Dimethylamines processing

According to this scheme, dimethylamine is produced without recycling monomethylamine to the aminator, since the monomethylamine is converted to dimethylamine by hydrogenating the transient aldimine. The advantages claimed for this dimethylamine process are that only the un-reactive trimethylamine is recycled and that it does away with fractional distillations under pressure. 

The yields of this reaction are typically 40—80%. C-nmr studies (41) indicate that the reaction is a second-order process between polyacrylamide and dim ethyl am in om eth an ol, which is one of the equiUbrium products formed in the reaction between formaldehyde and dimethylamine [124-40-3] C2H2N. The Mannich reaction is reversible. Extensive dialysis of Mannich polyacrylamides removes all of the dimethyl aminomethyl substituents (42). 

There are two processes used commercially for DMF manufacture. A two-step process iavolves carbonylation of methanol [67-56-1] to methyl formate [107-31 -3] and reaction of the formate with dimethylamine. 

The methanol carbonylation is performed ia the presence of a basic catalyst such as sodium methoxide and the product isolated by distillation. In one continuous commercial process (6) the methyl formate and dimethylamine react at 350 kPa (3.46 atm) and from 110 to 120°C to effect a conversion of about 90%. The reaction mixture is then fed to a reactor—stripper operating at about 275 kPa (2.7 atm), where the reaction is completed and DMF and methanol are separated from the lighter by-products. The cmde material is then purified ia a separate distillation column operating at atmospheric pressure. 

A second process is the direct carbonylation of dimethylamine [124-40-3] ia the presence of a basic catalyst or a transition metal. This carbonylation is often mn ia the presence of methanol ia order to help solubilize the catalyst (7), and presumably proceeds through methyl formate as an iatermediate. 

In another DMF process, hydrocyanic acid reacts with methanol ia the presence of water and a titanium catalyst (16), or ia the presence of dimethylamine and a catalyst (17). 

Oxidative processes can also be used to prepare DMF. For example, it can be produced from tetraoxane (a source of formaldehyde (qv)), oxygen, and dimethylamine over Pd—AI2O2 (24) or from trimethylamine and oxygen ia the presence of a metal haUde catalyst (25). 

MMHa.nd UDMH. MonomethyUiydrazine and yyz -dimethylhydrazine are manufactured by Olin Corp. using the same Raschig process and equipment employed for anhydrous hydrazine. Chloramine, prepared as described above, reacts with methylamine or dimethylamine instead of with... 

Batch or continuous processes can be used to prepare tertiary amines from alcohols and ammonia or a secondary amine, such as, dimethylamine. 

Woodward s strychnine synthesis commences with a Fischer indole synthesis using phenylhydrazine (24) and acetoveratrone (25) as starting materials (see Scheme 2). In the presence of polyphosphor-ic acid, intermediates 24 and 25 combine to afford 2-veratrylindole (23) through the reaction processes illustrated in Scheme 2. With its a position suitably masked, 2-veratrylindole (23) reacts smoothly at the ft position with the Schiff base derived from the action of dimethylamine on formaldehyde to give intermediate 22 in 92% yield. TV-Methylation of the dimethylamino substituent in 22 with methyl iodide, followed by exposure of the resultant quaternary ammonium iodide to sodium cyanide in DMF, provides nitrile 26 in an overall yield of 97%. Condensation of 2-veratryl-tryptamine (20), the product of a lithium aluminum hydride reduction of nitrile 26, with ethyl glyoxylate (21) furnishes Schiff base 19 in a yield of 92%. 

Restelli and Coull [AIChE J., 72 (292), 1966] have studied the transmethylation reaction of dimethylamine in a differential flow reactor using montmorillonite as a catalyst. They measured initial reaction rates under isothermal conditions for this heterogeneous catalytic process. Steady-state operating data were recorded. 

Even though the CMR and MBR operate under conditions in which pressure is developed, gaseous reactants or media often can be handled in these systems without problems arising through over-pressure. Mannich reactions with dimethylamine, Baylis-Hillman reactions with formaldehyde, aminoreductone formation with ammonia, all proceeded without difficulty, as did Willgerodt reactions in which gases are formed during the process. 

The addition product of ethyl acetoacetate and methyl a-methoxyacrylate was hydrolyzed, and the resulting dicarboxylic acid was treated with dimethylamine hydrochloride and aqueous formaldehyde. The product of the Mannich reaction was decarboxylated, reesterifed, and finally treated with methyl iodide to supply quaternary salt 469 as the main product. During the above one-pot process, elimination also took place, yielding unsaturated ketone 470, which was later utilized as its hydrogen bromide adduct 471. Reaction of 3,4-dihydro- 3-car-boline either with 469 or 471 furnished the desired indolo[2,3-a]quinolizine derivative 467 as a mixture of two diastereomeric racemates. 

This reaction is completely analogous to other acylation processes, such as the formation of the acetyl derivative from dimethylamine acetate. The only difference is, that since the C=0 double bond of acetic acid is less reactive than the N=0 double bond of nitrous acid, a higher temperature is required in the former case. 

In the leather and tanning industry dimethylamine sulphate is used in depilation processes. Under alkaline conditions, dimethylamine is released into the atmosphere and it reacts with nitrogen oxides produced from exhaust emissions, to give... 

Results Most of the process-related, nonagent compounds present in the GPCR product gas are measured using a bubbler and standard EPA collection techniques. The process-related, nonagent compounds for which a method was not developed included vinyl sulfide, mercaptans, dimethylamine, and ethanethiol. 

The Mannich reaction is best discussed via an example. A mixture of dimethylamine, formaldehyde and acetone under mild acidic conditions gives N,N-dimethyl-4-aminobutan-2-one. This is a two-stage process, beginning with the formation of an iminium cation from the amine and the more reactive of the two carbonyl compounds, in this case the aldehyde. This iminium cation then acts as the electrophile for addition of the nucleophile acetone. Now it would be nice if we could use the enolate anion as the nucleophile, as in the other reactions we have looked at, but under the mild acidic conditions we cannot have an anion, and the nucleophile must be portrayed as the enol tautomer of acetone. The addition is then unspectacular, and, after loss of a proton from the carbonyl, we are left with the product. 

The dienamine 346 on treatment with acetaldehyde-dimethylamine-acetic acid gave a small yield of carbazole 347. This process may proceed via... 

An example of the use of DMF as CO source in the Pd-catalyzed aminocarbonylation with microwave irradiation is shown in Scheme 28. Thus, n-bromotoluene was reacted with benzylamine (4 equiv.) in the presence of Pd-dppf catalyst, imidazole, KOBu, and DMF (17equiv.) with microwave irradiation for 20min to give amide 196 in 94% yield (Scheme 28). A proposed mechanism (Scheme 28) has a close similarity to that of the aminocarbonylation of aryl bromide with formamide (see Scheme 22). However, in this process, a large excess (4 equiv.) of benzylamine was used to suppress a possible reaction involving dimethylamine generated in situ from DMF under reaction conditions. 

The total yield of crude centrifuged methylamine hydrochloride is 830-850 g. This product contains, as impurities, water, ammonium chloride, and some dimethylamine hydrochloride. In order to obtain a pure product, the crude methylamine hydrochloride is recrystallized from absolute alcohol (Note 4). The crude salt is placed in a 5-I. round-bottom flask fitted with a reflux condenser protected at the top with a calcium chloride tube 2 1. of absolute alcohol is added and the mixture heated to boiling. After about half an hour the undissolved material is allowed to settle and the clear solution is poured off. When the alcoholic solution is cooled, methylamine hydrochloride crystallizes out. It is filtered off and centrifuged, and the alcohol used for another extraction. The process is repeated until the alcohol dissolves no more of the product (about five extractions are necessary). In the flask 100-150 g. of ammonium chloride remains, making the total recovery of ammonium chloride 850-950 g. The yield of recrystallized methylamine hydrochloride is 600-750 g. (45-51 per cent of the theoretical amount, based on the ammonium chloride used up in the process). 

Fazio, T., Damico, J. N., Howard, j. W., White, R. H., and Watts, J. O. (1971). Gas chromatographic determination and mass spectrometric confirmation on N-nitroso-dimethylamine in smoke-processed marine fish. J. Agric. Food Chem. 19, 250-253. 

Tannery A was the only tannery visited that was using Dimethylamine sulfate in the hide dehairing process. 

The highest level of NDMA (0.5 yg/ml) was found in a sample from a 36.5% aqueous solution of dimethylamine sulfate (DMAS). According to plant personnel, 117 liters of DMAS are used each day in the hide unhairing process. This would amount to less than 60 mg NDMA/day potential exposure from the contaminated DMAS. NDMA (0.0015 yg/ml) was also found in the re-lime pit (unhairing vat) process water. This process water contained 5.7 liters of DMAS in 8000 L of lime-saturated water. The other samples which contained NDMA (0.004 yg/ml and 0.006 yg/ml) were waste-water from the tannery outlet pipe collected at the local municipal waste-... 

A source for the NDMA was not found in this tannery. It was reported that they did use dimethylamine sulfate on an experimental basis and nitrosation of three of the bulk process water samples did result in the formation of 0.0015 to 0.0025 yg/ml of NDMA. We also collected three air samples using acid pH traps and after nitrosating the content, found twice the level of NDMA, thus indicating the presence of the NDMA precursor amine in the air. In a further experiment we sampled air over magnesium silicate coated with morpholine and found that from 3-20% of the 30 yg of morpholine had been converted to N-nitroso morpholine thus indicating an airborne nitrosating agent. 

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