Organic acids chemistry

Miyako, E., Maruyama, T., Kamiya, N., Goto, M. (2005). Supported hquid membrane encapsulating a surfactant-lipase complex for the selective separation of organic acids. Chemistry - A European Journal 11 1163-1170. 

The most common oxidation state of niobium is +5, although many anhydrous compounds have been made with lower oxidation states, notably +4 and +3, and Nb can be reduced in aqueous solution to Nb by zinc. The aqueous chemistry primarily involves halo- and organic acid anionic complexes. Virtually no cationic chemistry exists because of the irreversible hydrolysis of the cation in dilute solutions. Metal—metal bonding is common. Extensive polymeric anions form. Niobium resembles tantalum and titanium in its chemistry, and separation from these elements is difficult. In the soHd state, niobium has the same atomic radius as tantalum and essentially the same ionic radius as well, ie, Nb Ta = 68 pm. This is the same size as Ti ... 

Three different types of chemical mechanisms have evolved as attempts to simplify organic atmospheric chemistry surrogate (58,59), lumped (60—63), and carbon bond (64—66). These mechanisms were developed primarily to study the formation of and NO2 in photochemical smog, but can be extended to compute the concentrations of other pollutants, such as those leading to acid deposition (40,42). 

Protein (Section 26.4) A large peptide containing 50 or more amino acid residues. Proteins serve both as structural materials and as enzymes that control an organism s chemistry. 

Compounds of special interest whose preparation is described include 1,2,3-benzothiadiazole 1,1-dioxide (a benzyne precursor under exceptionally mild conditions), bis(l,3-diphenylimida-zolidinylidene-2) (whose chemistry is quite remarkable), 6- di-melhylamino)julvene (a useful intermediate for fused-ring non-benzenoid aromatic compounds), dipkenylcyclopropenone (the synthesis of which is a milestone in theoretical organic chemistry), ketene di(2-melhoxyethyl) acetal (the easiest ketene acetal to prepare), 2-methylcyclopenlane-l,3-dione (a useful intermediate in steroid synthesis), and 2-phenyl-5-oxazolone (an important intermediate in amino acid chemistry). 

Rawashdeh-Omary, M.A., Omary, M.A., Fackler, J.P. Jr, Galassi, R., Pietroni, B.R. and Burini, A. (2001) Chemistry and optoelectronic properties of stacked supramolecular entities of trinuclear Gold(I) complexes sandwiching small organic acids. Journal of the American Chemical Society, 123, 9689. 

Instead, this review seeks to cover less well-known and newly emerging aspects of metal-nucleobase chemistry. In addition to biomedical relevancies, nucleic acid chemistry offers a paradigm for organizing molecules via base pairing. Combining the hydrogen bonding... 

G. Kortum, W. Vogel, and K. Andrussow, Dissociation Constants of Organic Acids in Aqueous Solution, International Union of Pure and Applied Chemistry, Butterworths, London, 1961. 

Earlier studies showed that reactions of sugars with ammonia lead to small molecules such as amines or organic acids. A. L. Weber has reported important autocatalytic processes occurring when trioses are allowed to react with ammonia under anaerobic conditions, such reactions provide products which are autocatalyt-ically active. Their autocatalytic activity was determined directly by investigating their effect on an identical triose-ammonia reaction. Both an increase in the triose degradation rate and an increased rate of synthesis of pyruvate, the dehydration product of the triose, were observed. Such processes may have been of importance for prebiotic chemistry occurring on the primeval Earth (Weber, 2007). 

Biotin is an optically active organic acid. The vitamin has the structure shown in (II). Only the dextrorotary form shows activity. Its chemistry and physiology have been extensively reviewed (Tl). 

The anhydrides of the organic acids can also be regarded as di-acyhxides (acyl = acid radicle, e.g. CH3.CO = acetyl) and can be thus assimilated to the ethers, or dialkyl oxides. The ethers are amongst the most indifferent of all the conpounds of organic chemistry. Whence, then, comes the great reactivity of the similarly constituted anhydrides The weak point in the anhydride molecule is to be found, not at the... 

Dumas s argument stressed the malleability of the chemical "type" (in this case, the organic acid) that maintains its fundamental properties even when new and very different elements enter into its constitution. In chapter 4, more details will be given about the images and language employed in this new explanatory strategy in chemistry. Here we stress that Dumas now began to emphasize differences in properties and laws between physics and chemistry, rather than their similarity or complementarity, and he fairly quickly won converts to his view. 

Lowry praised the 1916 memoir of the American chemist Lewis as a "turning point in the history of chemistry" with its "plausible theory" of the electronic origin of the different types of chemical affinity and a clear differentiation between two kinds of valence, ionic and covalent. It is customary in mineral chemistry, he said, to consider reactions that occur between ions to be instantaneous, without attaching any importance to ionization in organic chemistry, except for the formation of salts from organic acids. 

Extensive collections of pK values are available in the literature, e.g., [98-101]. It is also possible to predict pK values for a broad range of organic acids and bases using linear free energy relationships based on a systematic treatment of electronic (inductive, electrostatic, etc.) effects of substituents which modify the charge on the acidic and basic center. Quantitative treatment of these effects involves the use of the Hammett Equation which has been a real landmark in mechanistic organic chemistry. A Hammett parameter (a), defined as follows ... 

Lord, D.L., Hayes, K.F., Demond, A.H., and Salehzadeh, A. Inflnence of organic acid solntion chemistry on snbsnrface transport properties. 1. Surface and interfacial tension. Environ. Sci Technol, 31(7) 2045-2051, 1997. 

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