Enthalpies of combustion of 2-iodosobenzoic acid and 4-nitrosophenol: The dissociation enthalpy of the I-O bond

Article abstract of DOI:10.1006/jcht.1999.0554

The standard (p^o = 0.1 MPa) molar enthalpies of combustion in oxygen, at T = 298.15 K, for crystalline 2-iodosobenzoic acid, (OI)C₆H₄COOH, and 4-nitrosophenol, (ON)C₆H₄OH, were measured by rotating-bomb calorimetry and static-bomb calorimetry, respectively. These values were used to derive the standard molar enthalpies of formation of the crystalline compounds. Δ_fH^o_m(cr)/(kJ · mol^-1) 2-iodosobenzoic acid 2-(OI)C₆H₄COOH -336.9 ± 2.5 4-nitrosophenol 4-(ON)C₆H₄OH -70.2 ± 2.1 An indirect method was used for assessing the dissociation enthalpy of the (I-O) bond in the iodoso derivative, D^o_m(I-O)/(kJ · mol^-1) = (264.5 ± 8.1), which is the first value reported for an iodine-oxygen bond in an organic molecule.

Full text of DOI:10.1006/jcht.1999.0554

J. Chem. Thermodynamics 1999, 31, 1551–1559
Article No. jcht.1999.0554
Available online at http://www.idealibrary.com on
Enthalpies of combustion of 2-iodosobenzoic acid
and 4-nitrosophenol: the dissociation enthalpy of
the I–O bond
Maria D. M. C. Ribeiro da Silva,a M. Agostinha R. Matos,
Maria Lu´ısa C. C. H. Ferra˜o, Lu´ısa M. P. F. Amaral, Margarida
S. Miranda,
Centro de Investigac¸a˜o em Qu´ımica, Departamento de Qu´ımica, Faculdade
de Cieˆncias, Universidade do Porto, Rua do Campo Alegre, 687,
P-4169-007 Porto, Portugal
W. E. Acree Jr,
Department of Chemistry, University of North Texas, Denton
TX 76203-0068, U.S.A.
and G. Pilcher
Department of Chemistry, University of Manchester, Manchester, M13 9PL
U.K.
o
The standard (p = 0.1 MPa) molar enthalpies of combustion in oxygen, at T
=
298.15 K, for crystalline 2-iodosobenzoic acid, (OI)C H COOH, and 4-nitrosophenol,
6
4
(ON)C H OH, were measured by rotating-bomb calorimetry and static-bomb calorimetry,
6
4
respectively. These values were used to derive the standard molar enthalpies of formation
of the crystalline compounds.
o
−1
)
1 H (cr)/(kJ · mol
f
m
2-iodosobenzoic acid 2-(OI)C H COOH −336.9 ± 2.5
6
4
6
4-nitrosophenol
4-(ON)C H OH
−70.2 ± 2.1
4
An indirect method was used for assessing the dissociation enthalpy of the (I–O) bond
o
−1
in the iodoso derivative, D (I–O)/(kJ · mol ) = (264.5 ± 8.1), which is the first value
m
c
reported for an iodine–oxygen bond in an organic molecule. ꢀ 1999 Academic Press
KEYWORDS: 2-iodosobenzoic acid; 4-nitrosophenol; dissociation enthalpy of the (I–O)
bond; enthalpy of combustion
a
To whom correspondence should be addressed (E-mail: mdsilva@fc.up.pt).
c
0021–9614/99/121551 + 09 $30.00/0
ꢀ 1999 Academic Press

1552
M. D. M. C. Ribeiro da Silva et al.
1. Introduction
To provide a predictive basis for the outcome of primary oxo transfer reactions, Holm
et al.(1, 2) introduced a simple reactivity scale, compiling the values of the enthalpies
of reaction for a series of reactions in a decreasing order. The utility of this scale is
analogous to that of a table of standard reduction potentials, in view of a prediction of the
direction of a large number of oxo transfer reactions. Holm’s compilation includes values
for enthalpies of reactions for strong donors and acceptors, but the thermodynamic data
required to calculate values for couples involving certain other strong oxo donors, such as
the iodosoarenes, have not been reported.
The enthalpy changes of the following reactions involving generalized acceptor/donor
couples oxygen atom, X/XO or Y/YO,
X + 1/2 O2(g) = XO
Y + 1/2 O2(g) = YO
(1)
(2)
may be obtained as the difference in standard molar enthalpies of formation of products
and reactants. If |T · 1rSm| ꢁ |1r Hm| and 1r Hm (1) > 1r Hm (2), the reaction:
XO + Y = X + YO
(3)
is thermodynamically favourable. For an oxidized molecule such as XO, the bond
dissociation enthalpy D(X–O) can be calculated as the enthalpy of the reaction:
XO(g) = X(g) + O(g).
(4)
A systematic investigation of the influence of the molecular environment in the
immediate vicinity of the (N–O) bond has received special attention in our research groups
for the last decade. The molar dissociation enthalpies of (N–O) bonds, Dmo (N–O), have
been reported for different classes of compounds, including some nitrocompounds.(3–5)
The determination of Dmo (N–O) in a nitrocompound, being the enthalpy of the dissociation
reaction RNO2(g) = RNO(g) + O(g), requires the knowledge of the standard molar
enthalpies of formation, in the gaseous state of both the nitro and nitroso compounds.
In this work, we aimed to calculate Dmo (N–O) for 4-nitrophenol, from the standard molar
enthalpies of formation of the gaseous 4-nitrophenol, 1f Hmo {4-(O2N)C6H4OH, g}(6, 7) and
4-nitrosophenol, 1f Hmo {4-(ON)C6H4OH, g}. For the latter, the energy of combustion of
the crystalline compound has been measured and the standard molar enthalpy of formation
in the condensed state was derived. Measurement of the enthalpy of sublimation of this
compound was found to be not possible due to thermal decomposition of 4-nitrosophenol
on heating.
The dissociation enthalpy of the iodine–oxygen bond in iodoso compounds Dmo (I–
O) may also be calculated as the enthalpy of the reaction RIO(g) = RI(g) + O(g), if the
standard molar enthalpies of formation of all the species involved are known. The literature
does not give any value for Dmo (I–O) in an organic molecule, and that is derived in this
paper by considering the couple 2-iodobenzoic acid and 2-iodosobenzoic acid.
The standard molar enthalpy of formation in the gaseous state for 2-iodobenzoic acid
can be obtained from the literature values for its standard molar enthalpy of formation in

o
D
(I–O) in iodosobenzoic acid
1553
m
the crystalline state,(8) and standard molar enthalpy of sublimation.(9) This paper reports
the standard molar enthalpy of formation of 2-iodosobenzoic acid in the crystalline phase,
being the first measurement of an iodosocompound. It has not been possible to measure its
enthalpy of sublimation because of thermal decomposition, which led us to use an indirect
method of assessing Dmo (I–O).
For the general reaction, in which all the reactants and products are in the solid state,
RNO + 2-IC6H4CO2H = RN + 2-(OI)C6H4CO2H,
(5)
if the enthalpies of sublimation of the species on the left hand side and right hand side
balance, then 1r Hmo = Dmo (N–O) − Dmo (I–O). We have tested this hypothesis with twelve
examples where Dmo (N–O)(3, 5, 10–15) has been determined, and a mean value with its
standard deviation for Dmo (I–O) was derived as (264.3±2.8) kJ · mol−1 showing the above
hypothesis to be reasonably well obeyed.
2. Experimental
The 2-iodosobenzoic acid was prepared by oxidation of 2-iodobenzoic acid with potassium
permanganate according to the method of Verma and co-workers.(16) The sample was
further purified by three recrystallizations from hot water. Elemental analyses were in
agreement with expected values and the compositions in mass fractions were: found
102 ·w(C) = 31.73, 102 ·w(H) = 1.96, 102 ·w(I) = 48.10; calculated 102 ·w(C) = 31.85,
102 · w(H) = 1.91, and 102 · w(I) = 48.07.
The 4-nitrosophenol was prepared according to a published literature method.(17) Phenol
was slowly dissolved in an ice-cooled aqueous solution of sodium hydroxide and potassium
nitrite. Sulfuric acid (3.5 mol · dm−3) was then slowly added to the resulting solution by
stirring. The reaction mixture was stirred for an additional 2 hours, and the temperature
of the mixture was maintained at 273 K. The crystalline product of 4-nitrosophenol was
collected by low-pressure filtration, washed several times with cold water, and then further
purified four times by vacuum sublimation. As the compound decomposes, it was kept
under nitrogen during purification and only freshly sublimed material was used in the
combustion experiments. Purity was checked by i.r. spectroscopy as well as the carbon
dioxide recovery ratio. The average ratio hri of the mass of carbon dioxide observed in
the combustion experiments to that calculated from the mass of sample, together with an
estimated density of the sample, was ρ(g · cm−3) = 1.2, hri = (0.9990 ± 0.0009), with
uncertainty of twice the standard deviation of the hri mean.
The enthalpy of combustion of 2-iodosobenzoic acid was determined with an isoperi-
bol rotating bomb calorimeter(18, 19) with a twin-valve stainless-steel bomb lined with plat-
inum. The rotation mechanism allowed simultaneous axial and end-over-end rotation of the
bomb. This rotation was started when the temperature rise of the main period reached about
0.63 of its total value, and was continued throughout the rest of the experiment. With this
procedure, the frictional work due to the rotation of the bomb is automatically included in
the temperature corrections for the work of water stirring and for the heat exchanged with
the thermostated jacket.(20) The calorimeter was calibrated using benzoic acid (Bureau
of Analysed Samples CRM 190-r) having a massic energy of combustion under standard

1554
M. D. M. C. Ribeiro da Silva et al.
bomb conditions of −(26432.3 ± 3.8) J · g−1. The calibration results were corrected to
give the energy equivalent ε(calor) corresponding to an average mass of water added to
the calorimeter of 5222.5 g. One set of six calibration experiments was made in oxygen at
p = 3.04 MPa, with 1.00 cm3 of water added to the bomb, leading to an energy equivalent
of the calorimeter ε(calor) = (25172.2 ± 1.5) J · K−1, where the uncertainty quoted is the
standard deviation of the mean. A series of six comparison experiments was also performed
by burning benzoic acid in the presence of a mass 1.0 g of solid iodine sealed in Melinex
polyester bags (0.025 mm thickness), and a volume 10.00 cm3 of KI (aq, 0.9 mol · dm−3).
These experimental conditions are similar to those observed after combustion of the iodine
derivative, and the value obtained for ε(calor) = (25191.2 ± 1.2) J · K−1 is 0.075 per cent
different from that previously obtained under certificate conditions. We decided to use this
value as ε(calor) for the combustion experiments of the iodine derivative to obviate any
systematic error in the calculation of the corrections for the standard state 1U6.
The procedure for determining the energies of combustion of 2-iodosobenzoic by
rotating bomb calorimetry is similar to the one already described for other iodine
compounds.(21) Samples in pellet form were ignited in oxygen at a pressure of 3.04 MPa
with a volume of 10.00 cm3 of KI of concentration 0.9 mol · dm−3 added to the
bomb. Ignition temperatures were chosen so that the final temperatures were close to
298.15 K. The electrical energy for ignition was determined from the change in potential
difference across a capacitor when discharged through the platinum ignition wire. For
all the combustion experiments with iodo-compounds, the final solution was titrated
against Na2S2O3(aq). The amount of I2 found was exactly as expected. A value for
1solUm(I2) = (3.7 ± 0.1) kJ · mol−1(22) was used for the molar energy of solution of
I2(cr) in KI(aq).
For dry Melinex, 1cuo = −(22902 ± 5) J · g−1 (23)
.
This value has been previously
confirmed by combustion in our laboratory. The mass of Melinex used in each experiment
was corrected for the mass fraction of water (0.0032) and the mass of carbon dioxide
produced from it was calculated using the factor previously reported.(23) Hexadecane
(Aldrich Gold Label, mass fraction w > 0.99) stored under nitrogen was used as an
auxiliary combustion aid in measurements. The standard massic energy of combustion
of the hexadecane was measured, −1cuo(l) = (47145.8 ± 1.3) J · g−1, and it is in
good agreement with the value of Fraser and Prosen(24) for a sample with w = 0.9996,
−1cuo(l) = (47155.0 ± 3.8) J · g−1
.
For the cotton thread fuse of empirical formula CH1.686O0.843, −1cuo
=
16250 J · g−1 (25)
;
this value has been previously confirmed in our laboratory. Cor-
rections for carbon formation were based on −33 kJ · g−1 for the massic energy of
combustion of carbon.(25) The nitric acid formed was determined using Devarda’s alloy
method(26) and corrections were based on −59.7 kJ · mol−1 for the molar energy of
formation of 0.1 mol · dm−3 HNO3(aq) from N2, O2, and H2O(l).(27) At T = 298.15 K,
(∂u/∂p)T for these solids was assumed to be −0.2 J · g−1 · MPa−1, a typical value for
organic solids. For the iodoso compound, −1cuo was calculated by the procedure given
by Hubbard et al.(28)
The enthalpy of combustion of 4-nitrosophenol was measured by using a static
bomb calorimeter(29, 30) with a Parr 1105 model bomb. The energy equivalent of the

o
D
(I–O) in iodosobenzoic acid
1555
m
calorimeter was determined from the combustion of benzoic acid (Bureau of Anal-
ysed Samples CRM 190-r) having a massic energy of combustion under standard
bomb conditions of −(26432.3 ± 3.8) J · g−1. From nine calibration experiments
ε(calor) = (15908.3 ± 1.0) J · K−1 for an average mass of water added to the calorimeter
of 3119.6 g, where the uncertainty quoted is the standard deviation of the mean. Hex-
adecane (Aldrich Gold Label, w > 0.99) stored under nitrogen was used as an auxiliary
combustion aid in measurements, to reproduce a convenient temperature rise in the
calorimeter, since difficulties in purifying the compound led to very small amounts of
purified samples. Samples in pellet form were ignited at T = (298.150 ± 0.001) K in
oxygen at a pressure of 3.04 MPa with a volume of 1.00 cm3 of water added to the bomb.
The electrical energy for ignition was determined from the change in potential difference
across a capacitor when discharged through the platinum ignition wire. The corrections for
the cotton thread fuse, carbon formation, and nitric acid formation were made as previously
described for the rotating bomb combustion calorimetry. At T = 298.15 K, (∂u/∂p)T for
these solids was assumed to be −0.2 J · g−1 · MPa−1, a typical value for organic solids.
For the nitroso compound, −1cuo was calculated by the procedure given by Hubbard et
al.(28) The relative atomic masses used throughout this paper were those recommended
by the IUPAC Commission in 1995.(31) The amount of substance used in each experiment
was determined from the total mass of carbon dioxide produced after allowance for that
formed from the cotton thread fuse and that lost due to carbon formation.
3. Results
Detailed results for a typical combustion experiment on each compound, as results for
a typical comparison experiment, are given in table 1; 1m(H2O) is the deviation of the
mass of water added to the calorimeter from the mass assigned for ε(calor) (5222.5 g for
the rotating bomb calorimeter and 3119.6 g for the static bomb calorimeter); 1U6 is the
correction to the standard state; the remaining terms are as previously described.(27) For
rotating bomb measurements, the final calorimeter temperature was close to T = 298.15 K,
whereas for the static bomb measurements samples were ignited at T = 298.15 K. The
1U(IBP) was calculated according to:
1U(IBP) = −{ε(calor) + cp(H2O, l) · 1m(H2O)}1Tad + εi(Ti − 298.15)/K +
εf(298.15 − Ti − 1Tad)/K + 1U(ign),
(6)
where 1Tad is the calorimeter temperature change corrected for heat exchange and
the work of stirring. The individual values of −1cuo together with the mean and
its standard deviation are given in table 2. Table 3 lists the derived standard molar
enthalpies of combustion and of formation in the crystalline state at T = 298.15 K.
In accordance with normal thermochemical practice, the uncertainties assigned to the
standard molar enthalpies of combustion and formation are twice the overall standard
deviation of the mean and include the uncertainties in calibration and in the auxil-
iary quantities used. To derive 1f Hmo from 1c Hmo , the standard molar enthalpies of
formation at T
=
298.15 K for H2O(l) : −(285.83 ± 0.04) kJ · mol−1(32) and for
CO2(g) : −(393.51 ± 0.13) kJ · mol−1 (32)
,
were used.

1556
M. D. M. C. Ribeiro da Silva et al.
TABLE 1. Typical combustion experimental results for a comparison
experiment, and for 2-iodosobenzoic acid and 4-nitrosophenol, at T =
298.15 K
Comparison 2-iodosobenzoic
4-nitrosophenol
experiment
acid
m(CO , total)/g
1.69578
2
m(BA)/g
0.60767
1.04538
m(I )/g
2
m(cpd)/g
0.85443
0.48157
m(Melinex)/g
0.05770
m(n-C
H
)/g
0.24844
0.00291
51.73
0.21178
0.00275
15.46
16 34
m(fuse)/g
0.00265
51.64
−1
−1
ε /(J · K
)
)
i
ε /(J · K
60.84
58.94
16.24
f
1m(H O)/g
1.9
−2.6
0.0
2
(T /K) − 273.15
24.3842
25.0871
0.69022
17429.16
1.43
24.1047
24.9914
0.86936
21933.62
3.46
25.0001
26.4431
1.37136
21837.09
37.85
i
(T /K) − 273.15
f
1T /K
ad
−1U(IBP)/J
1U(HNO )/J
3
−1U(C)/J
1U(ign)/J
1.32
1.29
15.24
1.93
5.99
1.19
1
U(I )/J
2
sol
1U /J
27.65
25.51
25180.3
12.04
6
−1
ε(calor)/(J · K
)
25191.0
1321.34
15908.3
o
−m1 u (Melinex)/J
c
o
−m1 u (n-C
H
16 34
)/J
11712.79
47.26
9984.65
44.66
c
o
−m1 u (fuse)/J
43.04
c
o
−1
)
−1 u (cpd)/(J · g
11879.96
24418.49
c
4. Discussion
Considering a hypothetical solid reaction (7), involving the pairs 2-iodobenzoic acid/2-
iodosobenzoic acid, (2-IC6H4COOH/2-(OI)C6H4COOH), and 4-aminonitrosobenzene/4-
aminonitrobenzene, {4-(CH3)2NC6H5NO/4-(CH3)2NC6H5NO2}:
4-(CH3)2NC6H5NO2(cr) + 2-IC6H4COOH(cr) = 4-(CH3)2NC6H5NO(cr)+
2-(IO)C6H4COOH(cr),
(7)
and using the values for the standard molar enthalpies of formation 1f Hmo [4-(CH3)2NC6
H5NO2, cr]
=
−(38.5 ± 1.6) kJ · mol−1 (5)
,
1f Hmo [(4-CH3)2NC6H5NO, cr]
=
(103.0 ± 1.6) kJ · mol−1 (5)
,
1f Hmo (2-IC6H4COOH, cr) = −(302.3 ± 4.1) kJ · mol−1 (8)
,
and 1f Hmo [2-(IO)C6H4COOH, cr] = −(336.9 ± 2.5) kJ · mol−1, measured in the present

o
D
(I–O) in iodosobenzoic acid
1557
m
o
TABLE 2. Individual values of the massic energy of combustion −1 u of 2-
c
o
iodosobenzoic acid and 4-nitrosophenol at T = 298.15 K (p = 0.1 MPa). The mean
o
values are represented by h1 u i
c
2-iodosobenzoic acid
4-nitrosophenol
o
−1
)
−1 u /(J · g
c
11853.52
11867.46
11854.39
11876.63
11858.55
11879.96
11873.17
24401.29
24414.14
24418.49
24442.82
24407.72
o
−1 a
)
−h1 u i/(J · g
c
11866.2 ± 4.1
24416.9 ± 7.1
a
Mean value and standard deviation of the mean.
TABLE 3. Derived standard (po = 0.1 MPa) molar energies of combustion
1cUmo , standard molar enthalpies of combustion 1c Hmo , for standard molar
enthalpies of formation 1f Hmo for 2-iodosobenzoic acid and 4-nitrosophenol
at T = 298.15 K. Uncertainties are given as twice the standard deviation of the
mean
o
o
o
−1 U (cr)
−1 H (cr)
1 H (cr)
f
m
c
c
m
m
−1
−1
−1
kJ · mol
kJ · mol
kJ · mol
2-iodosobenzoic acid
4-nitrosophenol
3132.9 ± 2.3
3006.0 ± 1.9
3132.3 ± 2.3
3005.4 ± 1.9
−336.9 ± 2.5
−70.2 ± 2.1
work, the enthalpy of the reaction (7) is calculated as 1r Hmo = (106.9 ± 5.3) kJ · mol−1
.
Because of the structural similarities, it is reasonable to assume that the enthalpies
of sublimation of the products will be nearly equal to those of the reactants so that
1r Hmo = Dmo (N–O) − Dmo (I–O).
The value of Dmo (N–O) in 4-dimethylaminonitrobenzene has been determined as
(371.4 ± 3.5) kJ · mol−1 (5)
,
hence Dmo (I–O) in 2-iodosobenzoic acid is assessed as
(264.5 ± 8.1) kJ · mol−1, where an additional uncertainty of ±5 kJ · mol−1 has been
included because of the assumption made about enthalpies of sublimation. Then, for the
reaction:
4-(O2N)C6H4OH(cr) + 2-IC6H4COOH(cr) = 4-(ON)C6H4OH(cr) +
2-(IO)C6H4COOH(cr),
(8)

1558
M. D. M. C. Ribeiro da Silva et al.
and using the values for the standard molar enthalpies of formation 1f Hmo {4-(O2N)C6H4
OH, cr} = −(207.1 ± 1.1) kJ · mol−1 (7)
{4-(ON)C6H4OH, cr} = −(70.2 ± 2.1) kJ · mol−1, the enthalpy of the reaction (8) is cal-
culated as 1r Hmo = (102.3±5.3) kJ · mol−1, showing that within the limits of experimental
uncertainty, Dmo (N–O) in 4-nitrophenol is equal to that in 4-dimethylaminonitrobenzene.
From the dissociation reaction:
,
and the two values measured in the present
=
work, 1f Hmo {2-(IO)C6H4COOH, cr}
−(336.9 ± 2.5) kJ · mol−1 and 1f Hmo
4-(O2N)C6H4OH(g) = 4-(ON)C6H4OH(g) + O(g),
(9)
and assuming the value for Dmo (N–O) (371.4±3.5) kJ · mol−1(5) in 4-nitrophenol, as well
as 1f Hmo (4-nitrophenol, g) = −(114.7 ± 1.2) kJ · mol−1(7) and 1f Hmo (O, g) = (249.17
±0.10) kJ · mol−1 (32)
,
then 1f Hmo (4-nitrosophenol, g) = (7.5 ± 3.7) kJ · mol−1. It has
been shown previously(4) that the increment in 1f Hmo (g) for substitution of NO on the
benzene ring is (122.4 ± 2.2) kJ · mol−1. With 1f Hmo (phenol, g) = −(96.4 ± 0.9) kJ·
mol−1 (8)
,
the estimated value for 1f Hmo (4-nitrosophenol, g) is (26.0 ± 2.4) kJ · mol−1
and, by comparison with the above experimental value, it is apparent that 4-nitrosophenol
is exceptionally stabilized by (18.5 ± 4.4) kJ · mol−1. A similar magnitude of additional
stabilization of 20 kJ · mol−1 was reported for 4-dimethylaminonitrosobenzene.(5) The
consequence of these exceptional stabilization energies is that dimerization in the solid
state would be endothermic. Actually this particular nitroso compound is monomeric and
green, not dimeric and white.
In terms of Holm’s scale,(2) we have 1r Hmo = −(136.1 ± 4.2) kJ · mol−1 for
reaction (10) and 1r Hmo = −(35.6 ± 4.8) kJ · mol−1 for reaction (11):
4-nitrosophenol(cr) + 1/2O2(g) = 4-nitrophenol(cr),
(10)
(11)
2-iodobenzoicacid(cr) + 1/2O2(g) = 2-iodosobenzoicacid(cr),
which would place the oxidizing potential of 4-nitrophenol at about the same level as
manganese dioxide, but kinetic considerations would almost certainly render 4-nitrophenol
useless as an oxidizing reagent. For 2-iodosobenzoic acid, the oxidizing potential would
be at a level similar to perchlorate, and this may find a use in oxidations.
Thanks are due to Fundac¸a˜o para a Cieˆncia e Tecnologia, FCT-Lisboa, for financial support
given through Centro de Investigac¸a˜o em Qu´ımica da Universidade do Porto (research
unit number 81) and for the research project PRAXIS XXI (project PCEX / QUI / 0062 /
96). One of us (LMPFA) thanks Fundac¸a˜o para a Cieˆncia e Tecnologia for the award of a
postdoctoral fellowship (PRAXIS XXI/BPD/16319/98).
REFERENCES
1. Holm, R. H. Chem. Rev. 1987, 87, 1401–1449.
2. Holm, R. H.; Donahue, J. P. Polyhedron 1993, 12, 571–589.
3. Acree Jr., W. E.; Tucker, S. A.; Pilcher, G.; Chowdhary, A.; Ribeiro da Silva, M. D. M. C.;
Monte, M. J. S. J. Chem. Thermodynamics 1993, 25, 1253–1261.
4. Acree Jr., W. E.; Bott, S. G.; Tucker, S. A.; Ribeiro da Silva, M. D. M. C.; Matos, M. A. R.;
Pilcher, G. J. Chem. Thermodynamics 1995, 27, 1433–1440.
5. Acree Jr., W. E.; Tucker, S. A.; Pilcher, G.; Toole, G. J. Chem. Thermodynamics 1994, 26,
85–90.

o
D
(I–O) in iodosobenzoic acid
1559
m
6. Finch, A.; Gardner, P G.; Wu, D. Thermochim. Acta 1983, 66, 333–342.
7. Sabbah, R.; Gouali, M. Aust. J. Chem. 1994, 47, 1651–1660.
8. Pedley, J. B. Thermochemical Data and Structures of Organic Compounds, Vol. 1. Thermody-
namics Research Center: College Station, TX: 1994.
9. Tan, Z.; Sabbah, R. Thermochim. Acta 1994, 231, 109–120.
10. Ribeiro da Silva, M. D. M. C.; Matos, M. A.; Vaz, M. C.; Santos, L. M. N. B. F.; Pilcher, G.;
Acree Jr.; Powell, J. R. J. Chem. Thermodynamics 1998, 30, 869–878.
11. Acree Jr., W. E.; Bott, S. G.; Tucker, S. A.; Ribeiro da Silva, M. D. M. C.; Matos, M. A. R.;
Pilcher, G. J. Chem. Thermodynamics 1996, 28, 673–683.
12. Acree Jr., W. E.; Tucker, S. A.; Zvaigzne, A. I.; Meng-Yan, Y.; Pilcher, G.; Ribeiro da Silva, M.
D. M. C. J. Chem. Thermodynamics 1991, 23, 31–36.
13. Leita˜o, M. L. P.; Pilcher, G.; Acree Jr., W. E.; Zvaigzne, A. I.; Tucker, S. A.; Ribeiro da Silva,
M. D. M. C. J. Chem. Thermodynamics 1990, 22, 923–928.
14. Acree Jr., W. E.; Tucker, S. A.; Ribeiro da Silva, M. D. M. C.; Matos, A. R.; Conc¸alves, J. M.;
Ribeiro da Silva, M. A.V.; Pilcher, G. J. Chem. Thermodynamics 1995, 27, 391–398.
15. Kirchner, J. J.; Acree Jr., W. E.; Pilcher, G.; Shaofeng, Li. J. Chem. Thermodynamics 1986, 18,
793–799.
16. Verma, K. A.; Sanghi, A. J.; Gupta, D. J. Chromatography 1988, 457, 345–353.
17. Leonard, N. J.; Curry, J. W. J. Org. Chem. 1952, 17, 1071–1076.
18. Ribeiro da Silva, M. A. V.; Ferra˜o, M. L. C. C. H.; Lopes, A. J. M. J. Chem. Thermodynamics
1993, 25, 229–235.
19. Ribeiro da Silva, M. A. V.; Ferra˜o, M. L. C. C. H.; Jiye, F. J. Chem. Thermodynamics 1994, 26,
839–846.
20. Good, W. D.; Scott, D. W.; Waddington, G. J. Phys. Chem. 1960, 60, 1080–1089.
21. Ribeiro da Silva, M. A. V.; Ferra˜o, M. L. C. C. H.; Silva, A. M. O. A. J. Chem. Thermodynamics
1995, 27, 633–641.
22. Carson, A. S.; Laye, P. G.; Pedley, J. B.; Welsby, A. M. J. Chem. Thermodynamics 1993, 25,
261–269.
23. Skinner, H. A.; Snelson, A. Trans. Faraday Soc. 1960, 56, 1776–1783.
24. Fraser, F. M.; Prosen, E. J. J. Res. Nat. Bur. Stand. 1955, 55, 329–333.
25. Coops, J.; Jessup, R. S.; van Nes, K. Experimental Thermochemistry, Vol. 1. Rossini, F. D.:
editor. Interscience: New York. 1956, Chap. 3.
26. Vogel, A. I. Quantitative Inorganic Analysis. Longmans: London. 1978.
27. The NBS Tables of Chemical Thermodynamic Properties. J. Phys. Chem. Ref. Data 1982, II,
Suppl. no. 2
28. Hubbard, W. N.; Scott, D. W.; Waddington, G. Experimental Thermochemistry, Vol. 1. Rossini,
F. D.: editor. Interscience: New York. 1956, Chap. 5.
29. Ribeiro da Silva, M. D. M. C.; Ribeiro da Silva, M. A. V.; Pilcher, G. J. Chem. Thermodynamics
1984, 16, 1149–1155.
30. Ribeiro da Silva, M. A. V.; Ribeiro da Silva, M. D. M. C.; Pilcher, G. Rev. Port. Qu´ım. 1984, 26,
163–172.
31. Copler, T. B. J. Phys. Chem. Ref. Data 1997, 26, 1239–1253.
32. CODATA Key Values for Thermodynamics. Cox, J. D.; Wagman, D. D.; Medvedev, V. A.:
editors. Hemisphere: New York. 1989.
(Received 4 March 1999; in final form 2 June 1999)
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