Checked by Cliff S. Hamilton, C. W. Winter, and Harry M. Walker.
1. Procedure
A
1-l. three-necked flask is employed as a reaction vessel from which the product can be steam-distilled
immediately after completion of the reaction (Note
1). It is convenient to arrange the apparatus for the reaction and that for the steam distillation on the same
steam bath, with provision for the rapid connection of the flask to the distillation assembly at the desired time. For use as a reaction vessel the flask is mounted on a steam bath and fitted with a
mechanical stirrer and a
reflux condenser; the third neck is closed by a cork.
In the steam-distillation assembly (Note
1) one of the small necks of the flask is fitted with a steam-inlet tube, connected through a water
trap to a steam line; the other small neck is closed by a cork. The central neck is fitted to a
Kjeldahl trap leading to a
50-cm. Allihn condenser set downward and connected in series to a
50-cm. Liebig condenser. The second condenser leads to a
500-ml. three-necked flask used as the
receiver. The receiving flask is immersed in an
ice bath and fitted with an Allihn reflux condenser.
When all the apparatus has been set up and tested the flask is connected to the reaction assembly, and 175 ml. of water,
105 g. (0.38 mole) of ferrous sulfate heptahydrate,
0.5 ml. of concentrated hydrochloric acid, and
6 g. (0.04 mole) of o-nitrobenzaldehyde (see
p. 641) are introduced in the order given. The stirrer is then started, and the flask is heated by means of the steam bath. When the temperature of the mixture reaches 90°,
25 ml. of concentrated ammonium hydroxide is added in one portion, and at 2-minute intervals three
10-ml. portions of ammonium hydroxide are added. Stirring and heating are continued throughout. The total reaction time is 8–10 minutes.
Immediately after the addition of the last portion of
ammonium hydroxide, the reflux condenser and stirrer are removed and the flask is connected to the steam-distillation assembly. The mixture is steam-distilled as rapidly as possible, and two 250-ml. fractions of distillate are collected during a period of 10–13 minutes (Note
2). The first fraction is saturated with
sodium chloride, and the solution is stirred at 5° until precipitation appears to be complete. The solid is collected on a
Büchner funnel and dried in the air. The product weighs
2.72–3.11 g. (
57–65%) and melts at
38–39°. The second fraction of the distillate is saturated with
sodium chloride and combined with the filtrate remaining from the first fraction. The combined solution is extracted with two
45-ml. portions of ether. The combined
ether extract is filtered, dried over anhydrous
sodium sulfate, and concentrated by distillation, finally under reduced pressure. The residue solidifies on cooling and weighs
0.6–1.0 g.; it can be purified by steam distillation from
40–50 ml. of saturated sodium chloride solution until 100 ml. of distillate is collected, saturation of the distillate with
sodium chloride, cooling, and filtration. The pure product so obtained weighs
0.42–0.87 g. The total yield (Note
3) is
3.3–3.6 g. (
69–75%).
2. Notes
1. Rapid removal of the product from the reaction mixture is essential to the success of this preparation. The steam-distillation assembly should be sturdily constructed, with all parts except the distilling flask in place at the time the reaction is started. To ensure the proper fitting of the distilling flask it is convenient to construct the distillation apparatus with the flask in place and, after testing of the apparatus, to remove the flask and incorporate it into the reaction assembly.
2. The first fraction is drawn into a
round-bottomed flask through a tube inserted into the third neck of the
receiver (by the use of a
water pump or a suction line) without interruption of the distillation.
3. The submitters have obtained yields of about 70% in runs eight times as large as that described. This amino aldehyde undergoes self-condensation on standing, especially in a
desiccator, and so the product should be used immediately.
3. Discussion
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