摘要:

Aspects of Environmental Protection in Chemistry Lab Courses – Suggestions for Teaching ChemistryIt should be a goal in chemical education to create consciousness for the urgent necessity of environmental protection. Lab courses offer the opportunity to meet some aspects of environmental protection like avoiding highly poisonous materials, reducing the amount of materials, collecting harmful materials separately, recycling waste. Some starting materials can be saved and the amount of waste be reduced significantly. Traditional goals of education remain intac

ISSN:0941-1216    

DOI:10.1002/prac.19933350302

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractThe photooxygenation of 4‐methoxy‐7‐methyl‐5 H‐furo[3,2‐g][1]benzopyran‐5‐one (Visnagin,1) in methanol in absence and in presence of a sensitizer (methylene blue) has been studied, 6‐Formyl‐7‐hydroxy‐5‐methoxy‐2‐methylchromone (4a), methyl 7‐hydroxy‐5‐methoxy‐2‐methylchromone‐6‐carboxylate (4b) and 7‐hydroxy‐5‐methoxy‐2‐methylchromone‐6‐carboxylic acid (4c) could be isolated and identified in each case. The formation can be interpreted in terms of intermediate production of a 1.2‐dioxetane like2.Acomparative study on the ozonolysis of Visnagin (1) in ethyl acetate both in absence and in presence of dimethyl sulfide, was also undertaken. Ozone attacks1either at the furan ring (to give4a,c) or at both the furan and γ‐pyrone site (to afford10). Possible reaction mechanisms are considered and the structures of the new

ISSN:0941-1216    

DOI:10.1002/prac.19933350303

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Electrochemical Reduction of Organic Compounds. 22. Preparation of Aromatic Aldehydes by Electroreduction of Esters and Amides in the Presence of ChlorotrimethylsilaneThe electroreduction of aromatic esters1and amides9in dry acetonitrile in the presence of chlorotrimethylsilane2affords aldehydes3in moderate to good yields depending on the aromatic substituents. The formation of3and characteristic by‐products is discusse

ISSN:0941-1216    

DOI:10.1002/prac.19933350304

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

New Macrocyclic Hosts for the Inclusion of Organic Guest Molecules – Crystal Structure of a Complex with Dimethylformamide (1 : 1)New pyridino crowns with amide and sulfonamide groups1band1care synthesized. They form numerous stoichiometric crystalline inclusion complexes with alcohols, various dipolar‐aprotic solvents, as well as cyclic ethers. Host‐guest stoichiometries are discussed and inclusion selectivities (relating to DMF) are shown. The structure of the crystalline DMF inclusion compound of the sulfonamide host1c(1 : 1) is determined by X‐ray diffraction, showing a lattice void inclusi

ISSN:0941-1216    

DOI:10.1002/prac.19933350305

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractThree (6a–c) of the four conceivable diastereomeric 1‐ferrocenylalkylamines can be synthesized from I‐(−)‐menthone and ferrocene in high enantiomeric purity.The many potential applications of such compounds, including their use as chiral templates in diastereoselective four component condensations (4CC, Ugi Reaction) are examined.Furthermore, NMR evidence for the first example of up‐down‐isomerism, a new type of conformational stereoisomerism of ferrocene derivatives,

ISSN:0941-1216    

DOI:10.1002/prac.19933350306

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Flue Dusts Containing Heavy Metal Ions and Chloride.I. Phase Analysis, Model Experiments for RecyclingFour flue dusts from a cement factory, an electric‐furnace steelmaking plant and a municipal waste plant were analyzed by powder diffraction methods. Chloride combines above all with alkali ions or heavy metal ions, especially yielding PbCl2and KPb2Cl5. The controlled sublimation of these chloride compounds in open crucibles was developed and optimized in our laboratory. Between 850°C and 1150°C and at reaction times from 30 min up to 12 h, the chloride content decreases to below 0.1 wt‐%. The sublimed phase mainly consists of alkali and lead chloride. Zinc is found in the flue dust as oxide and is enriched during this process. Recent investigations with a small waelz kiln give analogous results. With our procedure, the manufacturer by himself is able to exploit flue dusts containing a large amount of heavy metal elements and chloride which cannot be deposited. The remaining product contains mainly zinc oxide which can be recycled in the zinc industry or returned to the production process. The sublimed chloride compounds may be recycled in the potash ind

ISSN:0941-1216    

DOI:10.1002/prac.19933350307

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Synthesis of Glutaconaldehydes from Pyridinium Betaines of Squaric AcidThe pyridinium ring of squaric acid betaines (2) is opened by hydroxide ions. Electronegative substituents (RCl, CN) at C‐3 promote this reaction. The stereochemistry of the resulting 5‐(2‐hydroxy‐3,4‐dioxocyclobut‐1‐en‐1‐yl)aminopenta‐2,4‐dienales (3) is confirmed by NMR‐spectroscopy. Treatment of3with sodium hydroxide results in further hydrolysis to the sodium salts of glutaconaldehydes (5) and 3‐amino‐4‐hydroxycyclobut‐3‐ene‐1,2‐dione (6). These products are also directly obtained from the nicotinic acid derivates2 d(RCOOEt) and2 e(RCONH2), in the latter case cyclisation of the glutaconic acid derivate to the

ISSN:0941-1216    

DOI:10.1002/prac.19933350308

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractDithiocarboxylation of some halogenated pyridine sulphones with carbon disulphide and sodium hydride leads to the formation of thiomethyl derivatives via Smiles rearrangement of the initially produced dianion, fragmentation and subsequent methylation. In one instance the pyridino[2,3‐b]‐1,4‐dithiine7was obtained. The thioether2dwas also converted into a thiomethyl derivative when subjected to the same reaction seq

ISSN:0941-1216    

DOI:10.1002/prac.19933350309

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

Distribution Properties of Benzene Derivatives. III. On the Kinetics of the Diffusion‐controlled Distribution of Mono‐ and Disubstituted Benzene Derivatives in the System n‐Octanol/WaterThe kinetics of the diffusion‐controlled distribution of 22 mono‐ and disubstituted benzenes in the solvent system n‐octanol/water were investigated spectrophotometrically in the UV‐VIS range at various temperatures between 288 and 333 K.The first‐order rate constantsk1andk2and the activation parameters were determined graphically.In this way, an interesting deviation from theory could be observed in the temperature range from 300 up to 308 K, which is discussed on the basis of known anomalies of water at the interface.Studies on relationships between rate constants (lgk1, lgk2) and hydrophobicity (lgP) show a nearly constancy ofk1, while the rate of transport from the organic to the aqueous phase (k2) strongly depends on hydrophobicity described by lgP.The calculated regression equations correspond to analogous relationships found for mechanically influenced distributions and can therefore be explained by the same

ISSN:0941-1216    

DOI:10.1002/prac.19933350310

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractAddition of 1H‐benzimidazole‐2‐carbonitrile (1) to arylidenemalononitrile (2) gave 1‐amino‐3‐aryl pyrido[1,2‐a]benzimidazole‐2,4‐dicarbonitrile (3), 2‐aryl‐benzimidazole (4) and 1H‐benzimidazole‐2‐acetonitrile,α‐(arylmethylene) (5). Compounds (3) reacted with formamide yielding 4‐amino‐5‐aryl pyrimido[5′,

ISSN:0941-1216    

DOI:10.1002/prac.19933350311

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY