METHYLENE IODIDE
METHYLENE IODIDE DISTILLATION
In a 1-litre three-necked flask, fitted with a mechanical stirrer, reflux condenser and a thermometer, place 200 g. of iodoform and half of a sodium arsenite solution, prepared from 54′5 g. of A.R. arsenious oxide, 107 g. of A.R. sodium hydroxide and 520 ml. of water. Start the stirrer and heat the flask until the thermometer reads 60-65° ; maintain the mixture at this temperature during the whole reaction (1). Run in the remainder of the sodium arsenite solution during the course of 15 minutes, and keep the, reaction mixture at 60-65° for 1 hour in order to complete the reaction. Allow to cool to about 40-45° (2) and filter with suction
from the small amount of solid impurities. Separate the lower layer from the filtrate, dry it with anhydrous calcium chloride, and distil the crude methylene iodide (131 g. ; this crude product is satisfactory for most purposes) under Diminished pressure. Practically all passes over as a light straw-coloured (sometimes brown) liquid at 80°/25 mm. ; it melts at 6°. Some of the colour may be removed by shaking with silver powder. The small dark residue in the flask solidifies on cooling.Notes.
(1) If the temperature is allowed to rise, the yield is slightly diminished owing
to the formation of a little methyl iodide.
(2) If the temperature falls below 40°, a precipitate of sodium arsenate will
gradually separate and this will tend to produce an emulsion of the methylene
iodide, thus rendering filtration and separation difficult.
In: Synthetic Chemistry · Tagged with: DISTILLATION