Oxidative coupling nitric acid

Although attempts to make pyrrole diazonium salts couple inter-molecularly have been unsuccessful, 3-diazo-2,4,5-triphenylpyrrole (21) on prolonged heating in dilute sulfuric acid undergoes internal coupling (21- -41).21 That coupling occurred with the phenyl group in the 4-position rather than the 2-position is shown by the formation of the diketone (42) on oxidation with nitric acid. 

Nitric acid oxidation is used where carbohydrates, ethylene glycol, and propylene are the starting materials. The diaLkyl oxalate process is the newest, where diaLkyl oxalate is synthesized from carbon monoxide and alcohol, then hydrolyzed to oxahc acid. This process has been developed by UBE Industries in Japan as a CO coupling technology in the course of exploring C-1 chemistry. 

Benzyl chloride readily forms a Grignard compound by reaction with magnesium in ether with the concomitant formation of substantial coupling product, 1,2-diphenylethane [103-29-7]. Benzyl chloride is oxidized first to benzaldehyde [100-52-7] and then to benzoic acid. Nitric acid oxidizes directly to benzoic acid [65-85-0]. Reaction with ethylene oxide produces the benzyl chlorohydrin ether, CgH CH20CH2CH2Cl (18). Benzylphosphonic acid [10542-07-1] is formed from the reaction of benzyl chloride and triethyl phosphite followed by hydrolysis (19). 

Polypyrrole shows catalytic activity for the oxidation of ascorbic acid,221,222 catechols,221 and the quinone-hydroquinone couple 223 Polyaniline is active for the quinone-hydroquinone and Fe3+/Fe2+ couples,224,225 oxidation of hydrazine226 and formic acid,227 and reduction of nitric acid228 Poly(p-phenylene) is active for the oxidation of reduced nicotinamide adenine dinucleotide (NADH), catechol, ascorbic acid, acetaminophen, and p-aminophenol.229 Poly(3-methylthiophene) catalyzes the electrochemistry of a large number of neurotransmitters.230... 

Gold is too noble to react even with strong oxidizing agents such as nitric acid. Both the gold couples... 

Prior to analysis, solutions from seven-day T/D tests on cuprous oxide (Cu20) and nickel metal powder (Ni) were passed through a column with iminodiacetate functional groups using an ammonium acetate buffer. The alkali and alkali earth metals are not bound to the column thereby separating the cations associated with the saltwater matrix from the transition metals of interest which are subsequently eluted with nitric acid and analysed by ICP-AES (inductively-coupled plasma-atomic emission spectrometry). 

The conjugation in 2,2, 4,4, 6,6 -hexanitroazobenzene (HNAB) (90) is also reflected in its thermal stability (m.p. 220 °C). The synthesis of HNAB from picryl chloride and 2,4-dinitrochlorobenzene is discussed in Sections 4.8.1.2 and 4.8.1.3 respectively. 3,3, 5,5 -Tetraamino-2,2, 4,4, 6,6 -hexanitroazobenzene (149) has been synthesized by an unusual but efficient route which involves the nitration-oxidative coupling of 3,5-dichloroaniline (147) on treatment with nitric acid, followed by reaction of the resulting product, 3,3, 5,5 -tetrachloro-2,2, 4,4, 6,6 -hexanitroazobenzene (148), with ammonia. Both the tetrachloro (148) and tetraamino (149) derivatives exhibit high thermal stability. 

The reduction potential for the nitrate(V)/nitrate(III) couple in acid solution of +0.94 V indicates from the limited data in Table 6.12 that nitrate(V) ion in acidic solution is a reasonably good oxidizing agent. However, nitric acid as an oxidant usually functions in a different manner, with the production of brown fumes with a metal (e.g. copper) or a metal sulfide (e.g. FeS2). The brown fumes consist of N204 (brown gas) and its monomer N02 (colourless gas). Concentrated nitric acid consists of about 70% of the acid in an aqueous solution. In such a solution there is some dissociation of the nitric acid molecules to give the nitronium ion, N02, which represents the primary oxidizing species ... 

In the presence of a clay, it therefore seems possible to change nitric acid into an oxidative coupling agent. 

The synthesis of MDPM by this route is unprecedent and is an example for a new application of nitric acid. In fact, so far MDPM have been produced either by oxidative coupling in the presence of iron(III) salts,7or air on N Oj18, or by Friedd-Crafts alkylations catalyzed by Lewis acids19 or zeolites20. 

Replacement of sulfuric acid in "mixed acid" aromatic nitrations by inorganic solids, with accumulation or elimination of produced water results in a fundamental different behaviour of the "HN03 - solid" couple. If water accumulates, nitric acid becomes a selective oxidative coupling agent, whereas when water is eliminated efficiently, nitric acid alone behaves as a strong nitrating agent, with increased paraselectivity as compared to the sulfo-nitric system. 

Pantsar-Kallio and Manninen [85] optimised a unique coupled cation- and anion-exchange chromatographic system for Cr speciation. The need for Cr(III) species conversion by oxidation was eliminated by the use of dilute nitric acid eluents. Detection limits using the system were 0.3 pig l-1 for Cr(III) and 0.8 pug 1—1 for Cr(VI) in lake water samples. 

Elemental analysis by mass spectrometiy was performed using a Perkin-Elmer Sciex ELAN 6000 Inductively Coupled Plasma—Mass Spectrometer (ICP-MS) and a ThermoFinnigan Element 2 Inductively Coupled Plasma Sector Field Mass Spectrometer. The iron oxide colored fibers (Table III, 16, 17) were weighed into the following aliquots (1) 1 mg rabbit hair (RH), (2) 5 mg RH, (3) 1 mg of milkweed (MW), (4) 5 mg MW and (5) a mixture of 2.5 mg RH and MW each. These samples were combined with concentrated nitric acid. Wanning the mixture to just below boiling temperature for 5 to 7 minutes did not result in total digestion. Hence, the incubation time in the water bath was increased to 30 minutes. Afterward, these samples were analyzed in the spectrometer. 

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