Alloxan

2,4,5,6( 1H , 3H )-pyrimidinetetrone. _C4H2N2O4 ( _142.08 ). Also called _{meso -} oxalyl urea. It is the cyclic ureide of meso-oxalic acid. It is obtained by oxidation of uric acid or barbituric acid with nitric acid. The tetrahydrate is a colorless rhombic columnar crystal, which effloresces to the monohydrate, and becomes the anhydrate at temperatures above 150°C, and decomposes at 170°C. The anhydrate (from acetone or glacial acetic acid) is a columnar crystal. Decomposition point 230°C (discolors red), melting point 256°C (decomposition). K _a 2.3× ^10-7 (25°C). Soluble in water and ethanol. The iron(III) salt is deep blue. It is used as a raw material for the synthesis of a series of cyclic ureido derivatives. It is reduced to alloxanthin in the cold, dialuric acid when heated, barbituric acid when heated with concentrated sulfuric acid, parabanic acid when boiled with dilute nitric acid, and alloxanic acid in alkali. The oxime of alloxan is called violuric acid. LD ₅₀ 184 mg/kg (mouse, intravenous). [CAS 50-71-5]

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

2,4,5,6(1H,3H)-pyrimidinetetrone．C₄H₂N₂O₄(142.08)．メソオキサリル尿素ともいう．メソシュウ酸の環式ウレイドにあたる．尿酸，またはバルビツル酸を，硝酸で酸化すると得られる．四水和物は無色の斜方柱状晶で，風解して一水和物となり，150 ℃ 以上で無水和物となり，170 ℃ で分解する．無水和物(アセトンまたは氷酢酸より)は柱状晶．分解点230 ℃(赤変)，融点256 ℃(分解)．K_a 2.3×10^－7(25 ℃)．水，エタノールに可溶．鉄(Ⅲ)塩は濃青色を呈する．一連の環式ウレイド誘導体の合成原料となる．冷時還元によってアロキサンチンを，熱時ではジアルル酸を，濃硫酸と加温するとバルビツル酸に，希硝酸と煮沸するとパラバン酸に，アルカリでアロキサン酸になる．アロキサンのオキシムをビオルル酸という．LD₅₀ 184 mg/kg(マウス，静脈)．[CAS 50-71-5]

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