Preparation of Acetanilide

Preparation and purification of Acetanilide

Purpose:
a) To synthesis acetanilide by reaction of aniline and acetic anhydride.

b) To purify acetanilide by crystallization method from water

c) Purity check by melting range

Equipment / Materials and Hazars:

hot plate beakers(150,250mL) ice stirring rod spatula

Büchner funnel aniline weighing paper digital scales rubber tubing (hose) acetic anhydride filter paper Mel-temp apparatus

10- mL graduated cylinder large test tube medicine dropper

Compound	FW (g/mol)	MP (BP)	density	Hazards
Acetanilide	135.17	114 ºC	---	Irritant. Harmful if inhaled/ingested.
Aniline	93.13	(184 ºC)	1.022 g/mL	Irritant (eyes/skin). Harmful if inhaled/ingested. Possible carcinogen.
Acetic Anhydride	102.09	(138 ºC)	1.082 g/mL	Irritant (eyes/skin). Toxic by inhilation, Flammable (fp 49 ºC).

Discussion:

Recrystallization is a widely-used technique to purify a solid mixture. The desired product is isolated from its impurities by differences in solubility. Insoluble impurities and colored impurities can be removed from hot solvent through the use of activated carbon and filtration. Soluble impurities remain in the cold solvent after recrystallization. The desired product should be as soluble as possible in hot solvent and as insoluble as possible in cold solvent. The selection of solvent is, therefore, critical to the successful recrystallization.

Recrystallization is a purification procedure, which requires solubility of the impure solid in a heated solution and crystallization of the solid upon cooling. Clearly, this operation depends upon solute-solvent in traction involving a number of parameters including concentration, polarity of solute and solvent (like dissolves like), etc.

Choice of a solvent or solvent pair for recrystallization experiments generally involves preliminary tests using a small sample and various solvent systems. To determine the proper solvent or solvent system, the following steps are commonly performed.

I) The crude crystals should have low solubility in the chosen solvent at room temperature.

II) The crude crystals should have high solubility in the chosen solvent when heated to boiling.

III) The crude crystals should not react with the solvent

IV) The solvent should boil at temperature below the solid melting point.

V) The solvent should moderately be volatile so crystals dried readily.

VI) The solvent should be non-toxic, non-flammable, and inexpensive