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C. S. Marvel, Methylamine HydrochlorideOrganic Syntheses Coll.

Vol. I, pp347-350, 2nd Ed (1958)

In a 5 liter round-bottomed flask, fitted with a stopper holding a

condenser set for downward distillation and a thermomether whichwill extend well into the liquid, are placed 4 kg (3711 ml, 47-53

moles) of technical formaldehyde (35-40 percent; d 1.078 at 20C)and 2 kg (37 moles) of technical ammonium chloride. The mixture is

heated on the steam bath until no more distillate comes over andthen over a flame until the temperature of the solution reaches

104C. The temperature is held at this point until no more distillate

comes over (four to six hours). The distillate, which consists ofmethylal (bp 42-43C), methylformate and water may be treated with

NaOH solution to recover methylal and sodium formate. The contentsof the reaction flask are cooled too room temp and the ammonium

chloride which separates is filtered off. The mother liquor is

concentrated on the steam bath under reduced pressure to 2500 ml,and again cooled to room temp, whereupon a second crop of

ammonium chloride separates. The total recovery of ammoniumchloride up to this point amounts to 780-815 grams. The mother

liquor is again concentrated under reduced pressure until crystalsbegin to form on the surface of the solution (1400-1500 ml). It is

then cooled to room temperature, and a first crop of methylamine

hydrochloride, containing some ammonium chloride is obtained byfiltering the cold solution. At this point 625-660 grams of crude

product is obtained. The mother liquor is now concentrated underreduced pressure to about 1000 ml, and cooled, and a second crop of

methylamine hydrochloride (170-190 grams) is then filtered off. This

crop of crystals is washed with 250 cc of cold chloroform, and filteredto remove most of the dimethylamine hydrochloride which is present.

After the washing, the product weighs 140-150 grams. The originalmother liquor is then evaporated under reduced pressure, as far as

possible, by heating on a steam bath, and the thick syrupy solution

(about 350 ml) which remains is poured into a beaker and allowed tocool, with occasional stirring, in order to prevent the formation of a

solid cake, and the crystals obtained are washed with 250 ml of coldchloroform, the solution is filtered yielding 55-65 grams of product.

There is no advantage in further concentrating the mother liquor,

which contains mostly tetramethylmethylenediamine hydrochloride,but no trimethylamine hydrochloride. The total yield of methylamine

hydrochloride is 830-850 grams. The product contains water,ammonium chloride and some dimethylamine hydrochloride. In order

to obtain a pure product, the impure methylamine hydrochloride is

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recrystallized from absolute ethanol (solubility 0.6g/100ml at 15C),or preferably butyl alcohol (even less soluble). The recovery of

ammonium chloride amounts to 100-150 grams, making the totalrecovery 850-950 grams. The yield of recrystallized methylamine

hydrochloride is 600-750 grams (45-51 percent of theory, based on

the used up ammonium chloride).

A standard run, from 250 grams ammonium chloride and 500g 37%formaldehyde (containing 15% methanol), gives 100-134 grams

methylamine hydrochloride, 27 grams dimethylamine hydrochlorideand 81 grams of recovered ammonium chloride. The distillate

contains methylal (formaldehyde dimethyl acetal) and methyl

formate, which after treatment with NaOH can yield 25g of sodiumformate and 30 grams of methylal, as the compound cannot be

separated by fractional distillation, neutralization is the way to go.Ammonium chloride is very sparingly soluble in a concentrated

solution of methylammonium chloride, making the separation of the

compounds pretty sharp.

H. I. Jones, The Preparation of Methylamine, J. Am. Chem. Soc.

(?), pp1411-1515 (1918)

50 grams of ammonium chloride and 300g of 40% formaline solution

were slowly warmed together under vacuum, and soon a rapid

evolution of carbon dioxide began. The solution was refluxed at a 20mm pressure for four hours, until no more carbon dioxide was given

off, as tested with barium hydroxide solution. The reaction productwas then distilled in a vacuum, 2 hours being consumed in the

distillation. As soon as the residue from the distillation was cold, theammonium chloride which had crystallized out was filtered off with

suction, and the filtrate further concentrated by evaporation and

again cooled, allowing further ammonium chloride to crystallize. AsWerner has pointed out [1], the separation of ammonium chloride

and methylammonium chloride is pretty sharp, and the crystals are sodifferent that it is easy to see if one is contaminated with the other.

The collected ammonium chloride wighed 7.9 grams (0.17 mol). The

mother liquor left was evaporated until crystals began to form on the

surface, and was set aside to cool, and the first crop ofmethylammonium chloride was collected with suction. Furtherevaporation gave additional crops. In all four crops that were

obtained, which were freed from dimethylamine hydrochloride by

washing with chloroform, 27.2 grams of dimethylamine hydrochloride(0.51 mol)was obtained. The distillate weighed 37.3 grams, the

residue which didn't crystallize weighed 326 grams, and the total

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yield of methylamine hydrochloride was 82.5 grams, or 37% oftheory.