metals”). ESR spectra of the radical anions and trianions of these acceptors and the radical cations of these donors provide detailed information about the spin distribution in the respective species. 相似文献
4.
Radical formation during the radiolysis of polyethylacrylate (PEA) at ?196°C has been investigated by ESR. Partially deuterated samples of PEA were used to improve the identification of radicals. It is found that ethyl radicals are formed. They originate from ion-electron recombination since they are not observed in the presence of pyrene as electron scavenger. They add to the C = O double bond leading to the formation of the radical which is found after γ-irradiation. This radical decomposes under the action of visible light to give C2H5· and PEA. This reaction is reversible. Furthermore, the radicals and are formed during the radiolysis.Chlorine substitution in the ethyl-ester group (PCIEA) enhances radical formation by a factor of 3–4. The only radical observed at low temperature is It is formed by dissociative electron capture resulting in the cleavage of the whole side chain. After heating to –10°C, in PEA and PCIEA only the radical is observed which results from main chain scission. The results of ESR are correlated with investigations on product formation, crosslinking and main chain scission given in a previous paper. 相似文献
5.
Philippe Fornier de Violet Roland Bonneau Jacques Joussot-Dubien 《Chemical physics letters》1974,28(4):569-572
The laser flash photolysis of iodine-iodide mixtures in alcoholic solvents produces transient species absorbing in the red and near infrared region with maxima at 740 and 590 nm. The 740 nm absorption band has already been attributed to the well known I ion. In this work the 590 nm absorption band is assigned to the I radical anion which presumably could be formed by the equilibrium reaction: I + I3- ? I. The variations of the intensities of the 590 and 740 nm transient absorption bands as a function of I3? concentration, temperature and solvent, support this assignment. The kinetics of formation of I and I has been studied in solutions of tertiary butanol. An analysis of the experimental results shows that the I ion could be formed via a mechanism involving an I intermediate. 相似文献
6.
J.A. Connor 《Journal of organometallic chemistry》1978,144(3):C58-C62
The formation of newintermediates and especially germaimines R2GeNR′ has been observed in the reaction of germylenes with phenyl azide (precursor of phenylnitrene). These transient derivatives lead, by polycondensation reactions, to the corresponding cyclic or linear germazanes , and are characterized by insertion reactions into the germanium—nitrogen bond, cleavage and addition reaction with tetrahydrofuran, and pseudo-Wittig reactions with benzaldehyde. The latter produces the corresponding germoxanes via new intermediates and phenyl benzaldimine. 相似文献
7.
《Chemical physics letters》1987,136(5):465-470
Exposure of dilute solutions of CH3CCCH3 in CC12FCC1F2 and related solvents to ionizing radiation at 77 K produced the radical cation (CH3CCCH3)+. On annealing, these were initiallycpnverted into the corresponding dimer cation, c-C4(CH3)4+, which subsequently decomposed to give the propargyl radical . This novel result is supported by studies using CH3CCCD3 which gave, finally, the radicals and in a ratio of approximately 9:1. The absence of the radicals and indicates that the cyclobutadiene ring is strongly distorted (D2h) and that the initial dimers do not undergo equilibration via symmetrical dimers under our experimental conditions. These results are compared to liquid-phase data for c-C4(CH3)4+ radicals and explanations for the differences in behaviour are proposed. 相似文献
8.
J.W.F.L. Seetz F.A. Hartog H.P. Böhm C. Blomberg O.S. Akkerman F. Bickelhaupt 《Tetrahedron letters》1982,23(14):1497-1500
Careful addition of 1,3-dibromopropane to magnesium in Et2O yields 1,3-bis(bromomagnesio)propane which is purified via “magnesacyclobutane” . Reactions of with H2O, CO2, HgBr2 and Me3SnCl are reported. MgBr2 catalyses the decomposition of to allylmagnesium bromide . 相似文献
9.
10.
The cyclometallated monohydrides (R H or Me) react with NaOPri/PriOH/H2 to give fluxional tetrahydrides, probably . These are highly fluxional having magnetically equivalent hydridic hydrogens, even at ---100°C. When treated with HBr, , gives and with CO it gives a mixture of complexes which are probably (2 isomers) and . When treated with ButNC this tetrahydride undergoes similar reactions but another (major) product is formed which appears to be binuclear and fluxional and is probably of type , with four bridging hydrogens. 相似文献
11.
The direct formation of the excited singlet states 1P* in the electron transfer reaction between the cation radicals of certain N-aryl-2-pyrazolines and the anion radicals of some polycyclic aromatic hydrocarbons, and aryl-substituted oxazoles and oxadiazoles is observed in electrogenerated chemiluminescence studies using measurements of the relative emission intensities and investigations in a magnetic field. 相似文献
12.
《Tetrahedron》1988,44(3):925-940
Theoretical consideration reveals a unique relationship between NMR spectral parameters and possible types of the gramididin A spatial structure. By means of two dimensional NMR spectroscopy four distinct species were detected simultaneously in ethanol solution. Comparison of experimental data and theoretical conclusions demonstrates that species 1 and 2 are left-handed parallel double helices differing in relative arrangement of the two polypeptide chains within the dimers, species 3 is left-handed antiparallel double helix , and species 4 is a mirror image of species 1, i.e. right-handed parallel double helix . The results are compared with those on spatial structures of the peptide in complex with cesium (right-handed antiparallel double helix ) and of the gramicidin A transmembrane ionchannel (N-terminal to N-terminal single-stranded dimer ). 相似文献
13.
Kimiak Yamamura Kazumi Nakatsu Kenji Nakao Tomoo Nakazawa Ichiro Murata 《Tetrahedron letters》1979,20(52):4999-5002
A series of o-tropyliobiphenyl tetradfluoroborates has been synthesized. Evidences are presented to show that exhibit strong intramolecular charge-transfer interaction between tropylium ion and remote aryl ring. The structure of was determined by single crystal X-ray diffraction study. 相似文献
14.
In the electron transfer between the cation radicals of the amine moiety of four intramolecular anthra cene-amine systems and the anion radicals BXXX of some heterocyclic and carbonyl compounds in acetonitrile/toluene, the triplet state of the anthracene moiety is formed. As intermediates in this process, intramolecular and intermolecular triplet exciplexcs or and or are discussed. 相似文献
15.
A.V. Fokin 《Journal of fluorine chemistry》1980,16(6):565-566
Chlorine fluorosulfonate adds exceptionally easy not only to various alkenes, perfluorobenzene, but to alkynes too The addition of peroxydisulfuryldifluoride to alkyl- and perfluoroalkyliodides leads to unstable adducts, which decompose with the formation of alkylfluorosulfonates and iodine fluorosulfonate; the latter was trapped with fluoroalkenes The use of ClOSO2F allows to substitute selectively for the fluorosulfonate group the chlorine atom in monochloroacetic acid esters as well as the fluorine atom in hexafluoroacetone N-fluoroimine ClOSO2F serves as an exceptionally active chlorinating reagent for fluorinated alcohols, nitrosocompounds, perfluoroacid amides and particularly for benzene The reaction of (OSO2F)2 with perfluoroacid amides leads to the corresponding N,N-bis(fluorosulfonate)amides, which easily rearrange into alkylfluorosulfonates The hypochlorites of fluorinated alcohols are stable enough and they, similarly to ClOSO2F, are able to add to alkenes, fluoroalkenes (but not to perfluoroisobutylene), bis(trifluoromethyl)ketene, trifluoromethylisocyanate and perfluoronitriles The fluorosulfonatoacetic acid esters are unstable at the ambient temperature, but they can be widely used in situ as a very effective alkylating reagents 相似文献
16.
François Mathey 《Tetrahedron letters》1979,20(20):1753-1756
1-Benzyl-3,4-dimethylphosphate - is converted into 2-phenyl-4,5-dimethyl-λ3-phosphorin - through 1,2-dihydro-λ5-phosphorines and . 相似文献
17.
Solvent effects on phosphorescence and excitation spectra and its polarization characteristics indicate that the two major spin-orbit coupling mechanisms through which the 3ππ* state of Norharmane acquires dipole-allowed character via nπ* states are: 相似文献
18.
J. Carre M. Kollmannsberger J. Thourey G. Perachon J. Bousquet 《Journal of fluorine chemistry》1976,8(5):401-408
The standard enthalpy of formation of tellurium tetrafluoride has been determined: by combustion in fluorine: by reaction in a normal solution of soda: 相似文献
19.
In the reaction of CF3SOCl with NaN3 or (CH3)3SiN3, azide, CF3SON3 (I) is formed: Upon gentle warming to room temperature, (I) decomposes under evolution of N2 to give CF3SON (II), which however oligomerizes instantaneously, The monomeric nitride(II) can be captured in the presence of reactive halogene compounds to yield N-substituted trifluoromethan-imino sulfonyl chlorides. With CH3CN, a six-membered ring compound is obtained: 相似文献
20.
The stereoselective fluorination of four couples of diastereoisomeric 2-alkyl 3-hydroxy 3-phenylpropanoic methyl esters by the reaction of the phenyltetrafluorophosphorane with the corresponding trimethylsilylethers derivatives is described. The structure of the 2-alkyl 3-fluoro 3-phenyl propanoic methyl esters obtained quantitativly has been determined unambiguously by NMR analysis. 19F NMR results permit us to determine the relative populations of the rotamers for each of the isomers threo and erythro. 相似文献