Reaction chromatography determination

A modification of the pyridoxal—amino acid reaction (mentioned above) has been made for automatic analysis of amino acids by ligand-exchange chromatography [95]. This technique involves separation of the amino acids prior to fluorimetric reaction and determination. As the amino acids are eluted from the column, they are mixed with the pyridoxal-zinc(II) reagent to produce a highly fluorescent zinc chelate. Amounts of as low as 1 nmole of amino acid may be detected. The first reaction involved is the formation of the pyridoxyl-amino acid (Schiff base) as in Fig.4.46. The zinc then forms a chelate which probably has the structure shown in Fig. 4.48. 

Ketone Reduction. Pure samples of representative compounds were reacted with fluorenone to define the general pattern of reactivity. In a typical experiment, fluorenone (0.025 mmole), the hydroaromatic compound (0.025 mmole) and benzene (50pl) were reacted in an argon atmosphere in a glass vessel at 400°C for 60 minutes. The composition of the solution at the end of the reaction was determined by gas chromatography. The results for the seven compounds examined in this work are summarized in Table V. 

De Ruiter et al. [4] observed that photochemical decomposition by ultraviolet irradiation of dansyl derivatives of chlorinated phenolic compounds in methanol-water mixtures led to the formation of highly fluorescent dansyl-OH and dansyl-OH3 species. The optimal irradiation time was 5.5s. This reaction was utilised in a post-column photochemical reactor in the high performance liquid chromatography determination of highly chlorinated phenols in river water. The method calibration curve (for dansylated pentachlorophenol) was linear over three orders of magnitude. 

Generation of dimethylsilylene from hexamethylsilacyclopropane in the presence of cis- and trans-4-octene, cyclooctene, propenyltrimethylsilane, and trimethylethylethene gave the corresponding silacyclopropanes. The yields of these reactions were determined by gas-liquid chromatography (GLC) and structures indicated by their methanolysis products (Scheme 28) <76JOM(ll7)C5l>. 

Methods based on the same principle are employed in ultimate analysis for determining trace components in involatile compounds. For example, Juranek and Ambrova [104] applied reaction chromatography to the determination of carbon in the presence of sulphur in iron, its alloys and other materials by burning the sample in a flow of oxygen. The detection limit was 10" %. Methods for determining non-metals in metals were developed by Stuckey and Walker [105], Mungall and Johnson [106], Sukhorukov and Zhukhovitsky [107] and Sukhorukov and Ivanova [108]. 

As has already been mentioned, reaction chromatography is especially recommended for the analysis of reactive labile compounds. Hydrogen chloride in a mixture with acetylene and 1,1-dichloroethane [98] was determined from the carbon dioxide formed in a reaction between hydrogen chloride and sodium hydrogen carbonate [120]. 

The results obtained from the reaction were determined by gas chromatography, (5a) and (5b) were assigned by a comparison of the gas chromatograms obtained in several clay-catalysed reactions with those obtained in several reactions of (-)-menthyl acrylate with cyclopentadiene using homogeneous catalysts, whose diastereoselectivities and absolute configurations have been described [11]. 

The stereoselectivity of the reaction was determined by converting both p-lactams 204 and 205 into the corresponding hydroxy compounds 206 and 207, followed by removal of the chiral auxiliary under Birch reduction conditions and further benzoylation. The resulting P-lactams 208 and 209 were subjected to HPLC analysis indicating that the ratio of cis and trans isomers was 95 5 for both compounds. After purification by column chromatography the optical purity of the major isomer was found to be 70% ee. 

A recent study [154] has examined the nature of the catalytically active brown solution which results from reaction of oxygen with pyridine solutions of copper(I) chloride. The stoichiometry of this reaction as determined by oxygen uptake experiments is A(Cu )/A(02) = 4.0 0.2. The reaction products were separated by gel permeation chromatography with pyridine as the eluent. Elution of the product mixture results in two bands the first XXI, is brown and catalytically active, and the second, XXII, is green and inactive for the oxidative polymerization of phenols. 

Fig. 8. Transformation of methyl litho-cholate by Raney nickel. Gas chromatography of products from the reaction as determined with a Hewlett-Packard Model 402 gas chromatograph fitted with a hydrogen flame detector and a silanized glass U-shaped column (6 ft x 1/4 in o.d.) filled with 3% OV-17 on 100-120 mesh Gas Chrom Q under these conditions flash heater, 280 C column, 260 C detector, 280°C helium, 40 psi at a flow rate of 80 cc/min (85).

Reaction Procedure (Scheme 4.9) In an oven-dried, 10 mL round-bottomed flask equipped with a magnetic stirrer was added amide (0.5 mmol), 2-iodoaniline (0.5 mmol), Cul (20 mol%), K2CO3 (1.25 mmol) in anhydrous DMSO (1.5 mL). The reaction mixture was then stirred at 135 °C under a nitrogen atmosphere. After completion of the reaction, as determined by TLC, the reaction mixture was allowed to cool to room temperature. The crude reaction mixture was then purified by column chromatography without work-up using hexane-ethyl acetate as the eluent to yield the compound. 

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