Crystal structure and thermochemical properties of potassium pyruvate C3H3O3K(s)

Article abstract of DOI:10.1007/s10973-016-5648-7

One important compound potassium pyruvate C₃H₃O₃K(s) is synthesized and characterized by chemical analysis, elemental analysis, and X-ray crystallography. X-ray single-crystal structural analysis reveals that the compound is formed by one CH₃COCOO^? anion and one metal cation K⁺. An obvious feature of the crystal structure of the compound is the formation of the five-membered chelate ring, and it is good for the stability of the compound in structure. The lattice potential energy of the compound and ionic volume of the anion CH₃COCOO^? are obtained from crystallographic data. The lattice potential energy is determined to be: U_POT[C₃H₃O₃K(s)]?=?567.7?kJ?mol^?1. The V_? (the volume of the anion CH₃COCOO^?) is estimated to be 0.088?nm³. Molar enthalpies of dissolution of the compound at various molalities in the double-distilled water are measured by use of an isoperibol solution-reaction calorimeter at 298.15?K. According to Pitzer’s electrolyte solution theory, molar enthalpy of dissolution of C₃H₃O₃K(s) at infinite dilution is derived to be 22.9?kJ?mol^?1. The values of relative apparent molar enthalpies (^ΦL), relative partial molar enthalpies (Lˉ ₂) of the compound, and relative partial molar enthalpies (Lˉ ₁) of the solvent (water) at different concentrations m/(mol?kg^?1) are derived from the experimental values of the enthalpies of dissolution of the compound. Finally, the molar enthalpy of hydration of the anion CH₃COCOO^?(g) is calculated to be ?227.8?kJ?mol^?1 by the design of the thermochemical cycle.

Full text of DOI:10.1007/s10973-016-5648-7

J Therm Anal Calorim
DOI 10.1007/s10973-016-5648-7
Crystal structure and thermochemical properties of potassium
pyruvate C H O K(s)
3
3 3
1
2
2
1
You-Ying Di
•
Yu-Han Zhang
•
Yu-Xia Kong
•
Chun-Sheng Zhou
Received: 18 January 2016 / Accepted: 16 June 2016
Ó Akad e´ miai Kiad o´ , Budapest, Hungary 2016
Abstract One important compound potassium pyruvate
C H O K(s) is synthesized and characterized by chemical
of dissolution of the compound. Finally, the molar enthalpy
-
of hydration of the anion CH COCOO (g) is calculated to
3
3
3
3
-
be -227.8 kJ mol by the design of the thermochemical
1
analysis, elemental analysis, and X-ray crystallography. X-
ray single-crystal structural analysis reveals that the com-
-
pound is formed by one CH COCOO anion and one metal
cycle.
3
?
cation K . An obvious feature of the crystal structure of the
Keywords Potassium pyruvate Á Crystal structure Á Pitzer
theory Á Molar enthalpy of dissolution at infinite dilution Á
Enthalpy of hydration
compound is the formation of the five-membered chelate
ring, and it is good for the stability of the compound in
structure. The lattice potential energy of the compound and
-
ionic volume of the anion CH COCOO are obtained from
3
crystallographic data. The lattice potential energy is
-
Introduction
1
determined to be: UPOT[C H O K(s)] = 567.7 kJ mol
3
.
3 3
-
The V- (the volume of the anion CH COCOO ) is esti-
Pyruvic acid CH COCOOH is one of the basic metabolic
3
3
3
mated to be 0.088 nm . Molar enthalpies of dissolution of
intermediates involved in the whole organisms. In the
common food sources of animal and plant, the carbohy-
drate is used most commonly. The carbohydrate undergoes
a series of biochemical reactions and finally broken down
to pyruvate as one of the most important products in the
biological body, others including lactic acid, amino acids,
etc. This is regarded as the most effective way to gain
energy and carbon sources. In addition, the alanine as one
of important amino acids in biological body can be directly
generated from pyruvic acid because it can be combined
with amino transfer reaction. Therefore, it also plays an
important role in nitrogen metabolism. In addition, it can
react with CoA to form acetyl-CoA and also has an
important relationship with the fatty acid metabolism.
Pyruvic acid is an important organic acid and has a wide
usage. It can easily be dissociated to produce the pyruvate
anion in the weak basic solution of biological body. The
physiological functions of pyruvate are as follows: mass
reduction, increasing muscular endurance and physical
performance, antioxidation, reducing the blood fat and
cholesterin, protecting cardiac muscle and so on. Pyruvate
is widely used in the development and production of
the compound at various molalities in the double-distilled
water are measured by use of an isoperibol solution-reac-
tion calorimeter at 298.15 K. According to Pitzer’s elec-
trolyte solution theory, molar enthalpy of dissolution of
C H O K(s) at infinite dilution is derived to be
3
3 3
-
1
2
2.9 kJ mol . The values of relative apparent molar
U
ꢀ
enthalpies ( L), relative partial molar enthalpies (L ) of the
2
ꢀ
compound, and relative partial molar enthalpies (L ) of the
1
-
1
solvent (water) at different concentrations m/(mol kg
)
are derived from the experimental values of the enthalpies
&
You-Ying Di
diyouying@126.com; myyydi@eyou.com
1
Shaanxi Key Laboratory of Comprehensive Utilization of
Tailings Resources, College of Chemical Engineering and
Modern Materials, Shangluo University, Shangluo,
Shaanxi 726000, People’s Republic of China
2
Shandong Provincial Key Laboratory of Chemical Energy
Storage and Novel Cell Technology, College of Chemistry
and Chemical Engineering, Liaocheng University,
Liaocheng 252059, People’s Republic of China
123

Y. -Y. Di et al.
functional food, biochemical products, cosmetics, pesti-
cide, etc.
anhydrous ethanol solution. The mixed solution is boiled
under reflux for 2 h. And the mixed solution is left at room
temperature. After several days, colorless single crystals
are separated from the mother liquid and recrystallized
with anhydrous ethanol three times. Finally, the sample
with a crystal shape is placed in a vacuum desiccator to dry
in vacuum for 12 h at T = 303.15 K. The final product is
placed in a weighing bottle and preserved in a desiccator.
The purity of the compound has been analyzed by element
analyzer (model: PE-2400 II, PerkinElmer, USA), under its
‘‘CHN mode’’, and ‘‘O mode’’. The element analyzer has
three modes: ‘‘CHN mode’’, ‘‘CHNS mode’’, and ‘‘O
mode’’. We can analyze oxygen element exactly under its
‘‘O mode’’. The mass fraction purity of the C, H, and O are
determined. For C H O K(s), the percentage of the K is
Pyruvic acid and the salts it produces are widely used in
medical field. They are used for the production of seda-
tives, antioxidants, antivirals, synthetic drugs for treating
high blood pressure and so on. As for pyruvic acid [1], as
new type of medicine, pesticide, and daily chemical
intermediates, its market demand is growing very quickly
at home and abroad. With the improvement of people’s
living standard, the demand of the pyruvic acid salt series
products will be gradually expanded in the domestic and
abroad markets, especially the application as a kind of raw
material of mass-loss drug as well as the application and
development of new refrigerant is very promising [2].
In this paper, the crystal structure and some important
thermodynamic properties [3–7] of the compound
C H O K(s) are reported. And the lattice potential energy
3
3 3
calculated and the values (analysis, calculated for C H
3
3
O K(s): C 28.56, H 2.40, O 38.05, K 30.99 %; found:
3
3
3
3
of the compound and ionic volume of the anion are
obtained from crystallographic data. Molar enthalpies of
dissolution of the compound at various molalities are
measured by an isoperibol solution-reaction calorimeter at
C 28.57, H 2.41, O 38.06, K 30.96 %) show that the mass
fraction purity of the compound is [0.996.
X-ray crystallography
2
98.15 K in the double-distilled water. According to Pit-
zer’s theory, the molar enthalpy of dissolution of the title
A crystal with dimensionsof 0.47 mm 9 0.40 mm 9 0.20 mm
is glued to the fine glass fiber and then mounted on the Bruker
Smart-1000 CCD diffractometer with Mo–Ka radiation,
k = 0.071073 nm. The intensity data are collected in the u–x
scan mode at T = (298 ± 2) K. The empirical absorption cor-
rections are based on multi-scan. The structure is solved by direct
method and difference Fourier synthesis, and all non-hydrogen
compound at infinite dilution is obtained. The values of
U
relative apparent molar enthalpies ( L), relative partial
ꢀ
molar enthalpies (L2) of the compound and relative partial
ꢀ
molar enthalpies (L1) of the solvent (water) at different
-
concentrations m/(mol kg ) are derived from the experi-
1
mental values of the enthalpies of dissolution of the com-
2
pound. At last, the molar enthalpy of hydration of the anion
-
CH COCOO (g) is calculated.
atoms are refined anisotropically on F by full-matrix least-
squares method. All calculations are performed with the program
package SHELXTL [8, 9].
3
We have applied for the CCDC number 1035339 for the
Experimental
compound C H O K(s).
3 3 3
Synthesis of the title compound
Isoperibol solution-reaction calorimeter
Information on the provenances and purities of the chem-
icals used in the synthesis and calorimetric experiments is
listed in Table 1. In the paper, the compound C H O
3 3
The isoperibol solution-reaction calorimeter consists pri-
marily of a precision temperature controlling system, an
electric energy calibration system, a calorimetric body, an
electric stirring system, a thermostatic bath made from
transparent silicate glass, a precise temperature measuring
system, and a data acquisition and processing system.
3
K(s) is synthesized by the following procedure: pyruvic
acid reacts with potassium hydroxide at a mole ratio of
n (pyruvic acid): n (potassium hydroxide) = 1:1 in
Table 1 Information on the provenances and purities of the chemicals used in the synthesis and calorimetric experiments
Chemicals
Provenances
Mass fraction purity
Pyruvic acid
J&K Scientific Ltd. China
[0.99
[0.999
0.995
Potassium hydroxide
Anhydrous ethyl alcohol
Potassium pyruvate
Potassium chloride
J&K Scientific Ltd. China
Tianjin No. 3 Chemical Reagent Factory. China
Prepared by our laboratory
[0.99
[0.999
J&K Scientific Ltd. China
1
23

3 3 3
Crystal structure and thermochemical properties of potassium pyruvate C H O K(s)
During whole experiments, the water thermostat is auto-
Table 2 Summary of crystallographic data and refinement parame-
ters for C K(s)
3 3 3
H O
matically maintained at T = 298.15 K and the maximum
-
3
variation is found to be ± 1 9 10
K. The platinum
Empirical formula
3 3 3
C H O K(s)
resistance thermometer is used to measure the temperature
of the calorimetric chamber in the whole dissolution
experiment, and it has a high precision of ± 0.001 K.
Experiments have demonstrated that the precision of
Formula weight
Temperature/K
Wavelength/nm
Crystal system
Space group
a/nm
126.15
298 ± 2
0.071073
Monoclinic
P2(1)
-
4
measuring the temperature can reach ± 1 9 10 K. The
principle and structure of the calorimeter are described in
detail elsewhere [10].
0.40118(4)
0.58401(7)
2.2074(2)
90
b/nm
The reliability of the calorimeter is verified previously
by measuring the molar enthalpy of dissolution of KCl
c/nm
a/°
(
calorimetrically primary standard) in the double-distilled
b/°
c/°
V/nm
91.0270(10)
90
water. According to the molar ratio of KCl to water,
nKCl : nH O ꢀ 1 : 1110, a certain amount of KCl is dis-
2
3
solved in 100 cm of the double-distilled water at
3
0.51709(9)
4
T = (298.15 ± 0.001) K. The average molar enthalpy of
-
Z
1
-3
dissolution of KCl is (17,547 ± 13) J mol , which com-
pares with corresponding published data (17,536 ± 3.4)
Calculated density/(g cm
Absorption coefficient/mm
F(000)
)
1.620
-
1
0.916
-
1
J mol
under the same experimental condition [10].
256
3
Experiments demonstrate that the uncertainty between the
Crystal size/mm
0.42 9 0.42 9 0.33
3.61 to25.00
-4 B hB4
measuring value and the literature value is within ± 0.3 %.
Theta range for data collection/°
Limiting indices
-4 B kB6
Results and discussion
-25 B lB26
Reflections collected/unique
2379/905
R(int) = 0.0517]
Description of crystal structure
[
Completeness to h 25.02
99.2
The crystal data and structure refinement for the compound
are summarized in Table 2. The selected bond lengths and
angles of the title compound are listed in Table 3. Table 2
shows that the crystal system of C H O K(s) is monoclinic,
Absorption correction
Semiempirical from
equivalents
Refinement method
0.7520 and 0.6997
Full-matrix least-squares on F2
905/0/65
3
3
3
Data/restraints/parameters
Goodness of fit on F2
Final R indices [I [ 2sigma(I)]
R indices (all data)
the space group is P2(1), unit cell dimensions are
a = 0.40118(4) nm, b = 0.58401(7) nm, c = 2.2074(2)
nm, a = c = 90°, b = 91.0270(10)°, and Z = 4. The cal-
1.194
R1 = 0.0497
-
3
culated density of C H O K(s) is 1.620 g cm , and the
3
3
3
wR2 = 0.1291
R1 = 0.0549
3
volume of formula unit is 0.51709(9) nm . The molecular
Extinction coefficient
-
structure of each C H O K(s) includes one CH COCOO
3
3
3
3
wR2 = 0.1319
420 and -407
?
?
anion and one K cation. Each of K cation connects with
the keto oxygen and the carboxylate oxygen at the same
time. The five-membered chelate ring is formed by the
Largest diff. peak and hole/
-
3
)
(e nm
coordination of O atoms of carboxylate and keto form with
?
K
cation, and the chelate coordination structure is good
atoms (O2) from two pyruvate groups, and two oxygen
atoms (O1) from other two pyruvate groups (see Fig. 2).
The coordination mode of octahedral pattern around the
for the reduction of the energy and the structural stability of
the compound from the viewpoint of energy. These three
atoms form a chelate ring together with other two carbon
atoms. The structure of the molecule of the compound can
be seen from Fig. 1, and the stacking crystal structure of
the compound in unit cell is shown in Fig. 2.
?
central K is formed.
The distances (Table 3) of oxygen atoms to the metal cation
are lying in the range 0.2694(3)–0.3296(3) nm for C H O
3 3 3-
K(s). The C–C bonds are found to have lengths 0.1554(5) and
0.1490(6) nm. The C–O bonds (C1–O1 and C1–O2) in the
carboxylate group are found to have lengths 0.1248(4) and
0.1243(4) nm, respectively. The C–O bonds (C2–O3) in the
keto group are found to have lengths 0.1208(5) nm. The angles
For C H O K(s), single crystal X-ray analysis reveals
3
3 3
-
that in the whole crystal structure, the five CH COCOO
3
?
anions are six-coordinated to one K cation by two oxygen
atoms (O1and O3) of one pyruvate group, two oxygen
123

Y. -Y. Di et al.
3 3 3
Table 3 Selected bond lengths (nm) and bond angles (deg) for C H O K(s)
Bonds
Bond length/nm
Bonds
Bond angle/°
K(1)–O(2)#1
0.2694(3)
0.2718(3)
0.2724(3)
0.2760(3)
0.2819(3)
0.2853(3)
0.3190(3)
0.3296(4)
0.1248(4)
0.2718(3)
0.2760(3)
0.1243(4)
0.2694(3)
0.2819(3)
0.3190(3)
0.1208(5)
0.1554(5)
0.3296(4)
0.1490(6)
0.09600
O(2)#1–K(1)–K(1)#5
O(1)#2–K(1)–K(1)#5
O(1)–K(1)–K(1)#5
O(1)#3–K(1)–K(1)#5
O(2)#4–K(1)–K(1)#5
O(3)–K(1)–K(1)#5
O(2)#3–K(1)–K(1)#5
C(1)#3–K(1)–K(1)#5)
K(1)#2–K(1)–K(1)#5
O(2)#1–K(1)–K(1)#9
O(1)#2–K(1)–K(1)#9
O(1)–K(1)–K(1)#9
O(1)#3–K(1)–K(1)#9
O(2)#4–K(1)–K(1)#9
O(3)–K(1)–K(1)#9
O(2)#3–K(1)–K(1)#9
C(1)#3–K(1)–K(1)#9
K(1)#2–K(1)–K(1)#9
K(1)#5–K(1)–K(1)#9
O(2)#1–K(1)–K(1)#10
O(1)#2–K(1)–K(1)#10
O(1)–K(1)–K(1)#10
O(1)#3–K(1)–K(1)#10
O(2)#4–K(1)–K(1)#10
O(3)–K(1)–K(1)#10
O(2)#3–K(1)–K(1)#10
C(1)#3–K(1)–K(1)#10
K(1)#2–K(1)–K(1)#10
K(1)#5–K(1)–K(1)#10
K(1)#9–K(1)–K(1)#10
C(1)–O(1)–K(1)#5
C(1)–O(1)–K(1)
135.46(7)
137.43(6)
42.46(6)
83.75(6)
42.09(6)
78.74(8)
86.08(6)
81.82(6)
180.0
K(1)–O(1)#2
K(1)–O(1)
K(1)–O(1)#3
K(1)–O(2)#4
K(1)–O(3)
K(1)–O(2)#3
K(1)–C(1)#3
O(1)–C(1)
O(1)–K(1)#5
106.93(8)
40.34(6)
80.58(6)
76.97(6)
148.77(7)
100.63(8)
39.91(5)
59.30(7)
66.09(2)
113.91(2)
49.45(7)
100.29(7)
140.82(6)
39.61(6)
87.45(6)
160.35(7)
73.22(6)
56.75(7)
66.09(2)
113.91(2)
88.13(3)
130.0(2)
116.3(2)
94.97(9)
104.1(2)
100.05(8)
109.54(10)
146.1(3)
120.4(3)
93.37(9)
83.8(2)
O(1)–K(1)#6
O(2)–C(1)
O(2)–K(1)#7
O(2)–K(1)#8
O(2)–K(1)#6
O(3)–C(2)
C(1)–C(2)
C(1)–K(1)#6
C(2)–C(3)
C(3)–H(3A)
C(3)–H(3B)
0.09600
C(3)–H(3C)
0.09600
O(2)#1–K(1)–O(1)#2
O(2)#1–K(1)–O(1)
O(1)#2–K(1)–O(1)
O(2)#1–K(1)–O(1)#3
O(1)#2–K(1)–O(1)#3
O(1)–K(1)–O(1)#3
O(2)#1–K(1)–O(2)#4
O(1)#2–K(1)–O(2)#4
O(1)–K(1)–O(2)#4
O(1)#3–K(1)–O(2)#4
O(2)#1–K(1)–O(3)
O(1)#2–K(1)–O(3)
O(1)–K(1)–O(3)
O(1)#3–K(1)–O(3)
O(2)#4–K(1)–O(3)
O(2)#1–K(1)–O(2)#3
O(1)#2–K(1)–O(2)#3
O(1)–K(1)–O(2)#3
O(1)#3–K(1)–O(2)#3
O(2)#4–K(1)–O(2)#3
O(3)–K(1)–O(2)#3
O(2)#1–K(1)–C(1)#3
O(1)#2–K(1)–C(1)#3
O(1)–K(1)–C(1)#3
O(1)#3–K(1)–C(1)#3
O(2)#4–K(1)–C(1)#3
8.603(9)
16.868(10)
9.497(9)
8.891(9)
11.0.83(6)
1.0121(6)
9.337(9)
16.910(9)
8.351(9)
8.003(9)
11.093(10)
7.648(11)
5.862(8)
K(1)#5–O(1)–K(1)
C(1)–O(1)–K(1)#6
K(1)#5–O(1)–K(1)#6
K(1)–O(1)–K(1)#6
C(1)–O(2)–K(1)#7
C(1)–O(2)–K(1)#8
K(1)#7–O(2)–K(1)#8
C(1)–O(2)–K(1)#6
K(1)#7–O(2)-K(1)#6
K(1)#8–O(2)–K(1)#6
C(2)–O(3)–K(1)
15.961(10)
9.364(11)
11.701(7)
8.012(8)
7.422(8)
4.325(8)
90.65(9)
96.21(10)
116.5(2)
126.9(4)
116.4(3)
116.6(3)
74.2(2)
10.967(7)
12.429(9)
10.539(10)
9.772(9)
O(2)–C(1)–O(1)
O(2)–C(1)–C(2)
8.567(9)
O(1)–C(1)–C(2)
2.155(8)
O(2)–C(1)–K(1)#6
O(1)–C(1)–K(1)#6
9.293(9)
54.31(18)
1
23

3 3 3
Crystal structure and thermochemical properties of potassium pyruvate C H O K(s)
Table 3 continued
Bonds
Bond length/nm
Bonds
Bond angle/°
O(3)–K(1)–C(1)#3
O(2)#3–K(1)–C(1)#3
O(2)#1–K(1)–K(1)#2
O(1)#2–K(1)–K(1)#2
O(1)–K(1)–K(1)#2
O(1)#3–K(1)–K(1)#2
O(2)#4–K(1)–K(1)#2
O(3)–K(1)–K(1)#2
O(2)#3–K(1)–K(1)#2
C(1)#3–K(1)–K(1)#2
14.258(9)
2.202(8)
4.454(7)
4.257(6)
13.754(6)
9.625(6)
13.791(6)
10.126(8)
9.392(6)
9.818(6)
C(2)–C(1)–K(1)#6
O(3)–C(2)–C(3)
161.5(2)
122.5(4)
119.2(3)
118.3(4)
109.5
O(3)–C(2)–C(1)
C(3)–C(2)–C(1)
C(2)–C(3)–H(3A)
C(2)–C(3)–H(3B)
H(3A)–C(3)–H(3B)
C(2)–C(3)–H(3C)
H(3A)–C(3)–H(3C)
H(3B)–C(3)–H(3C)
109.5
109.5
109.5
109.5
109.5
Symmetry code: #1 x ? 1, y - 1, z; #2x ? 1, y, z; #3 - x?1/2, y - 1/2, -z?1/2; #4 x,y - 1, z; #5 x - 1, y, z; #6 -x?1/2, y ? 1/2, -z?1/2;
7 x - 1, y ? 1, z; #8 x, y ? 1, z; #9 -x?3/2, y ? 1/2, -z?1/2; #10 - x?3/2, y - 1/2, -z?1/2
#
0
0
where a and b are appropriate fitted coefficients chosen
according to the stoichiometry of the salt, n is the number
b
i
of ion with a charge z in the formula unit, and Vm is the
i
a
c
molecular volume.
For the salts MX(1:1), MX (1:2), and M X (2:1), the
2
2
Eq. (1) is changed to:
UPOT¼jz jjz jvða =V þ b0Þ
0
1=3
m
ð2Þ
þ
À
where z? and z- are the respective charges on the cation
and anion of the compound, and v is the number of ions per
molecule and equals (p ? q). In the case of the salt of
formula MX with charge ratio (1:1) like potassium pyru-
K
O
C
H
vate,
0
z? = 1,
z- = 1,
0
p = 1,
q = 1,
-1
v = 2,
-1
a = 117.3 kJ mol Ánm, b = 51.9 kJ mol [12], and Vm
3
is in unit of nm and expressed as follows [11]:
Vm ¼ Mm/qNA ¼ 1.66045 Â 10À3Mm/q
where NA is Avogadro’s constant, 6.02245 9 10
ð3Þ
2
3
-
1
moleculeÁmol , M is molar weight of the molecule, q is
m
3 3 3
Fig. 1 Molecular structure of potassium pyruvate C H O K(s)
the density of the substance, and Vm (MX) is calculated to
3
be 0.1038 nm from the formula (3), consequently. Thus,
O1–C1–C2, O2–C1–C2, and O3–C2–C1 are 116.6(3)°,
16.4(3)°, and 119.2(3)° (see Table 3).
For C H O K(s), there are no hydrogen bonds existing in
1
the Eq. (2) is changed to [11]:
3
3 3
1=3
UPOT ¼ cðq=MmÞ þd
ð4Þ
where the values of the constants for MX (1:1) are:
the whole crystal structure, and the stacking of the structure
is completed mainly by the electrostatic force, weak coor-
dination bond and Van der Waals interaction force.
-1
-1
c = 1981.2 kJ mol Ácm and d = 103.8 kJ mol . Lattice
potential energy of the compound C H O K(s) is deter-
3
3 3
Lattice potential energy of the compound and ionic
volume of pyruvate anion
-1
mined to be UPOT = 567.7 kJ mol , which reveals that
the structure of the compound is stable based on the larger
lattice potential energy.
Equation (1) used to estimate lattice potential energy of
general type of salt M X is obtained from the literature
In addition, for a salt of molecular formula M X ,
q
p
p
q
V ðMpXqÞ ¼ pVþ þ qVÀ
where V and V are the volumes of the anion and cation,
ð5Þ
m
[
11]:
ꢀ
ꢁ
X
2
0
1=3
m
þ b0
-
?
UPOT
¼
n z a =V
i i
ð1Þ
3
p = 1 and q = 1 for C H O K(s). V is 0.0277 nm
K?
3
3
3
123

Y. -Y. Di et al.
Fig. 2 Packing diagram of
3 3 3
potassium pyruvate C H O K(s)
c
a
b
K
O
C
?
according to the literature [13], the V (the volume of the
-
K
cation are similar to the three-ion interaction. v is the
-
3
anion CH COCOO ) is estimated to be 0.088 nm .
total number of ions formed from the salt (v = vM ? vX).
zM and zX are the respective charges on the cation and
anion of the compound. b is a parameter with the value
3
Molar enthalpy of dissolution at infinite dilution
and Pitzer’s parameters
1
/2
-1/2
1/2
1.2 kg mol
2
for all solutions.y’ = 2[1 - (1 ? aI ) exp
1
/2
1/2
-1/2
-1
(
-aI )]/a I and a = 2.0 kg mol . m/(mol kg ) is the
The title compound is soluble in the double-distilled water.
The experimental values of molar enthalpies of dissolution
molality of the compound in the solution. R is molar gas con-
-1
-1
stant, 8.3145 J K mol . A
enthalpy [14], A = 1986 J mol at T = 298.150 K.
For the case of salt of the formula MX with charge ratio
(1:1) such as C K(s), the apparent relative molar
enthalpy L for it may be expressed as: [15]
is Debye–Huckel parameter for
-1
H
(
DsHm) of the title compound in the double-distilled water
are given in Table 4, and the curvilinear relationship of
H
-
1
-1
D H /(kJ mol ) with molalities m/(mol kg ) is shown
H O
3 3 3
s
m
U
in Fig. 3.
The molar enthalpy of dissolution of the compound
D H ) in the double-distilled water is expressed as [14]:
U
1=2
2
ð0ÞL
þ y0b
ð1ÞL
(
L ¼2ðAH=2:4Þ lnð1 þ 1:2I Þ À 2RT ½mðb
Þ
s
m
MX
MX
U
DsHm ¼ DsHm1 þ L
U
ð6Þ
2
L
þ m C =2Š
ð8Þ
MX
1
in which D H is the molar enthalpy of dissolution at
infinite dilution, L is the apparent relative molar enthalpy.
From above equations, the working equation to determine
Pitzer parameters is shown as:
s
m
U
For the salts of MX (1:1), according to Pitzer’s electrolyte
solution theory, the apparent relative molar enthalpy U
1
=2
2
Y ¼ ½DsHm À AH lnð1 þ 1:2I Þ=1:2Š=ð2RT Þ
L
ð0ÞL
0
ð1ÞL
2
UL
MX
¼
where
a0 À mb
À my b
À m C =2
ð9Þ
may be expressed as:
MX
MX
U
1=2
2
ð0ÞL
Y
is the extrapolation function and a0 ¼
L ¼vjz z jA lnð1 þ bI Þ=2b À 2v v RT ½mb
M X
H
M
X
MX
1
2
D H =ð2RT Þ. Regression of Y against -m, -my’, and
U
s
m
0
ð1ÞL
1=2
2
L
þ my b
þ ðvMvXÞ m C =2Š
ð7Þ
2
MX
MX
-0.5 m is made by least squares to obtain a = 0.0155,
0
P
U
U
2
(0)L (1)L
L
MX
(0)L
(1)L
b
L
MX
where I is ionic strength, ( m z /2), b , bMX , and C
are Pitzer’s parameters for enthalpies, the coefficients b
and b account for various types of short-range interac-
tions between M and X, and for indirect forces arising from
b
MX = -33.91106,
MX = 37.93714 and
C
=
i i
MX
(0)L
280.16511 with a standard deviation of the fitting
-4
MX
(1)L
MX
3.13777 9 10 for C
H
3
O
K(s), respectively. The molar
K(s) at infinite dilution
-1
3
3
enthalpy of dissolution for C H O
3 3 3
U
1
the solvent, and the third coefficient C L represents for
is determined to be D Hm = 22.9 kJ mol . The three-
s
MX
dimensional chart of Y against -m and -my’ is plotted in
triple ion interactions and is important only at high con-
Fig. 4.
centrations or with strong triple ion interaction. In this
U
L
MX
To calculate the enthalpy of hydration of
-
CH COCOO (g), a thermochemical cycle is designed as
paper, C
may not be overlooked for the compound
3
C H O K(s) because formation and breaking of the five-
3
3 3
-
membered chelate ring of the [CH COCOO] anion with
follows (Scheme 1):
3
1
23

3 3 3
Crystal structure and thermochemical properties of potassium pyruvate C H O K(s)
123

Y. -Y. Di et al.
(0)L
MX
(1)L
The quantities b
range interaction between the cation and anion. The
and bMX are attributed to the short-
2
1
1
1
1
0
8
6
4
2
(0)L
(1)L
absolute values of b
and bMX are very small for an
usual electrolyte and have a tendency to increase along
MX
with the volume and the quantity of the ion. It may be
(1)L
(0)L
noted that the absolute values of b
and bMX are sig-
MX
nificantly greater than those of usual electrolytes mainly
since the volume of the anion is greater than that of the
usual electrolyte. This shows that various types of strong
short-range interactions exist between cation and anion in
the solutions obtained from dissolution of the title com-
(0)L
(0)
MX
pound. bMX has a negative value, that is (qb /qT) \ 0,
p
(0)L
MX
which indicates that the value of b
drops with the rise of
0
5
10
15
20
03 m /mol kg –1
the temperature. This shows that the interionic repulsive
force decreases with the increase of the temperature. The
1
Fig. 3 Plot of the measured D
s
H
m
against molality for potassium
U
L
MX
third coefficient C
for triple ion interaction has a very
3 3 3
pyruvate C H O K(s) at T = 298.15 K
high value in the research, it may be ascribed to the chelate
behavior of the title compound in the aqueous solution, and
the larger ionization energy of the electrovalent compound
in water is caused mainly by the formation and destruction
of the five-membered chelate rings. It can be seen from
Fig. 4 that ionization or dissociation of the compound in
pure water is not complete, it is a kind of the weak elec-
trolyte rather than strong electrolyte, and a certain ioniza-
tion degree or dissociation degree of counter ions emerges
among the solution. The pH values of the solutions after
An important formula can be obtained from the above
thermochemical cycle in Scheme 1:
1
DsH ¼ ðUPOT þ 2RTÞ þ ðDHþ þ DHÀÞ
In the formula (11), for C H O K(s), it is given that
ð11Þ
m
3
3
3
-
1
1
-1
UPOT = 567.7 kJ mol
,
DsH = 22.9 kJ mol
,
and
m
-
1
DH = -322 kJ mol , then the molar enthalpy of
?
-
hydration of the anion CH COCOO (g) is calculated as
3
-
1
DH = -227.8 kJ mol
.
-
Fig. 4 Three-dimensional
graphics of regression of
0
Y against -m and -my for
potassium pyruvate
3 3 3
C H O K(s) at T = 298.15 K
1
23

3 3 3
Crystal structure and thermochemical properties of potassium pyruvate C H O K(s)
∞
Δ H
water (L1) as the solvent and the title compound (L2) as the
solute are obtained. All the results calculated above are
listed in Table 4.
s
m
-
+
C H O K(s) + ∞H O(l) ⎯⎯→ C H O ⋅∞H O(aq) + K ⋅∞H O(aq) (10)
3
3
3
2
3
3
3
2
2
H
-
H
+
UPOT 2RT
Conclusions
-
+
C H O (g) + K (g)
3
3
3
1.
The potassium pyruvate C H O K(s) is synthesized.
3 3 3
Scheme 1 Thermochemical cycle
The crystal structure is determined by X-ray crystal-
lography. The lattice potential energy of the compound
-
and the volume V- of the anion CH COCOO are
dissolution are much more than 7 because the hydrolysis of
-
3
[
CH COCOO] takes place, so there are three kinds of ions
3
estimated.
?
existing in the solutions, including K , [CH COCOO] ,
-
3
2.
The molar enthalpy of dissolution of the compound at
infinite dilution is calculated by Pitzer’s electrolyte
-
and OH .
The degree of chaos of C H O K(s) is increased when it
3 3
(0)L
MX
(1)L
, bMX
3
solution theory. The Pitzer’s parameters (b
,
?
is dissociated to K (aq) and [CH COCOO] (aq) in the
-
3
U
and C ) are obtained through fitting of the curve of
L
MX
double-distilled water. It is concluded that the entropy
change of the dissolution reaction is greater than zero
according to the statistical explanation of the entropy in
statistical thermodynamics. From the values of molar
enthalpies of dissolution, we deduce the conclusion that the
dissolution of the title compound in the water is a typical
endothermic process, and an entropy-driven process
instead of enthalpy-driven process. It mainly ascribes to the
breaking of ionic bonds and chelate bonds existing in the
compound needing to absorb large amount of heat energy.
enthalpy of dissolution with molality of the electrolyte
according to Pitzer’s theory.
U
3
.
.
The values of apparent relative molar enthalpies ( L)
and relative partial molar enthalpies of the solvent (L1)
and the compound (L2) are derived. These results
indicate that the endothermic reaction takes place
when it is dissolved in the double-distilled water.
4
Finally, the molar enthalpy of hydration of
-
CH COCOO (g) is calculated as an important chem-
3
ical thermodynamic quantity.
Relative partial molar enthalpies
Acknowledgements This work is financially supported by the
National Natural Science Foundations of China under the contract
NSFC No. 21273171 and 21273100.
The relative partial molar enthalpies of solvent (L1) and
solute (L ) are important thermodynamic functions of the
2
electrolyte solutions. Generally, there are many ways used
to determine the relative partial molar enthalpies. In this
paper, they are obtained by the apparent relative molar
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1
23