Pinacol hexahydrate

Required Pinacol hexahydrate, 10 g. concentrated sulphuric acid, 15 ml. (28 g.). 

Pinacol (hexahydrate) [6091-58-3] M 194.3, m 46.5°, b 59°/4mm. Distd then crystd repeatedly from water. 

Kim HS, Jeffrey GA (1970) Crystal structure of pinacol hexahydrate. J Chem Phys 53 3610-3615... 

Pinacol (hexahydrate) [6091-58-3 (6H2O), 76-09-5 (anhydrous)] M 194.3, m 46.5 , b 59 /4mm. Distil pinacol, then crystallise it repeatedly from water. (See also below.) [Beilstein 1IV 2575.]... 

Add about 60 ml. of petroleum (b.p, 60-80°) with stirring to the fraction of b,p, 150-180°, thus precipitating the pure anhydrous pinacol (2 5-3 8 ) Filter this off, and then shake the filtrate with ca. 4 ml, of water the remaining pinacol now separates as the hexahydrate (5 g.). The two crops may be united and recrystallised from ca. 10 ml, of water (total yield of hexahydrate, 8-9 g,). Dry and bottle the product rapidly as described in (a). 

Pinacol possesses the unusual property of forming a crystalline hexahydrate, m.p. 45°, and the pinacol is separated in this form from the unreacted acetone and the tsopropyl alcohol. The magnciaium is conveniently amalgamated by dissolving mercuric chloride in a portion of the acetone mercury is then liberated by the reaction ... 

Pinacol formation from ketones and aldehydes by cathodic reduction has been enhanced in the presence of Cr(II) complexes. Electrolysis of a mixture of ben-zophenone (364) and chromium chloride hexahydrate in a DMF-NaCl04 system... 

Pinacol (anhydrous) [76-09-5] M 118.1, m 41.1°, b 172°. The hydrate is rendered anhydrous by azeotropic distn of water with benzene. Recrystd from benzene or toluene/pet ether, absolute EtOH or dry ethyl ether. Recrystn from water gives the hexahydrate. 

Pinacol. Pinacol hydrate may be dehydrated in the following manner (compare Section 2.23, p. 168, Drying by distillation). Mix 100 g of pinacol hydrate with 200 ml of benzene (CAUTION) and distil a mixture of water and benzene passes over. Separate the lower layer and return the upper layer of benzene to the distilling flask. Repeat the process until the benzene distillate is clear. Finally distil the anhydrous pinacol and collect the fraction boiling at 169-173 °C (50 g). The pure pinacol has m.p. 43 °C, but on exposure to moist air the m.p. gradually falls to 29-30 °C and then rises to 45-46 °C when hydration to the hexahydrate is complete. 

Fig. 21.15. Regular buckled pattern of pentagons formed by hydrogen-bonded water molecules in pinacol and piperazine hexahydrates and by water and hydroxyl groups in dimethyl hexane- and octanediol tetrahydrates...

The hydrate layer structures which display more regular buckled pentagonal nets belong to two main types. In one, the pentagonal nets consist exclusively of water molecules and are three-dimensionally connected by functional groups of the enclosed molecules. Thus, in piperazine hexahydrate [815], and in pinacol hexa-hydrate [816], the H2N- and HO-groups respectively form hydrogen bonds to the... 

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