Hexamethylenetetramine hexamine

Hexamine is also known as hexamethylenetetramine, aminoform, crystamine, methenamine or formin. It was first prepared in 1859 by Butlerov of Russia. It is a white, crystalline powder with a slight amine odor. It is soluble in water, alcohol, and chloroform, but it is insoluble in ether. However the aqueous solutions exhibit inverse solubility, i.e., less hexamine dissolves as the temperature increases. The hydrate, (CHi N O can be crystallized from the aqueous solution at temperatures below 14°C. Some additional properties are listed in Table 17.1. 

Molecular Weight Sublimation Temperature Flash Point 

Density of solid 20°C Bulk Density Particle Size Specific Heat 

Heat of Formation 25°C Heat of Combustion 25°C Solubility in Water 20°C 25°C 60°C 

This preparation illustrates another point of difference between formaldehyde and other aliphatic aldehydes. 

Mix 50 ml. of formalin, containing about 37 per cent, of formaldehyde, with 40 ml. of concentrated ammonia solution (sp. gr. 0- 88) in a 200 ml. round-bottomed flask. Insert a two-holed cork or rubber stopper carrying a capillary tube drawn out at the lower end (as for vacuum distillation) and reaching almost to the bottom of the flask, and also a short outlet tube connected through a Alter flask to a water pump. Evaporate the contents of the flask as far as possible on a water bath under reduced pressure. Add a further 40 ml. of concentrated ammonia solution and repeat the evaporation. Attach a reflux condenser to the flask, add sufficient absolute ethyl alcohol (about 100 ml.) in small portions to dissolve most of the residue, heat under reflux for a few minutes and filter the hot alcoholic extract, preferably through a hot water funnel (all flames in the vicinity must be extinguished). When cold, filter the hexamine, wash it with a little absolute alcohol, and dry in the air. The yield is 10 g. Treat the filtrate with an equal volume of dry ether and cool in ice. A further 2 g. of hexamine is obtained. 

Hexamethylenetetramine sublimes at about 260° and is very soluble in water. 

Place 50 g. of anhydrous calcium chloride and 260 g. (323 ml.) of rectihed spirit (95 per cent, ethyl alcohol) in a 1-litre narrow neck bottle, and cool the mixture to 8° or below by immersion in ice water. Introduce slowly 125 g. (155 ml.) of freshly distilled acetaldehyde, b.p. 20-22° (Section 111,65) down the sides of the bottle so that it forms a layer on the alcoholic solution. Close the bottle with a tightly fitting cork and shake vigorously for 3-4 minutes a considerable rise in temperature occurs so that the stopper must be held well down to prevent the volatilisation of the acetaldehyde. Allow the stoppered bottle to stand for 24-30 hours with intermittent shaking. (After 1-2 hours the mixture separates into two layers.) Separate the upper layer ca. 320 g.) and wash it three times with 80 ml. portions of water. Dry for several hours over 6 g. of anhydrous potassium carbonate and fractionate with an I efficient column (compare Section 11,17). Collect the fraction, b.p. 101- 

Acetals are usually liquid they are almost unaffected by alkalis and are not attacked by metallic sodium nor by Fehling s solution. They are identified by reference to the alcohol and aldehyde (or ketone if a ketal) which they yield when hydrolysed in acid solution. Hydrolysis proceeds readily in dilute acid solution (e.g., with 3-5 per cent, acid)  

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From ehloromethyl or bromomethyl aromatic compounds by heating with hexamethylenetetramine (hexamine) in aqueous alcohol or aqueous acetic acid. A quaternary ammonium compound is formed, which yields the aldehyde upon treatment with water in the presence of hexamine for example... 

Ma.nufa.cture. The two most common processes for making RDX and HMX use hexamethylenetetramine (hexamine) as starting material. The Woolwich or direct nitrolysis process used ia the United Kingdom proceeds according to ... 

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). 

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

Tracer Studies on the Nitro lysis of Hexamine to RDX and HMX. The formation of RDX and/or HMX molecules from the nitration or nitrolysis of Hexamethylenetetramine (Hexamine) is a complex process and has been postulated to take place via two separate paths. One involves the selective cleavage of the Hexamine molecule to the appropriate cyclic nitramine (RDX, HMX or both) depending on the specific... 

The oldest and simplest method of preparing cyclonite is based on the introduction of hexamethylenetetramine (hexamine) into an excess of concentrated nitric acid, s. g. 1.50-1.52, free of nitric oxides, at 25-30°C, thereafter pouring the whole into cold water. 

Aromatic and heteroaromatic aldehydes can alternatively be prepared from the corresponding methyl compound by subjecting the chloromethyl or bromomethyl derivative to the Sommelet reaction. This procedure involves an initial reaction between the halomethyl compound and hexamethylenetetramine (hexamine), and hydrolysing the resulting quaternary hexamine salt (4) with hot aqueous acetic acid. 

Annulation of haloacylamino and keto groups to produce a 1,4-benzodiaze pinone (p. 133) is improved when ammonia is replaced by ammonium carbonate [2992] and when hydrochloric acid is present [2993] a different mechanism is proposed on the basis of work using [ C]hexamethylenetetramine [2993]. The role of R and (see p. 133) in controlling the amount of the imidazolidine byproduct is discussed [2993]. The relative usefulness of ammonia (under pressure), ammonium carbonate and hexamethylenetetramine (hexamine) in this cyclization is considered [2992]. 

Both RDX and HMX are prepared by the first method. Reactant hexamethylenetetramine (hexamine, 4) may be directly nitrated with nitric add to produce a mixture of RDX and HMX (principally RDX) (Refe. 10,12). Another nitration procedure that employs nitric acid, ammonium nitrate, and acetic anhydride is used to prepare HMX (Refe. 11,17). 

The only known adamantane containing more than three endocyclic ring nitrogens is hexamethylenetetramine (hexamine, 1,3,5,7-tetraaza-adamantane, 4). It is readily prepared by reaction of formaldehyde and ammonia and was first described by Butlerov in 1859 (Ref. 82). Its preparation and properties have been reviewed (Ref. 83). The mechanism of formation from formaldehyde and ammonia has been studied (Refs. 84,85). Hexamine is employed as a reactant in the synthesis of RDX (3) and HMX (1). 

When ammonia is used as a catalyst, the resins formed are very different in some of their characteristics from other alkali-catalyzed resins the reaction mechanism appears to be quite different from the of sodium hydroxide-catalyzed resins. An obvious deduction is that intermediates containing nitrogen are formed. Several such intermediates have been isolated from ammonia-catalyzed PF reactions [10-12] and hexamine prepared resins [13-16] by various researchers. Similar types of intermediates are formed when amines or hexamethylenetetramine (hexamine) are used instead of ammonia. In the case of ammonia the main intermediates are dihydroxybenzylamines and trihydroxybenzylamines, such benzylamine bridges having been shown to be much more temperature stable than previously thought and to impart particular characteristics to the resin [13 16]. 

Formaldehyde is generally the aldehyde used in the preparation, setting, and curing of tannin adhesives. It is normally added to the tannin extract solution at the required pH, preferably in its polymeric form of paraformaldehyde, which is capable of fairly rapid depolymerization under alkaline conditions, and as urea-formalin concentrates. Hexamethylenetetramine (hexamine) may also be added to resins due to its potential formaldehyde releasing action under heat. Hexamine is, however, unstable in acid media [24] but becomes more stable with increased pH values. Hence under alkaline conditions the liberation of formaldehyde might not be as rapid and as efficient as wanted. Also, it has been fairly widely reported, with a few notable exceptions [25], that bonds formed with hexamine as hardener are not as boil resistant [26] as those formed by paraformaldehyde. The reaction of formaldehyde with tannins may be controlled by the... 

Possible crosslinkers are formaldehyde as aqueous solution [268], paraformaldehyde [263,265,267,269], UFC [270,271], UF resins [272], aqueous formaldehyde solution emulsified in an oil [273], dimethylolurea [274] or urea and phenol methylols with longer chains to overcome steric hindrance. Tannins can also be hardened by addition of hexamethylenetetramine (hexamine) [275], whereby these boards show a very low formaldehyde emission [269,275 281]. The autocatalytic hardening of tannins without any addition of formaldehyde or other aldehyde as crosslinker is possible, if alkaline Si02 is present as a catalyst at high pH or just as a consequence of the catalysis of the reaction induced by a lignocellulosic surface [282]. 

The first pro-drug, methenamine (3.22), was introduced as far back as 1899 by the Berlin firm, Schering. It was devised as a source of formaldehyde liberated from it by the acidity of the urine, and hence was a potent urinary antiseptic. This substance, hexamethylenetetramine (hexamine) is a cage-shaped molecule, very easily made by mixing ammonia and formaldehyde. If taken before meals, it encounters no acid until it enters the urine, and so it passes blandly through the body up to that stage. Since that time, many other urinary antiseptics have been discovered, yet methenamine continues to hold an effective place in treatment and is included in 20 of the World s pharmacopoeias. 

The nitration of hexamethylenetetramine (hexamine) takes place in a continuous stirred tank reactor (CSTR). The following data apply... 

Mimosa tannin extract (supplied by Silva, S. Michele Mondovi , Italy) of Stiasny value of 92.2 [17-19] was used. The tannin solution in water was prepared at 45% concentration and its pH adjusted to 10.4 with a 33% NaOH aqueous solution. The high pH was chosen as the hardener used performs best at such a pH [3]. The hardener used was 5% hexamethylenetetramine (hexamine) on tannin solids. This was added to the tannin extract solution as a 30% aqueous solution. 

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