A Publication
of Reliable Methods
for the Preparation
of Organic Compounds
Annual Volume
Org. Synth. 1925, 5, 91
DOI: 10.15227/orgsyn.005.0091
Submitted by G. A. Hill and E. W. Flosdorf.
Checked by C. S. Marvel and A. E. Gray.
1. Procedure
In a 2-l. round-bottomed flask, fitted with a stopper carrying a dropping funnel and a connection to a condenser set for distillation, are placed 750 g. of 6 N sulfuric acid (Note 1) and 250 g. of pinacol hydrate (Note 2). The mixture is then distilled until the upper layer of distillate ceases to increase in volume (Note 3). This requires about fifteen to twenty minutes. The pinacolone layer in the distillate is separated from the water and the water is returned to the reaction flask. First, 60 cc. of concentrated sulfuric acid is added to the water, and then a second 250-g. portion of pinacol hydrate. The distillation is repeated. This process is repeated twice more until 1 kg. (4.42 moles) of pinacol hydrate has been used (Note 4).
The combined pinacolone fraction is dried over calcium chloride, filtered, and fractionally distilled. There is first a small low-boiling portion; then the pinacolone comes over at 103–107°; and finally there is a higher-boiling portion which yields more pinacolone on redistillation. The yield from a run, as described, is 287–318 g. (65–72 per cent of the theoretical amount). This product occasionally turns slightly yellow on standing, but redistillation removes the color with almost no loss of product.
2. Notes
1. Phosphoric acid (50 per cent) or hydrated oxalic acid may be used to bring about this rearrangement. When these reagents are used, the reaction mixture should be boiled for three to four hours. A yield of pinacolone corresponding to 60–65 per cent of the theoretical amount is thus obtained.
2. The pinacol hydrate is the unrecrystallized product obtained as described on p. 459. The use of recrystallized pinacol hydrate increases the yield of pinacolone by about 4 per cent.
3. An oily layer always remains behind in the distilling flask.
4. Larger or smaller runs of pinacolone may be made without materially affecting the yield.
3. Discussion
Pinacolone can be prepared by heating pinacol hydrate with dilute sulfuric or dilute hydrochloric acid;1 by treating anhydrous pinacol2 with concentrated sulfuric acid at 0°; by heating pinacol or its hydrate with 5 per cent oxalic acid3 for twelve hours, or with 50 per cent tartaric, phosphoric, or oxalic acid3 for three to four hours. Pinacolone can also be prepared from pivalamide and methylmagnesium halides4 and from tert.-butylmagnesium chloride and acetyl chloride5 or sodium acetate.6
This preparation is referenced from:

References and Notes
  1. Fittig, Ann. 114, 56 (1860); Richard and Langlais, Bull. soc. chim. (4) 7, 459 (1910); Hill, Spear and Lachowicz, J. Am. Chem. Soc. 45, 1559 (1923).
  2. Scholl and Born, Ber. 28, 1364 (footnote) (1859); Delacre, Mem. sci. acad. roy. Belg. (1904) [Chem. Zentr. II, 496 (1906)].
  3. Vorländer, Ber. 30, 2266 (1897); Richard and Langlais, Bull. soc. chim. (4) 7, 459 (1910); Dehn and Jackson, J. Am. Chem. Soc. 55, 4286 (1933).
  4. Whitmore, Noll, and Meunier, J. Am. Chem. Soc. 61, 683 (1939).
  5. Badertscher and Whitmore, J. Am. Chem. Soc. 54, 825 (1932).
  6. Petrov and Sokolova, J. Gen. Chem. (U.S.S.R.) 8, 199 (1938) [C. A. 32, 5376 (1938)].

Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

sulfuric or dilute hydrochloric acid

pinacol or its hydrate

tartaric, phosphoric, or oxalic acid

methylmagnesium halides

calcium chloride (10043-52-4)

sulfuric acid (7664-93-9)

sodium acetate (127-09-3)

acetyl chloride (75-36-5)

Oxalic acid (144-62-7)

Pinacolone (75-97-8)

phosphoric acid (7664-38-2)

Pinacol hydrate (6091-58-3)

pinacol (76-09-5)

pivalamide (754-10-9)

tert.-butylmagnesium chloride (677-22-5)