PREPARATIONS 269 of the pale green cupric derivative (C) of the enol form. If the contents of the tube are now shaken with chloroform, the crystals of the cupric compound readily dissolve in the lower chloroform layer, showing clearly that it is not a normal ionised salt. CH 3 C: CH • C • OC 2 H 6 CH 3 COCH 2 COOC 2 H 5 + NaHSO 3 I Il I O O + \ / CH 3 C(OH).CH 2 COOC 2 H 6 Cu I / \ SO 3 Na (D) O O CH 3 CiCH-C-OC 2 H 5 (C) (3) To 2 ml. of the ester, add 2-3 drops of a saturated freshly prepared solution of sodium bisulphite. On shaking, a gelatinous precipitate of the bisulphite addition product (D) of the keto form separates, and on standing for 5-10 minutes usually crystallises out. This is a normal reaction of a ketone (see p. 344): hydrogen cyanide adds on similarly to give a cyanhydrin. Note. To obtain satisfactory results with tests (2) and (3), pure re-distilled ethyl acetoacetate should be used. For further experimental evidence for the presence of the
This is the end of the preview. Sign up
access the rest of the document.