Acetone [67-64-1] C3H6O, M 58.1, b 56.2o/atm, d € 4 20 0.791, n € D 25 1.35880, pK € 1 25 -6.1 (basic, monoprotonated), pK € 2 25 20.0
(acidic) The commercial preparation of acetone by catalytic dehydrogenation of isopropyl alcohol gives relatively pure material. Analytical reagent
quality generally contains less than 1% of organic impurities but may have up to about 1% of H2O. Dry acetone is appreciably hygroscopic. The main
organic impurity in acetone is mesityl oxide, formed by aldol condensation. It can be dried with anhydrous CaSO4, K2CO3 or type 4A Linde molecular
sieves, and then distilled. Silica gel and alumina, or mildly acidic or basic desiccants cause acetone to undergo the aldol condensation, so that its
water content is increased by pass98 age through these reagents. This also occurs to some extent when P2O5 or sodium amalgam is used. Anhydrous MgSO4
is an inefficient drying agent, and CaCl2 forms an addition compound. Drierite (anhydrous CaSO4) offers minimum acid and base catalysis for aldol
formation and is the recommended drying agent for this solvent [Riddick & Bunger Organic Solvents Wiley-Interscience, NY, 3rd edn, 1970]. Acetone
can be shaken with Drierite (25g/L) for several hours before it is decanted and distilled from fresh Drierite (10g/L) through an efficient column,
maintaining atmospheric contact through a Drierite drying tube. The equilibrium water content is about 10-2M. Anhydrous Mg(ClO4)2 should not be used
as drying agent as there is a high risk of EXPLOSION with acetone vapour. Organic impurities have been removed from acetone by adding 4g of AgNO3 in
30ml of water to 1L of acetone, followed by 10ml of M NaOH, shaking for 10 minutes, filtering, drying with anhydrous CaSO4 and distilling [Hawley et
al. Analyst (London) 58 333 1933, DOI: 10.1039/AN9335800333]. Alternatively, successive small portions of KMnO4 have been added to acetone at reflux,
until the violet colour persists, followed by drying and distilling. Refluxing with chromium trioxide (CrO3) has also been used. Methanol has been
removed from acetone by azeotropic distillation (at 35o) with methyl bromide, and treatment with acetyl chloride. Small amounts of acetone can be
purified as the NaI addition compound, by dissolving 100g of finely powdered NaI in 400g of boiling acetone, then cooling in ice and salt to -8o.
Crystals of NaI.3Me2CO are filtered off and, on warming in a flask, acetone distils off readily. [This method is more convenient than the one using
the bisulfite addition compound.] It has also been purified by gas chromatography on a 20% free fatty acid phthalate (on Chromosorb P) column at 100o.
For efficiency of desiccants in drying acetone see Burfield and Smithers [J Org Chem 43 3966 1978, DOI: 10.1021/jo00414a038]. The water content of
acetone can be determined by a modified Karl Fischer titration [Koupparis & Malmstadt Anal Chem 54 1914 1982, DOI: 10.1021/ac00248a072].
[Beilstein 1 IV 3180.] Rapid procedure: Dry over anhydrous CaSO4 and distil. Acetoxime (acetone oxime) [127-06-0] C3H7NO, M 73.1, m 63o, b 135o/760mm,
d 0.901, pK40 0.99, crystallises from petroleum ether (b 40-60o) and can be sublimed. [Beilstein 1 H 649, 1 IV 3202.] Acetone semicarbazone [110-20-3]
C4H10N3O, M 115.1, m 187o, pK25 1.33, crystallises from water or from aqueous EtOH. [Beilstein 3 H 101, 3 I 48, 3 II 81, 3 III 189, 3 IV 179.]
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