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Org. Synth. 1929, 9, 56
DOI: 10.15227/orgsyn.009.0056
METHYLENE BROMIDE
[Methane, dibromo-]
Submitted by W. W. Hartman and E. E. Dreger.
Checked by Frank C. Whitmore and C. J. Korpi.
1. Procedure
In a 2-l. round-bottomed flask placed on a steam bath and fitted with a stirrer, a separatory funnel, and a reflux condenser is placed 540 g. (1.9 moles) of commercial (88 per cent) bromoform (Note 1). There is then added 10 cc. of a solution of sodium arsenite made by dissolving 230 g. (1.16 moles) of c. p. arsenious oxide and 440 g. (11 moles) of sodium hydroxide in 1.4 l. of water. The mixture is warmed gently to start the reaction, and then the remainder of the sodium arsenite solution is added during about one hour at such a rate that the solution refluxes gently. When the addition is complete, the flask is heated for four hours on the steam bath. The reaction mixture is distilled with steam, the lower layer of methylene bromide separated, and the water layer extracted once with 100 cc. of ether (Note 2). The methylene bromide is dried with 10 g. of calcium chloride and distilled. The yield of slightly yellow liquid boiling at 97–100° is 290–300 g. (88–90 per cent of the theoretical amount).
2. Notes
1. The commercial bromoform used contained 12 per cent of alcohol. Its specific gravity was 2.59/25° as compared with 2.88/25° for pure bromoform.
2. The chief function of the extraction is to collect the fine droplets of methylene bromide which remain in the water layer.
3. Discussion
Methylene bromide can be prepared by the reaction of bromine with methylene iodide.1 The procedure described is adapted from the preparation of methylene iodide given below, and a like method giving a lower yield has been described.2

References and Notes
  1. Butlerow, Ann. 111, 251 (1859).
  2. Kocheshkov, J. Russ. Phys. Chem. Soc. 60, 1191 (1928) [C. A. 23, 2931 (1929)]; Ber. 61, 1659 (1928).

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

arsenious oxide

alcohol (64-17-5)

calcium chloride (10043-52-4)

ether (60-29-7)

sodium hydroxide (1310-73-2)

bromine (7726-95-6)

sodium arsenite

Methylene bromide,
Methane, dibromo- (74-95-3)

bromoform (75-25-2)

Methylene iodide (75-11-6)