Formaldehyde-hexamethylenetetramine

Acid Amides can be produced by acylating ammonia with esters, acid anhydrides, or the acids themselves (above 100 °C) an important product is formamide from methyl formate. Alternatively acid amides can be synthesized by reacting acid halides with ammonia. Catalytic hydrogenation converts the acid amides to primary amines. Ammonia and aldehydes or ketones are the basis for different stable products. With formaldehyde hexamethylenetetramine (urotropine) is obtained with acetaldehyde, ammono acetaldehyde with benzaldehyde, hydrobenzamide with ethylene and propylene oxides, aqueous ammonia reacts to form ethanol- or propanolamine. 

In additicm ro being an aiumono-formaldehyde, hexamethylenetetramine is also a tertiaiy amine and shows the characteristic properties of such amines, forming innumerable salts, addition compounds, and complexes. In this it resembles pyridine, triethanolamine, etc., but differs in possessing a lower degree of basicity. 

Upon heating the polymers, anhydrous gaseous formaldehyde is produced (compare Section 111,17). By allowing a mixture of concentrated ammonia solution and formalin to evaporate, hexamethylenetetramine (also called hexamine, vrotropine) CjHjjNj is formed ... 

Unlike aliphatic aldehydes (with the exception of formaldehyde which 3delds hexamethylenetetramine. Section 111,67) benzaldehyde yields hydrobenzamide (and not an aldehyde ammonia) with ammonia ... 

The benzylchloride compound made in the previous recipe can be converted to piperonal or benzaldehyde using a chemical called hexamine [137 p817, 37 p700, 136]. Hexamine, also known as methenamine or hexamethylenetetramine, is a weird looking chemical that is easily made from formaldehyde but is better off being purchased. 

Hexamine, more formally known as Hexamethylenetetramine, is easily and conveniently produced from Formaldehyde and Ammonia solutions. Formaldehyde may be easily produced by depolym-erizing, with heat, Paraformaldehyde (the only ingredient in OTC MildewCide). Hexamine is then reacted with Hydrochloric Acid and heated to yield Methylamine HCI in near quantitative yield. 

Two-Stage Resins. The ratio of formaldehyde to phenol is low enough to prevent the thermosetting reaction from occurring during manufacture of the resin. At this point the resin is termed novolac resin. Subsequently, hexamethylenetetramine is incorporated into the material to act as a source of chemical cross-links during the molding operation (and conversion to the thermoset or cured state). 

Hexamethylenetetramine. Pure hexamethylenetetramine [100-97-0] (also called hexamine and HMTA) is a colorless, odorless, crystalline sohd of adamantane-like stmcture (141). It sublimes with decomposition at >200° C but does not melt. Its solubiUty in water varies Htde with temperature, and at 25°C it is 46.5% in the saturated solution. It is a weak monobase aqueous solutions are in the pH 8—8.5 range (142). Hexamethylenetetramine is readily prepared by treating aqueous formaldehyde with ammonia followed by evaporation and crystallisation of the soHd product. The reaction is fast and essentially quantitative (142). 

The production of hexamethylenetetramine consumes about 6% of the U.S. formaldehyde supply (115). Its principal use is as a thermosetting catalyst for phenoHc resins. Other significant uses are for the manufacture of RDX (cyclonite) high explosives, in mol ding compounds, and for mbber vulcanisation accelerators. Some hexamethylenetetramine is made as an unisolated intermediate in the manufacture of nitfilotriacetic acid. 

Hexamethylenetetramine. Hexa, a complex molecule with an adamantane-type stmcture, is prepared from formaldehyde and ammonia, and can be considered a latent source of formaldehyde. When used either as a catalyst or a curative, hexa contributes formaldehyde-residue-type units as well as benzylamines. Hexa [100-97-0] is an infusible powder that decomposes and sublimes above 275°C. It is highly soluble in water, up to ca 45 wt % with a small negative temperature solubiUty coefficient. The aqueous solutions are mildly alkaline at pH 8—8.5 and reasonably stable to reverse hydrolysis. 

Ammonia is used in the fibers and plastic industry as the source of nitrogen for the production of caprolactam, the monomer for nylon 6. Oxidation of propylene with ammonia gives acrylonitrile (qv), used for the manufacture of acryHc fibers, resins, and elastomers. Hexamethylenetetramine (HMTA), produced from ammonia and formaldehyde, is used in the manufacture of phenoHc thermosetting resins (see Phenolic resins). Toluene 2,4-cHisocyanate (TDI), employed in the production of polyurethane foam, indirectly consumes ammonia because nitric acid is a raw material in the TDI manufacturing process (see Amines Isocyanates). Urea, which is produced from ammonia, is used in the manufacture of urea—formaldehyde synthetic resins (see Amino resins). Melamine is produced by polymerization of dicyanodiamine and high pressure, high temperature pyrolysis of urea, both in the presence of ammonia (see Cyanamides). 

A number of disinfectants apparentiy owe their activity to formaldehyde, although there is argument on whether some of them function by other mechanisms. In this category, the dmg with the longest history is hexamethylenetetramine (hexamine, urotropin) [100-97-0] which is a condensation product of formaldehyde and ammonia that breaks down by acid hydrolysis to produce formaldehyde. Hexamine was first used for urinary tract antisepsis. Other antimicrobials that are adducts of formaldehyde and amines have been made others are based on methylolate derivations of nitroalkanes. The apphcations of these compounds are widespread, including inactivation of bacterial endotoxin preservation of cosmetics, metal working fluids, and latex paint and use in spin finishes, textile impregnation, and secondary oil recovery (117). 

Tannins can also be hardened by addition of hexamethylenetetramine (hex-amine) [146,147], whereby these boards show very low formaldehyde emission [16-18,148-151]. 

Resol resins thermoset on heating and are used for adhesives. Novolacs require a further source of formaldehyde in the form of hexamethylenetetramine to produce molding powders. Phenolic moldings are resistant to heat, chemicals, and moisture with good electrical and heat insulation qualities. Complex phenols from, e.g., cashew-nut shell liquid, are used in making brake... 

The oxime of bromoacetylfurazan 123 was converted into the amine 125 by treatment with hexamethylenetetramine and subsequent acidic hydrolysis. Oxa-diazine derivative 126 was made from the amine and formaldehyde in 57% yield (Scheme 73) (97ROC1760, 97ZOR1844). 

Formaldehyde reacts with ammonia and produces hexamethylenetetramine (hexamine) ... 

The synthesis of 4-unsubstituted DHPs in a focused microwave reactor has been reported using alkyl acetoacetates and hexamethylenetetramine 19 as the source of both formaldehyde and ammonia, with additional ammonium acetate to maintain the stoichiometry [57], Irradiation for 100 s under solvent-free conditions gave, for example, 1,4-DHP 20 in 63% isolated yield (Scheme 5). 

An acidic-cure catalyst is added to the urea-formaldehyde resin before it is used as an adhesive. Ammonium chloride and ammonium sulfate are the most widely used catalysts for resins in the forest products industry. A variety of other chemicals can be used as a catalyst, including formic acid, boric acid, phosphoric acid, oxalic acid, and acid salts of hexamethylenetetramine. 

Hexamethylenetetramine this ammonia precursor does not cause fibre swelling and the unfixed dyes are removed efficiently at pH 6.5, compared with pH 8.5 with ammonia, thus causing less damage to the wool. However, the hydrolysis of this compound (Scheme 12.6) results in the formation of formaldehyde and this can modify the hue of certain dyes [2]. 

It is made by the nitration of hexamine (hexamethylenetetramine), itself prepared from formaldehyde and ammonia. Hexamine was originally nitrated with a large excess of concentrated nitric acid at temperatures below 30°C and the product recovered by adding the reaction liquor to an excess of chilled water. Later the yield was improved by adding ammonium nitrate to the reaction as this reacts with the liberated formaldehyde. A much-used process converts the hexamine first to its dinitrate, which is then reacted with ammonium nitrate, nitric acid and acetic anhydride (the last reagent being re-formed from the product by use... 

Part 23 Determination of formaldehyde and hexamethylenetetramine (HMTA) in food simulants In the case of HMTA, it is treated with acid and heated to release formaldehyde. Formaldehyde in simulant is determined colorimetrically by reaction with chromotropic add in the presence of sulfuric acid... 

Only 1,3,5,7-tetraazaadamantane is known. It is also called hexamethylenetetramine (93) (HMT), hexamine, aminoform, ammoform, cyctamin, cystogen, formin, uritone, urotropin, and methenamine. It is listed by the last name in the Merck Index. It is prepared from formaldehyde and ammonia. The chemistry of this well-known compound is not discussed in this review. 

Paquin in 1948 found that a strongly exothermic reaction occurred when 40% formaldehyde was added to a solution of sulfamide in 25% aqueous ammonia. At once beautiful crystals precipitated they were recrystallized from 96% alcohol to give a compound, C5H10N4SO2, mp 224-225 "C, in 88% yield.245 From the similar character to hexamethylenetetramine, he named this product pentamethylenetetramine sulfone it is 225. One year later, in 1949, Hecht and Henecka at Bayer research laboratory reported that a condensation product from one mole of sulfamide in strong mineral acid and two moles of formaldehyde showed very strong toxicity and was five times more toxic than strychnine. They called this product (226) tetra-methylenedisulfotetramine. 246... 

The early addition of Dimedon is reported234 to depress the formation of hexamethylenetetramine from formaldehyde in the presence of ammonia. O Dea282 found that the activated methylene center, sometimes formed in periodate oxidations of carbohydrates, reacts appreciably with the formaldehyde formed, thus giving low yields of apparent formaldehyde. He was able to depress this side reaction by the use of lowered temperatures and by the addition of benzaldehyde or of p-hydroxybenzaldehyde. The analyses for formaldehyde have often been more successful at a pH of 7.5 than at lower pH values.57, 68 59a 60 264... 

Experiment 6. Reaction with Ammonia.—Of the formaldehyde prepared 10 c.c. are mixed with a small excess of ammonia and the mixture is evaporated in a small glass dish on the water bath. The colourless crystals which remain consist of hexamethylenetetramine (CH2)6N4 (urotropine.) This reaction proceeds quantitatively. It should be so carried out and the result compared with that obtained by titration. 

Another reagent, hexamethylenetetramine (HMT) has also been used in place of urea for the homogeneous preparation of LDHs. HMT hydrolyzes at high temperature in aqueous solution with the release of ammonia, which makes the solution alkahne, and formaldehyde, which would not be expected to be incorporated into the LDH. Using HMT, well-crystalhzed 1-5 p.m -sized particles of chloride-intercalated LDHs were prepared in a pressure... 

Hexamethylenetetramine (HMTA) has important uses in modifying phenolic resin manufacture and is an intermediate in explosive manufacture. Although it is a complex three-dimensional structure, it is easily made by the condensation of formaldehyde and ammonia. 

Thus in a separate second part of this two-stage process a cross-linking agent is added and frirther reaction occurs. Although formaldehyde may be added, quite often hexamethylenetetramine is used, which decomposes to formaldehyde and ammonia. Occasional nitrogen bridges occur in the final structure of some phenolics made by this method. 

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