摘要:

Liquid‐Crystalline Heterocycloalkanes. III. Synthesis and Liquid‐Crystalline Properties of Substituted 1,3‐DioxadecalinesLiquid‐crystalline 2‐substituted and 2,6‐disubstituted 1,3‐dioxadecalines (4—6) were synthesized by acid‐catalyzed acetalization of trans‐2‐hydroxymethylcyclohexanol (1) or trans‐4‐alkyl‐trans‐2‐hydroxymethylcyclohexanoles (2) with aldehydes3whereby the desired transisomers were formed only. The syntheses of the various aldehydes are also described.Special attention is drawn on the evolution of mesogenic properties of the titlecompounds4—6in comparison with known decalines and 1,3‐dioxanes.It was found that the clearing temperatures of the synthesized 1,3‐dioxadecalines are always lower than those of the corresponding decaline derivatives, due to the deformation of the decalineringsystem by the introduction of two oxygen‐atoms. The comparison of 1,3‐dioxanes and 1,3‐dioxadecalines shows that the dioxadecaline ringsystem tends to suppress smectic mesophases in favour of nematics. A first example of a liquid crystalline cis‐

ISSN:0021-8383    

DOI:10.1002/prac.19883300102

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

ISSN:0021-8383    

DOI:10.1002/prac.19883300103

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe charge‐transfer (CT) spectra of the π‐complexes formed by several π‐acceptors with some polynuclear[2.2]paracyclophanes have been measured. Comparison of these CT complexes with those of model compounds supports the existence of the transannular electronic interactions in the paracyclophane nucleus. The infrared spectra of a number of CT complexes reveal the increase of the electron density on the π‐acceptor molecule in the CT complexes. Some crystalline CT complexes were prepared an

ISSN:0021-8383    

DOI:10.1002/prac.19883300104

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

ISSN:0021-8383    

DOI:10.1002/prac.19883300105

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

About the Influence of Pressure on the Catalyzed Liquid‐Phase Oxidation of cis‐ and trans‐Oct‐4‐eneThe investigation of the influence of pressure on the liquid‐phase oxidation of cis‐ and trans‐oct‐4‐ene shows that the reaction rate increases up to 491 kPa in the non‐catalyzed oxidation reaction, but up to 981 kPa in the MoO2(acac)2‐catalyzed reaction n‐oct‐1‐ene reacts more slowly than cis‐ and trans‐oct‐4‐ene as well in the pressure‐less reaction as in the oxidation under pressure. In the non‐catalyzed oxidation reaction the cis/trans‐ ratios don't depend on the pressure, but in the MoO2(acac)2‐catalyzed oxidation reaction the cis/trans‐epoxide ratios increase with increasing pressure. The optimum of the

ISSN:0021-8383    

DOI:10.1002/prac.19883300106

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

1,2,3‐Triazabutadienes. XX. Investigations of the Photochemical Z‐E‐Isomerization, Photolysis, Protonation and Acidic Cleavage of 1‐Aryl‐3‐3‐methylbenzthiazolinyliden‐(2)‐triazenes in Micellar SolutionsThe E‐isomers of the 1‐Aryl‐3‐[3‐methylbenzthiazolinyliden‐(2)]‐triazenes are soluble in aqueous micellar solutions of sodium dodecylsulfate (NDS) and cetyltrimethylammoniumbromide (CTAB). They are fixed in the Stern region of the micelles. The Z‐isomers decompose in aqueous micellar solutions by acidic cleavage. They can be stabilized by the use of alkaline buffer solutions. The concentration of protons is higher by the factor 103in the Stern region of NDS‐micelles than in the Stern region of CTAB‐micelles. This difference is explained by electrostatic attraction and repulsion between the protons and the micelles. The quantum yields of the photochemical isomerization in micellar solutions and in organic solvents are the same. Water soluble ionic dyes with relatively low triplet energies sensitize the photoisomerization in micellar solutions and the photostationary

ISSN:0021-8383    

DOI:10.1002/prac.19883300107

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

Pyrylium Compounds. 38. About the Ring Transformation of 2,4,6‐Triarylthiopyrylium Salts by Acetic Acid Anhydride to Arylbenzenes and Thiobenzophenones2,4,6‐Triarylthiopyrylium salts5react in the presence of an appropriate condensing agent (sodium acetate, carbonate, methoxide, tert‐butoxide or potassium acetate) with acetic acid anhydride to yield arylbenzenes3and thiobenzophenones6. This ring transformation represents the first example of the conversion of the moiety into the thiocarbonyl group Under the same conditions 3,5‐dimethyl‐2,4,6‐triphenylthiopyrylium perchlorate (13) forms via [1,5]‐sigmatropic rearrangement the thiobenzophenone15. The structure of the new compounds6was proved by spectroscopic methods as well as by degradation reactions. Thus, hydrogen peroxide converts6ato the known benzophenone4. Alkaline saponification gives the 2‐hydroxy‐benzophenone8, whereas heating with hydrochloric acid causes a selective cleavage of the acetoxy group to the 2‐hydrox

ISSN:0021-8383    

DOI:10.1002/prac.19883300108

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

ISSN:0021-8383    

DOI:10.1002/prac.19883300109

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractSome aromatic compounds containing the imino group (NH) were nitrated in acetic acid or anhydride, and the ortho/para ratios were measured. N‐Methyl derivatives of the aforementioned compounds are much less reactive when nitrated under comparable conditions and give significantly lower o/p ratios. These results along with the literature data support the hypothesis that the acetanilide‐type compounds are nitrated via N‐nitro intermed

ISSN:0021-8383    

DOI:10.1002/prac.19883300110

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

On the Reaction of Dicyclopentadiene Diepoxide with Acrylic AcidThe esterification of dicyclopentadiene diepoxide as a bifunctional epoxide with acrylic acid was investigated. The influence of solvent polarity, reaction temperature and the catalytic system used are discussed. It was found, that the reaction rate increased with increasing solvent polarity. By using tertiary amines as catalysts, only a small catalytic effect was observed. On the contrary, a good catalytic effect was achieved with Lewis‐acids. By means of FeCl3, a vinylester containing epoxide groups and CC‐double‐bonds is obtained, which polymerizes via various mec

ISSN:0021-8383    

DOI:10.1002/prac.19883300111

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY