Decomposition, thermal ammonium hydroxides

Chemical Properties. Reactions of quaternaries can be categorized iato three types (169) Hoffman eliminations, displacements, and rearrangements. Thermal decomposition of a quaternary ammonium hydroxide to an alkene, tertiary amine, and water is known as the Hoffman elimination (eq. la) (170). This reaction has not been used extensively to prepare olefins. Some cycHc olefins, however, are best prepared this way (171). Exhaustive methylation, followed by elimination, is known as the Hoffman degradation and is important ia the stmctural determination of unknown amines, especially for alkaloids (qv) (172). 

For solvent extraction of pentavalent vanadium as a decavanadate anion, the leach solution is acidified to ca pH 3 by addition of sulfuric acid. Vanadium is extracted in about four countercurrent mixer—settler stages by a 3—5 wt % solution of a tertiary alkyl amine in kerosene. The organic solvent is stripped by a soda-ash or ammonium hydroxide solution, and addition of ammoniacal salts to the rich vanadium strip Hquor yields ammonium metavanadate. A small part of the metavanadate is marketed in that form and some is decomposed at a carefully controlled low temperature to make air-dried or fine granular pentoxide, but most is converted to fused pentoxide by thermal decomposition at ca 450°C, melting at 900°C, then chilling and flaking. 

The kinetic preference for cis- over imns-olefin elimination from acyclic compounds is rare. Cope and co-workers 91) reported a slight preference for cis- over irans-2-butene and 2-pentene in the thermal decomposition of the quaternary ammonium hydroxides, and Andr u and co-workers 92,93) found a preponderance of cis- over trons-2-butene in the elimination of hydrogen chloride from 2-chlorobutane over solid catalysts. Neureiter and Bordwell 94) found the formation of cis-2-butene rather than alkene from a-chlorosulfone on treatment with alkali ... 

Hofmann exhaustive methyiation reaction org chem The thermal decomposition of quaternary ammonium hydroxide compounds to yield an olefin and water an exception is tetramethyiammonium hydroxide, which decomposes to give an alcohol. haf-mon ig z6s-tiv. meth-o la-shon re,ak-sh3n )... 

Cyclohexylurea has been prepared by the reaction of cyclo-hexyl isocyanate with gaseous ammonia or ammonium hydroxide, by thermal decomposition of cyclohexyl allophanamide, by treating cyclohexylamine hydrochloride with an aqueous solution of potassium cyanate," by heating nitrosomethylurea with cyclohexylamine, and by heating an ethanolic solution of cyclohexylamine and 3,5-dimethyl-l-carbamylpyrazole. 2,6-DimethyIphenyIthiourea has been synthesized by allowing 2,6-dimethylaniline hydrochloride to react with ammonium thiocyanate. ... 

Chemical Properties. Reactions of quaternaries can be categorized into three types Hoffman eliminations, displacements, and rearrangements. Thermal decomposition of a quaternary ammonium hydroxide to an alkene, tertiary amine, and water is known as the Hoffman elimination (eq. la). 

The copper chromium oxide (Cu/Cr = 1) has been prepared by coprecipitation of copper and chromium nitrates with ammonium hydroxide, followed by thermal decomposition in flowing nitrogen up to the final temperature (370"C), according to a previously described method (8). The apparatus and the catalytic procedure have also been described elsewhere in case of gas phase reactions (5) and liquid phase reactions (7). 

An alternative bimolecular elimination process involves the thermal decomposition in an atmosphere of nitrogen of a quaternary ammonium hydroxide (Hofmann exhaustive methylation procedure). 

Thermal decomposition of tetramethylammonium or trimethylanilinium salts was described for phenytoin methylation prior to its GC analysis in plasma [556] and diethyl-stilbestrol in biological fluids [557], Usually a liquid or homogenized sample is extracted into toluene, the respective tetrasubstituted ammonium hydroxide is added and the liquid phase is injected at 260—290°C. 

In this reaction two different procedures have been used. The first is the classical Hofmann degradation, which prepares the alkene by thermal decomposition of the quaternary ammonium hydroxide. Hofmann orientation is generally observed in acyclic and Zaitsev orientation in cyclohexyl substrates. The second is the treatment of quaternary ammonium halides with very strong bases, e.g. PhLi, KNH2 in liquid NH3. The formation of the alkene proceeds via an 1 mechanism, which means a syn elimination in contrast to the anti elimination which is observed in most of the classical Hofmann degradations. In some cases this type of elimination can also be accomplished by heating the salt with KOH in polyethylene glycol monomethyl ether. 

Another interesting comparison was reported by von Braun 150> in which various quaternary ammonium hydroxides were decomposed under Hofmann conditions and in the presence of glycerol. These results also show that the displacement reaction is favored in the presence of a hydroxylic solvent. It was also noted by Hanhart and Ingold 57> that displacement reactions are favored over elimination reactions in thermal decompositions of quaternary ammonium salts as the nucleophilicity of the anion is increased from chloride to acetate. 

NITROCARBOL (75-52-5) Forms explosive mixture with air (flash point 95°F/35°C). Thermally unstable. Shock, friction, pressure, or elevated temperature above 599°F/315°C can cause explosive decomposition, especially if confined. Violent reaction with strong oxidizers, alkyl metal halides, diethylaluminum bromide, formic acid, methylzinc iodide. Contact with acids, bases, acetone, aluminum powder, amines, bis(2-aminoethyl)amine, haolforms make this material more sensitive to explosion. Reacts, possibly violently, with ammonium hydroxide, calcium hydroxide, calcium hypochlorite, 1,2-diaminomethane, formaldehyde, hexamethylbenzene, hydrocarbons, hydroxides, lithium perchlorite, m-methyl aniline, nickel peroxide, nitric acid, metal oxides, potassium hydride, potassium hydroxide, sodium hydride. Mixtures with ammonia, aniline, diethylenetriamine, metal oxides, methyl amine, morpholine, phosphoric acid, silver nitrate form shock-sensitive compounds. Forms high-explosive compound with urea perchlorate. Mixtures with hydrocarbons and other combustible materials can cause fire and explosions. Attacks some plastics, rubber, and coatings. 

Kerr (d) has shown that during the thermal decomposition of ammonium Y zeolite at 500 °C there is a loss of aluminum if a deep bed geometry is employed. In the particular material that Kerr studied, sodium hydroxide treatment of the deep bed sample led to the increase... 

The selection of this reagent was based partly on the observation [209] that, because various quaternary ammonium carboxylates undergo thermal decomposition to methyl esters, such esters could be formed in situ in good yield by the simple injection of a methanolic solution of the quaternary ammonium carboxylate above 250°C. Thus, the use of the quaternary ammonium hydroxide in the transesterification scheme described above permits the simultaneous conversion of both glycerides and fatty acids to methyl esters. 

Li and coworkers [50] studied the zinc hydroxide carbonate precursor, Zii4C03(0H)6-H20, synthesized from zinc sulfate using ammonium carbonate as a precipitating agent. TG), DSC, transmission electronic microscopy (TEM), infiared spectroscopy (IR) and XRD were used to characterize die precursor and the decomposition product, while the non-isothermal kinetics of the thermal decomposition of zinc hydroxide carbonate were studied in nitrogen. The kinetic parameters were obtained using a model-free method and the reaction model was then derived by means of non-linear regression. The results showed that the decomposition of zinc hydroxide carbonate is a two-step reaction a reversible reaction of two-dimensional diffusion (D2), followed by an irreversible one of... 

Other unsuccessful attempted preparations of cyclobutadiene included the thermal decomposition of cyclobutanebis(trimethyl-ammonium) hydroxides [4]. 

Thermal decomposition of quaternary ammonium hydroxides Tert. amines and ethylene derivatives s. 18, 993 Tert. amines from quaternary ammonium salts s. 16, 728... 

Thermal decomposition of quaternary ammonium hydroxides is different because elimination occurs preferentially to form the least substituted double bond. Thermal decomposition of scc-butyltrimethylammonium hydroxide, for example, gives 1-butene as the major product. 

Thermal decomposition of the quaternary ammonium hydroxide in (a) follows the Hofmarm rule and gives 1-octene as the major product. E2 ehmination from an altyl iodide in (b) by sodium methoxide follows Zaitsev s rule and gives trans-2-octene as the major product. 

The procedure of methylation of amines and thermal decomposition of quaternary ammonium hydroxides was first reported by Hohnann in 1851, but its value as a means of structure determination was not appreciated until 1881, when he published a report of its use to determine the structure of piperidine. Following are the results obtained by Hohnann. 

After chemical oxidation of the monomers with FeCla in chloroform under nitrogen for 20 hours, the products were recovered by quenching in methanol and dedoped with ammonium hydroxide. Unlike the methyl- and methoxy-substituted polymers prepared earlier [38], these copolymers are soluble in chloroform, methylene chloride, carbon tetrachloride and THF. In addition, they are thermally stable with an onset of decomposition around 400°C for the reduced material under nitrogen based on the TGA. But GPC measurements of molecular weight indicate an average DP of 6-10. The conductivity of the neutral polymers is... 

The thermal decomposition of a quaternary ammonium hydroxide to alkene, tertiary amine and water was first observed by Hofmann in 1851 (equation 2) From his work with unsymmetrical amines. 

---