摘要:

AbstractThe adsorption properties of partially exchanged (Na,H) clinoptilolites and silanated H‐clinoptilolites have been investigated as a function of the degree of modification.A different sorption behaviour of N2, Kr and Xe in (Na, H) clinoptilolites is observed in three exchange regions. In samples having a proton loading lower than 10%, adsorption of N2at 77K, Kr at 195K and Xe at 273K only occurs in the main channels parallel to thec‐axis. Diffusion of Kr into the small channels, which are blocked by the presence of Na+ions, was observed at 273K. With a proton exchange of 10 to 70%, the small channels become accessible for all gas molecules. In higher exchanged samples (>70%), the maximum adsorption capacity is reached for N2at 77K and Kr at 195K. The increase of the adsorption capacity with increasing proton content describes a sigmoïdal curve, characteristic of a percolation process.Structural modification by means of silanation reduces the adsorption of both N2at 77K and Kr at 273K in a similar way, so that percolation was obse

ISSN:0165-0513    

DOI:10.1002/recl.19841030301

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

Abstract(Dimethylamino)allene and electrophilic alkenes react under mild conditions to give [2 + 2]‐ and [2 + 4]‐cycloadducts in excellent yields. Conversion of the amino group in the [2 + 2]‐adducts into quaternary salts, followed by elimination of tertiary amine and hydrogen halide, under the influence of l,8‐diazabicyclo[5. 4. 0]undec‐7‐ene (DBU) in hexamethylphosphoric triamide (HMPT), affords 3‐alkylidenecyclobutenes i

ISSN:0165-0513    

DOI:10.1002/recl.19841030302

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractThe gas‐phase negative‐ion chemistry of 2‐methylpropenal has been studied byFouriertransform ion cyclotron resonance mass spectrometry (FT‐ICR). Deuterium labelling has shown that the gas‐phase acidities of the methyl protons and the formyl proton are almost equal. The gas‐phase reactions of the 2‐formylallyl anion with several fluorinated substrates have been shown to proceed mainly via a cycloaddit

ISSN:0165-0513    

DOI:10.1002/recl.19841030303

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractTwo approaches to the synthesis of the title compounds3are described. The first consists of direct alkylation of the unsaturated β‐oxo esters1via their monoanions. The best results were obtained using the heterogeneous sodium methoxide/alumina system. Isolation of pure, mono‐α‐alkylated compounds requires chromatographic separation of the reaction products. The second approach makes use of theHorner‐ Wittigreaction. α‐Substituted phosphine oxides4were converted into their dianions and reacted with aldehydes and ketones to afford the mono‐α‐alkylated β‐oxo esters3in good yields. The requisite phosphine oxides were obtained from the corresponding γ‐bromo β‐oxo esters10via anArbusovreaction with ethyl diphenylphosphinite. Finally, it was found that α,α‐dialkylated and α,αγ‐trialkylated β‐oxo esters8and15can be obtained by reaction of1with an excess of alkyl halide in the presence of two or four equiv

ISSN:0165-0513    

DOI:10.1002/recl.19841030304

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractThe phosphitylating agent 2‐cyano January ‐dimethylethoxy dichlorophosphine and its mono‐N‐morpholino derivative proved to be suitable for the synthesis of DNA in solution and on a solid support. The 2‐cyano‐l,l‐dimethylethyl for protecting P‐0 could be removed selectively under mildly b

ISSN:0165-0513    

DOI:10.1002/recl.19841030305

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractA new chlorination procedure, involving as reagent the system chloroperoxidase/hydrogen peroxide/potassium chloride was developed for converting barbituric acid, 1‐methylbarbituric acid and 1,3‐dimethylbarbituric acid into their 5,5‐dichloro derivatives. It could be proved that the corresponding 5‐mono‐chlorobarbituric acids are intermediates in the

ISSN:0165-0513    

DOI:10.1002/recl.19841030306

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

Abstract5‐dFAD was prepared in a reasonable yield by condensing 2′, 3′, 4′‐tri‐0‐tetrahydropyranyl‐5′‐0‐phosphoromorpholino‐5‐deazaflavine with the tri‐n‐octylammonium salt of adenosine‐5′‐phosphate followed by removal of the acid labile

ISSN:0165-0513    

DOI:10.1002/recl.19841030307

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19841030308

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY