Acetonitrile displacement

FIGURE 11.9 Displacement separation of a crude MSH mixture with the same column used as in Figure 11.8. Carrier 0.25% formic acid, 0.5% triethylamine, 19% acetonitrile displacer, 50mM BDMA in 0.25% formic acid, 0.5% triethylamine, 21% acetonitrile. Flow rate O.lmL/min feed 35 mg MSH. (Reprinted with permission from Shukla, A.A. et ah, Biotechnol. Prog., 14, 92, 1998. Copyright 1998, American Chemical Society.)... 

Of particular interest in the case of the displacement separation of the melanotropins, acetonitrile was mixed with both the carrier and the displacer. The purpose was to suppress the sigmoidal isotherm of MSH which was then found to underlie the Langmuirian isotherm of the displacer in the area of operational interest. The idea of isotherm suppression through use of acetonitrile/displacer mixtures surfaced again later in the Horvath laboratory (see below). 

Attempts with (MeCN)3Cr(CO)3 meet with no success. For Mo (but not W) Mo(CO)g can be used in acetonitrile, as acetonitrile displaces CO at reflux, and the intermediate (MeCN)3Mo(CO)3 reacts at RT. In alcohols (or acetonitrile), Mo(CO)j reacts at reflux temperature with diallyl oxalate to form XIII in excellent yields ... 

The Ir(dmpe)2(C02X l complex may be handled in air for minutes as a solid. It may be stored indefinitely under nitrogen and is stable to vacuum. Ethylene does not react with it, but CO and SO2 displace the bound CO2. Hydrogen and acetonitrile displace the CO2 and oxidatively add, affording [Ir(H)2(dmpe)2]Cl and [lr(H)(CH2CNXdmpe)2]Cl, respectively. Most solvents that dissolve Ir(dmpe)2(C02)Cl react with it. As a consequence, growing crystals for a structure determination has been unsuccessful. Isotope labeling ( C02 and 02) has shown the bands at 1550(s) and 1230(s) cm (mull) to involve the bound COj. The weak bands at 2180 and 1640 cm are due to a minor impurity. ... 

CIO7, or Cl", deposited in a conducting film generated by copolymerization of the ruthenium complex with e.g., pyrrole or 3-methylthiophen, when this film is immersed in acetonitrile. Displacement of chloride is slower when the appropriate film is immersed in water this aquation process is photo-catalyzed." Variable-temperature NMR has given some information on intramolecular conformational changes in the constrained ligands (62) and (63) [X=—CHj— to — (CH2)4—]. The inversion barrier of 44kJmol" ... 

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