CRH6N2

CINNOLIN  , a compound isomeric with phthalazine, prepared by boiling dihydrocinnolin dissolved in benzene with freshly precipitated mercuric oxide . The solution is filtered and the hydrochloride of the base precipitated by alcoholic hydrochloric acid; the free base is obtained as an oil by adding caustic soda . It may be obtained in white silky needles, melting at 24-25° C. and containing a molecule of ether of crystallization by cooling the oil dissolved in ether . The free base melts at 39° C . It is a strong base, forming stable salts with mineral acids, and is easily soluble in water and in the ordinary organic solvents . It has a taste resembling that of chloral hydrate, and leaves a sharp irritation for some time on the tongue; it is also very poisonous (M . Busch and A . Rast, Berichte, 1897, 30, p . 521) . Cinnolin derivatives are obtained from oxycinnolin carboxylic acid, which is formed by digesting orthophenyl propiolic acid diazo chloride with water . Oxycinnolin carboxylic acid on heating gives oxycinnolin, melting at 2250, which with phosphorus pentachloride gives chlorcinnolin . This substance is reduced by iron filings and sulphuric acid to dihydrocinnolin .