The spectroscopic properties of solvent soluble derivatives of Brooker's simple merocyanine 4-[(1-methyl-4(1H)-pyridinylidene)ethylidene]-2,5-cyclohexadien-1-one, which can in principle exist in two distinct canonical forms, have been assessed both experimentally and theoretically using molecular orbital methods. H-1 and C-13 NMR evidence in a range of solvents suggests that the merocyanine exists as a resonance hybrid which is weighted toward the zwitterion even in solvents of low dielectric constants. In protic solvents, the large hypsochromic shift observed for the merocyanine in the visible region arises from both a dielectric effect and a hydrogen bonding effect. Theoretically, the PM3/COSMO method gives a reasonable account of the structure and spectroscopic shifts of the merocyanine in aprotic solvents, ?The large shifts observed arise because solvents with large dielectric constants have a much greater stabilizing effect on the more polar ground state of the merocyanine than they do on the first excited state. While the same method predicts stable hydrogen-bonded structures for a dihydrate and hexahydrate, it is unable to reproduce the known hypsochromic shift for these solvated species, In contrast, a version of the CNDO/S method does predict the correct trends on hydration though the magnitude of the effect is less than that found experimentally.
Untersuchungen an Stoffwechselprodukten von Mikroorganismen, XIX. Über die Synthese einiger antibiotisch wirksamer 2,5‐Dialkylresorcine — Synthese der Antibiotika DB 2073 und Stemphol
作者:Hans Achenbach、Werner Kohl、Brigitte Kunze
DOI:10.1002/cber.19791120534
日期:1979.5
Ausgehend Von 5-Alkylresorcin-dimethylethern wurden überdie entsprechenden 4-Alkyl-2.6-dimethoxybenzaldehyde Stemphol (2) und das Antibiotikum DB2073 (3) sowie eine Reihe weiterer 2.5-dialkylierter Resorcine dargestellt und biologisch getestet.
A resin composition and uses of the same are provided. The resin composition includes the following components:
(A) a cross-linking agent of the following formula (I):
(B) a polyphenylene ether resin, wherein the terminal ends of the polyphenylene ether resin are independently modified by a substituent with a carbon-carbon double bond; and
(C) a catalyst,
wherein, R
1
in formula (I) is a C
6
to C
16
alkyl or a C
6
to C
16
alkenyl, and the weight ratio of the polyphenylene ether resin (B) to the cross-linking agent (A) ranges from 0.5 to 5.
O-Hydroxyphenyl benzyl ketoximes, preferably containing as substituents one or more alkyl or alkoxy groups containing a total of from 3 to 25 carbon atoms, are used to extract metals from aqueous solutions of their salts as complex compounds soluble in water-immiscible organic solvents. The ketoximes are prepared from the corresponding ketones by reaction with hydroxylamine.