Amines chemical oxidation

Polymerization of ethylene oxide can occur duriag storage, especially at elevated temperatures. Contamination with water, alkahes, acids, amines, metal oxides, or Lewis acids (such as ferric chloride and aluminum chloride) can lead to mnaway polymerization reactions with a potential for failure of the storage vessel. Therefore, prolonged storage at high temperatures or contact with these chemicals must be avoided (9). 

Chemical Name N,N,3-tris(2-chloroethyl)-tetrahvdro-2H-1,3,2-oxaphosphorin-2-amine-2-oxide... 

For some organic compounds, such as phenols, aromatic amines, electron-rich olefins and dienes, alkyl sulfides, and eneamines, chemical oxidation is an important degradation process under environmental conditions. Most of these reactions depend on reactions with free-radicals already in solution and are usually modeled by pseudo-first-order kinetics ... 

The nickel hydroxide electrode resembles in its applications and selectivity the chemical oxidant nickel peroxide. The nickel hydroxide electrode is, however, cheaper, easy to use and in scale-up, and produces no second streams/ waste- and by-products [196], Nickelhydroxide electrode has been applied to the oxidation of primary alcohols to acids or aldehydes, of secondary alcohols to ketones, as well as in the selective oxidation of steroid alcohols, cleavage of vicinal diols, in the oxidation of y-ketocarboxylic acids, of primary amines to nitriles, of 2,6-di-tert-butylphenol to 2,2, 6,6 -tetra-rert-butyldiphenoquinone, of 2-(benzylideneamino)-phenols to 2-phenyloxazols, of 1,1-dialkylhydrazines to tetraalkyltetrazenes. For details the reader is referred to Ref. [195]. 

Few studies have systematically examined how chemical characteristics of organic reductants influence rates of reductive dissolution. Oxidation of aliphatic alcohols and amines by iron, cobalt, and nickel oxide-coated electrodes was examined by Fleischman et al. (38). Experiments revealed that reductant molecules adsorb to the oxide surface, and that electron transfer within the surface complex is the rate-limiting step. It was also found that (i) amines are oxidized more quickly than corresponding alcohols, (ii) primary alcohols and amines are oxidized more quickly than secondary and tertiary analogs, and (iii) increased chain length and branching inhibit the reaction (38). The three different transition metal oxide surfaces exhibited different behavior as well. Rates of amine oxidation by the oxides considered decreased in the order Ni > Co >... 

For the dehydrogenation of CH—XH structures, for example, of alcohols to ketones, of aldehydes to carboxylic acids, or of amines to nitriles, there is a wealth of anodic reactions available, such as the nickel hydroxide electrode [126], indirect electrolysis [127, 128] (Chapter 15) with I , NO, thioanisole [129, 130], or RUO2/CP [131]. Likewise, selective chemical oxidations (Cr(VI), Mn02, MnOJ, DMSO/AC2O, Ag20/Celite , and 02/Pt) [94] are available for that purpose. The advantages of the electrochemical conversion are a lower price, an easier scale-up, and reduced problems of pollution. 

Finally, it is important to note that many of the anodic reactions discussed above cannot be duplicated with traditional chemical oxidants. For this reason, the anodic oxidation of nitrogen-containing compounds represents a powerful class of reactions that has the potential to open up entirely new synthetic pathways to complex molecules. From the work already accomplished, it is clear that employing such an approach is both feasible and beneficial, and that the ability to selectively oxidize amines and amides is a valuable tool for any synthetic chemist to have at their disposal. 

For a review of chemical oxidations of amines and some amides see S.-I. Mura-hashi, Angew. Chem., Int. Ed. Engl. 1995, 34, 2443. 

In comparison with hydrocarbons, aromatic amines easily transform into cation radicals. Structures of these cation radicals are well documented on the basis of their ESR spectra and MO calculations (see, e.g., Grampp et al. 2005). The stable cation radical of A/,A,A, A -tetramethyl-p-phenylenediamine (the so-called Wuerster s blue) was one of the first ion radicals that was studied by ESR spectroscopy (Weissmann et al. 1953). The use of this cation radical as a spin-containing unit for high-spin molecules has been reported (Ito et al. 1999). Chemical oxidation of N,N -bis [4-(dimethylamino)-phenyl-A/,A -dimethyl-l,3-phenylenediamine with thianthrenium perchlorate in -butyronitrile in the presence of trifluoroacetic acid at 78°C led to the formation of the dication diradical depicted in Scheme 3.58. 

Among the CH oxidations, a most impressive case, for example, concerns the quantitative TFD oxidation of cyclohexane to cyclohexanone at —22° C in only 18 min (equation 26) There exists no other chemical oxidant, even metal-catalyzed systems, that may compete with this astounding oxidative reactivity of TFD. Whether the oxidation of an amine to a hydroxylamine involves the direct insertion of an oxygen atom into the N—H bond is mechanistically still uncertain, since alternatively (more probably the case on... 

Both electrochemical and chemical oxidative routes are most often utilized for the synthesis of PANI. In an interesting departure from the oxidative route, poly(phenylene amine imine) was prepared via a conventional condensation polymerization, as illustrated in Scheme 63 [302, 303]. Comparison of this structurally well-characterized polymer with oxidatively prepared PANI allowed confirmation of the PANI structure. However, the structure of PANI produced by electrochemical means is less understood. 

Whereas non-azo dyes are almost resistant to bacterial decolorization, azo dyes can be decolorized by bacteria under anaerobic conditions to form aromatic amines which show both toxic and carcinogenic potential [18]. Further aerobic mineralization can therefore only be initiated by additional chemical oxidation, for example, by partial ozonation, as reported by Krull et al. [19]. 

Amine A-oxides (34a-e) were resolved very efficiently by complexation with 14b. In this case, both enantiomers of 34 were obtained in an optically pure form.16 For example, when a solution of 14b (1.0 g, 3.6 mmol) and rac-34b (1.2 g, 7.2 mmol) in THF (20 ml)-hexane (10 ml) was kept at room temperature for 5 h, a 1 1 complex of 14b and (+)-34b was obtained as colorless prisms. The crystals were recrystallized from THF-hexane to give pure crystals (0.85 g, 53%, mp 167-169 °C). The complex was separated to its components by column chromatography on silica gel. Firstly, 14a (0.5 g) was recovered from a fraction eluted by ethyl acetate-benzene (1 4). Secondly, (+)-34b of 100% ee (0.29 g, 48%) was obtained from a fraction eluted by MeOH. Evaporation of the filtrate left after separation of the complex between 14b and (+)-34b, gave crude (-)-34b. Treatment of the crude (-)-34b with 14c by a similar manner to that described above, followed by column chromatography, yielded finally (-)-34b of 100% ee in 40% yield.16 Compounds 34a and 34c-e were also resolved effectively by complexation with 14b, and the corresponding (+)-enantiomers were obtained in the optical and chemical yields indicated, (+)-34a (100% ee, 21%), (+)-34c (73% ee, 39%), (+)-34d (100% ee, 30%), and (+)-34e (100% ee, 68%).16... 

N-McLhylmorpholine-N-oxidc monohydrate, a tertiary, aliphatic amine N-oxide, is able to dissolve cellulose directly, i.e. without chemical derivatization, which is used on an industrial scale as the basis of the Lyocell process [ 1, 2], This technology only requires a comparatively low number of process steps compared for instance to traditional viscose production. Cellulose material - mainly fibers - are directly obtained from the cellulose solution in NMMO no chemical derivatization, such as alkalization and xanthation for rayon fibers, is required [3]. The main advantage of the Lyocell process lies in its environmental compatibility very few process chemicals are applied, and in the idealized case NMMO and water are completely recycled, which is also an important economic factor. Even in industrial production systems NMMO recovery is greater than 99%. Thus, compared with cotton and viscose the Lyocell process pertains a significantly lower specific environmental challenge [4]. Today, Lyocell fibers are produced on an industrial scale, and other cellulosic products, such as films, beads, membranes and filaments, are also currently being developed or are already produced commercially. 

Ideally, dissolution of cellulose in the amine N-oxide is supposed to be an entirely physical process without any chemical changes of pulp or solvent. However, in real-world processes there are several chemical processes observed, which cause formation of appreciable amounts of byproducts. A strong discoloration of the solution due to chromophore formation has been observed, which is accompanied by degradation of both the solute cellulose and the solvent NMMO at the elevated process temperatures, which in turn can provoke very severe effects, such as degradation of cellulose, temporary or permanent discoloration of the resulting fibers, decreased product... 

Also anodic substitution reactions can be used for studies of the possible consequences of adsorption. Thus, anodic methoxylation of N,N-dimethylbenzyl-amine 62,63Ogives predominant substitution in the methyl group instead of the methylene group which is the site of attack in chemical oxidations. This was rationalized on the basis of adsorbed intermediates, the methyl group of the adsorbed species being more accessible for chemical attack ... 

Fleischmann et al. [549] studied the electro-oxidation of a series of amines and alcohols at Cu, Co, and Ag anodes in conjunction with the previously described work for Ni anodes in base. In cyclic voltammetry experiments, conducted at low to moderate sweep rates, organic oxidation waves were observed superimposed on the peaks associated with the surface transitions, Ni(II) - Ni(III), Co(II) -> Co(III), Ag(I) - Ag(II), and Cu(II) - Cu(III). These observations are in accord with an electrogenerated higher oxide species chemically oxidizing the organic compound in a manner similar to eqns. (112) (114). For alcohol oxidation, the rate constants decreased in the order kCn > km > kAg > kCo. Fleischmann et al. [549] observed that the rate of anodic oxidations increases across the first row of the transition metals series. These authors observed that the products of their electrolysis experiments were essentially identical to those obtained in heterogeneous reactions with the corresponding bulk oxides. 

An oxidatively induced ring closure occurs during the oxidation of various catecholamines (33)72 at a carbon paste electrode. Whereas the oxidation in 1 M H2SO4 yielded the 1,2-benzoquinone (34), sufficient free amine of 34 was present at pH 3 to allow an internal Michael addition of the adrenaline quinone. As would be expected, the resulting catechol (35) is more easily oxidizable than adrenaline and is converted into the quinone adrenochrome (36) by chemical oxidation by adrenaline quinone. 

DOT CLASSIFICATION 8 Label Corrosive SAFETY PROFILE Poison by inhalation. Moderately toxic by ingestion. A severe eye, skin, and mucous membrane irritant. Corrosive to body tissues. Flammable by chemical reaction. Explosive reaction with chlorine dioxide + chlorine, sodium, urea + heat. Reacts to form explosive products with carbamates, 3 -methyl-2-nitroben2anilide (product explodes on contact with air). Ignites on contact with fluorine. Reacts violently with moisture, CIO3, hydroxyl-amine, magnesium oxide, nitrobenzene, phosphorus(III) oxide, K. To fight fire, use CO2, dry chemical. Incompatible with aluminum, chlorine dioxide, chlorine. 

---