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Boronic acids are known to bind to active site serines and are part of inhibitors for porcine pancreatic lipase, [2] subtilisin [3] and the protease Kex2. [4] Furthermore, boronic acid derivatives constitute a class of inhibitors for human acyl-protein thioesterase 1 and 2, which are cancer drug targets within the Ras cycle. [5]
The reaction can also be carried out at the laboratory scale with diphosgene or triphosgene and an aqueous dimethylamine solution in the two-phase system of benzene–xylene and water in a stirred reactor with sodium hydroxide as an acid scavenger. However, considerably lower yields (56%) are achieved due to the hydrolysis sensitivity of DMCC.
Phenylboronic acid or benzeneboronic acid, abbreviated as PhB(OH) 2 where Ph is the phenyl group C 6 H 5 - and B(OH) 2 is a boronic acid containing a phenyl substituent and two hydroxyl groups attached to boron. Phenylboronic acid is a white powder and is commonly used in organic synthesis.
[3] [4] Examples include via a 1,3-dipolar cycloaddition of nitrile oxides with alkynes; or the reaction of hydroxylamine with 1,3-diketones or derivatives of propiolic acid. [ 5 ] Photochemistry
In a reaction that is typically avoided, hydrolysis of carbamoyl chlorides gives carbamic acids: R 2 NCOCl + H 2 O → R 2 NC(O)OH + HCl. Owing to the influence of the amino group, these compounds are less hydrolytically sensitive than the usual acid chlorides. A related but more useful reaction is the analogous reaction with alcohols: [2]
For example, at room temperature, in a 1-molar solution of acetic acid, only 0.001% of the acid are dissociated (i.e. 10 −5 moles out of 1 mol). Electron-withdrawing substituents, such as -CF 3 group , give stronger acids (the p K a of acetic acid is 4.76 whereas trifluoroacetic acid, with a trifluoromethyl substituent , has a p K a of 0.23).
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Carbamic acid is a planar molecule. [3]The H 2 N− group of carbamic acid, unlike that of most amines, cannot be protonated to an ammonium group H 3 N + −.The zwitterionic form H 3 N + −COO − is very unstable and promptly decomposes into ammonia and carbon dioxide, [6] yet there is a report of its detection in ices irradiated with high-energy protons.