Purification Methods
It has been recrystallised from pet ether, or purified by dissolving in *C6H6 washing with H2O, drying (MgSO4), evaporating and distilling in a vacuum, then recrystallising the residue. The liquid has a pleasant lemon-like odour. The semicarbazone has m 227o. [Loudon & Razdan J Chem Soc 4299 1954.] The oxime is prepared from 3g of chromanone, 3g NH2OH.HCl in EtOH (50mL), 6g K2CO3 and refluxed on a water bath for 6hours. The solution is poured into H2O, the solid is filtered off, dried and dissolved in hot *C6H6 which on addition of pet ether yields the oxime as glistening needles m 140o. Hydrolysis of this gives very pure chromanone. The benzal derivative is prepared from 3g of chromanone and 4g PhCHO in 50mL EtOH, heated to boiling, 10mL of conc HCl are added dropwise and set aside for several days. The derivative separates and is recrystallised from EtOH to give yellow needles, m 112o [Powell J Am Chem Soc 45 2711 1923]. Reaction with Pb(OAc)4 yields the 3-acetoxy derivative m 74o (from pet ether + trace of EtOAc) [Cavill et al. J Chem Soc 4573 1954, Beilstein 17/10V 14].
