摘要:

AbstractKetene‐S,N‐acetals of type1,2reacted with isocyanates to 5‐cyano‐uracils3and 5‐cyano‐pyrimidin‐2‐ones4,5. Reaction of these with N nucleophiles was investigated furnishing 6‐amino‐pyrimidinones6as well as condensed pyrimidin‐2‐ones7‐‐10and13. Cyanic acid esters gave 5‐cyano‐pyrimidin‐4‐ones16. Behavior

ISSN:0021-8383    

DOI:10.1002/prac.19873290502

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

Azomethine Dyes — Sensitizers, Quenchers and Reaction Partner for Singlet OxygenAzomethine dyes show photofading in photographic materials, possibly due to oxidation by singlet oxygen. The azomethine dyes1a–h,2a–h,3c,d,fare inefficient photosensitizers of singlet oxygen formation. In tetrachloromethane the quantum yield ϕ1O2is in the range between 8 · 10−4and 4 · 10−3.Contrary to the literature we found that azomethine dyes react with1O2(kr). The reaction constants were measured by a competetive technique using 9, 10‐diphenyl anthracene and methylene blue as1O2sensitizer. The values of krshow that the reaction of the dyes with1O2can not be ignored. Besides this reaction,1O2is also quenched by the dyes (kq). The values of kqpoint to quenching of1O2by the tertiary amino group of the dyes via a CT‐mechanism. This study shows that in photofading of azomethine dyes the oxydation by1O2must be taken in

ISSN:0021-8383    

DOI:10.1002/prac.19873290503

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractMe⊕(Me = Na; K) cations in MeClO3chlorates were complexed by crown ethers (CE): 12C4, 15C5 and 18C6 in solution. In the solid phase we could obtain only Na(15C5)ClO3and K(18C6)ClO3complexes significant shift in35Cl‐n.q.r. frequency with respect to the frequency of pure sodium and potassium chlorates was observed. The shifts at 77K were –2.879 MHz for Na(15C5)ClO3and –1.004 for K (18C6)ClO3.For other reaction mixtures the35Cl‐n.q.r. frequencies observed were the same as for the appropriate pure chlorates which confirmed that the expected complexation in the solid phase had not occurred. The investigation described in this paper proved a rapid increase in selectivity of crown ethers at the transition from the solution to the solid state. Moreover, in the solid phase of Me(CE)ClO3complexes a significant increase was found in the shielding effect of the Me⊕cation by the surrounding

ISSN:0021-8383    

DOI:10.1002/prac.19873290504

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractIt is shown that the anions of the enolate forms of 1, 2‐ and 1, 3‐indandiones have antiaromatic character. This conclusion is reached after studying the geometry, the electron density distribution and the energy spectrum of the molecules.The anion of the 1,2‐indandione enolate form is unstable because of strong electron‐vibronic inte

ISSN:0021-8383    

DOI:10.1002/prac.19873290505

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

Abstract2‐(Aroyl, methylidene)‐3‐aryl‐5‐dicyanomethylene thiazolidine‐4‐on derivatives2under morpholine treatment formed complex3. The acid hydrolysis of3leads to pyrrolo [3,4‐c]‐pyridine derivatives4. On treatment of3with aqueous sodium hydroxide and subsequent acidification [3,4‐c]pyridine der

ISSN:0021-8383    

DOI:10.1002/prac.19873290506

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractThe anodic behavior of the cardiotonic drug 3‐amino‐5‐(pyrid‐4‐yl)‐1,2‐dihydropyrid‐2‐one1and of 6 compounds with similar structure was investigated at platinum and vitreous carbon electrodes in acetonitrile and in aqueous medium. Caused by the 3‐amino group1is oxidized at a relatively small oxidation potential in an irreversible two‐electron process. Depending on the addition of a strong base or a strong acid the oxidation potential vs. SCE in acetonitrile is −0.08 V (anion), +0.66 V (neutral compound), +0.93 V (monocation) or +1.15 V (dication). In H2O a strong decrease of the oxidation potential with increasing pH was found as a reason for the sensitivity of1against oxygen in alkaline solution. The anodic oxidation of 3‐dimethylamino‐5‐(pyrid‐4‐yl)‐1, 2‐dihydro‐pyrid‐2‐one3in 0.1 m H2SO4leads to 5‐(pyrid‐4‐yl)‐piperidine‐2,3,6‐trione9aor 5‐(pyrid‐4‐yl)‐piperidine‐2,3,4‐trione9b, which is also the oxidation product of1at small concentration. At high concentration of1coupling reactions at the 3

ISSN:0021-8383    

DOI:10.1002/prac.19873290507

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

AbstractA nonlinear least‐squares method is presented which enables the estimation of the partial quantum yields of a photoreversible two component system by fitting the corresponding kinetic equation directly to experimentally measured data.The principles of this method are discussed with reference to the photochromic transformation of phytochrome as an adequate model. It is demonstrated that this method yields sufficiently accurate and highly reliable results.In addition, the advantage of the nonlinear least‐squares method when compared with the so‐called formal integration method and with the initial rate approach is empha

ISSN:0021-8383    

DOI:10.1002/prac.19873290508

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

Organic Electron Conductors and Precursors. V. Synthesis of Poly (organylthio‐acetylenes)Poly(bis‐organylthio‐acetylenes)2and poly(mono‐organylthio‐acetylenes)3have been synthesized by complex catalyzed polymerization of the corresponding acetylenes (4resp.5). Yields and properties of the polymers2,3depend on reaction conditions, the catalyst and the nature of the acetylenes. Relations between these influence factors are

ISSN:0021-8383    

DOI:10.1002/prac.19873290509

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

Neighbouring Group Participation in Electrophilic Additions Initiated by N‐BromosuccinimideStarting from endo‐5‐hydroxymethyl‐norbornene as well as 5‐(hydroxymethyl)‐methyl‐cyclohexene the methoxybromination procedure gives cyclic ethers by participation of the hydroxymethyl group. Unsaturated formyl compounds or their acetals, respectively by contrast, gave methoxybromination products. After oxidation of the functional groups bromo methoxy methyl carboxylates are formed depending on the molar ratio of the sub

ISSN:0021-8383    

DOI:10.1002/prac.19873290510

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY

摘要:

Thermal Reaction of Mono‐n‐alkyl‐benzenesThe pyrolysis of ethyl‐(1), n‐propyl‐(2), n‐hexyl‐(3) and n‐octylbenzene (4) has been studied under conditions of steam cracking (600 to 800°C) in a laboratory scale tubular reactor. The overall activation energies determined for (1) to (4) were found to be nearly identical (221 to 227 kJ · mol−1) obviously caused by similar initial steps. The main liquid product observed was styren accompanied by ω‐phenyl‐1‐alkenes and α‐olefins. Benzene is an important side product of1. It might be formed mainly by a hydrogen assisted dealkylation via a cyclohexadienyl type r

ISSN:0021-8383    

DOI:10.1002/prac.19873290511

出版商:WILEY‐VCH Verlag GmbH    

年代:1987

数据来源: WILEY