Tartrate analysis

Description of Method. Salt substitutes, which are used in place of table salt for individuals on a low-sodium diet, contain KCI. Depending on the brand, fumaric acid, calcium hydrogen phosphate, or potassium tartrate also may be present. Typically, the concentration of sodium in a salt substitute is about 100 ppm. The concentration of sodium is easily determined by flame atomic emission. Because it is difficult to match the matrix of the standards to that of the sample, the analysis is accomplished by the method of standard additions. 

For the separate determination of the four principal components in the total alkaloids, the method in general use is based on the isolation of quinine and cinchonidine as d-tartrates, of cinchonine as the base in virtue of its sparing solubility in ether, and of quinidine as the hydriodide. Types of this method have been described by Chick, and special modifications designed for use in the analysis of totaquina are given in the British Pharmacopoeia 1932 and in a special report by the Malaria Commission of the League of Nations. Goodson and Henry have critically examined this process and shown that, with care, it gives satisfactory... 

The stereochemistry of the first step was ascertained by an X-ray analysis [8] of an isolated oxazaphospholidine 3 (R = Ph). The overall sequence from oxi-rane to aziridine takes place with an excellent retention of chiral integrity. As the stereochemistry of the oxirane esters is determined by the chiral inductor during the Sharpless epoxidation, both enantiomers of aziridine esters can be readily obtained by choosing the desired antipodal tartrate inductor during the epoxidation reaction. It is relevant to note that the required starting allylic alcohols are conveniently prepared by chain elongation of propargyl alcohol as a C3 synthon followed by an appropriate reduction of the triple bond, e. g., with lithium aluminum hydride [6b]. 

Potassium acetate, 20 629-630 Potassium acid tartrate, 20 637 Potassium alkoxides, 20 604-605 Potassium a-hydrohexafluoroisobutanoyl fluoride, 13 724 Potassium amides, 20 605 Potassium analysis, of water, 26 31 Potassium arsenite (Fowler s solution), 3 276... 

In principle, any reaction with a racemate using a chiral reagent can be used to effect a kinetic resolution. Kagan (56) has recently given an analysis of the relationship between the extent of reaction and die enantiomeric excess that can be achieved, while Sharpless (57) has applied kinetic resolution successfully to racemic allyl alcohols using his titanium alkoxide tartrate epoxidation reaction. 

The purity of the ligand depends largely on the purity of the dibenzyl ester. Flash chromatography was carried out with silica gel purchased from Merck (Kieseigel 60, Art. 9385). For TLC analysis, Merck silica gel F-254 TLC plates were used, with, 3 1 5 hexane-ether-dichloromethane as eluent. Mono(2,6-dimethoxybenzoyl)tartrate has an Rf of ca. 0.35 in this solvent system. 

A standard Lowry-based protein assay has been adjusted to the special conditions encountered with skin [126], Basically, proteins reduce an alkaline solution of Cu(II)-tartrate to Cu(I) in a concentration-dependent manner. Then, the formation of a blue complex between Folin-Ciocalteau reagent (a solution of complex polymeric ions formed from phosphomolybdic and phosphotungstic heteropoly acids) and Cu(I) can be measured spectrophotometrically at 750 nm. A calibration curve can be obtained by dissolving known amounts of stratum corneum in 1 M sodium hydroxide. A piece of tape that has not been in contact with skin is subjected to an identical procedure and serves as negative control. The method was recently adapted to a 96-well plate format, notably reducing analysis times [129],... 

An approach, similar to that employed in the analysis of tartrate mixtures, has been used for the chiral discrimination of amino acid (M/j/s) mixtures, using an amino acid of defined configuration as reference (S). The proton-bound trimers [S2-M H]+ form [S M H]+ and [S2H]+ fragments upon CID or MIKE decay (equations (9)-(12)). With two independent measurements of the fragmentation ratio [S-M-H] /[S2H] from either [S2-M -H] and [52-M5-H]" , the differences in binding energies can be determined. The relative gas phase basicities (GB) of the molecular pairs [S-M] and [S2] can be derived from equations (13) and (14). 

Dimethyl allylboronates (e.g., 17,18) are sensitive to hydrolysis, and the allylboronic acids are unstable in the presence of O2. The pinacoi and tartrate esters, however, are quite stable and many have been purified by distillation. We routinely monitor the isomeric purity of the crotyl reagents by capillary GC analysis (ref 3e). 

Many substances can rotate the plane of polarization of a ray of plane polarized light. These substances are said to be optically active. The first detailed analysis of this phenomenon was made by Biot, who found not only the rotation of the plane of polarization by various materials (rotatory polarization) but also the variation of the rotation with wavelength (rotatory dispersion). This work was followed up by Pasteur, Biot s student, who separated an optically inactive crystalline material (sodium ammonium tartrate) into two species which were of different crystalline form and were separately optically active. These two species rotated the plane of polarized light equally but in opposite directions and Pasteur recognized that the only difference between them was that the crystal form of one was the mirror image of the other. We know to-day, in molecular terms, that the one necessary and sufficient condition for a substance to exhibit optical activity is that its molecular structure be such that it cannot be superimposed on its image obtained by reflection in a mirror. When this condition is satisfied the molecule exists in two forms, showing equal but opposite optical properties and the two forms are called enantiomers. 

This tetranuclear complex was first prepared by Jorgensen (2), and was resolved into optical isomers by Werner (5), who thereby disposed of the vitalist contention that organic carbon is an essential concomitant of optical activity. Werner named the complex hexol after the bridging ligands. The structure of this tetranuclear species has now been established by an X-ray crystal-structure analysis of the racemic salt (52). The complex racemizes fairly readily and rates of racemization depend heavily on pH the first-order rate constants at pH 2.0, 7.0, and 8.1, are respectively, k = 2 x 10 6, 2 x 10 3, and 4 x 10 2 sec-1 at 22"C. Tartrate and selenate decrease the rate of racemization, probably as a result of ion pairing between the hydroxo bridges and the anions (56). 

Diels-Alder reaction, 169-170 aromatic TS, 151 benzyne, 160 butadiene + ethylene, 169 diastereoselectivity, 292 interaction diagram, 169 orbital analysis, 169-170 orbital correlation diagram, 198, 201 reverse demand, 169 substituent effects, 169-170 Diethyl tartrate, 11 Difluorocarbene ( CF2), 115... 

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