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Organic Synteses vol 23 - Smith L.I.

Smith L.I. Organic Synteses vol 23 - John Wiley & Sons, 1943. - 63 p.
Download (direct link): organicsynthesesvol231943.pdf
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is left in the bottle to cover the catalyst (Note 3). The product boils at 85-86, but it need not be distilled for many purposes. The yield is practically quantitative.
2. Notes
1. Purified nitrogen is a convenient inert gas, but natural gas containing no oxygen, or sulfur compounds, is equally suitable; the checkers used hydrogen.
2. As the catalyst becomes older, it loses its activity somewhat and a longer time is required for the pressure to drop to the theoretical value.
3. The same catalyst may be used many times. For the next run the dihydropyrane is merely poured into the bottle containing the catalyst which is wet with the product of the previous run.
3. Methods of Preparation
Tetrahydropyrane has been prepared by hydrogenation of dihydropyrane using a platinum black catalyst;1 by heating pentamethylene bromide with water;2'3 or with water and zinc oxide in a sealed tube;4 or by heating pentamethylene glycol with three volumes of 60 per cent sulfuric acid in a pressure tube.5
1 Paul, Bull. soc. chim. (4) 53, 1489 (1933).
2 Hochstetter, Monatsh. 23, 1073 (1902).
s Demjanow, J. Russ. Phys. Chem. Soc. 45, 169 (1913) [C. A. 7, 2226 (1913)].
4 Clarke, J. Chem. Soc. 101, 1802 (1912); Allen and Hibbert, J. Am. Chem. Soc. 56, 1398 (1934).
6 Demjanow, J. Russ. Phys. Chem. Soc. 22, 389 (1890) [J. Chem. Soc. 62, 1292 (1892)].
TETRAPHEN YLCY CLOPENTADIEN ONE (Cyclopentadienone, tetraphenyl-)

+ 2H20

Submitted by John R. Johnson and Oliver Grummitt. Checked by Nathan L. Drake and Stuart Haywood.
1. Procedure
In a 500-cc. round-bottomed flask, 21 g. (0.1 mole) of benzil (Org. Syn. Coll. Vol. 1, 1941, 87) and 21 g. (0.1 mole) of dibenzyl ketone (Note 1) are dissolved in 150 cc. of hot alcohol. The flask is fitted with a reflux condenser, the temperature of the solution is raised nearly to the boiling point, and a solution of 3 g. of potassium hydroxide in 15 cc. of alcohol is added slowly in two portions through the condenser. When the frothing has subsided the mixture is refluxed for fifteen minutes and then cooled to 0. The dark crystalline product is filtered with suction and washed with three 10-cc. portions of 95 per cent alcohol. The product melts at 218-220 and weighs 35-37 g. (91-96 per cent of the theoretical amount) (Note 2).
2. Notes
1. The dibenzyl ketone should melt at 34-35.
2. This product is sufficiently pure for most purposes. It may be crystallized from a mixture of alcohol and benzene using 155-160 cc. solvent for 5 g. of tetraphenylcyclopentadienone; the melting point of the recrystallized material is 219-220.
3. Methods of Preparation
Tetraphenylcyclopentadienone has been prepared by the action of phenylmagnesium bromide on benzaldiphenylmaleide,1 and by reduction, dehydration, and oxidation of the methylene-desoxybenzoin obtained by condensing formaldehyde with desoxy-benzoin.2 The present procedure is essentially that of Dilthey.3
An intimate mixture of 35 g. (0.094 mole) of tetrapljenylcy-clopentadienone (p. 92) and 9.3 g. (0.095 mole) of maleic anhydride is placed in a 200-cc. round-bottomed flask (Note 1), and to it is added 25 cc. of bromobenzene. After the mixture has been refluxed gently for three and one-half hours (Note 2), it is cooled
lLowenbein and Uhlich, Ber. 58, 2662 (1925).
! Ziegler and Schnell, Ann. 445, 266 (1925).
3 Dilthey and Quint, J. prakt. Chem. (2)128, 146 (1930); Ger. pat. 575,857 [Frdl. 20, 503 (1933); C. A. 28, 1356 (1934)].
(Phthalic anhydride, tetraphenyl-)
Submitted by Oliver Grdmmitt.
Checked by Nathan L. Drake apd Charles M. Eaker.
1. Procedure
(Note 3), a solution of 7 cc. of bromine in 10 cc. of bromobenzene is added through the condenser, and the flask is shaken until the reagents are thoroughly mixed. After the first exothermic reaction has subsided, the mixture is refluxed gently for three hours (Note 4). The flask is then immersed in a cooling bath and the temperature of the mixture is held at 0^10 for two or three hours. The mixture is filtered with suction, and the crystalline product is washed three times with 10-cc. portions of petroleum ether (b.p. 60-68). After the product has been dried in the air, it weighs 37-38 g. (87-89 per cent of the theoretical amount) and melts at 289-290. It is light brown in color, but when pulverized it is almost colorless. The filtrate, when diluted with an equal volume of petroleum ether and cooled to 0-10, yields an additional 2-3 g. of a less pure product which melts at 285-288. The impure material may be purified by recrystallization from benzene, using 8-9 cc. of benzene per gram of solid (.Note 5).
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