摘要:

AbstractIn the last ten years, offset printing has achieved the broadest application on the printing market due to its inherent advantages. Light sensitive offset plates for contact UV exposure are mainly used at present. The chemistry of these plates are based on the photoreactions of quinone diazides, diazo resins and radical photopolymers. For the further development of offset printing plates the improvement of the light sensitivity and extension of spectral sensitivity to the visible range is a market‐driven requirement to realize transfer of computer stored informations by laser. For this requirement electrophotographic systems, systems based on silver halides and photoinduced polymerizations are most important. New literature data dealing with these systems in relation to printing plates are summarize

ISSN:0941-1216    

DOI:10.1002/prac.19943360502

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

Recent Developments in Iminium Salt ChemistryIminium salts are of continuing interest as versatile building blocks in organic synthesis. This progress report from different laboratories highlights some current research activities in iminium salt chemistry. Several contributions focus on novel synthetic applications of isolable, functionalized iminium systems such as α,β‐unsaturated iminium salts (e.g. vinamidinium, 3‐trifloxy, 3‐chloro‐, 3‐isocyanato‐ and 3‐thiopropene iminium, as well as propyne iminium salts), furthermore on phosgene iminium chloride and trifluoromethyl‐substituted iminium salts. Iminium intermediates occur in various synthetic transformations; for example, cyclopropane iminium ions are intermediates in nucleophilic substitution reactions at bicyclic aminocyclopropanes. Also reported is the synthesis of a variety of novel orthoamides and their use as synthetic building blocks. Research directed to the application of vinamidinium salts in materials science

ISSN:0941-1216    

DOI:10.1002/prac.19943360503

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

Investigations of Adsorptive Separation of Glycerol/Propane‐1,3‐diol in Aqueous Solution on Zeolites by Liquid Phase AdsorptionThe possibilities of adsorptive separation of propane‐1,3‐diol/water and glycerol/water mixtures on zeolitic adsorbents were studied in aqueous solution. The excess isotherms of both mixtures were determined on NaZSM‐5 and on K+and Ca2+modified X and Y zeolites. The equilibrium constants of the examined mixtures and the theoretical mixture propane‐1,3‐diol/glycerol were calculated. The interactions of the three O atoms of glycerol with Ca2+ions on Y zeolites led to the highest separation factor glycerol/propane‐1,3‐diol. Propan‐1,3‐diol is separabl

ISSN:0941-1216    

DOI:10.1002/prac.19943360504

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

Ultratrace Analysis in High Purity Phosphorus by Thermal Trace‐matrix‐separation via ETV‐ICP‐MSElemental (red) phosphorus can be effectively volatilized and separated from ultra trace contaminants by electrothermal vaporization (ETV) in a graphite furnace. The tube must be covered with WC and some hydrogen added to the transport argon. Detection limits of 0,01 to 10 ng/g in the phosphorus sample are obtained for most analytes by ICP‐MS in single ion monitoring mode. Exceptions are some carbide forming elements (B, Si, V), some contaminants from the graphite (B, Si) and some easily volatile traces (As, Sb, Te, I). ETV in multi element scan mode or alternatively wet chemical trace matrix separation (SMT) with an cation exchanger plus nebulizer aspiration allow detection limits about one order higher. The proposed technique requires a minimum of chemical manipulation and therefore reduces risk of cont

ISSN:0941-1216    

DOI:10.1002/prac.19943360505

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractUnlabeled 1‐vinylnaphthalene (1) as well as positionally D‐labeled1have been prepared and subjected to gas phase pyrolysis at low partial pressures of the educt compounds in nitrogen. At 700°C,1rearranges exclusively to acenaphthene (2). Under the conditions applied a significant H‐D‐exchange in the 1‐vinylnaphthalene as well as in the formed acenaphthene takes place. The results obtained in this way and those resulting from pyrolysis in hydrogen (instead of nitrogen) show that despite the very high degree of dilution the high selectivity of cycloisomerization from1to2is firstly controlled by H‐atom driven radical chain processes, in which the cyclization of the 2‐naphthylethylradical dominates the r

ISSN:0941-1216    

DOI:10.1002/prac.19943360506

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

Macrocyclic Arsinous Acid Ester. IVThe three‐valent arsenic atom is a Lewis‐acid, which formes inter‐ or intramolecular adducts. The reaction with aminoalcoholes and diols, described in this paper, leads to the formation of cyclic and non‐cyclic arsinous acid esters (3,5,6,7,9,10,12,13,15,16,18), some of them containing a N→As

ISSN:0941-1216    

DOI:10.1002/prac.19943360507

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractThe acidity constants (pKa) in the ground, excited singlet and triplet state of 10‐methylacridone have been studied in the 80% water and 20% ethanol sulfuric acid solutions. The pKa, pKa*(S) and pKa*(T) were determined to be −1.04 ±0.02, 1.10 ± 0.05 and 3.46 ± 0.10 at 23°C by means of the UV absorption, the fluorescence and the T‐T absorption measurement in various acid conce

ISSN:0941-1216    

DOI:10.1002/prac.19943360508

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractTheoretical calculations on different xanthene derivatives and related structures were performed and as a result conclusions could be drawn for the acid‐lability of substituted xanthenes. (9‐Hydroxyxanthene‐3‐oxy)acetic‐ and valeric acid (6aand6b) were selected, synthesized in a six‐step route, and6bwas tested for its applicabiliy as a handle for solid phase synthesis

ISSN:0941-1216    

DOI:10.1002/prac.19943360509

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

Synthesis of New 3‐Substituted 2H‐Thiopyran Derivatives via [4+2] Cycloaddition Reactions using Acceptor Substituted Enaminothiones3‐ and 4‐Nitro acetophenones as well as 3‐ and 4‐trifluoromethyl acetophenones react with POCl3/DMF (Vilsmeier reagent) to give dimethyliminium perchlorates1a–dafter addition of perchloric acid to the reaction mixture. Substitution of the chloro atom in1by using sodium sulfide nonahydrate occurs under mild conditions (in case of nitro compounds at −5°C) leading to enaminothiones2a–d. Reactions with acroleine and methylvinylketone in refluxing benzene give exclusively 2H‐thiopyran derivatives4a–h, which were isolated in good yields after spontaneous fast elimination of dimethylamine. In contrast, the introduction of 1‐nitro‐2‐phenylethene as the dienophile allows stepwise reaction to give stable adducts3kand3l, respectively, and also3munder mild conditions (reaction at room temperature).1H n.m.r. spectroscopic data as well as the elimination of dimethylamine to4k–mpermit the elucidation o

ISSN:0941-1216    

DOI:10.1002/prac.19943360510

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractUpon treatment with KF in acetonitrile the zwitterionic Meisenheimer complexes3undergo β‐elimination leading to potassium 7‐(2‐aryl‐2‐oxo‐ethylidene)‐4,6‐dinitro‐7,x‐dihydrobenzofurazanide 1‐oxides4in 72–87% yield. Compounds4give 7‐(2‐aryl‐2‐oxo‐ethyl)‐4,6‐dinitrobenzofuroxans6when treated with hydrochloric acid. 4‐(2‐Aryl‐1‐dimethylsulfonio‐2‐oxo‐ethylidene)‐5,7‐dinitro‐4,x‐dihydrobenzofurazanides5are obtained by reaction of3with sodium methoxide. The structure of5eis confirmed by X‐ray structure analysis. The reaction of complexes8with acetic acid/potassium acetate at 80°C affords 4‐(2‐aryl‐2‐oxo‐1‐pyrid

ISSN:0941-1216    

DOI:10.1002/prac.19943360511

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY