Pikrotoxinin, C15H16O6, is best obtained from pikrotoxin by brominating the latter, when in hot aqueous solution, with a slight excess of bromine water, and then, by means of zinc dust and acetic acid, removing the bromine from the monobromopikrotoxinin, which crystallises out; it crystallises from hot water in colourless, anhydrous needles, but from cold aqueous solutions in rhombic plates containing 1H2O, melts at 200-201°, is readily soluble in all the usual solvents on warming, and also in cold alcohol or chloroform; it is also soluble in alkalies, but is not reprecipitated on the addition of acids. Sulphuric acid develops an intense orange red coloration, and when hydrogen chloride is led into an ethereal solution of the compound, polymerisation occurs, and pikrotoxide, melting at 308-310°, is formed. Aqueous solutions reduce ammoniacal silver nitrate in the cold, but it contains neither an aldehydic nor a ketonic group. It has an extremely bitter taste, and is the active principle of pikrotoxin; its specific rotatory power [a]D=—5⋅85°.
Bromopikrotoxinin, C15H15BrO6, which is most readily obtained by adding bromine water to a hot, nearly saturated aqueous solution of pikrotoxinin until the solution remains permanently yellow, may be purified by recrystallisation from absolute alcohol; it separates in glistening needles, melts at 259-260° (Schmidt gives 250-255°; Paterno and Oglialoro give 240-250°), and has [a]17/D=—132⋅5°.
Chloropikrotoxinin crystallises from alcohol in a mixture of needles and plates, melting at 272°.
Iodopikrotoxinin, obtained by the action of iodic acid and a solution of iodine in potassium iodide C15H14O6Ac2, as it can readily be obtained by the action of acetic chloride on pikrotoxinin; it sublimes in slender needles melting at 254°—255°, and forms an unstable compound with bromine.
Pikrotin, C15H18O7, is best obtained from the filtrate from bromopikrotoxinin, part separating out on cooling, whilst the remainder may be obtained by evaporation; it can be purified by several extractions with small quantities of hot chloroform, followed by recrystallization from water; it forms small, felted needles, or thick, rhombic prisms, melting at 248-250°, is readily soluble in absolute alcohol or acetic acid, but only sparingly in ether, chloroform, or benzene. Its specific rotatory power [a]D=—64⋅7°, and it reduces Fehling's solution, etc., but only on warming. Its molecular formula has been determined by molecular weight determinations and by the analyses of its benzoyl and acetyl derivatives.
Benzoylpikrotin, C15H17O7BZ, crystallises from absolute alcohol in colourless needles, melts at 236°, and is readily soluble in chloroform, sparingly in ether or alcohol.
Dibenzoylpikrotin, obtained when pikrotin (1 mol.) is heated with benzoic chloride (3 mols.) at 190°, crystallises from alcohol in needles melting on a hot aqueous solution of pikrotoxinin, crystallises from alcohol in colourless needles and melts at 198-199°.Dromopikrotoxic acid, C14H16BrO6⋅COOH+H2O, is obtained when 10 percent. potassium hydroxide solution is slowly added to finely divided bromopikrotoxinin suspended in 10 times its weight of boiling water, until all has dissolved; on the addition of hydrochloric acid, the acid crystallises out in colourless needles, melting at 245-246°; it has no bitter taste, and is optically