A.
Methylthio-2-propanone.
2 A
2-l., three-necked, round-bottomed flask is equipped with a sealed
mechanical stirrer and a
two-necked adapter holding a
thermometer and a
condenser topped with a
silica gel drying tube. After
700 ml. of anhydrous methanol has been added, the third neck is stoppered, and the flask is immersed in an ice
water bath. Stirring is begun, and
108 g. (2.00 moles) of sodium methoxide (Note
1) is added in small portions at a rate sufficiently gradual to prevent a large exotherm (Note
2). When all of the
methoxide has dissolved and the temperature has returned to 5°, the stopper is replaced with a
200-ml., pressure-equalizing, jacketed addition funnel (Note
3). This funnel, charged previously with
130 ml. (2.20 moles) of methanethiol (Note
4), contains a 2-propanol-dry ice slurry in the cooling jacket, and is topped with a silica gel drying tube. Stirring and cooling are continued while the
methanethiol is run into the flask over a 20-minute period, and for 15 minutes thereafter. The jacketed addition funnel is then replaced by a standard, 200-ml., pressure-equalizing addition funnel, which is used to add
185 g. (2.00 moles) of chloroacetone (Note
5) to the reaction mixture over 1 hour. When this addition is complete, the
ice bath is removed, and the suspension is stirred overnight at room temperature. The insoluble material, largely inorganic salts, is removed by filtration through Celite, and the filter cake is washed with two
150-ml. portions of absolute methanol. After
methanol has been removed from the combined filtrates by distillation, the residue is distilled through a
300-mm. Vigreux column, yielding
155–158 g. (
74–76%) of
methylthio-2-propanone, b.p.
153–154°,
nD23 1.4728.