Effect of acetonitrile concentration

Kazusaki et al. [91] studied the effect of acetonitrile concentration on the resolution of ftS -2-(4-bromo-2-fluorobenzyl)-( 1,2,3,4-tetrahydropyrro Io[1,2-a]-pyrazine-4-spiro-3,-pyrrolidine)-l,2,3,5,-tetrone, and the results are given in Figure 16a,b. These authors reported that the resolution factor decreased with an increase in acetonitrile concentration. Aboul-Enein and Ali [92] have studied the effect of acetonitrile content on the chiral resolution of flubiprofen on Chiralpak AD-RH columns at different temperatures. Figure 16c indicates the... 

Fig. 11. The effect of acetonitrile concentration on the retention times of polypeptides using a Hypersil ODS column with a mobile phase of 0.1 M NaHiP04-H3P04. pH 2.1, and acetonitrile at the concentration shown in the figure. The flow rate was 1 ml/min. Adapted from O Hare and Nice (1979).

The effect of acetonitrile concentration on the pH of buffered water/acetonitrile solutions has been studied by J. Barbosa and V. Sanz-Nebot [14]. They showed that each 10 % increase of acetonitrile content in water causes a pH increase of approximately 0.3 units. Their experimental data measured for different buffers are shown in Fig. 5-28. 

Figure 4.4 Effect of TFA concentration on peptide retention. A series of five synthetic peptides containing 0, 1,2, 4, or 6 basic residues were separated on an octadecyl reversed-phase column using a 1%/min linear gradient from water to acetonitrile. Both solvents contained TFA at the indicated concentrations. (Reproduced from D. Guo, C.T. Mant, and R.S. Hodges, J. Chromatogr., 386 205 [1987]. With permission from Elsevier Science.)...

Fig. 2.84 Effect of the concentration of the acetic acid on the net peak currents of 1 x 10 mol/L azobenezene solution recorded in an acetate buffer (7) and an acetate buffer containing 50% (v/v) acetonitrile (2). The other experimental conditions are Ejw = 20 mV, AE = 4 mV, / = 40 Hz, Idelay — 15 S, Egcc — 0.0 V...

Figure 13.23. Examples of vapor-liquid equilibria in presence of solvents, (a) Mixture of-octane and toluene in the presence of phenol, (b) Mixtures of chloroform and acetone in the presence of methylisobutylketone. The mole fraction of solvent is indicated, (c) Mixture of ethanol and water (a) without additive (b) with 10gCaCl2 in 100 mL of mix. (d) Mixture of acetone and methanol (a) in 2.3Af CaCl2 ip) salt-free, (e) Effect of solvent concentration on the activity coefficients and relative volatility of an equimolal mixture of acetone and water (Carlson and Stewart, in Weissbergers Technique of Organic Chemistry IV, Distillation, 1965). (f) Relative volatilities in the presence of acetonitrile. Compositions of hydrocarbons in liquid phase on solvent-free basis (1) 0.76 isopentane + 0.24 isoprene (2) 0.24 iC5 + 0.76 IP (3) 0.5 iC5 + 0.5 2-methylbutene-2 (4) 0.25-0.76 2MB2 + 0.75-0.24 IP [Ogorodnikov et al., Zh. Prikl. Kh. 34, 1096-1102 (1961)].

FIGURE 5 Effect of the concentration of acetonitrile on (a) the retention (k) and the (b) separation (a) factors for the chiral resolution of (O) dansyl asparagine and ( ) dansyl valine on a Chiralpak WH column using 0.25 M ammonium acetate as the major component of the mobile phase. (From Ref. 53.)... 

FIGURE 11 Effect of the concentrations of organic modifiers in TLC (a) of acetonitrile on the chiral resolution of dansyl-DL-serine, (O) D- and ( ) L-enantiomers (from Ref. 101), and (b) of methanol on the chiral resolution of RS-aminoglutethimide (from Ref. 103). 

Figure 10 Effect of buffer concentration and temperature on EOF in CEC. Column CEC-Hypersil C18, 3 pm, 250 (350) X 0.1 mm mobile phase 80% acetonitrile/ Tris-HCI, pH 8, buffer concentration and temperature given in the figure voltage, 20 kV dead-time marker, thiourea. (Reprinted with permission from Ref. 47, copyright 1997, Wiley.)...

A closer examination was made of the mechanism of deprotonation of HMB radical cation in acetonitrile. Tables 7 and 8 show the effect of substrate concentration and temperature, respectively, on the apparent rate constants for the deprotonation of the radical cations of HM B and HMB-dig measured by DCV (Parker, 1981b). Although data for both substrates gave a very good fit to theoretical data for the disproportionation mechanism, the observed rate constants were concentration dependent. This indicates that Raib is greater than 1 and less than 2 suggesting a complex mechanism. The com-... 

Figure 4-57. Effect of tetrafluoroborate concentration on analyte apparent efficiency and tailing factor. Column Zorbax Eclipse XDB-C8. Mobile phase 0.1 v/v% phosphoric acid -H XBE4 [l-50mM] acetonitrile, ophthalmic compounds (10% acetonitrile), phenols (25% acetonitrile). (A) N(ji/2) versus tetrafluoroborate concentration. (B) Tailing factor versus tetrafluoroborate concentration. (Reprinted from reference 153, with permission.)...

We employ acetonitrile as an aprotic solvent, in order to control the concentration of water in the electrolyte solution. We attempt to reveal the effect of water concentration in the electrochemical reduction of CO2 by adding water into acetonitrile electrolyte. 

It has been reported that use of a suitable co-solvent increases the concentration of the olefin in water (catalyst) while retaining the biphasic nature of the system. It has been shown that using co-solvents like ethanol, acetonitrile, methanol, ethylene glycol, and acetone, the rate can be enhanced by several times [27, 28], However, in some cases, a lower selectivity is obtained due to interaction of the co-solvent with products (e.g., formation of acetals by the reaction of ethanol and aldehyde). The hydroformylation of 1-octene with dinuclear [Rh2(/t-SR)2(CO)2(TPPTS)2] and HRh(CO)(TPPTS)3 complex catalysts has been investigated by Monteil etal. [27], which showed that ethanol was the best co-solvent. Purwanto and Delmas [28] have reported the kinetics of hydroformylation of 1-octene using [Rh(cod)Cl]2-TPPTS catalyst in the presence of ethanol as a co-solvent in the temperature range 333-353 K. First-order dependence was observed for the effect of the concentration of catalyst and of 1-octene. The effect of partial pressure of hydrogen indicates a fractional order (0.6-0.7) and substrate inhibition was observed with partial pressure of carbon monoxide. A rate eqution was proposed (Eq. 2). 

The effect of the concentration of interfacial transfer catalysts in aprotic solvents in contact with solid salts (sodium 2,4-dinitrophenolate) has been investigated with regard to their effectiveness for reaching the solid-liquid equilibrium in benzene, chlorobenzene, dichloromethane and acetonitrile at 25 °C [185], Polyethylene glycols with 300, 600 and 2000 mol. wt., trianthrylmethylammonium chloride, dodecyldi-methylammonium chloride, tetrabutylammonium chloride and a crown ether, have... 

Toxicology At low concentrations, acetonitrile causes headache and nausea, whilst at high concentrations, causes convulsions and death. Acetonitrile is toxic and flammable. It is metabolised into highly toxic HCN and thiocyanate. The main toxic effects of acetonitrile are attributed to the metabolic release of cyanide, in fact, specific cyanide antidotes are used in acetonitrile poisonings [5-7]. 

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