The mechanisms of acid-catalyzed hydrolysis of n-(4-substituted arylthio) phthalimides

Article abstract of DOI:10.1080/10426507.2010.517584

The acid-catalyzed hydrolysis of N-(4-substitutedarylthio)phthalimides was studied in aqueous solutions of sulfuric, perchloric, and hydrochloric acids at 40.0 ±0.1° C. Analysis of the data by the excess acidity method, activation parameters, and substituent effects indicates hydrolysis by an A-2 mechanism at low acidity. At higher acidities, a changeover to an A-1 mechanism is observed.

Full text of DOI:10.1080/10426507.2010.517584

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Phosphorus, Sulfur, and Silicon and the
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The Mechanisms of Acid-Catalyzed
Hydrolysis of N-(4-Substituted Arylthio)
Phthalimides
Halil Kutuk a & Hasan Yakan a
a Ondokuz Mayis University, Faculty of Arts and Sciences, Chemistry
Department , Kurupelit , Samsun , Turkey
Published online: 04 Aug 2011.
To cite this article: Halil Kutuk & Hasan Yakan (2011) The Mechanisms of Acid-Catalyzed Hydrolysis
of N-(4-Substituted Arylthio) Phthalimides, Phosphorus, Sulfur, and Silicon and the Related Elements,
186:7, 1460-1469, DOI: 10.1080/10426507.2010.517584
To link to this article: http://dx.doi.org/10.1080/10426507.2010.517584
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Phosphorus, Sulfur, and Silicon, 186:1460–1469, 2011
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2010.517584
THE MECHANISMS OF ACID-CATALYZED HYDROLYSIS
OF N-(4-SUBSTITUTED ARYLTHIO) PHTHALIMIDES
Halil Kutuk and Hasan Yakan
Ondokuz Mayis University, Faculty of Arts and Sciences, Chemistry Department,
Kurupelit, Samsun, Turkey
GRAPHICAL ABSTRACT
Abstract The acid-catalyzed hydrolysis of N-(4-substitutedarylthio)phthalimides was studied
in aqueous solutions of sulfuric, perchloric, and hydrochloric acids at 40.0 0.1 ◦C. Analysis
of the data by the excess acidity method, activation parameters, and substituent effects indicates
hydrolysis by an A-2 mechanism at low acidity. At higher acidities, a changeover to an A-1
mechanism is observed.
Keywords Acid-catalyzed hydrolysis; arylthiophthalimides; excess acidity; sulfenimides
INTRODUCTION
N- of trichloromethanesulfenylchloride with sodium phthalimide was the first sulfen-
imide(thiophthalimide) 1 reported in the literature. The synthesis of some arylthiophthal-
imides was reported by Klivenye and coworkers.2 Several sulfenimides were prepared by
Bu¨chel and Conte3 by the reaction of disulfides with the desired N-bromoimides. Alkyl and
aryl sulfenimides have been synthesized by the reaction of sulfenyl chlorides with imides in
the presence of a tertiary amine.4 The stability of sulfenyl chloride solutions has been found
to be dependent on the temperature and the polarity of the solvent.4 Some sulfenimides
Received 22 June 2010; accepted 18 August 2010.
Address correspondence to Prof. Dr. Halil Kutuk, OMU Fen-Ed. Fakultesi, Kimya Bolumu, Kurupelit,
Samsun 55139, Turkey. E-mail: hkutuk@omu.edu.tr
1460

ACID-CATALYZED HYDROLYSIS
1461
function as sulfenyl transfer reagents and can be used to prepare sulfenamides 2. When
thiophthalimides react with thiols to form unsymmetrical disulfides 3 and phthalimide. The
thiophthalimides are the best known of these reagents (Eqs. (1) and (2)).5,6
O
O
NH
R2
H
N
N
S R
+
+
R
S N
(1)
R1
R2
R1
O
O
sulfenamides
sulfenimides
1
2
O
O
N
S R
R'SH
RSSR'
+
(2)
+
NH
3
O
O
A study of the kinetics and mechanism of the acid-catalyzed hydrolysis of a se-
ries of N-(4-substituted arylsulfinyl)phthalimides,7 amidosulfites,8 N-(4-substituted aryl-
sulfonyl)phthalimides,9 arenesulfinamides,10 and benzohydroxamic acids11 have been stud-
ied in concentrated aqueous mineral acids in our laboratory. There has been no system-
atic study of the acid-catalyzed hydrolysis of N-(4-substituted arylthio)phthalimides in
highly acidic solutions. We report a complementary study of acid-catalyzed hydrolysis of
a series of N-(4-substituted arylthio)phthalimides (4a–c) in concentrated aqueous mineral
acids as shown in Scheme 1.
O
R
S N
O
4 a: R = H
b: R = CH3
c: R = Cl
Scheme 1
RESULTS AND DISCUSSION
The first-order rate coefficients, k1, for the hydrolysis of N-(4-methylphenylthio)
phthalimide 4b in aqueous solutions of mineral acids are shown in Figure 1. Rate maxima
are observed for both perchloric and hydrochloric acid because hydrolysis was studied

1462
H. KUTUK AND H. YAKAN
Figure 1 Plots of k1 for the acid-catalyzed hydrolysis of 4b in aqueous acid solutions at 40.0 ◦C; , HCl;
H2SO4; ꢀ, HClO4.
,
•
over a wider range of acidity. In all cases, the rates of hydrolysis decrease continuously
with increasing concentration of sulfuric acid up to 7.00 M, whereas at acid concentrations
above 8.00 M the rate increases and there is an indication of a rate maximum about 12.00
M (Table 1). Values of k1 for the perchloric acid-catalyzed hydrolysis of 4a–c are shown
in Figure 2.
The order of catalytic effectiveness of the acids observed for the hydrolysis of 4b
was HCl H SO > HClO at low acidity. Bunton et al.12,13 suggested that such an order
is characteristic of a bimolecular (A-2) mechanism, because the transition states of positive
character are preferentially stabilized by anions of high charge density such as Cl−, whereas
the opposite is usually the case for an A-1 mechanism.
∼
=
2
4
4
The kinetic data in Table 1 were also analyzed by the excess acidity treatment of Cox
and Yates.14 A simplified version of their relationship for mainly unprotonated substrates
Figure 2 Plots of k1 for the perchloric acid–catalyzed hydrolysis of 4a–c at 40.0 ◦C; , p-CH3; , p-H; ꢀ, p-Cl.
•

ACID-CATALYZED HYDROLYSIS
1463
Table 1 Values of 104 k1 (s−1) for the hydrolysis of N-(4-substituted arylthio) phthalimides at 40.0 0.1 ◦C
4a
4b
4c
Acid (M)
H2SO4
HClO4
HCl
H2SO4
HClO4
HCl
H2SO4
HClO4
HCl
0.50
1.00
2.00
2.50
3.00
3.50
4.00
4.50
5.00
5.50
6.00
6.50
7.00
8.00
9.00
10.00
11.00
11.50
12.00
12.50
13.00
14.00
15.00
15.50
16.00
17.00
—
—
1.22
1.43
—
1.86
—
2.49
—
2.56
—
1.03
1.40
1.49
—
1.25
—
1.11
—
1.08
—
—
—
0.93
1.13
—
1.86
—
2.25
2.36
2.63
2.86
3.30
3.88
4.02
3.52
3.06
—
—
1.04
1.41
1.48
—
0.94
—
0.58
—
0.41
—
1.08
1.47
1.75
—
1.64
—
1.27
—
1.03
—
1.66
1.57
—
1.46
—
1.29
—
1.05
—
4.26
4.00
—
3.66
—
3.16
—
2.49
—
2.34
1.89
—
1.22
—
0.81
—
0.47
—
2.55
—
3.27
3.72
3.84
3.57
3.01
2.75
2.94
3.68
—
—
—
—
—
0.72
—
2.14
—
1.17
—
1.38
—
2.51
—
0.23
—
0.33
—
1.11
—
0.54
0.49
0.68
1.35
1.87
—
2.03
1.80
0.95
0.35
0.28
—
1.82
2.03
2.23
2.41
—
—
—
—
—
—
—
—
—
1.32
1.63
2.15
2.98
3.82
—
—
—
—
—
0.61
0.39
0.56
0.99
1.72
2.64
3.04
2.86
2.23
1.56
1.37
1.98
3.23
4.69
2.37
2.54
2.77
3.12
3.93
—
—
—
—
—
0.28
0.37
0.53
0.71
0.81
—
0.94
—
0.84
0.29
0.13
—
0.37
0.44
0.6
0.87
—
—
—
—
—
—
—
—
—
1.27
1.52
1.94
2.55
3.62
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
1.13
2.85
0.24
0.44
—
—
—
(Eq. (3)) was used.
log k1 − log CH+ − log Cs/(Cs + CSH+) = m∗m=X + r log aNu + log (ko/KSH+
)
(3)
+
In Eq. (3), k1 is the pseudo first-order rate constant, CH is the concentration of
aqueous acid, X is the excess acidity constant, and m∗ m= is the combined slope parameter,
where m= is characteristic of the type of reaction (for A-1 processes m= > 114; for A-2
14
∗
processes m= 1 ), and m is obtained from protonation studies; r log a for the A-2
∼
=
Nu
reaction represents the nucleophilic activity, where r is the number of water molecules
involved in forming the transition state.
Due to the extremely low basicity of the N-(4-substituted arylthio)phthalimides stud-
ied, the protonation correction term [log Cs/(Cs + CSH+)] can be neglected. Values of X
for the aqueous solution of the acid were used.15,16
+
A plot of log k1 − logCH versus X is shown in Figure 3 for the hydrolysis of
4b in sulfuric acid solution. Similar graphs were observed for 4a and 4c in sulfuric acid
solution. Initially, all such graphs for the arylthiophthalimides in the low-acidity region
exhibit downward curvature, typical of A-2 reactions involving water.17
As can be seen in Figure 3, in the 1.00–8.00 M region with increasing acid con-
centration, the plot shows that the rate of reaction was reduced and there was no catalytic
effect of the acids. With increasing acid concentration, the activation of water decreased

1464
H. KUTUK AND H. YAKAN
Figure 3 Plots of log k1 − logCH+ versus excess acidity (X) for the sulfuric acid–catalyzed hydrolysis of 4b at
40.0 ◦C.
and so the rate of reaction was reduced. After 8.00 M with increasing acid concentration,
the rate of hydrolysis increased and there was a catalytic effect of the acids. A curve is ob-
served in the 9.00–14.00 M region. A straight line was obtained in the acidity region (9.00–
14.00 M); values of 3 logaH2O can be subtracted from the left-hand side of Eq. (3) and the
result plotted against X. A good straight line correlation (Figure 4 and Table 1 where r = 3)
is obtained for arylthiophthalimides. These changes with increasing acidity to an upward
linear region are characteristic of an A-1 process. This suggests that a gradual changeover
in mechanism from A-2 to A-1 occurs with increasing concentration of acid.
Similar behavior has been observed for the hydrolysis of azophenyl ether,16 N-methyl-
N-nitrobenzamides,18 benzohydroxamic acids,11 and p-substituted phenyl N-(-4-substituted
arylamino)sulfonate esters.19
The temperature dependence of the rate constants of the hydrolysis reaction was
analyzed by a least-squares procedure using a spreadsheet program (Eyring equation).
Figure 4 Plots of log k1 − logCH+ versus excess acidity for the 9.00–14.00 M sulfuric acid–catalyzed hydrolysis
of 4b at 40.0 ◦C.

ACID-CATALYZED HYDROLYSIS
1465
Table 2 Values of 104 k1 (s−1) for the hydrolysis of 4a–c at different temperatures
Acid (M)
Compounds
30.0 ◦C
35.0 ◦C
40.0 ◦C
45.0 ◦C
50.0 ◦C
1.00 M HCIO4
5.00 M HCIO4
10.00 M HCIO4
1.00 M HCI
5.00 M HCI
10.00 M HCI
1.00 M H2SO4
4a
0.63
1.38
1.06
0.69
0.48
1.17
0.79
1.85
1.18
0.52
0.99
0.21
0.57
0.42
0.33
0.53
0.056
0.31
0.76
0.06
0.88
1.82
1.48
0.94
0.69
2.05
1.15
2.73
1.69
0.77
1.55
0.33
0.90
0.64
0.46
0.88
0.083
0.57
1.71
0.12
1.22
2.56
2.41
1.40
1.08
2.98
1.66
4.26
2.34
1.05
2.49
0.47
1.35
0.99
0.71
1.37
0.130
1.13
3.23
0.24
1.70
3.53
3.40
1.92
1.53
4.90
2.37
6.04
3.15
1.75
3.45
0.65
2.01
1.48
0.98
2.19
0.194
1.97
5.65
0.56
2.23
4.82
4.54
2.41
2.12
7.38
3.13
7.67
4.11
2.38
5.00
0.91
2.99
2.40
1.41
3.49
0.296
4.67
9.38
0.97
4a
4b
4c
4a
4b
4c
4a
4b
4c
4b
4c
4a
4b
4c
5.00 M H2SO4
10.00 M H2SO4
15.00 M H2SO4
16.00 M H2SO4
The values at different temperatures and Arrhenius parameters are shown in Tables 2 and
3, respectively. Acid-catalyzed hydrolyses of esters and amides20 proceeding by an A-1
mechanism have ꢀS= of about 0 to −41.8 JK−1mol−1, whereas those proceeding by an
A-2 mechanism have ꢀS= of −62.8 to −125.5 JK−1mol−1. Over the range 1.00–16.00 M
Table 3 Arrhenius parameters for the hydrolysis of N-(4-substituted arylthio) phthalimides
Compounds
Acid
[H+]/M
ꢀH= (kJ/mol)
ꢀS= (J/molK)
Temperature Range (◦C)a
R2
HClO4
1.00
5.00
10.00
1.00
5.00
10.00
1.00
51.99
51.51
60.98
52.43
61.39
74.23
56.00
63.78
67.84
108.45
59.36
65.86
70.40
76.25
101.50
50.84
58.74
59.63
68.06
115.77
−154.50
−149.80
−120.60
−152.30
−125.80
−75.79
30–50
30–50
30–50
30–50
30–50
30–50
30–50
30–50
30–50
30–50
30–50
30–50
30–50
30–50
30–50
30–50
30–50
30–50
30–50
30–50
0.999
0.998
0.994
0.995
0.998
0.998
0.999
0.994
0.999
0.993
0.992
0.997
0.998
0.999
0.994
0.999
0.997
0.998
0.999
0.997
HCl
4a
H2SO4
−137.10
−120.30
−104.20
+25.31
5.00
10.00
16.00
1.00
H2SO4
H2SO4
−121.10
−104.80
−97.35
5.00
4b
4c
10.00
15.00
16.00
1.00
−75.92
+11.08
−152.90
−141.10
−134.80
−121.80
+36.09
5.00
10.00
15.00
16.00
aMeasurements were made at 5 ◦C intervals.

1466
H. KUTUK AND H. YAKAN
Figure 5 The plot of logk1 versus Hammett σ values for acid-catalyzed hydrolyses (10.00 M HClO4) of N-(4-
substituted arylthio)phthalimides at 40.0 ◦C.
sulfuric acid the values of ꢀS= changed from −137.10 to +25.31, −121.10 to +11.08, and
−152.90 to +36.09 JK−1mol−1 for the hydrolysis of 4a, 4b, and 4c, respectively. Similar
behavior has been observed for the acid-catalyzed hydrolysis of (4-methoxybenzoyl)-4-
tolueniminosulfonate.21 Values of ꢀS= for the hydrolysis of 4a–c become increasingly less
negative or positive with increased acidity, suggesting a mechanistic changeover from A-2
to A-1. This suggests an A-2 mechanism at low acid concentrations and an A-1 mechanism
at high acid concentrations.
In the acidity range studied, electron-donating substituents cause the highest rate
of hydrolysis (4b > 4c), and the substituent effects are well correlated by a satisfactory
Hammett ρσ plot (at 10.00 M HClO4, ρ = −1.586 [corr. 0.978]) as shown in Figure 5.
At these acidities electron-donating substituents both facilitate protonation of the substrate
and stabilize the sulfur cation in the case of an A-1 mechanism. At lower acidities, however
(e.g., 1.00 M HClO4, ρ = 0.803 [corr. 0.996]) as shown in Figure 6, 4c hydrolyzes more
rapidly than 4b, consistent with a predominantly A-2 mechanism, in which substituent
effects on the protonation and slow step operate in opposite directions. There is no di-
rect evidence concerning the site of protonation of N-(4-substituted arylthio)phthalimides;
Figure 6 The plot of logk1 versus Hammett σ values for acid-catalyzed hydrolyses (1.00 M HClO4) of N-(4-
substituted arylthio)phthalimides at 40.0 ◦C.

ACID-CATALYZED HYDROLYSIS
1467
O
O
S
H
N
N
H3O+
+
R
S
H2O
+
R
O
O
H2O
slow
O
O
δ
H
S
OH2
N
fast
HN
+
R
S
O
R
OH2
δ
O
fast 2H2O
O
S
H+
R
OH
+
O
Scheme 2
however, protonation of sulfinamides,10,22 sultams,23 and cyclic sulfamate esters24 occurs
preferentially at the nitrogen atom.
In light of the overall evidence, we propose that the acid-catalyzed hydrolysis of
N-(4-substituted arylthio)phthalimides occurs according to an A-2 mechanism at lower
acidities and an A-1 mechanism at higher acidities, as shown in Schemes 2 and 3, respec-
tively. Sulfinic acids are known to be readily oxidized; for instance, p-toluenesulfinic acid
undergoes facile autoxidation in acetonitrile at 40.0 ◦C to give p-toluenesulfonic acid and
the autoxidation is accelerated by the presence of a Cl− or Cu(II) ion.25
EXPERIMENTAL
Materials
N-(4-Substituted arylthio)phthalimides 4a–c were prepared from the corresponding
4-substituted thiophenol by reaction with phthalimide in hot acetonitrile and pyridine and
then a solution of bromine in acetonitrile, as described by Klose et al.26 1H-NMR spectra
were recorded on a Bruker AC 200 MHz spectrometer using tetramethylsilane (TMS) as
an internal standard. Infrared spectra were recorded on a Vertex 80v Fourier transform
infrared (FTIR) spectrometer. All melting points were obtained using an electrothermal
digital melting point apparatus. 4a: m.p. 161–163 ◦C (lit.26 160–161 ◦C); 4b: m.p. 204–205
◦C. Found C, 67.60; H, 4.28; N, 5.28; S, 11.88. Calcd. for C15H11NO2S: C, 66.89; H, 4.12;
N, 5.20; S, 11.91%; 4c: m.p. 179–181 ◦C (lit.26 179–181 ◦C).

1468
H. KUTUK AND H. YAKAN
O
O
S
N
S
N
H3O+
+
H2O
H
+
R
O
O
R
slow
O
S
OH2
S
fast
+
HN
H2O
R
R
O
2H2O
OH
fast
O
S
H+
R
+
O
Scheme 3
Kinetic Studies
The rates of hydrolysis of N-(4-substituted arylthio)phthalimides were followed spec-
trophotometrically at 225–240 nm using a GBC Cintra 20 model ultraviolet-visible (UV-
Vis) spectrophotometer (Australia) with a thermostated cell compartment ( 0.05 ◦C). Good
first-order behavior was observed with clean isosbestic points. Values of k1 were calculated
from the standard equation using a least-squares procedure. All kinetic measurements were
duplicated and the average deviation from the mean was <3%.
Product Analysis
The products of hydrolysis were determined by comparing the UV spectrum obtained
after completion of the kinetic experiment with the spectrum of the expected products at
the same concentration and under the same conditions. Thus, for the hydrolysis of N-(4-
methylphenylthio)phthalimide, the UV spectrum recorded at the end of the reaction was
identical with that of a 1:1 mixture of phthalimide and p-toluenesulfonic acid. Phthalimide
was obtained from Fluka (Buchs SG, Switzerland) and p-toluenesulfonic acid was prepared
as described in the literature.27
REFERENCES
1. Kittleson, A. R. U.S. Patent 2.533.770, 1951; Chem. Abstr. 1951, 45, 6792.
2. Klivenye, F.; Szabo, J.; Vinkler, E. Acta Chim. Acad. Sci. Hung. 1955, 6, 373; Chem. Abstr. 1957,
51, 1882.
3. Bu¨chel, K. H.; Conte, A. Chem. Ber. 1967, 100, 1248.
4. Behforouz, M.; Kerwood, J. E. J. Org. Chem. 1969, 34, 51–55.

ACID-CATALYZED HYDROLYSIS
1469
5. Harpp, D. N.; Back, T. G. Tetrahedron Lett. 1971, 12, 4953–4956.
6. Harpp, D. N.; Ash, D. K.; Back, T. G.; Gleason, J. G.; Orwig, B. A.; VanHorn, W. F. Tetrahedron
Lett. 1970, 11, 3551–3554.
7. Kutuk, H.; Bekdemir, Y.; Soydas, Y. J. Phys. Org. Chem. 2001, 14, 224–228.
8. Kutuk, H.; Bekdemir Y.; Turkoz, N. Phosphorus, Sulfur Silicon Relat. Elem. 2006, 181, 931–937.
9. Kutuk, H.; Ozturk, S. Phosphorus, Sulfur Silicon Relat. Elem. 2009, 184, 332–340.
10. Asefi, H.; Tillett, J. G. J. Chem. Soc. Perkin Trans. 2 1979, 1579–1582.
11. Ghosh, K. K.; Ghosh, S. J. Org. Chem. 1994, 59, 1369–1374.
12. Bunton, C. A.; Crabtree, J. H.; Robinson, L. J. Am. Chem. Soc. 1968, 90, 1258–1265.
13. Bunton, C. A.; Fendler, J. H. J. Org. Chem. 1966, 31, 3764–3771.
14. Cox, R. A.; Yates, K. Can. J. Chem. 1979, 57, 2944–2951.
15. Cox, R. A.; Yates, K. J. Am. Chem. Soc. 1978, 100, 3861–3867.
16. Cox, R. A. Adv. Phys. Org. Chem. 2000, 35, 1–66.
17. Yates, K.; McCelland, R. A. J. Am. Chem. Soc. 1967, 89, 2686–2692.
18. Challis, B. C.; Rosa, E.; Iley, J.; Norberto, F. J. Chem. Soc. Perkin Trans. 2 1990, 1, 179–183.
19. Celik, S. Doctoral Thesis, Synthesis of Sulfamate Esters and Acids Catalysed Hydrolysis Re-
action Mechanism, Department of Chemistry, University of Ondokuz Mayis, Samsun, Turkey,
2006.
20. Schaleger, L. L.; Long, F. A. Adv. Phys. Org. Chem. 1963, 1, 1–33.
21. Kutuk, H.; Tillett, J. Phosphorus, Sulfur Silicon Relat. Elem. 1993, 85, 1, 217–224.
22. Bujnicki, B.; Drabowicz, J.; Mikolajczyk, M.; Kolbe, A.; Stefaniak, L. J. Org. Chem. 1996, 61,
7593–7596.
23. Bekdemir, Y.; Tillett, J. G.; Zalewski, R. I. J. Chem. Soc. Perkin Trans. 2 1993, 1643–1646.
24. Bekdemir, Y.; Kutuk, H.; Celik, S.; Tillett, J. G. Phosphorus, Sulfur Silicon Relat. Elem. 2002,
177, 973–980.
25. Oae, S. Organic Chemistry of Sulfur; Plenum Press: New York, 1977, pp. 612–613.
26. Klose, J.; Reese, C. B.; Song, Q. Tetrahedron Lett. 1997, 53, 14411–14416.
27. Furniss, B. S.; Hannaford, A. J.; Smith, P. W.; Tatchell, A. R. Vogel’s Textbook of Practical
Organic Chemistry, 5th ed.; John Wiley & Sons: New York, 1989, pp. 874–875.