Kinetics and mechanism of the aminolysis of thiophenyl methylacetates in acetonitrile

Article abstract of DOI:10.1002/1097-4601(2000)32:8<485::AID-KIN6>3.0.CO;2-X

The aminolysis of Z-thiophenyl methylacetates (C₂H₅C(double bond O)SC₆H₄Z) with X-benzylamines in acetonitrile has been investigated at 45 °C. The reaction is found to proceed by a stepwise mechanism in which the rate-determining step is the breakdown of the zwitterionic tetrahedral intermediate, T^±, with possibly a hydrogen-bonded four-center-type transition state. These mechanistic conclusions are drawn based on (i) the large magnitude of β_X (= 1.2 to approximately 2.5) and β_z (= -0.9 to approximately -1.5), (ii) the normal kinetic isotope effects (k_H/k_D?1.2) involving deuterated benzylamines (XC₆H₄CH₂ND₂), (iii) a large positive ρ_xz (= 2.4) and (iv) adherence to the reactivity-selectivity principle in all cases. The extremely large β_X (β_nuc) values can be accounted for by the loss of a strong localized cationic charge on the N atom of benzylamines in the expulsion from the T^±. The pK_a° (≥10.0) is high due to a large ratio of the expulsion rates of the amine (k_-a) to thiophenolate (k_b) (k_-a/k_b) from the T^±.

Full text of DOI:10.1002/1097-4601(2000)32:8<485::AID-KIN6>3.0.CO;2-X

Kinetics and Mechanism of
the Aminolysis of
Thiophenyl Methylacetates
in Acetonitrile
HYUCK KEUN OH,1 JIN HEE YANG,1 IN HO CHO,1 HAI WHANG LEE,2 IKCHOON LEE2
1Department of Chemistry, Chonbuk National University, Chonju 561-756, Korea
2Department of Chemistry, Inha University, Inchon 402-751, Korea
Received 17 December 1999; accepted 14 March 2000
ABSTRACT: The aminolysis of Z-thiophenyl methylacetates (C2H5C("O)SC6H4Z) with X-ben-
zylamines in acetonitrile has been investigated at 45ЊC. The reaction is found to proceed by
a stepwise mechanism in which the rate-determining step is the breakdown of the zwitterionic
tetrahedral intermediate, TϮ, with possibly a hydrogen-bonded four-center-type transition
state. These mechanistic conclusions are drawn based on (i) the large magnitude of ␤X (ϭ 1.2
ϳ 2.5) and ␤z (ϭ Ϫ0.9 ϳ Ϫ1.5), (ii) the normal kinetic isotope effects (kH/kD Х 1.2) involving
deuterated benzylamines (XC6H4CH2ND2), (iii) a large positive ␳ (ϭ 2.4) and (iv) adherence
xz
to the reactivity-selectivity principle in all cases. The extremely large ␤X (␤nuc) values can be
accounted for by the loss of a strong localized cationic charge on the N atom of benzylamines
o
in the expulsion from the TϮ. The pKa (Ն 10.0) is high due to a large ratio of the expulsion
rates of the amine (kϪa) to thiophenolate (kb) (kϪa/kb) from the TϮ. ᭧ 2000 John Wiley & Sons, Inc.
Int J Chem Kinet 32: 485–490, 2000
O
O
S
INTRODUCTION
R9COC6H4Z R9CSC6H4Z R9CSC6H4Z
The mechanism of aminolysis of oxyesters (I) has
been extensively studied. In contrast, relatively little
is known about the mechanism for the aminolysis of
thiol esters (II). The Brønsted-type plots for the re-
actions of primary, secondary, and tertiary amines
with oxyesters [e.g., substituted phenyl acetates (Ia)
and benzoates (Id)], show a break at pKao from a large
(␤nuc ϭ 0.9 Ϯ 0.1) to a small (␤nuc ϭ 0.2 Ϯ 0.2) de-
pendence of the rate on the basicity of the attacking
amine, which has been interpreted to indicate a mech-
anistic changeover from a breakdown to formation of
the tetrahedral intermediates, TϮ [1–3]. Our previous
I
II
III
O
R ϭ a. CH3
b. C2H5
d. C6H5
g.
h.
e. CH2OC6H5
S
c. OC2H5 f. NHC6H5
work on the aminolysis of thiol esters [e.g., thiophenyl
benzoates (IId)] with benzylamines [4], however,
showed an unusually large ␤nuc(␤X) value of 1.86 in
acetonitrile, which was considered to proceed through
a rate-limiting breakdown of TϮ. Benzylamines are
primary amines with relatively high basicities (pKa Ն
9.0) due to localized cationic charge on the benzylam-
Correspondence to: I. Lee (ilee@dragon.inha.ac.kr)
᭧ 2000 John Wiley & Sons, Inc.

486
OH ET AL.
monium ion. Benzylamines’ relative leaving ability
from TϮ can be much different from that of anilines
(also a primary amine, but the positive charge in the
anilinium ion delocalizes into the ring leading to
smaller pKa values) and the secondary and tertiary
amines, especially from a sulfur zwitterionic tetrahe-
dral intermediate, since it is known that ArSϪ is a
poorer nucleofuge from a tetrahedral intermediate than
an isobasic ArOϪ group [5–8].
therefore, be described completely by Eq. (5), where
Ar ϭ C6H4Z, XNH represents benzylamines with sub-
stituent X. The proton transfer can occur during or
after the rate-limiting step, kb. The proton is of course
rapidly consumed as XNH2 under the excess amine
concentration, as shown in Eq. (1).
ϩ
O
ka
In this work, we carried out kinetic studies on the
aminolysis of thiophenyl methylacetates (IIb) with
benzylamines in acetonitrile at 45ЊC, Eq. (1). We aim
to elucidate the mechanism of the aminolysis,
Eq. (1), of thiol esters with an ethyl group, C2H5
C2H59C9SAr ϩ XNH
ka
ϪO
kb
C2H59C9SAr
ϩ
HNX
TϮ
O
MeCN
O
2 XC6H4CH2NH2 ϩ C2H5CSC6H4Z
45°C
C2H59C9NX ϩ ArSϪ ϩ Hϩ (5)
O
C2H5CNHCH2C6H4X ϩ ϩNH3CH2C6H4X
ϩ ϪSC6H4Z (1)
ka
kN ϭ
kb ϭ K kb
(6)
kϪ
a
(IIb) rather than phenyl, C6H5 (IId). Our interests in
this work also lie in the unusually large ␤nuc(␤X) values
obtained in the aminolysis of thiol esters with benzy-
lamines in acetonitrile, and application of the cross-
Since the reactions were conducted in acetonitrile,
the magnitude of ␤X(␤nuc) and ␤Z(␤lg) determined us-
ing the pKa values in water may not be reliable. How-
ever, as we have pointed out previously [11–12], the
␤X values can be considered to represent reliable val-
ues, although the absolute values of pKa in MeCN dif-
fer from those in water, a constant ⌬pKa (pKCH3CN Ϫ
pKH2O Х 7.7 Ϯ 0.3) was experimentally found [13].
Our recent theoretical work of the solvent effects on
the basicities of pyridines [14] has shown that the
⌬pKa (Х 7.7) value arises solely from the ion solvation
energy difference of Hϩ ion in water and in acetoni-
interaction constant [9–10], ␳ in Eq. (2), where X
xz
and Z denote substituents in the nucleophile and leav-
ing group, respectively, as a mechanistic tool.
log(kXZ/kHH) ϭ ␳ ␴X ϩ ␳ ␴Z ϩ ␳ ␴ ␴
XZ X Z
(2a)
(2b)
X
Z
␳
XZ ϭ Ѩ␳Z/Ѩ␴X ϭ Ѩ␳X/Ѩ␴
Z
RESULTS AND DISCUSSION
trile, ␦⌬Gso(Hϩ) ϭ 10.5 kcal molϪ , which corre-
1
sponds to ⌬pKa ϭ 7.7, at the MP2/6-31G*//MP2/6-
31G* level [15] of theory. Moreover, we are
comparing the magnitude of ␤X and ␤Z values deter-
mined for the reactions carried out under the same
reaction condition (i.e., in acetonitrile). Since we used
pKa values of thiophenolates in water, the comparison
of ␤Z values may not be entirely reliable.
We note that the magnitude of ␤X in Table I (␤X ϭ
1.2 ϳ 2.5) is considerably larger than those for the
corresponding reactions with anilines [16] and other
secondary and tertiary amines (␤X ϭ 0.6 ϳ 1.0) pro-
ceeding by rate-limiting breakdown (kb) of a zwitter-
ionic tetrahedral intermediate, TϮ, Eq. (5). On this ac-
count (i.e., large ␤X values), the aminolysis of
thiophenyl methylacetates with benzylamines in ace-
tonitrile, Eq. (1), is most likely to occur by rate-lim-
iting expulsion, kb, in Eq. (5), of thiophenolate ion,
ArSϪ, from TϮ.
The aminolysis of thiophenyl methylacetates (IIb)
with a large excess of benzylamines in acetonitrile
obeyed the simple kinetic law given by Eqs. (3) and
(4), where P is thiophenolate anion and N is benzy-
lamine. Plots of kobs against [N] were linear, and the
kN values were determined from the slopes of these
plots. The kN values are summarized in Table I, where
the ␳x, ␤x(␤nuc), ␳Z, and ␤Z(␤lg) values are also shown.
d[P]/dt ϭ kobs [substrate]
obs ϭ kN [N]
(3)
(4)
k
The clean second-order kinetics obtained, Eqs. (3)
and (4), is an indication that there are no complications
arising from competition of the fast proton transfer
from an intermediate TϮ, nor from general base catal-
ysis by the amines. The mechanism of the reaction can,

AMINOLYSIS OF THIOPHENYL METHYLACETATES IN ACETONITRILE
487
Table I The Second-Order Rate Constants kN ϫ 103 dm3 molϪ1 sϪ1 for the Reactions of Z-Thiophenyl
Methylacetates with X-Benzylamines in Acetonitrile at 45ЊC
Z
a
b
X
p-Me
H
p-Cl
m-Cl
␳
␤
z
z
13.6
10.7c
185
146
114
141
90.6
p-OMe
26.8
16.2
7.37
2.34
92.1
2.12 Ϯ 0.09
Ϫ0.90 Ϯ 0.01
8.29d
p-Me
H
78.2
3.08
0.759
Ϫ2.48 Ϯ 0.03
2.51 Ϯ 0.01
66.0
34.4
14.6
2.37 Ϯ 0.11
2.74 Ϯ 0.11
3.33 Ϯ 0.10
Ϫ1.01 Ϯ 0.01
Ϫ1.18 Ϯ 0.02
Ϫ1.39 Ϯ 0.05
p-Cl
47.5
Ϫ1.18 Ϯ 0.01
1.20 Ϯ 0.01
a
␳
␤
Ϫ2.09 Ϯ 0.02
2.11 Ϯ 0.01
Ϫ1.62 Ϯ 0.01
1.64 Ϯ 0.02
x
e
x
a The ␴ values were taken from Dean, J. A. Handbook of Organic Chemistry; McGraw-Hill: New York, 1987; Table 7–1. Correlation
coefficients were better than 0.998 in all cases.
b The pKa values were taken from Buckingham, J. Dictionary of Organic Chemistry; Chapman and Hall; New York, 1982; 5th, ed. The
pKa value for Z ϭ m-Cl was estimated using pKa ϭ Ϫ2.36␴ ϩ 6.45 (n ϭ 3, r ϭ 0.996). Correlation coefficients were better than 0.998 in
all cases.
c At 35ЊC.
d At 25ЊC.
e The pKa values were taken from Fischer, A.; Galloway, W. J.; Vaughan, J. J Chem Soc 1964, 3588. Correlation coefficients were better
than 0.999 in all cases. The pKa value for X ϭ p-CH3O was estimated using the relation: pKa ϭ Ϫ1.057␴ Ϯ 9.355 (n ϭ 13, r ϭ 0.984).
We have compared ␤X and ␤Z values for the ami-
nolysis reactions of various thiol esters with benzy-
lamines in acetonitrile in Table II. The magnitude of
both ␤X and ␤Z is large compared to those for the
corresponding reactions with anilines and other sec-
ondary and tertiary amines proceeding by rate-limiting
breakdown of TϮ. For example, the aminolysis of
phenyl dithiobenzoates (IIId) with anilines [17] gave
the ␤X values ranging from 0.80 to 1.07 in acetonitrile
at 55ЊC. This reaction is believed to proceed by rate-
limiting breakdown of TϮ. Similarly, for the amino-
lysis of dithioacetates [11] (IIIa) with anilines and
N,N-dimethylanilines in acetonitrile, the ␤X values of
0.80 ϳ 0.87 were obtained. For these two series, IIIa
and IIId, the push provided by ArS from TϮ to expel
observed kN is a complexquantity given by Eq. (6).
Therefore, the dependence of log kN on the basicity of
amines becomes
␤X (ϭ ␤nuc) ϭ dlog kN/dpKa(X)
ϭ dlog ka/dpKa(X)
Ϫ dlog kϪ /dpKa(X)
a
ϩ dlog kb/dpKa(X)
(7)
The rate constant for leaving group expulsion from
TϮ(kb) can be safely assumed to be independent of the
nature of the attacking amine nucleophile [2,19], so
that the last term in Eq. (7) vanishes. On the other
hand, it is well known that the ␤X values for the rate-
limiting formation of TϮ(␤a) is lower with 0.2 ϳ 0.3,
␤a (ϭ dlog ka/dpKa(X)) Х 0.2 ϳ 0.3 [2]. This means
that the observed ␤X(␤nuc) ϭ 1.2 ϳ 2.5 for the ami-
the amine, benzylamine, is much hindered (i.e., kϪ /kb
a
is reduced) due to change of
to
in TϮ
SϪ
OϪ
9C9 9C9
[18]. It is known that the decrease in kϪ /kb either by
nolysis with benzylamines lead to the ␤Ϫa (ϭ dlog kϪ /
a
a
increasing kb with a better nucleofuge or by decreasing
dpKa(X)) value of Ϫ0.9 ϳ Ϫ2.2 [ϭ (0.2 ϳ 0.3) Ϫ
(1.2 ϳ 2.5)]. For aniline nucleophiles, ␤X Х 0.8 ϳ 1.0
so that ␤Ϫa ϭ Ϫ0.5 ϳ Ϫ0.7. Thus the loss of a strong
localized cationic charge on the nitrogen atom of ben-
zylammonium ion in the TϮ is so large that the ben-
zylamine expulsion rates from TϮ are 2 ϳ 3 times
more sensitive to the substituent variation in the ben-
zylamine than the sensitivity of aniline expulsion rates
from the corresponding TϮ to the substituent charge
kϪ with a weakly basic amine leads to a lowering of
a
pKao, where kϪ ϭ kb [8].Thus the pKao value should
a
be lower in the dithio series (III, pKao Յ 9.0) than that
in the corresponding thiol series (II, pKao Ն 10). This
is the reason why the expulsion of ArSϪ from TϮ is
rate-limiting for IId, while a concerted mechanism or
a rate-limiting formation of TϮ applies to IIId.
The ␤X (␤nuc) values for the aminolysis with ben-
zylamines for which breakdown of TϮ is rate-limiting
are large (␤X ϭ 1.2 ϳ 2.5). For such mechanism, the
in the aniline. For this reaction, the ratio kϪ /kb is also
a
high so that the pKao lies above the pKa’s of the con-

488
OH ET AL.
Table II The ␤X(␤nuc) and ␤Z(␤1g) Values for Acyl Transfer Reactions with Benzylamine Nucleophiles in Acetonitrile
O
O
S
R9COC6H4Z R9CSC6H4Z R9CSC6H4Z
I
II
III
O
R ϭ a. CH3
b. C2H5
d. C6H5
g.
h.
e. CH2OC6H5
S
c. OC2H5 f. NHC6H5
a
a
␤
Substrate
␤
X
Remarks
Ref.
Z
Ic
Ie
If
Ig
IIb
IId
IIg
IIh
IIIa
IIId
IIIg
IIIh
1.66
1.57
1.65
1.06
2.11
1.86
1.40
1.53
0.55
0.60
1.40
1.02
Ϫ1.71
Ϫ1.77
Z ϭ p-NO2, 25ЊC
Z ϭ p-NO2, 25ЊC
Z ϭ p-NO2, 25ЊC
Z ϭ p-NO2, 25ЊC
45ЊC
12
b
c
d
Ϫ1.03
Ϫ1.18
Ϫ1.63
Ϫ1.41
Ϫ1.42
Ϫ0.50
Ϫ0.24
Ϫ0.81
Ϫ0.56
This work
55ЊC
50ЊC
50ЊC
20ЊC
30ЊC
15ЊC
15ЊC
e
22
22
11
f
23
23
a Unless otherwise noted, ␤X is for Z ϭ H and ␤Z is for X ϭ H.
b Koh, H. J.; Kim, T. Y.; Lee, B. S.; Lee, I. J Chem Res (S) 1996, 482.
c Koh, H. J.; Kim, O. S.; Lee, H. W.; Lee, I. J Phys Org Chem 1997, 10, 725.
d Koh, H. J.; Lee, J. W.; Lee, H. W.; Lee, I. New J Chem 1997, 21, 447.
e Lee, I.; Koh, H. J. New J Chem 1996, 20, 131.
f Oh, H. K.; Shin, C. H.; Lee, I. Bull Korean Chem Soc 1995, 16, 657.
jugate acids of benzylamines used in this work. This
poorer nucleofugality of ArSϪ than ArOϪ (smaller kb)
high ratio of kϪ /kb can be attributed to several factors.
and the stronger “push” provided by the ArS group in
a
(i) The low stability of TϮ formed (larger kϪ ) by ben-
TϮ (larger kϪ ) to expel the amine than that exerted by
a
a
zylamines due to highly localized cationic charge on
the Nϩ 9H moiety. The tetrahedral intermediates TϮ
formed by anilines and secondary and tertiary amines
an isobasic ArO group in an analogous TϮ [8]. The
pKao was lower for pyridines than for alicyclic amines
under the same reaction conditions due to the lower
are relatively stable (smaller kϪ ) due to cationic
kϪ , whereas it was lower for a more delocalized phen-
a
a
charge delocalization to the ring and/or alkyl groups
(inductive donors, ϩI groups) within TϮ. (ii) The
olate ion (2,4,6-trinitrophenolate ion) expulsion due to
the higher kb value [8,20]. (iii) The aprotic solvent,
Table III The Secondary Kinetic Isotope Effects for the reactions of Z-Phenyl Thiolmethylacetates with Deuterated
X-Benzylamines in Acetonitrile at 45ЊC
Ϫ
Ϫ
1
Ϫ
Ϫ1
X
Z
kH ϫ 104(M 1 s
)
kD ϫ 104(M 1 s
)
kH/kD
p-OMe
p-OMe
p-OMe
p-OMe
p-Cl
p-Cl
p-Cl
p-Cl
p-Me
H
pCl
m-Cl
p-Me
H
p-Cl
m-Cl
1.36 (Ϯ 0.02)
2.68 (Ϯ 0.05)
9.21 (Ϯ 0.06)
18.5 (Ϯ 0.3)
0.0759 (Ϯ 0.0004)
0.234 (Ϯ 0.003)
1.46 (Ϯ 0.02)
1.11 (Ϯ 0.02)
2.19 (Ϯ 0.04)
7.62 (Ϯ 0.05)
15.6 (Ϯ 0.2)
0.0612 (Ϯ 0.0005)
0.192 (Ϯ 0.004)
1.22 (Ϯ 0.03)
1.23 Ϯ 0.03a
1.22 Ϯ 0.04
1.21 Ϯ 0.01
1.19 Ϯ 0.02
1.24 Ϯ 0.01
1.22 Ϯ 0.03
1.20 Ϯ 0.04
1.18 Ϯ 0.02
4.75 (Ϯ 0.04)
4.03 (Ϯ 0.06)
a Standard deviations.

AMINOLYSIS OF THIOPHENYL METHYLACETATES IN ACETONITRILE
489
Table IV Activation Parametersa for the Reactions of
Z-Phenyl Thiolmethylacetates with X-Benzylamines in
Acetonitrile
MeCN, stabilizes the TS for the breakdown of TϮ to
form uncharged products (kϪ ) relative to that for the
a
formation of thiophenolate anion and cationic amide
(kb).
ꢀ
Ϫ
1
ꢀ
Ϫ
Ϫ1
X
Z
⌬H /kcal mol
Ϫ⌬S /cal mol 1 K
The proposed mechanism is also supported by a
p-OMe p-Me
p-OMe m-Cl
4.1 Ϯ 0.1
4.0 Ϯ 0.1
4.6 Ϯ 0.1
3.9 Ϯ 0.1
55 Ϯ 1
53 Ϯ 1
60 Ϯ 1
53 Ϯ 1
large positive cross-interaction constant [9] (␳
ϭ
XZ
2.36 Ϯ 0.16, r ϭ 0.999) and adherence to the reactiv-
ity–selectivity principle (RSP), which are believed to
constitute necessary conditions for the rate-limiting
breakdown of TϮ [20,21]. The secondary kinetic iso-
tope effects (Table III) involving deuterated nucleo-
philes [10], XC6H4CH2ND2, are greater than unity, kH/
kD Х 1.2. This suggests a possibility of forming
hydrogen-bonded, four-center-type TS as has often
been proposed [22,23]. However, due to a lower
charge on the thiophenolate leaving group, the kH/kD
values are not high and variations depending on the
substituents, X and Z, are small. The low activation
m-Cl
m-Cl
p-Me
m-Cl
a Calculated by the Eyring equation. Errors shown are standard
deviations.
in all cases. These are in line with the proposed mech-
anism.
EXPERIMENTAL
Materials
d2
OϪ
Merk GR acetonitrile was used after three distillations.
The benzylamine nucleophiles, Aldrich GR, were used
without further purification. Thiophenols and pro-
pionyl chloride were Tokyo Kasei GR grade.
d2
C2H59C
S
Z
dϩ
dϩ
HN
CH2
H
Preparations of Phenyl
Thiolmethylacetates
Thiophenol derivatives and propionyl chloride were
dissolved in anhydrous ether and KOH was added
carefully, keeping the temperature at 0 ϳ 5ЊC. Ice was
then added to the reaction mixture and the ether layer
was separated, dried over MgSO4, and distilled under
reduced pressure to remove solvent. IR (Nicolet 5BX
X
Proposed TS
ꢀ
ꢀ
parameters, ⌬H and ⌬S (Table IV) are also in line
with the mechanism proposed. The expulsion of thio-
phenolate anion is aided by hydrogen bonding by the
benzylamine present in TϮ requiring not much energy
in the activation, but highly structured TS leads to
large negative entropies of activation.
1
FT-IR) and H and 13C NMR (JEOL 400 MHz) data
are as follows.
p-Methylphenyl Thiolmethylacetate. Liquid, IR
(KBr), 2979 (C9H, CH2), 2938 (C9H, CH3), 1494,
1459 (C"C, aromatic), 1710 (C"O); 1H NMR (400
MHz, CDCl3), 1.61 (3 H, t, CH3, J ϭ 6.35 Hz), 2.31
(3 H, s, CH3), 2.60 (2 H, q, CH2,, J ϭ 6.35 Hz), 7.16–
7.26 (4 H, m, aromatic ring); 13C NMR (100.4 MHz,
CDCl3), 198.4 (C"O), 139.4, 134.4, 129.9, 124.3 (ar-
omatic), 36.9 (CH2), 21.2 (CH3), 9.57 (methyl).
SUMMARY
The aminolysis of thiophenyl methylacetates with ben-
ylamines in acetonitrile proceeds by rate-limiting ex-
pulsion of thiophenolate anion from a tetrahedral zwit-
terionic intermediate TϮ. The extremely large ␤X(␤nuc
values can be accounted for by a strong localized cat-
ionic charge on the nitrogen atom of benzylamines in
TϮ, which is lost in the benzylamine expulsion from
TϮ (kϪ ). The breakdown rate ratio of kϪ (expulsion
of amine)/kb (expulsion of ArSϪ) is large due to large
kϪa and relatively small kb. The cross-interaction con-
)
Phenyl Thiolmethylacetate. Liquid, IR (KBr), 2993
(C9H, CH2), 2939 (C9H, CH3), 1477, 1440 (C"
1
C, aromatic), 1710 (C"O); H NMR (400 MHz,
CDCl3), 1.19 (3 H, t, CH3, J ϭ 6.35 Hz), 2.63 (2 H,
q, CH2,, J ϭ 6.44 Hz), 7.41–7.36 (5 H, m, aromatic
ring); 13C NMR (100.4 MHz, CDCl3), 198.1 (C"O),
134.5, 129.8, 129.3, 129.0, 127.4 (aromatic), 37.1
(CH2), 9.58 (methyl).
a
a
stant ␳ is large positive and the RSP is adhered to
XZ

490
OH ET AL.
p-Chlorophenyl Thiolmethylacetates. Liquid, IR
(KBr), 2980 (C9H, CH2), 2946 (C9H, CH3), 1477,
1460 (C"C, aromatic), 1712 (C"O); 1H NMR (400
MHz, CDCl3), 1.18 (3 H, t, CH3, J ϭ 7.81 Hz), 2.64
(2 H, q, CH2,, J ϭ 7.81 Hz), 7.28–7.35 (4 H, m, ar-
omatic ring); 13C NMR (100.4 MHz, CDCl3), 197.5
(C"O), 135.7, 135.6, 126.3 (aromatic), 37.1 (CH2),
9.51 (methyl).
CDCl3), 198.2 (C"O), 130.8, 129.3, 129.1 (aro-
matic), 55.4 (CH2), 42.87 (CH2), 21.0 (methyl), 14.18.
The authors wish to acknowledge the financial support of
the Korea Research Foundation made in the program year
of 1998. I. Lee also thanks Inha University for the continued
support for this series of work.
m-Chlorophenyl Thiolmethylacetate. Liquid, IR
(KBr), 2972 (C9H, CH2), 2932 (C9H, CH3), 1462,
1408 (C"C, aromatic), 1714 (C"O); 1H NMR (400
MHz, CDCl3), 1.20 (3 H, t, CH3, J ϭ 7.33 Hz), 2.67
(2 H, q, CH2,, J ϭ 7.33 Hz), 7.27–7.41 (4 H, m, ar-
omatic ring); 13C NMR (100.4 MHz, CDCl3),
197.2(CϭO), 134.6, 134.2, 132.6, 130.1, 129.5,
129.4(aromatic), 37.2(CH2), 9.52(methyl).
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CH3CH2C("O)NHCH2C6H4 9OCH3. : m.p, 55–
57ЊC, IR (KBr), 3249 (N9H), 3080 (C9H, benzyl),
2993 (C9H, CH2), 2946 (C9H, CH3), 1711 (C"
1
O), 1460 (C"C, aromatic); H NMR (400 MHz,
CDCl3), 1.12 (3 H, t, CH3, J ϭ 7.81 Hz), 2.19 (2 H,
q, CH2,, J ϭ 7.81 Hz), 3.75 (3 H, s, OCH3), 4.08 (1
H, br, N9H), 4.29 (2 H, d, J ϭ 5.86 Hz, CH2), 6.81–
7.16 (4 H, m, aromatic ring); 13C NMR (100.4 MHz,
24. Guggenheim, E. A. Phil Mag 1926, 2, 538.