Temperature chromatography

Hastings, J. W., Balny, C., Le Peuch, C., and Douzou, P. (1973). Spectral properties of an oxygenated luciferase-flavin intermediate isolated by low-temperature chromatography. Proc. Natl. Acad. Sci. USA 70 3468-3472. 

Figure 24-10 Comparison of (a) isothermal (constant temperature) and ( >) programmed temperature chromatography. Each sample contains linear alkanes run on a 1.6-mm-diameter x 6-m-long packed column containing 3% Apiezon L (liquid phase) on 100/120 mesh WarAport 30 solid support with He flow rate of 10 mL/min. Detector sensitivity is 16 times greater in panel a than in panel b. [From H. M McNair and E. J. Bonelli, Basic Gas Chromatography (Palo Alto. CA Varian Instrument Division. 1968).]...

In support of an ingenious scheme for the biosynthesis of vinca and iboga alkaloids proposed by Wenkert is an interesting synthesis accomplished by Kutney, Brown, and Piers by transannular cyclization of carbomethoxydihydrocleavamine (I), accomplished by oxidation with mercuric acetate in acetic acid at room temperature. Chromatography afforded as the main product the vinca alkaloid vincadifformine. 

Table 5.1 Selected Data on Adsorption Enthalpies, Aa(jsH in kJ mol 1, from IC and the Programmed Temperature Chromatography Experiments Obtained by the Second Law Approach [6]...

Low-Temperature Chromatography Column for Routine Use in Organometallic Separations... 

J. D. Venable, L. Okach, S. Agarwalla and A. Brock. (2012) Subzero Temperature Chromatography for Reduced Back-Exchange and Improved Dynamic Range in Amide Hydrogen/Deuterium Exchange Mass Spectrometry, Ana/ytica/ Chemistry, 84 (21), 9601-9608. 

Mesitylate esters are common intermediates in chemical synthesis and are very unstable. In order to monitor the extent of a reaction, it is often necessary to monitor all reaction species the precursor, mesylate intermediates, and end products. The mesylation reaction of 3-(2-isopropylphenyl)-l-hydroxy-1-R-propane (where R is a bulky chlorinated hydrocarbon) was followed on a diol column (A = 320 nm) using a 15-min 15/85 5/95 (75/25 hexane/toluene)/ethyl acetate gradient [883]. Intramolecular ring closure of the analyte occurred on the silica support at room temperature. Chromatography yielded a large, tailed cyclic ether peak followed by the mesylated material followed by the unieacted diol compound. Elution was complete in 14 min. The silica-facilitated reaction was greatly reduced when the system temperature was taken down to 10°C and was prevented when the system tenqterature was -30°C. 

The reaction of sterically hindered alkylamines, such as tert-butylamine 403 and 1,1,3,3-tetramethylbutylamine 405, performed in dichloromethane under the same reaction conditions (Method B, low-temperature chromatography see Section... 

In high-temperature chromatography using conventional columns, preheating the mobile phase before entering the column is recommended in order to avoid radial temperature differences. 

Cyclopentadiene (Cp) is thermodynamically unstable, converting itself to the Diels-Alder dimer. As is well known, cracking of the latter at 180°C is the standard method for the laboratory-scale production of Cp. By preparing a,o)-alkylidene bis (Cp), StiUe and Plummer (S P) employed the reversible dimerization of Cp as a possible polymerization reaction [9]. These scientists found, not surprisingly, that their monomers 3 were rather unstable at room temperature, so they purified them by low temperature chromatography. They also observed that their polymers became insoluble after a period of time at room temperature and even though they stored the monomers and polymers under anaerobic conditions, the polymers still became... 

Cell temperature Chromatography Experimental Liquid-liquid equilibrium Non-random two-liquid... 

Programmed-Temperature Chromatography. A procedure in which the temperature of the column is changed systematically dnring a part or the whole of the separation. 

Cyclopentadienyl and Other Complexes.— The three products [(n-C5H4Me)Mn(C0)2(NC5H4CN)l, ((n-CgH4Me)Mn(CO)2(NCC H N)] and [ (Ti-CgH4Me)Mn(CO)2 2 tyNCCgH N)), separable by low temperature chromatography, result from the reaction of... 

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