Acetone is the most important member of the ketone family.
Acetone Laboratory Preparation.
Acetone is prepared in the laboratory by oxidation of isopropyl alcohol (2-Propanol) with acidified sodium dichromate solution.
The apparatus used is the same as for acetaldehyde. A mixture of isopropyl! alcohol and sodium dichromate solution is run into boiling dilute H2SO4, As the liquid comes in contact with the acid, a vigorous reaction takes place and the orange dichromate is reduced to green chromic sulphate. Impure acetone distils over.
The impure acetone is purified by adding sodium bisulphite solution, filtering off the crystals of the bisulphite compound obtained, and regenerating acetone by decomposing the crystals with dilute acid or alkali. The acetone is then distilled (bp 56°C).
Acetone is manufactured:
(1) By air-oxidation of isopropyl alcohol at 500°C. No catalyst is required
(2) By dehydrogenation of isopropyl alcohol. Isopropyl alcohol vapours are passed over the heated copper catalyst at 300°C.
(3) By Wacker Process. This involves the treatment of propene with an acidified aqueous solution of palladium chloride and cupric chloride.
Acetone is also obtained as a by-product of Cumene Process for the manufacture of phenol. The processes for the preparation of acetone by fermentation of carbohydrates and also from calcium acetate, are obsolete.
Acetone physical properties.
Acetone is a colourless, volatile, highly flammable liquid, bp 56°C. It has an ethereal odour. It is miscible with water, ethanol, and ether in all proportions.
Acetone Chemical properties.
The chemical properties of acetone have already been discussed under General reaction of aldehydes and ketones.
(1) Haloform Reaction.When acetone is treated with bleaching powder (CaOCl2 = CaO+Cl2), Which supplies both chlorine and alkali, it first forms trichloroacetone which on hydrolysis gives chloroform.
A similar reaction with iodine and alkali gives iodoform.
(2) Condensation Reaction. Acetone underdoes the following condensation reaction:
(a) when treated with der HCl, acetone first gives mesityl oxide and then phorone.
Formation of mesityl Oxide:
(b) When heated with H2SO4, acetone gives mesitylene.
(c) When treated with Ba (OH)2, acetone undergoes aldol condensation to form diacetone alcohol.
Acetone is used:
- As a solvent for acetylene, cellulose derivatives, varnishes, lacquers, resins, and plastics.
- In the production of chloroform and diacetone alcohol.
- In the manufacture of thermosoftening plastic perspex.
Acetone chemical formula is C3H6O and molar mass is 58.080 g·mol−1 and consists of three carbon atoms, 6 hydrogen atoms, and 1 oxygen atom.
Main acetone hazards are Eye contact. Skin contact. Inhalation.
Inhalation: irritate the nose and throat.high concentrations: harm the nervous system. Symptoms include nausea, headache, dizziness, drowsiness and confusion.
Skin Contact: May cause mild irritation. Can be absorbed through the skin, but harmful effects are not expected.
Eye Contact: Eyes Irritation. Causes moderate to severe irritation. Symptoms include sore, tearing, and red eyes. The vapour also irritates the eyes.