Carbon dioxide amine conversion

Conversely, the use of elevated temperatures will be most advantageous when the current is determined by the rate of a preceding chemical reaction or when the electron transfer occurs via an indirect route involving a rate-determining chemical process. An example of the latter is the oxidation of amines at a nickel anode where the limiting current shows marked temperature dependence (Fleischmann et al., 1972a). The complete anodic oxidation of organic compounds to carbon dioxide is favoured by an increase in temperature and much fuel cell research has been carried out at temperatures up to 700°C. 

Another reaction that can be used for conversion of carboxylic acids to the corresponding amines with loss of carbon dioxide is the Hofmann rearrangement. The classic reagent is hypobromite ion, which reacts to form an A-bromoamide intermediate. Like the Curtius reaction, this rearrangement is believed to be a concerted process and proceeds through an isocyanate intermediate. 

The nucleophilic attack by alkoxides, amines, and water is of great interest to homogeneous catalysis. A dominant reaction in syn-gas systems is the conversion of carbonyls with water to metal hydrides and carbon dioxide ("Shift Reaction"), see Figure 2.27. 

Originally, the Lossen rearrangement specifically referred to the conversion of a hydroxamic acid to an amine with the loss of carbon dioxide ... 

Suzuki et al.[57 explored the Pd-catalyzed ring-opening of the monomer 5,5-dimethyl-6-ethenylperhydro-l,3-oxazin-2-one to give a hyperbranched polyamine. The polymerization was conducted at ambient temperature in THF and catalyzed with Pd2(dba)3-2 dppe, affording after the evolution of carbon dioxide, the desired hyperbranched polyamine. NMR spectroscopy confirmed the high yield conversion of the monomer. The degree of branching was ascertained (from NMR data) as the ratio of tertiary amine units to the total of secondary and tertiary moieties. 

Epoxidation of styrene with tBuOOH catalysed by Au/Si02 in the presence of zinc and tetrabutylammonium bromides and carbon dioxide led directly to styrene carbonate at 1 MPa pressure and 353 K, conversion was 90% and selectivity 35%.47 Gold on functionalised polymer also catalyses the reaction of carbon dioxide with various epoxides to give lactones, and with amines to give carbonates.48... 

For low catalytic conversions a white precipitate was obtained, melting at room temperature. It could be identified as dimethylammonium N,/V-dimethylcarbamate [14], formed reversibly in a temperature and pressure dependent side reaction of dimethylamine and carbon dioxide. Under GC conditions this carbamate decomposes to amine and carbon dioxide. 

An interesting expansion of the reaction cited above is the conversion of epoxide, carbon dioxide and a third component, especially amines. 4-llydroxy-... 

Handling, Storage, and Precautions conversion of the freshly distilled amine to its hydrochloride salt is a convenient way to store and handle the compound. The free amine reacts with atmospheric carbon dioxide to produce the respective carbonate. The free amine should be stored tightly sealed under argon or nitrogen immediately after distillation to avoid CO2 adsorption. 

The conversion of salt to hydroxide by use of a strongly basic anion-exchange resin, followed by titration with standard acid, is usually not so appropriate as the conversion of salt to acid because the resin-regeneration procedure is less convenient. Hydrolysis of the resin to give amines may occur, as well as absorption of carbon dioxide. The anion-exchange method can be used, for example, in the determination of alkali metal phosphates or sulfites. 

Erga, O., Juliussen, O., and Lidal, H. Carbon dioxide recovery by means of aqueous amines. Energy Conversion and Management, 1995, 36, 387. 

Besides the above CD processes, some of the recent novel applications of CD are outlined below. The production of amines from the hydrogenation of aniline and the selective production of diethanolamine from the reaction of monoethanolamine and ethylene oxide have been reviewed. A patent on the production of phenol from cumene hydroperoxide disclosed that solid acid catalysts such as zeolites, ion-exchange resins achieved 100% conversion with about 60 /o selectivity to phenol at 50-90°C and 0-10 psig. This process utilizes the heat of the decomposition of cumene hydroperoxide to effect the separation of the lower boiling components and hence reduces the energy cost and carbon dioxide emissions. 

Carbon dioxide reacts with primary amines to form a carbamic acid (Pine et al., 1980). Carbamic acids are unstable the very act of dissolving the carbamic acid in a solvent for titration or for conducting NMR studies, for example, converts the acid back to amine plus CO2 (Elsbernd, 1988). Heating the acid to about 50-100°C can force the reaction in the reverse direction, and if the CO2 that is generated is removed, the amine can be recovered. Although the conversion of carbamic acid back to amine plus CO2 occurs quite readily (Pine et al., 1980) the reversion is not instantaneous (Gallagher and Krukonis, 1987). What can also occur during the reverse reaction is reaction between any unconverted carbamic acid and the amine that has just reformed to form a urea. 

The conversion of naphthalene to 2-naphthoic acids by irradiation with carbon dioxide and electron donors (e.g. amines or dimethoxybenzene) has been further investigated and the quantum yields of the reaction measured for different solvents and donors. Electron transfer also occurs in the photochemical phosphonation of naphthalene and phenanthrene achieved by irradiation with trialkyl-phosphites and electron acceptors such as 1,3-dicyanobenzene. The photonitration of phenol in aqueous solutions of nitrate ion has been reported and phenols have been prepared by irradiation of substituted benzenes with the aromatic N-oxide (132). ... 

Researchers van der Broeke and coworkers[" created perfluoro-functionalized poly(propyleneimine) dendrimers (23 Fig. 4) and demonstrated their potential as phase-transfer catalysts in supercritical carbon-dioxide-water mixtures and as anionic species extractants. The dendrimers were accessed via reaction of perfluorinated, linear alkyl acid chlorides with the terminal amines. Extraction of perinanganate or dichromate from aqueous to CO2 solution was described as rather low, whereas their use as phase-transfer catalysts in a halogen exchange reaction [benzyl chloride to benzyi bromide (24)] resulted in high rates of conversion. 

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