Kinetics of elimination reactions of 1,2-diphenyl ethyl substrates in acetonitrile: A mechanistic change in the presence of a strong base

Article abstract of DOI:10.1002/kin.20329

Kinetics of elimination of methanesulfonic acid from 1,2- diphenylethylmethane sulfonate and its 1-p-methylphenyl- and 1-p-chlorophenyl-substituted derivatives is studied. The results show that the elimination reaction is unimolecular (E1) as reported in the case of l-chloro-l-(4-methoxyphenyl)-2-phenylethane. The rate of the elimination reaction in the presence of added weak base pyridine is independent of the concentration of the base, but in the presence of a strong base piperidine the rate shows a linear upward drift and this is due to the appearance of a bimolecular component along with the unimolecular pathway. The shift from the unimolecular to bimolecular process takes place independently of the nature of the leaving group and the parasubstituent in the 1,2-diphenylethyl substrate.

Full text of DOI:10.1002/kin.20329

Kinetics of Elimination
Reactions of 1,2-Diphenyl
Ethyl Substrates in
Acetonitrile: A Mechanistic
Change in the Presence
of a Strong Base
D. SANTHOSH KUMAR,1 S. BALACHANDRAN2
1Department of Chemistry, Govt. Arts College, Thiruvananthapuram 695 014, Kerala, India
2Department of Chemistry, N.S.S. College, Cherthala 670 055, Alapuzha, Kerala, India
Received 2 June 2007; revised 14 October 2007, 6 January 2008; accepted 4 February 2008
DOI 10.1002/kin.20329
Published online in Wiley InterScience (www.interscience.wiley.com).
ABSTRACT: Kinetics of elimination of methanesulfonic acid from 1,2-diphenylethylmethane
sulfonate and its 1-p-methylphenyl- and 1-p-chlorophenyl-substituted derivatives is studied.
The results show that the elimination reaction is unimolecular (E1) as reported in the case
of 1-chloro-1-(4-methoxyphenyl)-2-phenylethane. The rate of the elimination reaction in the
presence of added weak base pyridine is independent of the concentration of the base, but
in the presence of a strong base piperidine the rate shows a linear upward drift and this is
due to the appearance of a bimolecular component along with the unimolecular pathway. The
shift from the unimolecular to bimolecular process takes place independently of the nature
of the leaving group and the parasubstituent in the 1,2-diphenylethyl substrate. ꢀ 2008 Wiley
C
Periodicals, Inc. Int J Chem Kinet 40: 481–487, 2008
to addition of nucleophilic species, giving substitution
products DN + AN (SN1), or loss of a β-hydrogen,
giving elimination products DN + ANDE (E1). As an-
other possibility, the substrate may undergo base- or
solvent-promoted bimolecular elimination reactions if
one of its β-hydrogens is acidic, which is parallel to
the ionization pathway [2,3]. Since the barrier for the
loss of hydrogen from a highly reactive carbocation is
small, the leaving group within an ion pair or the sol-
vent molecules in the solvation shell can act as a base
to effect the dehydrogenation process, which may also
INTRODUCTION
Substitution and elimination reactions often compete
with each other and generally take place simultane-
ously in solvolytic reactions [1]. Tertiary substrates
follow the ionization mechanism in solvolysis reac-
tions, and the formed carbocation may be subjected
Correspondence to: S. Balachandran; e-mail: sbcnair@sify.com.
2008 Wiley Periodicals, Inc.
c
ꢀ

482
SANTHOSH KUMAR AND BALACHANDRAN
The preparation and kinetic measurements of
1-chloro-1-(4-methoxyphenyl)-2-phenylethane is re-
ported earlier [5]. The mesylates were prepared by the
dropwise addition of methanesulfonyl chloride (3 mL)
to the corresponding alcohols (5 g) in dry pyridine
(25 mL) kept at 0◦C. The reaction mixture was stirred
for 3 h. The excess pyridine was removed by adding
the reaction mixture to 100 mL cold 6 N HCl con-
taining 75 mL ether. The water layer was extracted
twice with 50 mL portions of ether. The ether frac-
tions were combined and washed consecutively with
two 50 mL portions of water, 20 mL of 10% cad-
mium chloride solution, and 20 mL of water. After
drying over anhydrous sodium sulfate, the ether was
removed at room temperature under reduced pressure
(20 mmHg) and the residue was crystallized from pen-
tane. The solid mesylates were dried under vacuum and
stored at −10◦C under which condition they were quite
stable.
Scheme 1 Elimination reaction pathways.
be promoted by added bases. In a solvent-favoring ion-
ization, acetonitrile, the reaction undergoes a pure E1
mechanism in the absence of a suitable nucleophile [4].
In the unimolecular dehydrochlorination of 2-
chloro-2-phenylpropane (cumyl chloride) [4] and
1-chloro-1-(4-methoxyphenyl)-2-phenylethane (1-p-
anisyl-2-phenylethyl chloride) [5] in acetonitrile, it is
established that the added weak base pyridine does
not enter into the rate equation. The pyridine merely
abstracts the eliminated hydrogen chloride without in-
volving in the abstraction of β-hydrogen. The possi-
bility of substitution with a solvent [6] or base can be
completely discarded [7–9] since the product analysis
showed only the presence of alkene. In the pure E1
reaction, the product should be completely nonstere-
ospecific, since the carbocation is free to adopt its most
stable conformation before giving up the proton [1,5].
A strong base can not only neutralize the formed
acid but also abstract the β-proton, shifting the mech-
anism toward E2 (Scheme 1). A change from the uni-
molecular to bimolecular mechanism was suggested in
the presence of strong bases such as methoxide ions
in methanolysis reactions [10–12]. In methanolysis
[12,13] as well as in aqueous organic solvolysis reac-
tions [14–16], the possibility of various pathways that
are difficult to be distinguished by kinetic and product
analysis led to controversial suggestions without con-
firmative results. The E1 mechanism established re-
cently [5] in the dehydrochlorination of 1-chloro-1-(4-
methoxyphenyl)-2-phenylethane in acetonitrile, with
a lone thermodynamically stable transproduct, is a
promising system for the study of mechanistic changes
in the presence of the added strong base.
The solvent A.R. acetonitrile (BDH, Mumbai,
India) was further purified by the method of Pocker
and Wong [17], and the DMSO (BDH) was purified by
repeated distillation under vacuum.
A Hitachi 220A double-beam spectrophotometer
fitted with a thermostated cell holder and an automatic
printer was used for the rate measurements. The sol-
vents were taken in a 25-mL standard flask kept at
a thermostat, having the temperature same as that of
the thermostat attached to the spectrophotometer. The
solution of the substrate in the concentration range of
10−8 M was injected by means of a Hamilton syringe
into the flask, stirred well, and 3 mL of solution was
transferred into the cuvettes (for solid substrate a suit-
able solution in ether was prepared). The rate constants
were calculated from the monitored peak heights of
the product peaks using the integrated first-order rate
equation. The rate coefficients were also obtained by
the method of least squares [18]. All runs were con-
ducted at least in duplicate, and the mean values of the
rate constants calculated by the least-square method
were used for the analysis.
MATERIALS AND METHODS
RESULTS AND DISCUSSION
The 1,2-diphenylethyl alcohol and its p-substituted
derivatives were prepared by the Grignard reaction of
benzyl chloride (Thomas Baker & Co., Mumbai, India)
with the corresponding parasubstituted benzaldehydes.
The alcohols were extracted with suitable solvents and
purified by repeated crystallization in petroleum ether,
and the melting points were compared with the stan-
dard values. The purity of alcohols was confirmed by
TLC, and the authenticity was established by elemental
analysis, IR, and NMR spectra.
The rate coefficients for the dehydrochlorination of
1-chloro-1-(4-methoxyphenyl)-2-phenylethane inpure
acetonitrile (Scheme 2) in the presence of different ini-
tial concentrations of added pyridine (a weak base)
and piperidine (a strong base) under pseudo-first-order
conditions are given in Table I. The added weak base
pyridine has practically no effect on the rate of elimi-
nation, but the strong base piperidine increases the rate
of elimination substantially. This finding indicates that
International Journal of Chemical Kinetics DOI 10.1002/kin

KINETICS OF ELIMINATION REACTIONS OF 1,2-DIPHENYL ETHYL SUBSTRATES
483
Scheme 2 Elimination reaction in 1,2-diphenylethyl system, when X = Cl, Y = OCH3; X = OO2SCH3, Y = H, CH3, or Cl.
Table I Effect of Added Base Pyridine and Piperidine
on the Rate of Dehydrochlorination of 1-Chloro-1-
(4-methoxyphenyl)-2-phenylethane in Acetonitrile at
40.0◦C
[Base]
(M)
Pyridine
Piperidine
105 k
2
10−5k (s−1 a
)
10−5k (s−1 b
)
(M−1 s−1
)
1
1
Nil
5.42
5.44
5.46
5.42
–
5.42
–
7.47
8.17
9.68
12.4
0.050
0.10
0.20
0.30
0.50
13.8
14.2
14.0
–
Figure 1 Determination of order of the reaction by
log k versus log [piperidine]. (a) 1-p-methylphenyl-2-
1
[Substrate] = 10−8 M.
phenylethylmesylate (slope = 0.32, s = 0.0048, r = .9979),
(b) 1-p-chlorophenyl-2-phenylethylmesylate (slope = 0.73,
s = 0.0028, r = .9998), (c) 1-chloro-1-(4-methoxyphenyl)-
2-phenylethane (slope = 0.46, s = 0.0343, r = .9572),
(d) 1,2-diphenylethylmesylate (slope = 0.87, s = 0.0084,
r = .9993), where s is standard deviation and r is correlation
coefficient.
Estimated uncertainty: aless than 0.2%; bless than 0.3%.
the increase in the rate in the presence of the added
strong base piperidine is not due to any change in the
ionic strength effect as in the primary salt effect. As
shown in Scheme 1, there are two possible pathways
to accommodate the above-mentioned observation: a
complete shift in mechanism from E1 to E2, where the
base piperidine abstracts β-hydrogen, limiting the ion
pair formation to a minimum level, or a mixed mech-
anism (E1 + E2), where the base piperidine abstracts
β-hydrogen along with the unimolecular dehydrohalo-
genation. The order with respect to piperidine is deter-
mined [18] by plotting log k1 versus log [piperidine].
The slope of the linear plot was only 0.46 (plot c in
Fig. 1), suggesting the operation of a mixed mecha-
nism. The possibility of ANDE + DN (E1cB) can be
discarded on the account of the mass law effect shown
by this substrate. A rate enhancement in the presence
of weak bases like chloride ion is expected in an E1cB
mechanism, whereas a rate deceleration with a charac-
teristic mass law constant value of 11 (α = k−1/k2) is
reported in the presence of added tetrabutyl ammonium
chloride [5].
The observed rate constants in the presence of
piperidine in solvent acetonitrile represent the sum of
the rate constants for the pseudo-first-order reaction
with piperidine (excess of piperidine in solvent acetoni-
trile [19]) and the unimolecular elimination reaction.
The difference between the observed rate constants in
the presence and absence of piperidine gives the value
of the pseudo-first-order reaction with piperidine. The
second-order rate coefficients for the reaction between
piperidine and the substrate were obtained by dividing
the pseudo-first-order rate coefficients with the corre-
sponding concentrations of piperidine.
k1 − k0
k2 =
(1)
[Base]
where k1 is the observed rate constant in the presence
of added base piperidine and k0 is the first-order rate
constant in the absence of base.
The constancy of the values of the second-order rate
coefficients for all the initial concentrations of piperi-
dine suggests the operation of a mixed mechanism
(E1 + E2) for the elimination reaction in the presence
of piperidine (Table I).
Mixed mechanisms of unimolecular and bimolecu-
lar processes obey a rate law [20].
Rate = k1[S] + k2[B][S]
(2)
where k1 and k2 are the specific rate constants for uni-
molecular and bimolecular processes and [S] and [B]
are concentrations of substrate and base, respectively.
Rate
= k1 + k2[B]
(3)
[S]
A plot of the rate constant values against concentrations
of a base gave a straight line with slope, which is
International Journal of Chemical Kinetics DOI 10.1002/kin

484
SANTHOSH KUMAR AND BALACHANDRAN
Table II Kinetic Data for the Elimination of Hydrogen Chloride from 1-Chloro-1-(4-methoxyphenyl)-2-phenylethane
in Acetonitrile
[Substrate] = 10−8
−ꢀS= 298 K
M
Added
Base
Temperature
(◦C)
105k (s−1 a
at 298 K
)
ꢀH= 298 K
(kJ mol−1
ꢀG= 298 K
(kJ mol−1
1
105k (s−1 a
)
)
(J mol−1 K−1
)
)
1
24.0
35.0
40.0
50.0
1.08
3.39
5.42
Nilb
1.22
2.30
74.2 0.2
58.6 0.1
90.5 0.6
101.1 0.2
99.6 0.2
13.1
Piperidine
(0.10 M)c
19.0
24.0
35.0
40.0
1.37
2.16
5.12
7.47
137.4 0.8
243.2 0.9
105k M−1 s−1
2
(using Eq. (1))
1.08
24.0
35.0
40.0
1.73
2.05
1.13
28.8 0.1
101.3 0.2
a Estimated uncertainty is less than 2%.
b Data reported earlier in [5].
c The observed rate constants are used for the calculation of activation parameters.
and entropy of activation is −244 J K−1 mol−1. There
is a very large drop in the energy of activation (from 74
to 29 kJ mol−1) and entropy of activation (from −137
to −243 J K−1 mol−1) as suggested by Long et al.
1-Chloro-1-(4-methoxyphenyl)-2-phenylethane is
stabilized by electron donation of the p-methoxy group
and an extended system of conjugation throughout the
benzene rings. The stability of carbocation intermedi-
ate is well understood from the observed mass law and
special salt effect in acetonitrile [5,22]. The secondary
aralkyl halides have a tendency to undergo solvolysis
by a borderline mechanism, and it is a matter of
controversy among physical organic chemists for a
long time [23]. The unsubstituted compound, i.e.
1,2-diphenylethyl chloride, is a better choice to study
these aspects, especially when the steric factors
influence the stability–yield relationship of SN1–E1
process in aqueous organic solvents [24,25], but
too slow in solvent acetonitrile. A better nucleofuge
mesylate, which is 104 times faster than chloride in
1-phenylneopentyl system in aqueous acetone [26], is
selected for the study.
equal to k2 and the intercept k1. The values of k2 and
k1 obtained were 13.6 × 10−5 M−1 s−1 and 5.66 ×
10−5 −1, respectively. There is a close agreement of
s
these values with those obtained by the subtraction
method (Table I).
The activation parameters for the elimination re-
action calculated using the observed rate constants of
1-chloro-1-(4-methoxyphenyl)-2-phenylethane in the
presence of 0.10 M piperidine (Table II) show that there
is a substantial decrease in enthalpy of activation (15 kJ
mol−1) and entropy of activation (47 J K−1 mol−1). In
a bimolecular reaction, two initial state particles may
join together to form one transition-state particle, the
translational and rotational entropies of the two par-
ticles become reduced to those of one, and there is
small additional entropy of vibration but not enough
to compensate for the loss of entropy. These changes
constitute a negative contribution to entropy in the bi-
molecular process in comparison to the unimolecular
process of the same molecule. The suggestion of Long
et al. [21] that bimolecular reactions should generally
possess small positive or greater negative entropies of
activation than most nearly analogous unimolecular re-
action supports the E2 component in this reaction. The
activation parameters for the bimolecular components
of the reaction can be calculated from the calculated
values of k2 using Eq. (1) at different temperatures and
are given in Table II. For the bimolecular component of
the reaction, the enthalpy of activation is 29 kJ mol−1
The rate of elimination of methane sulfonic
acid from 1,2-diphenyl methane sulfonate and its
1-p-methylphenyl- and 1-p-chlorophenyl-substituted
derivatives is given in Table III. The rate of elimi-
nation of 1,2-diphenyl methane sulfonate in DMSO
solvent and its solvolysis rate in 90% acetonitrile are
given for comparison. In DMSO, the elimination rate
International Journal of Chemical Kinetics DOI 10.1002/kin

KINETICS OF ELIMINATION REACTIONS OF 1,2-DIPHENYL ETHYL SUBSTRATES
485
Table III Kinetic Data for the Elimination of Methane Sulfonic Acid from 1,2-Diphenylethyl Methane Sulfonate in
Acetonitrile
[Substrate] = 10−8
−ꢀS= 298 K
M
Temperature
(◦C)
105k (s−1 a
at 298 K
)
ꢀH=298 K
(kJ mol−1
ꢀG= 298 K
1
Substituent
H
105k (s−1 a
)
)
(J mol−1 K−1
)
(kJ mol−1
)
1
40.0
65.0
75.0
85.0
1.40
17.3
49.7
106
0.240
10.0
88.0 0.2
70.0 0.1
91.6 0.5
57.7 0.9
105.2 0.2
96.0 0.1
19.0
24.0
35.0
40.0
5.48
9.03
26.1
40.2
CH3
Cl
87.1 0.4
75.0
85.0
95.0
13.1
34.8
76.5
0.0575
57.5 2.0
108.7 0.6
101.1 0.5
In the presence of 0.10 M piperidine
33.0
40.0
45.0
56.0
2.48
3.96
6.40
13.9
1.23
61.2 0.4
133.8 1.3
H
In 90% aqueous acetonitrile
19.0
24.0
33.0
40.0
13.9
23.9
60.5
116
H
H
26.5
74.5 0.5
63.9 1.2
93.5 0.6
In DMSO
24.0
35.0
40.0
50.0
4.14
12.9
24.1
66.8
4.50
83.3 0.5
49.0 1.1
97.9 0.5
a Estimated uncertainty is less than 2%.
is 20 times than that in acetonitrile (dielectric constants
of acetonitrile and DMSO are 35.94 and 46.45, respec-
tively) and is characteristic for a unimolecular mech-
anism [5]. In 90% aqueous acetonitrile, the rates of
hydrolysis and elimination are measured by noting the
absorbance due to the formation of 1,2-diphenylethyl
alcohol at 265 nm and trans-stilbene at 295 nm. The
same rate observed clearly indicates a common rate-
determining step, i.e. the elimination is E1 and substi-
tution is SN1. The activation parameters in 90% ace-
tonitrile and pure acetonitrile indicate the unimolecular
mechanism [4,5]. The reduction in the rate in pure ace-
tonitrile is due to a decrease in water content rather
than a change in the nature of mechanism [4].
The free energy of activation for p-methyl is less by
9 kJ and that of p-chloro is more by 4 kJ than the un-
substituted compound. Application of Brown equation,
[27] log k/k0 = ρ+σ+, gave an average value of −5.30
for ρ+. For the standard substrate cumyl chloride in
90% acetone [22,28], it is −4.54 and for the dehy-
drochlorination reaction in acetonitrile [4] the value
is −4.73. The more negative ρ+ value observed for
the 1,2-diphenyl ethyl substrate shows more electron
demand at the carbocation center, confirming the uni-
molecular elimination. The 1,2-diphenylethyl mesylate
even though secondary undergoes the elimination re-
action by the unimolecular mechanism. The change
in the nucleofuge from chloride to mesylate does not
cause a change in the mechanism of the reaction but
only alters the rate of reaction.
The rate of elimination from p-methyl-substituted
compound is very much higher (k(p-CH )/k(p-H) = 43)
3
and that for p-chloro-substituted compound is lower
than (k(p-Cl)/k(p-H) = 0.25) the unsubstituted compound.
The effect of added pyridine and piperidine on the
rate of elimination of sulfonic acid from 1,2-diphenyl
International Journal of Chemical Kinetics DOI 10.1002/kin

486
SANTHOSH KUMAR AND BALACHANDRAN
Table IV Effect of Added Base Pyridine and Piperidine on the Rate of Elimination of Methane Sulfonic Acid from
(p-Substituted) 1,2-Diphenylethyl Methylsulfonate in Acetonitrile at 40◦C
Pyridinea
Piperidineb
105k (M−1 s−1
)
2
p-Substituent
[Base] M
10−5k (s−1
)
10−5k (s−1
)
1
1
Nil
1.40
1.41
1.39
1.42
1.40
1.38
1.40
3.96
7.56
14.1
16.7
19.6
–
0.10
0.25
0.50
0.60
0.75
25.6
24.6
25.3
25.4
24.3
H
Nil
44.8
44.5
44.6
44.7
44.8
44.8
55.1
60.3
70.5
76.0
–
0.10
0.15
0.25
0.30
103
103
103
104
CH3
Nil
1.67
1.69
1.68
1.66
1.68
1.67
2.99
4.28
5.69
8.31
–
0.10
0.20
0.30
0.50
13.2
13.1
13.4
13.3
Cl
(at 54◦C)
[Substrate] = 10−8 M.
Estimated uncertainty: aless than 2%; bless than 3%.
ethyl mesylate and its 1-p-substituted derivatives is
given in Table IV. As in the case of 1-chloro-1-(4-
methoxyphenyl)-2-phenylethane, here also the weak
base pyridine has no effect on the rate of elimination.
In the presence of the strong base piperidine, the rate
of reaction increases linearly with the concentration
of added base. The fractional orders with respect to
piperidine indicate the simultaneous occurrence of E1
and E2 mechanisms (Fig. 1).
ment by p-methyl in the absence of piperidine is
43, which is much higher than that in the presence
of piperidine. A shift from E1 to E1 + E2 reduced
the electron demand at positively charged intermedi-
ate (Scheme 1). For p-chloro-substituted compound,
(k(p-Cl)/k(p-H) is 0.25 in the absence of piperidine and
0.63 in the presence of piperidine. The reduced rate
of retardation in the presence of piperidine reflects the
less demand for electron density at the charged inter-
mediate due to the shift in the mechanism.
1,2-Diphenylethyl mesylate and its p-substituted
compounds undergo elimination of methane sulfonic
acid in acetonitrile by the E1 mechanism. The addition
of a weak base pyridine has no effect on the rate of the
reaction, indicating the absence of solvent/weak base
involvement in the stability of the reaction interme-
diate. In the presence of a strong base piperidine, all
these substrates undergo elimination by a mixed E1 +
E2 pathway. Thus, the change in the leaving group or
parasubstituents resulted the same change of mecha-
nism in the presence of the strong base piperidine even
though the extent of changes was different as shown
by the different values of fractional orders with respect
to the piperidine (Fig. 1).
The rate constant values for the bimolecular reaction
with piperidine, by t−h1e graphical method using Eq. (3),
s
−1, and
are 24.4 × 10−5
M
s
−1, 104 × 10−5 M−1
13.4 × 10−5 M−1 s−1 for 1,2-diphenylethylmesylate
and its p-methyl and p-chloro derivatives, respec-
tively. The values observed by the subtraction method
(Table IV) correlate with those obtained by the
graphical method. The enthalpy, entropy, and free
energy of activation for the elimination reaction of
1,2-diphenylethyl mesylate in the presence of 0.10 M
piperidine are 61 kJ mol−1, 134 J K−1 mol−1, and
101 kJ mol−1, respectively. The substantial decrease in
enthalpy (25 kJ mol−1) and entropy of activation (77 J
K−1 mol−1) on the addition of piperidine (Table III)
confirms the shift of mechanism from E1 to E1 + E2.
The rate of elimination in the presence of 0.10 M
piperidine from p-methyl-substituted compound is
higher (k(p-CH )/k(p-H) = 14) and that for p-chloro-
The authors express their gratitude to Dr. M R Nair (Retd.
Professor), Department of Chemistry, University of Kerala,
Trivandrum, for his guidance throughout the study.
3
substituted compound is lower than (k(p-Cl)/k(p-H) =
0.63) the unsubstituted compound. The rate enhance-
International Journal of Chemical Kinetics DOI 10.1002/kin

KINETICS OF ELIMINATION REACTIONS OF 1,2-DIPHENYL ETHYL SUBSTRATES
487
16. Richard, J. P.; Amyes, T. L.; Vontor, T. J Am Chem Soc
1991, 113, 5871.
BIBLIOGRAPHY
17. Pocker, Y.; Wong, W. H. J Am Chem Soc 1975, 97,
7097.
1. March, J. Advanced Organic Chemistry, 4th ed.; Wiley:
New York, 1999; pp. 983–998.
18. Zuman, P.; Patel, R. C. Techniques in Organic Reaction
Kinetics; Wiley: New York, 1985; p. 115.
19. Laidler, K. J. Chemical Kinetics, 3rd ed.; Pearson Edu-
cation Company: Singapore, 1987; p. 26.
20. Moore, J. W.; Pearson, R. G. Kinetics and Mechanisms,
3rd ed.; Wiley: New York, 1981; p. 289.
21. Long, F.; Pritchard, J. G.; Stafford, F. E. J Am Chem
Soc 1957, 79, 2362.
22. Balachandran, S.; Santhosh Kumar, D.; Sudha Devi, R.
Asian J Chem 2005, 17(2), 1216.
23. Shorter, J. Correlation Analysis of Organic Reactivity
with Particular Reference to Multiple Regression;
Wiley: New York, 1982.
24. Amyes, T.; Mizerski, T.; Richard, J. P. Can J Chem 1999,
77, 922.
25. Richard, J. P.; Amyes, T.; Lin, S-S.; O’Donoghue,
A. C.; Totera, M.; Tsuji, Y.; Williams, K. B. Adv Phys
Org Chem 2000, 35, 67.
26. Nair, M. R.; Nair, S. V. Indian J Chem B 1979, 18,
341.
27. Brown, H. C.; Okamoto, Y. J Am Chem Soc 1958, 80,
4979.
2. Meng, Q.; Gogoll, A.; Thibblin, A. J Am Chem Soc
1997, 119, 1217.
3. Meng, Q.; Du, B.; Thibblin, A. J Am Chem Soc 1999,
12, 116.
4. Balachandran, S.; Santhosh Kumar, D. Indian J Chem B
2005, 44, 1731.
5. Santhosh Kumar, D.; Balachandran, S. Indian J Chem B
2006, 45, 2751.
6. Meng, Q. Thibblin, A. J Am Chem Soc 1997, 119, 4834.
7. Cho, B. R.; Kim, Y. K.; Maing Yoon, C. O. J Am Chem
Soc 1997, 119, 691.
8. Cho, B. R.; Kim, Y. K.; Seong, Y. J.; Pyun, S. Y. J Org
Chem 2000, 65, 1239.
9. Pyun, S. Y.; Cho, E. J.; Seok, H. J.; Kim, J. C.; Lee,
S. H.; Cho, B. R. Bull Korean Chem Soc 2007, 28, 917.
10. Bunnett, J. F.; Eck, D. L. J Org Chem 1971, 36, 897.
11. Bunnett, J. F.; Sridharan, S. J Org Chem 1979, 44, 1459.
12. Bunnett, J. F.; Migdal, C. A. J Org Chem 1989, 54, 3037.
13. Toteva, M. M.; Richard, J. P. J Am Chem Soc 1996, 118,
11434.
14. Meng, Q.; Thibblin, A. J Chem Soc, Perkin Trans 2,
1999, 1397.
15. Amyes, T. L.; Richard, J. P. J Am Chem Soc 1991, 113,
8960.
28. Fujio, M.; Goto, M.; Mishima. M.; Tsuno, Y. Bull Chem
Soc Jpn 1990, 63, 1121.
International Journal of Chemical Kinetics DOI 10.1002/kin