Organic Syntheses, Coll. Vol. 3, p.701 (1955); Vol. 28, p.83 (1948).
A dry 5-l. three-necked flask
is provided with a stirrer (Note 1)
, a nitrogen inlet tube
, a 500-ml. Pyrex separatory funnel
, and a large Allihn reflux condenser
. To the upper end of the condenser are attached an outlet tube and a 1-l. separatory funnel
. Both separatory funnels and the outlet tube are provided with calcium chloride drying tubes
. To the flask is added 50.3 g. (2.07 gram atoms) of magnesium turnings (Note 2)
gas, dried by bubbling through concentrated sulfuric acid
, is passed in to displace the air in the flask. The nitrogen
atmosphere is maintained until the hydrolysis of the Grignard addition product is completed. Five hundred and fourteen grams (2 moles) of crude 9-bromophenanthrene (p. 134) (Note 3)
is melted and poured into the Pyrex separatory funnel (Note 4)
. One liter of anhydrous ether
(dried over sodium
wire) is placed in the upper separatory funnel. About 200 ml. of the ether
and 10 ml. of the melted bromophenanthrene
are allowed to run into the reaction flask. The reaction of the bromophenanthrene
is initiated by the addition of a few crystals of iodine
and 1 ml. of ethyl bromide
; the reaction begins after the mixture is stirred for a few minutes without external heating. As the reaction proceeds, the ether
and the bromo compound are added at rates sufficient to maintain gentle refluxing. The relative rates of addition should be such that the two separatory funnels will be emptied at about the same time. After the additions are complete, but while the reaction is still in progress, the Grignard reagent begins to precipitate on the sides of the flask. One liter of dry, thiophene-free benzene
is added from the Pyrex separatory funnel at such a rate as to keep the Grignard reagent in solution. When refluxing due to the exothermic reaction stops, the mixture is heated at gentle reflux with stirring for 4 hours.
The mixture is allowed to cool until refluxing ceases, and 296.4 g. (2 moles) of ethyl orthoformate (Note 5)
is added from the lower separatory funnel over a period of about 30 minutes. The mixture is then refluxed gently for 6 hours.
The reaction mixture is cooled with stirring in an ice bath
, and 1 l. of cold 10% hydrochloric acid (Note 6)
is added from the separatory funnel; the acid is added dropwise at first and more rapidly after the reaction subsides. The benzene
layer is separated from the aqueous layer and concentrated under reduced pressure in a 5-l. round-bottomed flask on a steam bath
. One liter of 25% sulfuric acid
is added to the residue, and the mixture. is refluxed gently for 12 hours.
The mixture is then cooled in an ice bath, the acid is decanted, and the residue is washed twice by decantation with water. The residue is dissolved in 1 l. of benzene
in the same flask, and 1.5 l. of water and 1.2 kg. of sodium bisulfite
are added. The flask is fitted with a stirrer, and the mixture is stirred vigorously overnight. The mixture is filtered through an 8-in. Büchner funnel
, and the bisulfite addition product is washed on the funnel with 500 ml. of benzene
The filter cake is broken up and returned to the same 5-l. flask. A saturated solution of sodium bicarbonate
is added slowly (Note 7)
with stirring until there is no further evidence of decomposition. The mixture is stirred for 2 hours longer. The solution is kept alkaline to litmus throughout by the addition of more sodium bicarbonate
if necessary. The crude aldehyde is collected on an 8-in. Büchner funnel, washed with water, and allowed to dry as completely as possible. The product is dissolved in 1 l. of chloroform
, the small aqueous layer is separated (Note 8)
, and the solution is dried with Drierite
or another suitable drying agent.
A 250-ml. modified Claisen flask
, equipped with a dropping funnel
, a thermometer
, a water-cooled condenser
, and a receiver
, is arranged for distillation. The chloroform
solution is filtered into the dropping funnel, from which it is admitted to the flask slowly as the solvent is distilled (Note 9)
. When the solvent has been removed, the dropping funnel is replaced by a stopper and the condenser by a 250-ml. distilling flask as a receiver. The residue is distilled at 160–170°/1 mm.
The distillate weighs 206–216 g.
). This material is recrystallized once from glacial acetic acid (approximately 1 g. to 0.9 ml.)
and then from ethanol (about 1 g. to 3 ml.)
to give 166–174 g.
over-all yield) of phenanthrene-9-aldehyde
melting at 100–101°
A mercury seal
may be used, but a glycerol-rubber tube seal
The checkers operated on one-fifth the scale specified.
It is not feasible to add the 9-bromophenanthrene
as an ether
solution because of the limited solubility of the substance in this solvent. Since the melting point of the crude 9-bromophenanthrene
is about 50° it is desirable to heat the melted material to 70° in order to prevent crystallization in the funnel. If the bromo compound begins to solidify in the funnel it may be melted again by careful heating with a microburner
The ethyl orthoformate
should be freshly distilled with rejection of the fraction boiling below 140°.
If this procedure is used for the preparation of the acetal instead of the aldehyde, it may be preferable to use ammonium chloride
solution for hydrolysis instead of 10% hydrochloric acid
The alkaline solution must be added carefully to avoid excessive foaming.
The water in the filter cake is removed with difficulty by drying in air or even in an oven
under reduced pressure. If the water is not removed as indicated in the procedure, difficulty may be encountered in the early part of the distillation.
The distillation of the solvent may be carried out at reduced pressure if desired.
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