Handbook of Solvents - George Wypych - ChemTech - Ventech!

13.3 Effects of organic solvents on phase-transfer catalysis 815
Table 13.3.11. Effect of the inert organic
substance on the PNO-catalyzed
CH 3COONa-PhCOCl reaction in a twophase
H 2O/CH 2Cl 2 medium
Organic
substance, R
kapp×10 3
min -1
Dipole
moment, D
C6H5CH2CN 61.2
C6H5CN 60.5 4.18
C6H5N(Et) 2 56.8
C6H5NO2 57.0 4.22
CH3COOC2H5 53.1 1.78
C3H7COOC2H5 48.5
CH2Cl2 48.5 1.60
CCl4 42.5 0
Data obtained from Wang et al. 148 1.00×10 -2 M of
PhCOCl, 0.500 M of CH 3COONa, 0.500 M of R,
2.00×10 -4 M of PNO, 50 mL of H 2O, 50 mL of CH 2Cl 2,
18 o C
such as nitrobenzene and ethyl acetate or
basic organic substance, such as
diethylaniline. The k app-value increased to a
greater extent with added highly polar and
basic organic substance, such as benzyl cyanide
and benzonitrile. In the second set of
experiments, reactions were carried out
with nonpolar CCl 4 added to the CH 2Cl 2 as
the mixed organic solvent. As shown in
Figure 13.3.6, that due to decreased polarity,
the value of k app also decreased with increased
amount of added CCl 4 to a
minimum. 148 Then, it increased slightly on
further addition of CCl 4 due to the increased
rate of PNO-catalyzed hydrolysis of
PhCOCl. Since the distribution of PhCOCl
in the CH 2Cl 2 decreases with increased
amount of CCl 4, the reaction rate of
PhCOCl with PNO in the aqueous phase
leads to the hydrolysis of PhCOCl. Wang,
Ou and Jwo 148 observed that the yields of
PhCOOCOCH 3 decrease with increased
content of CCl 4.
Table 13.3.12. Effect of the amount of inert organic substance on the PNO-catalyzed
CH 3COONa-PhCOCl reaction in a two-phase H 2O/CH 2Cl 2 medium
Inert organic
kapp×10
Substance [R]org
3 min -1 with [R]org, M
0.100 0.300 0.500 0.800 1.00 1.50 2.00
C6H5CH2CN 57.3 61.3 62.4 71.8
C6H5NO2 49.0 57.0 62.7 60.7 60.9
C6H5N(Et) 2 55.1 61.1 56.8 54.9
CCl4 47.6 42.1 38.3 28.5 24.7
Data obtained from Wang et al. 148 1.00×10 -2 M of PhCOCl, 0.500 M of CH 3COONa, 2.00×10 -4 M of PNO, 50 mL
of H 2O, 50 mL of CH 2Cl 2,18 o C
In Table 13.3.12, k app approached a constant value when nitrobenzene (1.0 M) was
added. This result indicates that solvation of the transition structure for the reaction of
benzoyl chloride with sodium nitrate reached an upper limit. Benzyl cyanide is a polar solvent.
The value of k app increased with increased content of benzyl cyanide. Further, highly
basic diethylaniline (C 6H 5N(Et) 2) could increase the concentration of free PNO and also the
reaction rate. However, this compound is less polar than dichloromethane and the polarity
decreased with increased proportion of diethylaniline, which caused the value of k app to de-