Phase-transfer-catalyzed reaction of tricarbonyl [η6-2-chloro-1-(trifluoromethyl)benzene]chromium with phenylacetonitrile

Article abstract of DOI:10.1021/om981018+

The reaction of tricarbonyl[η⁶-2-chloro-1-(trifluoromethyl)benzene]chromium with in situ generated phenylacetonitrile anion affords two diastereomeric products, which yield α-phenyl-α-[2-(trifluoromethyl)phenyl]-acetonitrile upon decomplexation

Full text of DOI:10.1021/om981018+

Organometallics 1999, 18, 2727-2730
2727
P h a se-Tr a n sfer -Ca ta lyzed Rea ction of
Tr ica r bon yl[η6-2-ch lor o-1-(tr iflu or om eth yl)ben zen e]ch r om iu m
w ith P h en yla ceton itr ile
Sof´ıa Varela Calafat, Edgardo N. Durantini, J uana J . Silber, and
Stella M. Chiacchiera*
Departamento de Quı´mica y Fı´sica, Universidad Nacional de R´ıo Cuarto, Agencia Postal # 3,
5800 Rı´o Cuarto, Argentina
Received December 15, 1998
Summary: The reaction of tricarbonyl[η6-2-chloro-1-(tri-
fluoromethyl)benzene]chromium with in situ generated
phenylacetonitrile anion affords two diastereomeric prod-
ucts, which yield R-phenyl-R-[2-(trifluoromethyl)phenyl]-
acetonitrile upon decomplexation. The SNAr intrinsic
rate constant was evaluated, and the activation of the
tricarbonylchromium moiety was compared with that of
the nitro group.
We previously reported studies of SNAr reactions with
activated substrates and different nucleophiles in both
homogeneous9 and PTC media.10,11 This work reports
the reaction between tricarbonyl[η6-2-chloro-1-(trifluo-
romethyl)benzene]chromium and the in situ generated
phenylacetonitrile anion under PTC conditions. The
reaction was performed in toluene using tetrabuthyl-
ammonium bromide (TBAB) as the catalyst in the
presence of 50% NaOH aqueous solution. Quantitative
yields of two diastereoisomeric pairs of the ipso-chloro-
substituted complexes were obtained. The products
appear at different rates and, upon I2 decomplexation
or photodissociation, afford racemic phenyl[2-(trifluo-
romethyl)phenyl]acetonitrile.
The reaction under consideration is useful in the syn-
thesis of substituted diphenylmethanes. These com-
pounds have diverse and important application as
comonomers in polymer production,12 spacers in heli-
cans synthesis,13 antistaminics, and biologically active
compounds.14
In tr od u ction
Aromatic nucleophilic substitution (SNAr) reactions
of activated aryl halides with carbanionic nucleophiles
involve C-C bond formation and are synthetically
relevant. However, the synthetic potential of the SNAr
reactions are limited by the requirement that the
aromatic substrate should be activated with suitable
withdrawing groups. This requirement severely limits
the synthetic potential of the SNAr reactions.
The temporal activation of the aromatic substrate by
metal transition complexation renders the ring more
susceptible to nucleophilic attack.1 Thus, tricarbonyl-
(η6-arene)chromium, for example, has found powerful
applications in the field of organic synthesis.2 The main
problem with these reactions is finding a medium where
both the neutral and anionic reagents are compatible.
In systems involving in situ generated nucleophiles, by
base deprotonation of a weak acid precursor, phase-
transfer catalysis (PTC) conditions can be an useful
approach. The nucleophile, extracted into the organic
phase as a fully lipophilic ion pair with the PT catalyst,
reacts with the aromatic substrate in the organic phase.3
The combination of PTC and Cr(CO3) complexation
of haloarenes has been successfully employed in SNAr
reactions.4-8 The substitution product can be freed from
the complex via oxidative decomplexation with I2.8
Exp er im en ta l Section
Gen er a l Con sid er a tion s. The HPLC measurements were
performed on a Varian 5000 liquid chromatograph, equipped
with a UV-visible variable-wavelength detector (Varian 2550)
operating at 250 nm. A Varian MicroPak SI-5 (150 mm × 4
mm i.d.) column was used with 1% 2-propanol in n-hexane as
eluent. UV-visible spectra were recorded on
a Hewlett-
Packard HP 8452 spectrophotometer. NMR spectra were
acquired with a 200 MHz Bruker spectrometer. IR spectra
were recorded with a Nicolet Impact 400 FT-IR. Mass spectra
were taken on a gas chromatograph (Hewlett-Packard 5890)
with a mass detector (Hewlett-Packard 5972). The melting
point was taken in a Bu¨chi apparatus.
(9) (a) Chiacchiera, S. M.; Singh, J . O.; Anunziata, J . D.; Silber, J .
J ., J . Chem. Soc., Perkin Trans. 2 1987, 987. (b) Chiacchiera, S. M.;
Singh, J . O.; Anunziata, J . D.; Silber, J . J ., J . Chem. Soc., Perkin Trans.
2 1988, 1585. (c) Chiacchiera, S. M.; Cattana, R. I.; Singh, J . O.;
Anunziata, J . D.; Silber, J . J ., J . Phys. Org. Chem. 1989, 2, 631. (d)
Durantini, E. N.; Zingaretti, L.; Anunziata, J . D.; Silber, J . J . J . Phys.
Org. Chem. 1992, 2, 557.
(10) Durantini, E. N.; Chiacchiera, S. M.; Silber, J . J . Synth.
Commun. 1996, 26, 3849.
(11) Durantini, E. N.; Chiacchiera, S. M.; Silber, J . J . J . Org. Chem.
1993, 58, 7115.
(12) (a) Stevens, M. P. Polymer Chemistry-An Introduction, 2nd ed.;
Oxford University Press: Oxford, U.K., 1990. (b) Bruno, J . G.; Chang,
M. N.; Choisledeski, Y. M.; Green, D. M.; McGarry, D. G.; Regan, J .
R.; Volz, F. A. J . Org. Chem. 1997, 62, 5174. (c) Tao, X. T.; Suzuki, H.;
Watanabe, T.; Lee, S. H.; Miyata, S.; Sasabe, H. Appl. Phys. Lett. 1997,
70, 1503. (d) Kultys, A. J . Polym. Sci., Part A: Polym. Chem. 1997,
35, 547. (e) Hulubei, C.; Cojocariu, C.; Pecincu, S.; Popescu, F. J .
Macromol. Sci., Pure Appl. Chem. 1997, A34, 1085.
(13) Constable, E. C.; Rees, D. G. F. New J . Chem. 1997, 21, 369.
(14) (a) Seno, H.; Hattori, H.; Kumazawa, T.; Suzuki, O. Forensic
Sci. Int. 1993, 62, 187. (b) Yamato, T.; Sakaue, N.; Shinoda, N.; Matsuo,
K.; J . Chem. Soc., Perkin Trans. 1 1997, 1193.
(1) (a) Schellhaas, K.; Schmalz, H.-G.; Bats, J . W. Chem. Eur. J .
1998, 4, 57. (b) Fretzen, A.; Ripa, A.; Liu, R.; Bernardelli, G.; Kundig,
E. P. Chem. Eur. J . 1998, 4, 251. (c) Pearson, A. J .; Gontcharov, A. J .
Org. Chem. 1998, 63, 152.
(2) (a) Semmelhack, M. F. In Comprehensive Organometallic Chem-
istry II; Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.; Pergamon:
Oxford, U.K., 1995; Vol. 12, pp 979-1015. (b) Davies, S. G.; McCarthy,
T. D. In ref 2a, pp 1039-1070.
(3) Dehmlow, E. V.; Dehmlow, S. S. Phase Transfer Catalysis, 3rd
ed.; Verlag Chemie: Weinheim, Germany, and New York, 1993.
(4) Alemagna, A.; Baldoli, C.; Del Buttero, P.; Licandro, E.; Maio-
rana, S. Gazz. Chim. Ital. 1995, 115, 555.
(5) Alemagna, A.; Del Buttero, P.; Licandro, E.; Maiorana, S. J . Org.
Chem. 1983, 48, 605.
(6) Alemagna, A.; Cremonesi, P.; Del Buttero, P.; Licandro, E.;
Maiorana, S. J . Org. Chem. 1983, 48, 3114.
(7) Brunelle, D. J . J . Org. Chem. 1984, 49, 1309.
(8) Baldoli, C.; Del Buttero, P.; Licandro, E.; Maiorana, S. Gazz.
Chim. Ital. 1988, 118, 409.
10.1021/om981018+ CCC: $18.00 © 1999 American Chemical Society
Publication on Web 06/15/1999

2728 Organometallics, Vol. 18, No. 14, 1999
Notes
Sta r tin g Ma ter ia ls. 2-Chloro-1-(trifluoromethyl)benzene
(CTB), 2-chloro-5-nitro-1-(trifluoromethyl)benzene (CNT), and
phenylacetonitrile (HNu) from Aldrich and tetrabutylammo-
nium bromide (TBAB) and sodium hydroxide from Fluka were
used without further purification. Toluene, n-hexane, and
dichloromethane from Sintorgan (HPLC quality) were used as
received. Tetrahydrofuran (Sintorgan) and dibutyl ether (Al-
drich) were distilled from acetophenone/sodium, collected over
molecular sieves, and used immediately after purification.
Syn th esis of Tr ica r bon yl[η6-2-ch lor o-1-(tr iflu or om eth -
yl)ben zen e]ch r om iu m (CTB-TCC). The tricarbonyl complex
was synthesized using the apparatus described by Toma et
al.15 The synthesis of the complex was performed by following
the procedure suggested for a related compound.16 Thus,
2-chloro-1-(trifluoromethyl)benzene (107 mmol) in a dry argon-
purged mixture of tetrahydrofuran (3.5 mL) and dibutyl ether
(37.5 mL) was reacted with Cr(CO)6 at 140-145 °C for 12 h.
The reaction mixture was filtered over Celite and evaporated
at reduced pressure to dryness. The pure complex was obtained
by sublimation of the solid residue at reduced pressure. Mp:
71 °C. Yield: 80%. The pure compound shows the spectroscopic
properties reported in the literature.17
F igu r e 1. Typical HPLC chromatogram of the reaction
mixture of CTB-TCC with phenylacetonitrile under PTC
conditions.
solved in toluene (5 mL) and transferred to the reactor cell.
The organic solution was stirred at 1000 ( 50 rpm, and 4 mL
of 50% NaOH was added. The reactor was kept at 40.0 ( 0.1
°C under an argon atmosphere. At given times, the stirring
was stopped, the two phases were allowed to separate, and a
50 µL aliquot of the organic phase was withdrawn from the
reactor. The extraction sample was quenched by dilution to 5
mL of hexane, stirred with 0.2 mL of hydrochloric acid (20%
v/v), and analyzed by HPLC. The complexed products appear
at 10.9 and 13.7 min in the HPLC chromatogram (column
Varian MicroPak SI-5 (150 mm × 4 mm i.d., eluent 1%
2-propanol in n-hexane, flow rate 0.5 mL/min). A typical HPLC
chromatogram of the reaction mixture is shown in Figure 1.
The reaction mixture was protected from direct light
exposure. The pseudo-first-order rate constants (kobs) were
calculated from a nonlinear least-squares fit of the plot of the
experimental concentrations vs time values.
2-Ch lor o-5-n itr o-1-(tr iflu or om eth yl)ben zen e Rea ction .
The kinetic experiments were carried out as described above
using equimolar amounts of CNTB and TBAB. Under this
condition the ipso-chloro substitution product, phenyl[2-(trif-
luoromethyl)-4-nitrophenyl]acetonitrile, was obtained. Flash
chromatography of the dry organic phase (silica gel, petroleum
ether/dichloromethane gradient) afforded the pure product.
Yield: 89%. 1H NMR (200.13 MHz, DCCl3, TMS): δ (ppm) 5.70
(s, 1H), 7.45 (m, 5H, C6H5), 7.76 (d, 1H, J ) 8.5 Hz), 8.40 (dd,
1H, J ) 2.3, 8.5 Hz), 8.59 (d, 1H, J ) 2.4 Hz). 13C NMR (50.32
MHz, DCCl3, TMS): δ (ppm) 38.0, 117.4 (-CN), 121.9, 122.6
(-CF3), 127.4, 128.8, 129.2, 129.8, 132.6, 133.4, 141.1, 147.3
(C-NO2). MS (m/z): 306 (M+) (306 calculated for C15H9F3N2O2).
Ca lcu la tion of Φ. To calculate Φ (eq 10), experiments were
carried out as described above but without adding CTB-TCC.
The amount of [TBA+Nu-] in the organic phase was spectro-
photometrically determined by using the UV absorption band
of Nu- at λmax 340 nm (log ꢀ ) 2.36). A calibration curve was
constructed using solutions of TBA+Nu- of known concentra-
tions. The Nu- was quantitatively generated from the carbon
acid through reaction with an excess of clean sodium metal
under nitrogen, following a similar procedure as described for
the quantitative generation of sodium methoxide.19 TBAB was
added to keep the anions in solution.
Syn th esis of Tr ica r bon yl[η6-r-p h en yl-r-(2-(tr iflu or o-
m eth yl)p h en yl)a ceton itr ile]ch r om iu m . CTB-TCC (0.14
mmol), HNu (8.55 mmol), and TBAB (0.014 mmol) in 4 mL of
toluene were placed in a three-necked flask equipped with an
efficient mechanic stirrer and a gas inlet tube. After 10 min
of stirring under an argon atmosphere, 4 mL of a 50.0% NaOH
aqueous solution was added. The mixture was kept at room
temperature for 1.5 h. The reaction mixture was neutralized
with hydrochloric acid, washed with water, and extracted with
dichloromethane. The organic phase was dried with MgSO4
and the excess of the nucleophile and the solvent removed
under reduced pressure. Flash chromatography (silica gel,
Merck, 60 mesh, eluent 2:1 petroleum ether-dichloromethane)
afforded the pure diastereomeric products (1 and 2) as
determined by HPLC and GC-MS. The first eluted fraction
presented the following spectral characteristics: 1H NMR
(200.13 MHz, DCCl3, TMS) δ (ppm) 5.34 (d, 1H, J ) 6 Hz, Ar
H), 5.37 (dd, 1H, J ) 0.6 and 6 Hz, Ar H), 5.44 (d, 1H, J ) 6
Hz, Ar H), 5.62 (s, 1H, -CH), 5.63 (dd, 1H, J ) 6 and 6 Hz, Ar
H), 7.30-7.50 (m, 5H, C6H5); 13C NMR (50.32 MHz, DCCl3,
TMS) δ (ppm) 38.0 (-CH), 86.8, 88.1, 88.4, 89.4, 90.1, 92.8,
117.5 (-CN), 123.0 (-CF3), 128.6 (2-CH, C6H5), 129.5 (1-CH,
C6H5), 129.9 (2-CH, C6H5), 134.3 (1-C, C6H5), 228.9 (3-CO); MS
(m/z) 397 (M+, 15, 397 calculated for C18H10CrF3NO3), 313 (46),
261 (31), 222 (82), 203 (22), 196 (100), 176 (26).18 Anal. Calcd:
C, 54.42; H, 2.54; N, 3.53. Found: C, 54.48; H, 2.47; N, 3.59.
The second eluted fraction was characterized by the follow-
ing spectral data: 1H NMR (200.13 MHz, DCCl3, TMS) δ (ppm)
5.27 (dd, 1H, J ) 0.6 and 6 Hz, Ar H), 5.28 (d, 1H, J ) 6 Hz,
Ar H), 5.43 (dd, 1H, J ) 6 and 6 Hz, Ar H), 5.46 (d, 1H, J )
6 Hz, Ar H), 5.69 (s, 1H, -CH), 7.30-7.50 (m, 5H, C6H5); 13C
NMR (50.32 MHz, DCCl3, TMS) δ (ppm) 39.2 (-CH), 87.5, 87.9,
88.5, 90.2, 90.9, 93.6, 117.1 (-CN), 123.2 (-CF3), 128.7 (2-
CH, C6H5), 129.4 (1-C, C6H5), 129.8, (2-CH, C6H5), 133.9 (1-C,
C6H5), 225.2 (3-CO); MS (m/z) 397 (M+, 27, 397 calculated for
C
18H10CrF3NO3), 313 (62), 261 (13), 222 (68), 203 (76), 196
(100), 176 (22).18 Anal. Calcd: C, 54.42; H, 2.54; N, 3.53.
Found: C, 54.37; H, 2.59; N, 3.56.
Kin etic Exp er im en ts. Ch r om iu m Ca r bon yl Med ia ted
Rea ction s. The kinetic experiments were carried out as
previously described.10 In a typical run, CTB-TCC (0.31 mmol),
HNu (17.45 mmol), and TBAB (0.02-0.04 mmol) were dis-
Resu lts a n d Discu ssion
A kinetic study of the reaction of CTB-TCC with HNu
was performed under PTC conditions. The organic
reactants dissolved in toluene were stirred with 50%
aqueous sodium hydroxide in the presence of different
catalytic amounts of TBAB (Scheme 1).
(15) Hudecek, M.; Toma, S. J . Organomet. Chem. 1990, 393, 115.
(16) Rose-Munch, F.; Rose, E.; Semra, A.; Bois, C. J . Organomet.
Chem. 1989, 363, 103.
(17) Rose-Munch, F.; Khourzom, R.; Djukic, J .-P.; Rose, E. J .
Organomet. Chem. 1993, 456, C8.
(18) The complexed products almost completely decompose to the
free substitution product at the injector temperature of the gas
chromatograph.
(19) Crampton, M. R.; Stevens, J . A. J . Chem. Soc., Perkin Trans 2
1991, 1715.

Notes
Organometallics, Vol. 18, No. 14, 1999 2729
Sch em e 2
F igu r e 2. Kinetic profile for the reaction of CTB-TCC with
phenylacetonitrile under PTC conditions: (9) substrate; (2)
complexed products.
Sch em e 1
No reaction was observed either in the absence of
catalyst or in aqueous sodium hydroxide. All the kinetic
studies were performed using an excess of nucleophile
precursor, HNu. Typical HPLC chromatograms of the
reaction mixture at different times show a quantitative
decrease in the CTB-TCC peak area (tR ) 7.2 min) and
the appearance of two new peaks (Figure 1). The kinetic
profiles show a complete conversion of the CTB-TCC at
infinite time (Figure 2). Under the present experimental
conditions no poisoning of the catalyst by the complexed
product was observed.
Taking in consideration the racemic nature of the
substrate (CTB-TCC), the reaction with the prochiral
HNu yields almost quantitatively two diastereomeric
ipso-chloro-substituted complexed pairs of enantiomers
(racemic 1 and 2) shown in Scheme 2. An exo addition
of the nucleophile to CTB-TCC yields two intermediates
with differing steric congestion. The most stable transi-
tion state, i.e., one bearing the bulkiest groups further
apart, leads to the formation of 2, which is produced in
higher proportion.
Both products exhibit the characteristic MLCT ab-
sorption of (arene)tricarbonylchromium complexes at
320 nm.20 From the kinetics data, the ratio 1:2 ) 0.23:
0.77 was obtained, assuming that the molar extinction
coefficients for both products are the same. Irradiation
of the reaction mixture at 320 nm produces bleaching
of the solution. The only detected product was R-phenyl-
R-[2-(trifluoromethyl)phenyl]acetonitrile, as shown by
GC-MS analysis of the photolyzed solution. (MS m/z
(relative intensity) 261 (M+, 40), 242 (10), 221 (100), 192
(10), and 165 (24)).
Effect of TBAB Con cen tr a tion . The variation of
the pseudo-first-order rate constant with the catalyst
concentration, keeping other experimental conditions
fixed, is shown in Figure 3. A linear dependence with
kobs was found with a slope of (2.5 ( 0.2) × 10-2 M-1
s-1. Such linear behavior is characteristic when the HNu
deprotonation occurs at the interface and the rate-
limiting step is the nucleophilic substitution.21 The
intercept of the plot in Figure 3 is negligible, showing
that the uncatalyzed reaction does not occur.
Assuming that nucleophile precursor deprotonation
takes place at the interface, the following mechanism
can be proposed:3
HNuint + HO-
y
Kz Nu- + H2Oint
(1)
(2)
int
int
Ks
TBA+X- + Nu- z TBA+Nu- + X-
y\
int org int
org
CTB-TCCorg + TBA+Nu-org 9k8
productsorg + TBA+X-
(3)
org
where the subscripts int and org indicate the interface
and the organic phase, respectively. k is the overall
second-order rate coefficient for the reaction of CTB-
TCC with TBA+Nu-org. K represents the acid-base
equilibrium constant at the phase boundary defined as
[Nu-]int[H2O]int
[HNu]int[OH-]int
K )
(4)
The free organic product was also obtained by oxida-
tive decomplexation of 1 and 2 with iodine (ether
solution, room temp, 3 h).
The Na+ salt of the interface generated carbanion can
migrate neither into the organic phase nor into the
highly saline aqueous phase.22 Ks is the selectivity
(20) Geoffroy, G. L.; Wrighton, M. S. Organometallic Photochemistry;
Academic Press: New York, 1979.
(21) Solaro, R.; D’Antone, S.; Chiellini, E. J . Org. Chem. 1980, 45,
4179.

2730 Organometallics, Vol. 18, No. 14, 1999
Notes
KKs[OH-]int
[X-]int[H2O]int
Φ )
)
[TBA+ + Nu-]org
([TBAB0] - [TBA+ + Nu-]org)[HNu]int
(10)
A Φ value of 0.124 M-1 was obtained for 50% NaOH
aqueous phase, as described in the Experimental Sec-
tion. The overall second-order rate coefficient k (eq 3),
for the intrinsic SNAr reactions in the organic phase,
can be evaluated from the slope of the kobs vs [TBAB0]
plot according to eq 9 (Figure 3). The introduction of
the calculated Φ value in eq 9, with the assumption that
[HNu]int equals [HNu]org, provides the value k ) (8.0 (
0.4) × 10-2 M-1 s-1
.
The activation process either by tricarbonyl complex-
ation or nitro group substitution has been the subject
of theoretical studies, but no direct theoretical compari-
son between the relative ipso activation could be per-
formed.23 To evaluate the degree of the activation effect
exerted by the tricarbonyl moiety, a study was carried out
using 2-chloro-5-nitro-1-(trifluoromethyl)benzene (CNTB)
as substrate.24 The reaction was performed at [CNTB]/
[TBAB] ) 0.1, but the other experimental conditions
were kept the same as with CTB-TCC. Under these con-
ditions no poisoning of the catalyst by the product occurs
and the ipso-chloro substitution product is obtained in
quantitative yield. For CNTB a value of 0.76 s-1 M-1
was obtained for the intrinsic second-order rate constant
of the SNAr reaction (kCNTB). The results show a rate
constant relationship for the nitro-activated substrate
relative to the one activated by the tricarbonyl moiety
(kCNTB/k) = 10. The finding agrees with the previously
reported reactivity order for electron-deficient arenes.2a
F igu r e 3. Dependence of kobs on catalyst concentration
[TBAB] for the reaction of CTB-TCC with phenylacetoni-
trile under PTC. Experimental conditions: 0.3 mmol of
CTB-TCC, 17.5 mmol of HNu, TBAB in 5 mL of toluene,
and 4 mL of 50% aqueous NaOH, T ) 40.0 ( 0.5 °C.
constant3 for the extraction of HNu- with respect to that
of X-, defined as
[TBA+Nu-]org[X-]int
[TBA+X-]org[Nu-]int
Ks )
(5)
Since the two parallel reactions that lead to the
diastereomeric products are of the same kinetic order,
the following rate (r) expression can be written:
r ) -d[CTB - TCC]/dt )
k[TBA+Nu-]org[CTB-TCC] (6)
Con clu sion
Tricarbonyl[η6-2-chloro-1-(trifluoromethyl)benzene]-
chromium reacts with phenylacetonitrile under PTC
conditions to yield the ipso-chloro substitution product
as two racemic mixtures of diastereoisomers. The free
product, racemic phenyl[2-(trifluoromethyl)phenyl]acet-
onitrile, can be obtained by either photolysis or oxidative
decomplexation with I2.
where k involves the sum of the two individual rate
constants for product formation. When both HNu and
base are in great excess over the catalyst, it can be
assumed that [TBA+ Nu-]org remains constant through-
out the reaction and eq 7 can be written
r ) kobs[CTB-TCC]
(7)
A general mechanism that includes the interfacial
deprotonation of the phenylacetonitrile has been pro-
posed and the intrinsic second-order rate constant for
the SNAr reaction evaluated. The activation power of
the chromium tricarbonyl moiety is 10 times smaller
than that exerted by a p-nitro group.
The combination of PTC methodology with the stoi-
chiometric activation of aromatic substrates by chro-
mium carbonyl complexation is an interesting approach
to the synthesis of diphenylacetonitrile derivatives.
by application of the preequilibrium approximation to
this mechanism and taking into account that [TBAB0]
) [TBA+X-]org + [TBA+Nu-]org (eq 8) can be obtained:
kKKs[TBAB0][HNu]int[OH-]int
[X-]int[H2O]int + KKs[HNu]int[OH-]int
kobs
)
(8)
Equation 8 can be rewritten in the form of eq 9:
Ack n ow led gm en t. Financial support from the Con-
sejo Nacional de Investigaciones Cient´ıficas y Te´cnicas
(CONICET), the Consejo de Investigaciones Cientı´ficas
y Tecnolo´gicas de la Provincia de Co´rdoba (CONICOR),
and Universidad Nacional de R´ıo Cuarto is gratefully
acknowledged. S.V.C. thanks CONICOR for a research
fellowship.
k[TBAB0][HNu]int
Φ-1 + [HNu]int
kobs
)
(9)
The evaluation of Φ under the experimental condi-
tions can be carried out with the KKs product expression
and the amount of TBA+Nu- in the organic phase, as
shown in eq 10:
OM981018+
(24) Chiacchiera, S. M.; Durantini, E. N.; Varela Calafat, S.; Silber,
J . J . η6-(2-Chlorotrifluoromethylbenzene)Tricarbonyl Chromium In The
Synthesis Of Phenyl-2-Trifluoro Methylphenylacetonitrile Under Phase
Transfer Catalysis. Abstracts, 32nd International Conference on
Coordination Chemistry, Santiago de Chile, Chile, Aug 1997; Issue 117,
p 112.
(22) Makosza, M.; Fedorynski, M. Advances in Catalysis; Eley, D.
D., Pines, H., Weisz, P. B., Eds.; Academic Press: London, 1987; Vol.
35, p 375.
(23) Morgantini, P. Y.; Fluekiger, P.; Weber, J . J . Chim. Phys. Phys-
Chim. Biol. 1992, 89, 301.