摘要:

Mass Spectroscopy of 5‐Halogenated PyrimidinglucuronidesUsing the ion source according to von ARDENNE, useful spectra of negative and positive ions from sensitive glycosides were obtained either by electron attachment (EA‐) or low voltage electron impact (EI‐) mass spectroscopy.Spectra of glucuronides derived from 5‐halogenated uracil, 2‐thiouracil, 4‐thiouracil and 6‐mercaptopurin in their peracetylated, esterified and free acidic form are described. Most stable peracetylated 2‐ and 4‐thiouracil glucuronides reveal intensive peaks of molecule ions.The halogen‐carbon bonding strength, calculated from complementary aglycon peaks, demonstrates expected tendencies

ISSN:0021-8383    

DOI:10.1002/prac.19823240202

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

On the Role of EDA‐Complexes in Cationic Polymerization. IX. The Solvent Influence on the Complex Formation of Monomeres with Cationic Chain EndThe influence of solvents on CT‐interaction of carbenium ions with aromatic bπ‐donors (substituted stilbenes, benzenes and naphthalenes), using stable carbenium ions salts as model compounds (triphenyl methyl hexachlorantimonate and tropylium tetrafluoroborate), has been investigated by spectroscopic, calorimetric and conductometric methods. These data as well as conclusions from thermodynamic measurements indicate that the complex formation to be a competetion of the bπ‐donor with the counterion and/or the solvent, depending on the degree of dis

ISSN:0021-8383    

DOI:10.1002/prac.19823240203

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

Studies on the Mechanism of the Chlorohydrination of OlefinsWe studied the rate‐determining and the product‐determining steps of the chlorohydrination of olefins with Cl2/H2O and HOCl. In competitive kinetic experiments with 3‐ethylpent‐2‐ene and cyclohexene we determined the relative rate constants krel= 1,5 (with Cl2/H2O) and krel= ∞ (with HOCl). This shows that the rate‐determining steps of the chlorohydrination with Cl2/H2O and with HOCl are different. In order to investigate the product‐determining steps we determined the proportion of alkyl‐(2‐chloroethyl)‐ethers3and ethylene chlorohydrine2in the reaction of ethylene with Cl2and with HOCl in alcohol/water‐mixtures. The proportion of both the reaction products3/2was independent of the chlorinating agent used. Also the proportion of MARKOVNIKOVand anti‐MARKOVNIKOVproducts in the chlorohydrination of propylene with Cl2/H2O or HOCl was independent of the type of chlorinating agent. In the chlorohydrination of cyclohexene both agents (Cl2/H2O and HOCl) yielded only the trans‐chlorohydrine. From the results obtained it may be concluded that the product‐determining step of chlorohydrination is the same for both th

ISSN:0021-8383    

DOI:10.1002/prac.19823240204

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

Photochemistry of Adsorbed Molecules. V. E.S.R.‐Investigations of Phenyl Cations during Photolysis of Arendiazonium Salts in the Polycrystalline and the Adsorbed StateDuring photolysis of 4‐NR2‐substituted arene diazonium salts ground state triplets occur at low temperatures in the e.s.r.‐spectra with (π)5(sp2)1configuration in the polycrystalline as well as in the adsorbed state on SiO2. The influence of anions and the reaction order of decay processes are discussed. The decay of the aryl cations were also investigated in the presence of pyrene as π‐electron donor. Reaction takes place with coadsorbed molecules and the decay mechanism changes from ionic character to radica

ISSN:0021-8383    

DOI:10.1002/prac.19823240205

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

Light Induced Polymer and Polymerization Reactions. III. Photoinduced Decomposition of Arene Diazonium Salts by Benzoin DerivativesThe combination benzoin derivate/arene diazonium salt is suitable as a bivalent photoinitiator system for radicalic and cationic photopolymerization. By means of product analysis, quantum yield measurements and photo‐CIDNP‐studies a mechanism was proposed including the electron transfer from α‐substituted benzyl radicals formed by benzoin derivate photolysis to arene diazonium salts. The quantum yields for diazonium salt decomposition in acetonitril were about 0.65. They show only a small dependence on substituents of diazonium salt but are strong influenced by the solvent. In methanol or dioxane quantum yields were found from 11 to 460.13C‐photo‐CIDNP‐measurements agree with a mechanism of benzoin ether photolysis on the t

ISSN:0021-8383    

DOI:10.1002/prac.19823240206

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

Derivatives of Imidazolidines from Oxalic AmidinesTetraarylsubstituted oxalic amidines1react with acyl chlorides, phosgene, thiophosgene, chlorocarbonylsulfenylchloride, isocyaniddichlorides, and N‐aroyl‐1‐chlorothio‐formimidoylchlorides7to give the corresponding 5‐membered heterocycles3, 4, 5and8.Isocyanates9and isothiocyanates10react with oxalic amidines to yield imidazolidines11, 12and ureas13, 14.Hydrolysis of3–5, 8, 11, 12leads to the corresponding oxo comp

ISSN:0021-8383    

DOI:10.1002/prac.19823240207

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

Studies on the Sensitized Photolysis of 2‐Diazo‐1‐oxo‐1,2‐dihydronaphthalenes in Solid LayersThe photolysis of 5‐substituted 2‐diazo‐1‐oxo‐1,2‐dihydronaphthalenes can be sensitized by proper dyes as could be detected in various binders. Whereas the quantum yield of the direct photolysis is hardly influenced by the glass transition temperature Tgof the binder matrix the spectral sensitization is only effectiv in a rigid binder matrix (Tg>room temperature Tr). In deformable binders (Tg

ISSN:0021-8383    

DOI:10.1002/prac.19823240208

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

Photochemistry of Arylsubstituted Δ2‐1,3,4‐Oxadiazolines. II. The Influence of the Substituents and the Solvent on the Absorption and Fluorescence Properties of Arylsubstituted Δ2‐1,3,4‐OxadiazolinesThe electronic absorption and the fluorescence spectra of 16 arylsubstituted Δ2‐1,3,4‐oxadiazolines were measured in benzene at room temperature.The push‐pull effect of the substituents supports an increasing intramolecular charge‐transfer in the electronically excited singlet state, which increases its dipole moment relative to the ground state.The significant linear correlation of the Hammett σp‐values with the energies of the fluorescence and absorption maxima of the Δ2‐oxadiazolines, p‐substituted in the phenylring at the C 2‐atom, demonstrate these intramolecular charge transfer.The titel compounds demonstrate with increasing solvent polarity a bathochromic shift of the absorption maxima.For some oxadiazolines the dipole moment for the excited singlet state proved to be about 30 Cm as Stoke's shift dipenden

ISSN:0021-8383    

DOI:10.1002/prac.19823240209

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

Heterocyclic Substituted Coumarines from β‐Chloropropeniminium Salts3‐Chloro‐3‐coumar‐3′‐yl‐propeniminium salts7or the derived aldehydes10are versatile synthons for the preparation of heterocyclic substituted coumarines5. The transformation of the starting materials into the coumarines5can be carry out in more steps or in o

ISSN:0021-8383    

DOI:10.1002/prac.19823240210

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY

摘要:

Benzalaniline und 2‐Phenyl‐indolenine — Charakterisierung ihrer elektronischen Anregungszustände und Interpretation ihrer UV‐SpektrenDie UV‐Spektren einiger substituierter Benzalanilin‐ und 2‐Phenylindolenin‐derivate werden unter Verwendung des PPP‐ und des CNDO/S‐Verfahrens berechnet. Die Übereinstimmung zwischen theoretischen Übergangsenergien und experimentellen Spektren ist gut, wenn man die PPP‐Methode benutzt, aber weniger befriedigend für das CNDO/S‐Verfahren. Eine Mischung zwischen nπ*‐ und ππ*‐Übergang führt zu einer Bandenaufspaltung im langwelligen Spektralbereich, wenn der Chromophor des Benzalanilins nicht‐planar wird. Die elektronischen Übergänge werden interpretiert durch PPP‐Konfigurationsanalyse der angeregten Zustände, wobei auf unterschiedliche Teilchromophore abgebildet wird. Fr

ISSN:0021-8383    

DOI:10.1002/prac.19823240211

出版商:WILEY‐VCH Verlag GmbH    

年代:1982

数据来源: WILEY