Methylene bromide

CHBr3 + NaOH + Na3As03 — CHaBra + Na3As04 + NaBr 

Submitted by W W Hartman and E E Drecer Checked by Frank C Whitmore and C. J Korpi. 

In a a-l. round-bottom 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) bromo-form (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 445 g. (11 moles) of sodium hydroxide in 1.4 1. 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 horns 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). 

The commercial bromoform used contained 12 per cent of alcohol. Its specific gravity was 2.59/250 as compared with 2.88/25° for pure bromoform. 

The chief function of the extraction is to collect the fine droplets of methylene bromide which remain in the water layer. 

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Methylene bromide (CHjBfj) and methylene iodide (CHjIj) are easily prepared by the reduction of bromoform or iodoform respectively with sodium arsenite in alkaline solution ... 

In a 1-litre three-necked flask, mounted on a steam bath and provided respectively with a separatory funnel, mechanical stirrer and double surface condenser, place 165 g. of bromoform (96 per cent.). Add 10 ml. of a solution of sodium arsenite made by dissolving 77 g. of A.R. arsenious oxide and 148 g. of A.R. sodium hydroxide in 475 ml. of water. Warm the mixture gently to start the reaction, and introduce the remainder of the sodium arsenite solution during 30-45 minutes at such a rate that the mixture refluxes gently. Subsequently heat the flask on the steam bath for 3-4 hours. Steam distil the reaction mixture (Fig. 11, 41, 1) and separate the lower layer of methylene bromide (79 g.). Extract the aqueous layer with about 100 ml. of ether a further 3 g. of methylene bromide is obtained. Dry with 3-4 g. of anhydrous calcium chloride, and distil from a Claisen flask with fractionating side arm. The methylene bromide boils constantly at 96-97° and is almost colourless. 

The reaction itself works by the action of Na or K from NaOH or KOH which form what is called a catechoxide dianion with the two OHs of the catechol species. This makes the two ripe for an attack by a methylene halide which can be either DCM (methylene chloride, or dichloromethane), DBM (methylene bromide, or di-bromomethane) or DIM (methylene iodide, or diiodomethane). DCM is cheap and works pretty well, but DBM and DIM work better yet are more expensive. 

Allyl chloride A 36 Dipropyl ether B 65 Methylene bromide A... 

When the reactions in DMF or DMSO are carried out in the presence of methylene bromide, an insertion product is also formed [31] (equation 22)... 

Methylene bromide is essentially less effective in radical reactions as a chain transfer agent as a result, the reactions with methylene bromide proceed non-selectively and with small conversion of starting substrate. 

Methylene bromide, 112 Methyl ethyl ketone, 23 a-Methyl d-glucoside, 112 Methyl Oxalate, 70 Myristyl alcohol, 64... 

Methyldinitrophenol, d715, d716 Methyl enanthate, m266 Methylene bromide, dl 10 Methylene bromochloride, b305 Methylene chloride, d235... 

Methylene blue, 9 517-518 Methylene bromide, 4 348 Methylenecarbenes, 21 144, 146 Methylene chloride, 16 371-380 analytical methods for, 16 376 binary azeotropes of, 16 373t chlorocarbon/chlorohydrocarbon of industrial importance, 6 227t consumption, 6 244t dry, 16 372... 

Methylene bromide can function as the coupling reagent if it is used in an excess. This unusual coupling reaction succeeds, presumably, because the intermediate a-bromo ether, 3, reacts much more rapidly with the phenoxide endgroup of another polymer than methylene bromide does to produce the formal linked product, 4. 

Methylene chloride also acts as a coupling reagent but is less effective than methylene bromide. Examples of coupling material containing structure are shown in Table II. 

When the reaction was repeated using methylene chloride (3.0 mL) instead of methylene bromide, the polymer had values of [q] 0.49 dl/g and OH 0.134. 

Photolysis of an aqueous solution containing bromoform (989 pmol) and a catalyst [Pt(colloid)/Ru(bpy) VMV/EDTA] yielded the following products after 25 h (pmol detected) bromide ions (250), methylene bromide (475), and unreacted bromoform (421) (Tan and Wang, 1987). 

Dithiomethane, see Bromochloromethane, Methylene bromide. Methylene chloride... 

T- (Methylenebis (thio))bis-ethane, see Phorate Methylene bromide, see Bromoform Methylene chloride, see Carbon tetrachloride. Chloroform... 

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