摘要:

AbstractThe visible light‐induced photolysis of trityl salts with different anions was investigated in vacuo. The following order of photostability, determined from the rates of decoloration of the dichloroethane solutions of these salts, was found: (C6H5)3C+PF6−>(C6H5)3C+AsF6−>(C6H5)3C+BF4−>(C6H5)3C+SbCl6−≥ (C6H5)3C+FeCl4−. By model reactions it was proved that the 9‐phenylfluorenyl cation, formed on irradiation as a main product in the early stage of the photolysis, takes part in the regeneration of (C6H5)3C+. The changes in electronic spectra, as well as the composition of the reaction mixtures after photolysis and the model reactions, confirm some stages of the earlier

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860901

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe structure of poly(phthalidylidenearylene)s, synthesized by electrophilic substitution reactions, was studied using1H and13C NMR spectroscopy. Homopolycondensation of 3‐aryl‐3‐chlorophthalides1a – din nitrobenzene leads to para‐substituted linear polymers2a – d, whereas polycondensation of phthaloyl dichloride and bis[4‐(3‐chloro‐3‐phthalidyl)phenyl] ether (6) with diphenyl ether results in polymers5contain

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860902

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe asymmetric addition of hydrogen cyanide to an aliphatic aldehyde, catalyzed by a synthetic dipeptide, cyclo[(S)‐phenylalanyl‐(S)‐histidyl] (1), leads to a product having a higher optical yield than that reported for the reaction using an enzyme (D‐oxynitrilase) as c

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860903

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractA series of poly(dimethylsiloxane)s was synthesized containing either electron donor or electron acceptor groups, statistically arranged along the polymer chain or only at the chain ends (telechelic polymers). Blending of the donor and acceptor modified statistical copolymers led to a strong increase of the melt viscosity as a consequence of complex formation. In contrast to this, complex formation had no significant influence on the viscosity in blends from telechelic polymers. This different behaviour seems to be caused by the different molecular architecture favouring crosslinking by complex formation for the statistical copolymers and a linear chain extension for the telechelic polymers.

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860904

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractA series of soluble polymers was prepared by copolymerization of the 4‐nitrophenol ester ofN‐methacryloylated ω‐amino acids (1a – i), ofN‐methacryloyldiglycine (2b), of 6‐(N‐methacryloylglycylamino)‐ and of 6‐(N‐methacryloylglycylglycylamino)hexanoic acid (3aand3b) withN‐(2‐hydroxypropyl)methacrylamide (HPMA). The resulting polymers contained roughly 3 mol‐% of nitrophenol groups. Polymeranalogous reaction with 4′‐nitro L‐phenylalanineanilide (4a) or with itsN‐glycyl andN‐glycylglycyl derivates (4band4c), yielded polymers which at the end of their side chain of various length and structure had a bond degradable with chymotrypsin. The rate of enzymatic hydrolysis was investigated as a function of the length and structure of side chain. It was found that in copolymers possessing side chains formed by ω‐amino acid residues, the rate of hydrolysis increases with increasing length of the side chain. The rate of cleavage of the peptide bond has a maximum value for a spacer that possesses six methylene groups. With increasing length of the side chain the rate of hydrolysis again decreases. A similar dependence was observed for side chains formed by dipeptides of ω‐amino acids and glycine. In copolymers with oligoglycine side chains, the rate of enzymatic hydrolysis also increases with increasing length of side chain. In other types of side chains formed by combination of hydrophobic and hydrophilic segments, a number of factors become operative which affect the rate of enzymatic hy

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860905

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe asymmetric Robinson cyclization reaction was studied by using polymer‐boundL‐prolines as catalysts, in which the degree of crosslinking, the content of proline and the spacers of bindingL‐proline to the polymers were varied. Incorporation of a spacer for binding theL‐proline moiety onto a polymer support was found to improve the catalytic efficiency considerably, which is reflected by the value of enantiomeric

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860906

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe1H NMR spectra ofN‐acetyl‐D‐glucosamine (1) and methyl‐B‐D‐chitobioside (2), the monomer and dimer of chitin, respectively, were determined in the aprotic solvents,N,N‐dimethylacetamide (DMA) and DMA containing lithium chloride. It could be shown that dissolution of1and2in DMA/LiCl proceeds via interaction of one LiCl molecule with each labile proton (OH or NH). Observation of the temperature‐dependent hydroxyl proton chemical shift revealed the particular behaviour of the OH3hydroxyl of2. This dependence was assigned to the existence of an intramolecular hydrogen bond between OH3and O5′(the heterocyclic atom) of the other D‐glucopyranosyl unit. Similar results were found for chitin i

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860907

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractA variant of the reduction with lithium aluminium hydride (LAH), involving the complex of LAH with a high‐molecular‐weight, linear poly(N‐methylethyleneimine) (PMEI), is described. The reduction of simple aldehydes, ketones, or esters was found to proceed essentially within the solid LAH‐PMEI complex suspended in pentane and the resulting pure alcohols can be isolated by working up only the separated soli

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860908

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractDiethoxyphosphino‐substituted acetamides (1and2) and the polymer gel bearing dialkoxy‐phosphino groups (3,4, and5) were prepared by reaction of chlorophosphites with acetamide and crosslinked polyacrylamides, respectively, in the presence of triethylamine. By using1,2and the polymer as condensing reagents, various peptides were synthesized directly fromN‐protected amino acids and amino acid esters in high yields with little racemization. The highly crosslinked polymeric reagents simplified the procedure and were recycled by treatment with chlorophosp

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860909

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractPhosphonyl radicals of the structure OṖR1(R2) with R1and R2: C6H5(1); C6H5, OCH(CH3)2(2); CH3, OCH3(4) and OC2H5(5) were generated by UV‐photolysis of appropriate acylphosphine oxides or acylphosphonates which are effective initiators of the free radical polymerization of olefinic compounds. All five radicals are very reactive towards monomers such as methacrylonitrile, styrene and methyl methacrylate (k R .+M= 5 · 107to 2 · 1081 · mol−1· s−1), as was found by employing laser flash photolysis techniques. In the cases of acrylonitrile, methyl acrylate, butyl vinyl ether, and vinyl acetatek R .+Mranged from 106–1071 · mol−1· s−1. The high reactivity of the radicals1 – 5is due to their tetrahedral structure. TheQ‐escheme of Alfrey and Price proved useful to recognize trends in the dependence ofk R .+Mon the chemical nature of

ISSN:0025-116X    

DOI:10.1002/macp.1985.021860910

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY