77 results about "Fries rearrangement" patented technology

Polycarbonates containing low or undetectable levels of Fries rearrangement products and comprising repeat units derived from one or more of resorcinol, hydroquinone, methylhydroquinone, bisphenol A, and 4,4′-biphenol have been prepared by the melt reaction of one or more of the aforementioned dihydroxy aromatic compounds with an ester-substituted diaryl carbonate such as bis-methyl salicyl carbonate. Low, or in many instances undetectable, levels of Fries rearrangement products are found in the product polycarbonates obtained as the combined result of a highly effective catalyst system which suppresses the Fries reaction and the use of lower melt polymerization temperatures relative to temperatures required for the analogous polymerization reactions using diphenyl carbonate.

Triazine ring based polymers for photoinduced liquid crystal alignment introduces photoactive groups for inducing, reinforcing, improving and preserving liquid crystal alignment, for example photoreactor such as cinnamate, coumarin, chalcone and maleimide, as a chain to have at least one photoactive group. One of the photoactive groups can experience Fries rearrangement which induces liquid crystal alignment, and other groups can experience photodimerization, photoisomerization, photocrosslinking or photodegradation to reinforce, change or preserve the generated alignment.

A preparation method of a benzoic acid herbicide dicamba relates to the technical filed of pesticide production. The invention employs 2,5-dichlorophenols as a raw material and carries out esterification, Fries rearrangement, etherification and oxidation to obtain 3,6-dichloro-2-methoxybenzoic acid. The synthetic method has simple technology, easily available raw material, low cost, generates little "three wastes (waste gas, waste water and industrial residue)" and is more environment-friendly and more suitable for industrialized production.

The invention discloses a compound shown as a structural formula (I) as a latent epoxy resin curing agent. The structure of the latent epoxy resin curing agent is phenolic aldehyde phenyl mercaptan ester. The preparation raw materials comprise phenylmercaptan, a carboxyl compound, an aldehyde compound and aromatic secondary amine. The curing agent is a low-viscosity liquid at normal temperature, after being matched with epoxy resin, the curing agent has a long working life, after the temperature is raised, the phenyl mercaptan ester is subjected to Fries rearrangement so as to dissociate an active group thiol, and the active group thiol can quickly react with the epoxy resin under the catalytic action of a tertiary amine group, so that the curing agent is particularly suitable for the field of prepregs with requirements on long operation time.

The present invention discloses a method for preparing 5-bromo-2-hydroxy-3-nitrophenylethanone. The method comprises that: (1) in the presence of an alkali, tetrachloroethylene is adopted as a reaction solvent, bromophenol completesly reacts with an acetylation reagent to obtain a tetrachloroethylene solution of bromoacetic acid phenolester; (2) Lewis acid is added to the resulting solution from the step (1) to completely carry out a Fries rearrangement reaction to obtain a tetrachloroethylene solution of 5-bromo-2-hydroxy acetophenone; (3) a nitration reagent is added to the resulting solution from the step (2) in a dropwise manner to completely carry out the reaction to obtain the 5-bromo-2-hydroxy-3-nitroacetophenone. According to the preparation method provided by the present invention, the three-step reaction is adopted, the tetrachloroethylenes having the same batch are adopted for purifying the final product, such that the solvent consuming is reduced, the cost is reduced, the post-processing time is shortened and the operation steps are simplified; the toxicity of the tetrachloroethylene is far less than the toxicities of chloroform and carbon tetrachloride, such that the hazards on the human body and the environment are less; the tetrachloroethylene is easy to reclaim; the industrialization is easy to realize.

The purpose of the invention is to control, by using a colorless alignment control monomer, the alignment of liquid crystal molecules of a liquid crystal display element that does not include an alignment film, and to provide a liquid crystal composition with which the colorless alignment control monomer exhibits excellent compatibility. The invention uses a liquid crystal display element that comprises an alignment control monomer including an aromatic ester that undergoes photo-Fries rearrangement by light irradiation, and that employs a liquid crystal composition having a negative dielectric anisotropy. The invention also uses the liquid crystal composition.