A solution of 4-hydroxybenz aldehyde 3.944g (0.01 mole) in 25 ml ethanol and an ethanol solution of 4-aminoazobenzene 1.22g (0.01 mole) in 25 ml with few drops of
glacial acetic acid was refluxed for 4 hr.
All HPLC-grade solvents (acetonitrile, methanol,
glacial acetic acid, and triethylamine) were obtained from Fisher Scientific (Pittsburgh, PA, USA) and Merck Taiwan Ltd.
The precipitate was collected by centrifugation and then was added to 60%
glacial acetic acid. The solution was heated and kept reflux until all solid was dissolved.
Each of the solutions were kept under constant agitation at 25 [degrees]C during 1 h and the pH was adjusted between 3.0 and 3.5 by adding
glacial acetic acid. During this stage the silanols are formed.
To a solution of the compound 3, in of
glacial acetic acid at the boiling point, four drops of hydrobromic acid were added.
n-Hexane: ethyl acetate:
glacial acetic acid in ratio of 8.5: 1.0: 0.5 v/v/v shown good resolution for vasicine, glycyrrhizin, eugenol, and cineole with Rf value of 0.53, 0.44, 0.75, and 0.77, respectively.
To a stirred cold solution of [beta]-keto sulfones 3a-e (10 mmol) or oximes 4a-e (10 mmol) in
glacial acetic acid (30 mL), sulfuric acid (5 mL, 50%) was added.
In addition to CPL, the company's major products include AN (acrylonitrile), GAC (
glacial acetic acid), nylon chip and AS (ammonium sulfate).
Glacial acetic acid was obtained from Sigma Chemicals, USA; aspirin was obtained from Square Pharmaceuticals Ltd., Bangladesh.