Acidic agent

Fig. 12. Tryptic map of it-PA (mol wt = 66,000) showing peptides formed from hydrolysis of reduced, alkylated rt-PA. Separation by reversed-phase octadecyl (C g) column using aqueous acetonitrile with an added acidic agent to the mobile phase. Arrows show the difference between A, normal, and B, mutant rt-PA where the glutamic acid residue, D, has replaced the normal arginine residue, C, at position 275.

A mixture of dimethyl sulfate with SO is probably dimethyl pyrosulfate [10506-59-9] CH2OSO2OSO2OCH2, and, with chlorobenzene, it yields the 4,4 -dichlorodiphenylsulfone (153). Trivalent rare earths can be separated by a slow release of acid into a solution of rare earth chelated with an ethylenediaminetetraacetic acid agent and iodate anion. As dimethyl sulfate slowly hydrolyzes and pH decreases, each metal is released from the chelate in turn and precipitates as the iodate, resulting in improved separations (154). 

Kost et al. have studied related reactions of 2-acyl-1-phenylpyrazolidines (422) and l-phenyl-2-thiocarbamoylpyrazolidines (423). The former are converted on reaction with phosphorus oxychloride into tetrahydropyrimido[l,2-a]indoles (424) (72CHE57) and the latter into tetrahydropyrimido[2,l-f ]benzothiazoles (425) under the influence of acidic agents (80CHE169). 

Elastomers, plastics, fabrics, wood and metals can be joined with themselves and with each other using nitrile rubber/epoxy resin blends cured with amines and/or acidic agents. Ethylene-propylene vulcanizates can also be joined using blends of carboxylated nitrile rubber, epoxy resin and a reactive metal filler (copper, nickel, cobalt). However, one of the largest areas of use of nitrile rubber modified epoxy systems is in the printed circuit board area [12]. 

Each component of Jessner s solution has specific effects (Fig. 3.1). Salicylic acid (ortho hydroxy benzoic acid) is a beta hydroxy acid agent... 

Salicylic acid (ortho hydroxybenzoic add) is a beta hydroxy acid agent. It is a lipophilic compound which produces desquamation of the stratum corneum via removal of intercellular lipids [3] (see salicylic acid section). Given its keratolytic effects, it has become an increasingly popular superficial peeling agent. Salicylic acid peels induce injury via thinning or removal of the stratum corneum. In addition, salicylic acid potentially enhances the penetration of TCA. 

Concerning anthropogenic sources, methyl arsenic compounds such as methyl arsonic acid and dimethylarsinic acid have been used as herbicides, and were once a significant source of environmental residues. Dimethyl-arsinic acid (Agent Blue) was used as a defoliant during the Vietnam War. 

In the cyclization of 7V-(het)arylaminomethylenemalonates, a wide variety of acidic agents have been used. Under such circumstances, not only iV-mono but also N /V-disubstituted derivatives could readily be cyclized. 

H. Bundgaard, N. M. Nielsen, Esters of /V,/V-Disubstiluted 2-Hydroxyacetamides as a Novel Highly Biolabile Prodrug Type for Carboxylic Acid Agents ,./. Med. Chem. 1987, 30,451-454. 

N. M. Nielsen, H. Bundgaard, Glycolamide Esters as Biolabile Prodrugs of Carboxylic Acid Agents Synthesis, Stabibty, Bioconversion and Physicochemical Properties , J. Pharm. Sci. 1988, 77, 285 - 298. 

Ion-radical reactions also open convenient routes to fused benzoheterocycles as a result of intramolecular cyclization. The fused heterocycles are useful as compounds of potential physiological activity. Many of them are used as medications. Certainly, only those syntheses that do not change the functional groups needed to provide or enforce the curative effect, are of interest. At the same time, it is desirable to exclude acidic agents that lead to the splitting of the final heterocycles, which... 

The elimination proceeds rapidly at room temperature with a catalytic amount of acid or fluoride, however, it has also been observed to occur upon distillation of the isoxazolidine (16,18). Because of the facile elimination, several procedures have been developed in which the reaction is quenched with an acidic agents, and the isoxazoline is isolated directly (108). Isoxazolines are useful in the preparation of p-hydroxy ketones and amino alcohols (138). 

The Extractants. The extractants are classified into different groups, according to their reaction type solvating, salt forming (acidic agents) or ionic exchanging. 

CA 71, 51824v(1969) [Gelled nitric acid agent, such as contg HNOa (42°Be) 14.0,... 

Chloral condensations with aromatic hydrocarbons (and related derivatives) give rise to diaryltrichloroethane compounds, and are brought about in the presence of acid catalysts, proceeding with the formation of carbinol intermediates (Scheme 2.1). Commonly used catalysts include concentrated H2SO4 and its monohydrate, HCl, HF, I O,-, Lewis acids and a series of other acid agents [1, 2]. 

Another herbicide, 2,4,5-trichlorophenoxyacetic acid, is synthesized by starting with the chlorination of benzene to give 1,2,4,5-tetrachloroben-zene, which reacts with caustic to give 2,4,5-trichlorophenol. Conversion to the sodium salt followed by reaction with sodium chloroacetate and acidification gives 2,4,5-trichlorophenoxyacetic acid. Agent Orange is a 1-to-l mixture of the butyl esters of 2,4,5-trichlorophenoxyacetic acid and 2,4,-dichlorophenoxyacetic acid. 

Indole and its derivatives are acidophobic systems [55, 56], susceptible to the formation of products from dimerization and polymerization under the influence of acidic agents. This makes it possible to suppose that processes involving polymerization of phosphorus-containing indoles can occur at elevated temperatures under the influence of the acidic impurities present in amidophosphites. 

Nielson, N.M., Bundgaard, H. (1988) Glycolamide esters as biolabUe prodrugs of carboxylic acid agents synthesis, bioconversion and physicochemical properties. J. Pharm. Sci. 77(4), 285-298. 

Earlier we mentioned that a common measure of acidity is pH, which is a measure of the concentration of hydronium ions (H O", the acidic agent) in solution. Now we can be more specific a solution with a tenth of a mole of hydronium ions per liter has a pH of 1. A solution with a hundredth of a mole of hydronium ions per liter has a pH of 2. Every time the concentration of hydronium ions decreases by a multiple of ten, the pH goes up by one unit. 

Flavor enhancers are used imiversally in the food and pharmaceutical industries. Sugar, carboxylic acids (e.g., citric, malic, and tartaric), common salt (NaCl), amino acids, some amino acid derivatives (e.g., monosodium glutamate—MSG), and spices (e.g., peppers) are most often employed. Although extremely effective with proteins and vegetables, MSG has limited use in pharmaceuticals because it is not a sweetener. Citric acid is most frequently used to enhance taste performance of both liquid and solid pharmaceutical products, as well as a variety of foods. Other acidic agents, such as malic and tartaric acids, are also used for flavor enhancement. In oral liquids, these acids contribute unique and complex organoleptic effects, increasing overall flavor quality. Common salt provides similar effects at its taste threshold level in liquid pharmaceuticals. Vanilla, for example, has a delicate bland flavor, which is effectively enhanced by salt. 

The compounds of formula II can be sjmthesized by condensing in the presence of an acid agent, a resorcinol of the formula ... 

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