Purification Methods
It is a very volatile yellow oil with a strong pungent odour. EXPLOSIVE [distillation even under reduced pressure is dangerous and may result in an explosion — TAKE ALL THE NECESSARY PRECAUTIONS IF DISTILLATION IS TO BE CARRIED OUT]. It explodes in contact with conc H2SO4-trace acid causes rapid decomposition. It is slightly soluble in H2O, but is miscible with EtOH, *C6H6, pet ether and Et2O. To purify, dissolve it in Et2O [using CH2Cl2 instead of Et2O, protects the ester from acid], wash it with 10% aqueous Na2CO3, dry (MgSO4), filter and repeat as many times as possible until the Et2O layer loses its yellow colour, then remove the solvent below 20o (vacuum). Note that prolonged heating may lead to rapid decomposition and low yields. It can also be purified by steam distillation under reduced pressure but with considerable loss in yield. Place the residual oil in a brown bottle, keep below 10o, and use as soon as possible without distilling. For preparing esters usually the ethereal solution is used directly without purification. [Womack & Nelson Org Synth Coll Vol III 392 1955, UV: Miller & White J Am Chem Soc 79 5974 1957, Fieser 1 367 1967, Beilstein 3 IV 1495.]
China
