Organic Syntheses, Coll. Vol. 4, p.457 (1963); Vol. 32, p.68 (1952).
This preparation should be conducted in a hood to avoid exposure to chloropicrin.
A solution of sodium ethoxide
is prepared under nitrogen
from 70 g. (3.04 g. atoms) of sodium
and 2 l. of absolute ethanol (Note 1)
in a 3-l. three-necked flask
which is equipped with mechanical stirrer
, efficient reflux condenser
, dropping funnel
, and a thermometer
which dips below the level of the liquid in the flask. Chloropicrin (100 g., 0.61 mole) (Note 2)
is placed in the dropping funnel, and the stirred solution is heated to 58–60° with a water bath
. The chloropicrin
is added at a rate of 30–35 drops per minute until the reaction becomes self-sustaining (about 20 minutes), at which point the water bath is removed and the balance of the chloropicrin
is added at a rate sufficient to maintain the temperature at 58–60° (Note 3)
. When the addition, which requires nearly 2 hours, is complete, the stirrer is stopped and the mixture is allowed to stand overnight.
The flask is connected to a 2 by 50 cm. Vigreux column equipped with a total-reflux partial take-off head
, and all but about 400 ml. of the ethanol
is removed at 200 mm. pressure with a reflux ratio greater than 5:1 (Note 4)
The residue is cooled, diluted with 1.2 l. of water, and transferred to a 2-l. separatory funnel
. The organic layer is separated, washed with 200 ml. of saturated salt solution, and dried over anhydrous magnesium sulfate
. The aqueous layer is extracted with a total of 800 ml. of ether
used in several small portions. The ethereal extracts are combined, washed first with 500 ml. of water then with 500 ml. of saturated salt solution, and finally dried over anhydrous magnesium sulfate
. The ether
is removed through a 1.8 by 25 cm. glass-helix-packed fractionating column with a total-reflux partial take-off head
. The residue is combined with the balance of the crude product and distilled through the fractionating column at atmospheric pressure. The yield of ethyl orthocarbonate
is 54–57.5. g.
); b.p. 158–161°; nD25
The absolute ethanol was a good commercial grade
and contained less than 0.1% of water according to the paraffin-oil test.2
is a skin irritant and a lachrymator. No difficulty was experienced when the preliminary steps were carried out in a good hood.
Care should be taken to regulate the temperature and rate of addition of chloropicrin as specified in order to avoid accumulation of unreacted chloropicrin
in the reaction mixture during the induction period; otherwise the reaction, which is strongly exothermic, may get out of control.
A water bath should be used as a heat source to avoid over-heating, which leads to lowered yields. This distillation should be carried out carefully to prevent loss of product by co-distillation with the ethanol
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