Ammonium dimeric

Manufacture. For the commercial production of DPXN (di-/)-xylylene) (3), two principal synthetic routes have been used the direct pyrolysis of -xylene (4, X = Y = H) and the 1,6-Hofmaim elimination of ammonium (HNR3 ) from a quaternary ammonium hydroxide (4, X = H, Y = NR3 ). Most of the routes to DPX share a common strategy PX is generated at a controlled rate in a dilute medium, so that its conversion to dimer is favored over the conversion to polymer. The polymer by-product is of no value because it can neither be recycled nor processed into a commercially useful form. Its formation is minimised by careful attention to process engineering. The chemistry of the direct pyrolysis route is shown in equation 1 ... 

Irradiation of ethyleneimine (341,342) with light of short wavelength ia the gas phase has been carried out direcdy and with sensitization (343—349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, / -butane), and the dimer of the ethyleneimino radical. The nature and the amount of the reaction products is highly dependent on the conditions used. For example, the photoproducts identified ia a fast flow photoreactor iacluded hydrocyanic acid and acetonitrile (345), ia addition to those found ia a steady state system. The reaction of hydrogen radicals with ethyleneimine results ia the formation of hydrocyanic acid ia addition to methane (350). Important processes ia the photolysis of ethyleneimine are nitrene extmsion and homolysis of the N—H bond, as suggested and simulated by ab initio SCF calculations (351). The occurrence of ethyleneimine as an iatermediate ia the photolytic formation of hydrocyanic acid from acetylene and ammonia ia the atmosphere of the planet Jupiter has been postulated (352), but is disputed (353). 

Ttinitroparaffins can be prepared from 1,1-dinitroparaffins by electrolytic nitration, ie, electrolysis in aqueous caustic sodium nitrate solution (57). Secondary nitroparaffins dimerize on electrolytic oxidation (58) for example, 2-nitropropane yields 2,3-dimethyl-2,3-dinitrobutane, as well as some 2,2-dinitropropane. Addition of sodium nitrate to the anolyte favors formation of the former. The oxidation of salts of i7k-2-nitropropane with either cationic or anionic oxidants generally gives both 2,2-dinitropropane and acetone (59) with ammonium peroxysulfate, for example, these products are formed in 53 and 14% yields, respectively. Ozone oxidation of nitroso groups gives nitro compounds 2-nitroso-2-nitropropane [5275-46-7] (propylpseudonitrole), for example, yields 2,2-dinitropropane (60). 

Uninhibited chloroprene suitable for polymerisation must be stored at low temperature (<10° C) under nitrogen if quaUty is to be maintained. Otherwise, dimers or oxidation products are formed and polymerisation activity is unpredictable. Insoluble, autocatalytic "popcorn" polymer can also be formed at ambient or higher temperature without adequate inhibition. For longer term storage, inhibition is required. Phenothiasine [92-84-2] / fZ-butylcatechol [2743-78-17, picric acid [88-89-17, and the ammonium salt of /V-nitroso-/V-pheny1hydroxy1 amine [135-20-6] have been recommended. 

The use of guanidine for cyclization gives amino substituted derivatives (e.g. 212) (52CB1012), and in this case o-aminonitriles may be used to furnish diamines (e.g. 8UOC1394). An unusual reaction involving nitriles occurred during the preparation of nicotinonitrile from the amide and ammonium sulfamate, when a 60% yield of the dimeric by-product (213) was formed via the nitrile (69BSB289). Similar products have been obtained from... 

Pyrroline-N-oxides (12) are sometimes isolated when using zinc-ammonium chloride (19,20), iron-sulfuric acid (14) or hydrazine-Raney nickel (21) as reducing agents. During the reduction, dimerization has been often observed (22). 

Wahrend man in verdiinnter Schwefelsaure aus Chinolin bzw. Methyl-chinolinen an Blei-Kathoden jeweils Gemische der Dihydro- und der Tetrahydro-Derivate2 erhalt, lauft in starker saurem Medium (Schwefelsaure bzw. Perchlorsaure) die Reduktion des Chino-lins bis zum Tetrahydro-chinolin (67% d.Th.)6. Je nach angelegtem Kathodenpotential entstehen aus 3-Cyan-chinolin dimere Produkte (—1,3 V vs. SCE) oder3-Cyan-1,4-dihydro-chinolin (- 1,6 V 60% d.Th., F 120-122° in 95%igem Athanol mit Ammonium-acetat, geteilte Zelle, Quecksilbcr-Kathode)7. 

The lower trialkyltin hydroxides and oxides, which are usually readily interconverted, have been characterized by IR and Mossbauer spectroscopy (212). The dimer of di-n-butyltin oxide (Bu2SnO)2 has been reported to be formed as a crystalline solid when dibutyltin dichloride is hydrolyzed with ammonium hydroxide (213). 

There are a number of methods for the oxidation of primary alcohols or ethers to dimeric esters, and secondary alcohols to ketones. We recently also found that quaternary ammonium tribromides, especially BTMA Br3, are useful oxidizing agents for the purpose described above (ref. 31). 

Silyi enol ethers can be dimerized to symmetrical 1,4-diketones by treatment with Ag20 in DMSO or certain other polar aprotic solvents." The reaction has been performed with R , R = hydrogen or alkyl, though best yields are obtained when r = r = H. In certain cases, unsymmetrical 1,4-diketones have been prepared by using a mixture of two silyi enol ethers. Other reagents that have been used to achieve either symmetrical or cross-coupled products are iodosobenzene-Bp3-Et20," ceric ammonium nitrate," and lead tetraacetate." If R =0R (in which case the substrate is a ketene silyi acetal), dimerization with TiCU leads to a dialkyl succinate (34, r =0R)." ... 

Dimerization of methylketene is catalyzed by an amine, trimethylsilylquinine, to give the P-lactone enantioselectively (Scheme 27) [129]. The catalyst amine attacks the ketene to form an ammonium enolate, an electron donating alkene. The donor is strong enough to react with a ketene across the C=0 bond. That is why the P-lactone is obtained instead of the 1,3-cyclobutandione, the uncatalyzed dimerization product of the monosubstituted ketene. 

Slow, except in presence of alkalis products formed are complex polymeric quaternary ammonium salts dimerizes fairly rapidly in water. 

Rossotti and co-workers45 introduced the term "oligomers for dimers and even multimers or ra-mers in non-aqueous solutions real examples of such self-aggregates (non-hydrogen bonded) have been reported46 for quaternary ammonium thiocyanates, iodides and perchlorates with ra-mers with n even up to 20. 

Cyanuric chloride reacts vigorously and exothermically with DMF after a deceptively long induction period. The 1 1 adduct initially formed decomposes above 60° C with evolution of carbon dioxide and formation of a dimeric unsaturated quaternary ammonium salt. Dimethylformamide is appreciably basic and is not a suitable solvent for acyl halides. 

Partial substitution of halides on bismuth predictably gives alkoxy-bismuth halides, and salts of bismuth anions are obtained by reaction of the alkoxide with an ammonium or phosphonium halide (28). Two isostructural derivatives [Bi2Cl4(thf)2(ju,-OAr)2] (Ar = C6H3Me2-2,6 and C6H2Me3-2,4,6) are composed of dimeric units residing on a C2 axis 8. The bismuth is in a five-coordinate distorted square pyramidal geometry in each case. The apical sites are occupied by terminal... 

Ammonium cerium(IV) nitrate on reaction with acetone or acetophenone generates acetyl- or benzoylformonitrile oxides, respectively (99). These nitrile oxides dimerize to furoxans and give, in the presence of alkenes and alkynes, 3-acetyl- or 3-benzoyl-4,5-dihydroisoxazoles and 3-acetyl- or 3-benzoylisoxazoles, respectively the yield of the isoxazole derivatives was improved on using ammonium cerium(III) nitrate tetrahydrate-formic acid (99). 

Welland A process for making nitroguanidine, an explosive. Cyanamide dimer is reacted with ammonium nitrate to form guanidine nitrate, which forms nitroquanidine when dehydrated by heating with 96 percent sulfuric acid. See also Marquerol and Loriette. 

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