Urotropine alkylation

Reaction of alkyl halides 1 with hexamethylenetetramine 2 (trivial name urotropine) followed by a hydrolysis step, leads to formation of primary amines 3 free of higher substituted amines. This method is called the Delepine reaction, a comparable method is the Gabriel synthesis. 

In the former Soviet Union much use is made of industrial by-products to prepare acid inhibitors. The PB class is obtained by treating technical butyraldehyde with ammonia and polymerising the resulting aldehyde-ammonia. PB-5, for example, with O-Ol-O-15% of an arsenic salt is used in 20-25% HCl. A mixture of urotropine (hexamethyleneimine, hexamine) with potassium iodide, a regulator and a foaming agent is the ChM inhibitor. BA-6 is prepared from the condensation product of hexamine with aniline. A more recent development is the Katapin series which consists of /7-alkyl benzyl pyridine chlorides Katapin A, for example, is the /7-dodecyl compound. 

A two-component plugging material [1763] consists of an aqueous suspension of bentonite clay powder (20% to 25%), ground chalk (7% to 8%), sulfanol (0.10% to 0.15%), and carboxymethylcellulose (1.0% to 1.5%) as the first component. This solution is pumped into the formation. A gel is formed if diluted hydrochloric acid is pumped down and mixes with the first component. The hydrochloric acid is inhibited with a mixture of alkyl-polybenzyl pyridinium chloride and urotropin. 

A further synthesis of primary aliphatic amines was developed by Dele-pine 464 he alkylated urotropine to the monoquaternary salt and cleaved that by alcoholic hydrochloric acid. Chlorides and bromides often react very slowly with urotropine, but they can be converted in situ into the iodides by adding an equivalent amount of sodium iodide. 

Urotropine (1 mole) is dissolved in 8-10 times its weight of hot 95% ethanol and treated slowly with sodium iodide (1 mole) and then with the alkyl chloride or bromide (1 mole). When precipitation is complete, the mixture is saturated with gaseous hydrogen chloride, whereupon the precipitate redissolves and ammonium chloride is precipitated. This is removed, the alcohol is distilled off from the filtrate, and the residue therefrom is treated with an excess of alkali the liberated amine is distilled. 

Pure primary amines may also be obtained by alkylating urotropine with dialkyl sulfates and cleaving the resulting quaternary salt.839... 

Primary amines have occasionally been prepared, e.g., allylamine,839 by alkylation of urotropine and hydrolysis of the resulting quaternary uro-tropinium salt. 

Formaldehyde is unsuitable for alkylation of ammonia as it yields urotropine. Lower aliphatic aldehydes are added only gradually to the reaction mixture to avoid aldol condensations. Higher aliphatic aldehydes and aromatic aldehydes react smoothly and special precautions are generally unnecessary. 

This reaction was initially reported by Delepine in 1895. It is the preparation of primary aliphatic amines by acidic hydrolysis of quaternary amines formed from alkyl halides and urotropine (i.e., hexamethylene tetramine). Therefore, this reaction is generally known as... 

Rozenfeld investigated hetero-alkylated amines and urotropine hydroiodide, and found them to be more effective than the unsubstituted amines. Chlorinated amines were also investigated by Tamura et al. Recently, Tagmazyan et al. discovered that alkyl(2-hydroxyethyl)dimethylammonium bromides are effective corrosion inhibitors for steel in HCI. Aldoximes and ketoximes can also be very effective, according to Costain and Terry. ... 

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