A.
Phenylsulfenyl chloride. A
250-mL, three-necked, round-bottomed flask, fitted with a
nitrogen inlet, a
pressure-equalizing 125-mL dropping funnel, and a
magnetic stirring bar, is charged with
thiophenol (21 mL) (Note
1), dry
triethylamine (0.25 mL), and dry
pentane (100 mL) (Note
2) under a blanket of
nitrogen. The remaining neck of the flask is stoppered and the
nitrogen is allowed to sweep gently through the flask and out of the pressure-equalizing dropping funnel. The flask and its contents are cooled to 0°C with an
ice bath and stirring is begun. The
dropping funnel is charged with
sulfuryl chloride (19 mL) (Note
1). The
sulfuryl chloride is added dropwise over a 1-hr period to the chilled
thiophenol solution with stirring. During this addition, a thick layer of white solid forms. It gradually dissolves as it is broken down. After the addition is complete, the ice bath is removed and the mixture is allowed to stir for 1 hr longer while slowly warming to room temperature. During the course of the addition and subsequent stirring, the clear, pale-yellow solution becomes dark orange-red. The dropping funnel is replaced with an outlet adapter connected to a
vacuum pump and the
nitrogen inlet is exchanged for a ground
glass stopper. The
pentane and excess
sulfuryl chloride are removed under reduced pressure at room temperature. The outlet adapter is replaced by a short-path distillation apparatus adapted for use under reduced pressure. The oily red residue is distilled to give
phenylsulfenyl chloride as a blood-red liquid (
26 g,
87%), bp
41–42°C (1.5 mm) (Note
3). This compound is stored under
nitrogen until used in Part B (Note
4).
B.
(Phenylthio)nitromethane. Freshly cut
sodium metal (4.8 g) is added to absolute
ethanol (100 mL) in a
500-mL Erlenmeyer flask with a ground-glass joint and allowed to react until the metal is completely consumed (Note
5). To this mixture is added a solution of
nitromethane (12 g) (Note
6) in absolute
ethanol (100 mL) with swirling. The
phenylsulfenyl chloride (prepared earlier) is quickly poured into a
1000-mL, three-necked, round-bottomed flask fitted with a
mechanical stirrer, a
nitrogen inlet/outlet adapter, and a
calcium chloride drying tube, and is diluted with dry
tetrahydrofuran (THF) (250 mL) (Note
7). Stirring is begun, the drying tube is removed, and the
sodium nitromethane–
ethanol slurry is added quickly in one portion to the THF solution (Note
8). The deep-red solution immediately turns yellow and stirring is continued for a further 10 min. The reaction mixture consists of solid and liquid. It is dissolved in
200 mL of a 1 N sodium hydroxide solution and poured into a
1000-mL separatory funnel.
Dichloromethane (200 mL) is added (Note
9), the aqueous layer (lower layer) is separated, and the organic layer further extracted with
1 N sodium hydroxide (2 × 100 mL) (Note
10). The combined aqueous layers are washed with
dichloromethane (500 mL) and acidified to pH 3 using 1
N hydrochloric acid. The brown organic layer that appears is separated, diluted with
50 mL of dichloromethane, dried over
magnesium sulfate, filtered, and concentrated at water aspirator pressure to give
18–19 g (
60–65%) of crude
(phenylthio)nitromethane as an orange-red oil. This material is of sufficient purity for many purposes. Further purification may be effected by distilling at reduced pressure to give
(phenylthio)nitromethane (
14 g,
50%) as a pale-yellow oil, bp
85–95°C at 0.05 mm (Note
11),(Note
12),(Note
13),(Note
14).