Thermochemical characteristics of phosphorous acid derivatives

Article abstract of DOI:10.1134/S1070363207020107

Enthalpies of formation enthalpies of a series of phosphorous acid derivatives were estimated from the heat effects of their reactions. The collected thermochemical data was used to analyze, on the basis of the additive scheme, the experimental enthalpies

Full text of DOI:10.1134/S1070363207020107

ISSN 1070-3632, Russian Journal of General Chemistry, 2007, Vol. 77, No. 2, pp. 248 252.
Pleiades Publishing, Ltd., 2007.
Original Russian Text
E.V. Sagdeev, Yu.G. Safina, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77, No. 2, pp. 275 279.
Thermochemical Characteristics
of Phosphorous Acid Derivatives
E. V. Sagdeev and Yu. G. Safina
Kazan State Technological University, ul. K. Marksa 68, Kazan, Tatarstan, 420015 Russia
e-mail: sagadeev@list.ru
Received April 8, 2006
Abstract Enthalpies of formation enthalpies of a series of phosphorous acid derivatives were estimated
from the heat effects of their reactions. The collected thermochemical data was used to analyze, on the basis
of the additive scheme, the experimental enthalpies of formation and vaporization of four-coordinate phos-
phorus derivatives.
DOI: 10.1134/S1070363207020107
Earlier we considered the possibility of calculating
basic enthalpy characteristics of organophosphorus
compounds on an example of thermochemical forma-
tion data for phosphoranes [1]. This allowed us to
apply the same approach for estimating basic thermo-
chemical characteristics for other organophosphorus
compounds, primarily P(IV) derivatives which are not
only the most stable and abundant, but also possess
scientifically interesting and practically useful pro-
perties, first of all amphotericity [2] and high biolo-
gical activity [3, 4].
and formation one can estimate the enegries of bonds
responsible for the reactivity of a compound and its
potential biological activity [5, 6]. Thus, thermo-
chemical characteristics of phosphorous acid and its
derivatives are quite urgent to estimate.
Aiming at extending the experimental database for
this class compounds, we, based on our previous
thermochemical results for the reaction between phos-
phorous esters I III, XI, XIV, and XV and nitrogen-
containing compounds, including substituted mor-
pholines IV and V, N-cyclohexylbut-2-enaldimine
(XII), and diphenyldiazomethane (XVI), determined
enthalpies of formation for six -aminophosphonates
VI X and XIII and four phosphonates XVII XX
(Table 1).
However, it is follows from the literature that the
termochemistry of P(IV) compounds, including phos-
phorous acid derivatives, has been poorly studied. On
the other hand, with known enthalpies of vaporization
2
N)C=CR22
IV, V
(RO)2P(O)H + R1(O
,
(1)
(2)
(RO)2P(O)C(N
O)R1CHR2
I III
VI X
,
(CH3O)2P(O)CHNH
CH=CHCH3
XIII
(CH3O)2P(O)H + CH3CH=CH CH=N
XI
XII
O
O
O
O
.
(3)
P(O)H + (C6H5)2CN2
P(O)CH(C6H5)2 + N2
R
R
XIV, II, XV, III
XVI
XVII XX
The gas-phase enthalpies of reactions (1) (3)
(Table 2) were determined by Eq. (4) from the heats
of the reactions in condensed phase and the enthalpies
of solvation in organic solvents for each reagent and
reaction product.
Hr(gas) = Hr(solvent) +
Hsolv(reagents)
Hsolv(products).
(4)
The enthalpies of formation of compounds VI X,
248

THERMOCHEMICAL CHARACTERISTICS OF PHOSPHOROUS ACID DERIVATIVES
249
1
Table 1. Experimental and calculated enthalpies of vaporization and formation (kJ mol , 298 K) of parent compounds
and products of reactions (1) (3)
H0vap
Hf0
gas phase
condensed phase
Comp.
no.
Compound
I
(C2H5O)2P(O)H
49.5a *
45.7
43.8
877.4b
883.0
926.7b
909.1c
928.7
889.1
(C2H5O)2P(O)H
O
II
43.1a *
60.3a
50.4d
65.5d
99.2e
866.1 28.0c *
867.0 45.0c *
845.3
876.7
124.7
1.7
P(O)H
O
O
P(O)H
O
III
IV
V
49.8
49.7
66.4
87.6
927.3c
926.5
174.4
64.7
CH=C(CH3)2
O
N
C6H5 C=CH2
O
N
O
P(O)CHCH(CH3)2
N
VI
1070.1f,g
1030.7f,h
952.3f *
1105.1
1169.3f,g 1192.7
O
O
O
O
P(O)CHCH(CH3)2
N
VII
99.0e
93.6
1136.5
954.5
1129.7f,h 1230.1
O
O
VIII
96.3d 104.9
1048.6f
1059.4
1096.9
P(O)C(C6H5)CH3
N
O
O
O
O
P(O)C(C6H5)CH3
N
IX
107.0d 111.0
930.6f *
985.9
1037.6f
O
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250
SAGDEEV, SAFINA
Table 1. (Contd.)
H0vap
Hf0
gas phase
condensed phase
Comp.
no.
Compound
(C2H5O)2P(O)CHCH(CH3)2
N
X
88.4e *
39.5a *
89.5
39.5
1037.0f,h
1142.7
1125.4f,h 1232.2
851.4
O
XI
(CH3O)2P(O)H
811.9
34.1
XII
CH3CH=CH CH=N
XIII
89.8i
94.9
903.9f *
890.0
993.7f
984.9
(CH3O)2P(O)CHHN
CH=CH CH3
XIV
XV
(C6H5O)2P(O)H
82.1a
67.3a
86.7
49.5
604.5
926.3
691.2
975.8
O
P(O)H
O
XVI
(C6H5)2CN2
230.8
457.7
XVII (C6H5O)2P(O)CH(C6H5)2
149.5
106.6
471.9f *
746.4f *
607.2
805.1
O
XVIII
698.5
P(O)CH(C6H5)2
O
O
XIX
112.3
112.6
811.5f *
779.5
891.8
842.5
P(O)CH(C6H5)2
O
O
XX
720.9f *
729.9
P(O)CH(C6H5)2
O
a
b
c
d
e
f
g
h
i
Data of [10]. Data of [11]. Data of [12]. Data of [13]. Data of [14]. Our data. At 323 K. At 358 K. Data of [15].
XIII and XVII XX were calculated according to the
V, XII, and XVI, the H0f values for these compounds
were calculated with data in [16] by the additive
scheme (Table 1).
Hess law for the gas phase:
Hr(gas) =
H0f (gas)reagents.
H0f (gas)products
With the resulting thermochemical database for
four-coordinate phosphorus derivatives (Table 1), we
could determine, in terms of the additive approach,
group increments in the enthalpies of formation and
(5)
In view of the absence of required experimental
gas-phase enthalpies of formation for compounds IV,
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THERMOCHEMICAL CHARACTERISTICS OF PHOSPHOROUS ACID DERIVATIVES
251
vaporization, aimed at further estimating thermo-
chemical characteristics for a wide range of phos-
phorous acid derivatives. The calculations were per-
formed by the Enthalpy program [17]. The experi-
mental enthalpies of formation and vaporization of
P(IV) derivatives, used for calculation by the additive
scheme of group increments for corresponding phos-
phorus-containing groups are asterisked in Table 1.
Table 2. Enthalpies of reactions (1) (3) in solution and in
the gas phase [7]
1
Hr, kJmol
Reagents
Products
p-xylene
gas phase
I
II
III
II
III
XI
XIV
II
XV
III
IV
IV
IV
V
V
XII
X
VI
25.2a
67.0b
26.4a
72.3
34.9
79.3
39.0
87.9
65.3
126.1
98.2
111.1
116.0
84.7
The calculated group increments in the enthalpy of
formation and vaporization of a P(IV) atom sur-
rounded by heteroatoms are listed in Tables 3 and 4.
The increments are designated according to the
Benson Buss symbolism [18]. According to Benson
and Buss, PO (O)2(H) denotes phosphoryl group in
phosphorous acid, connected with two alkoxyl oxygen
atoms, O (C)(PO) denotes ester oxygen atom attached
to carbon atom and phosphoryl group, etc. [18].
VII
VIII
IX
XIII
XVII
XVIII
XIX
XX
48.5
124.5c
82.8d
97.9d
101.3d
70.3d
XVI
a
b
c
Measured at 358 K. Measured at 23 K. Tetrachloromethane.
Data of [9].
Using our calculated (Tables 3 and 4) and pub-
lished [16, 19, 20] group increments in the enthalpy of
formation and vaporization, we calculated, by the
Enthalpy program [17], H0f and Hv0ap for all the
compounds listed in Table 1.
d
Table 3. Group increments Xi for calculation of gas-phase
1
enthalpies of formation, kJ mol
Run no.
Group
Xi
As seen from Table 1, the calculated enthalpies of
formation and vaporization nicely fit experiment for
most P(IV) derivatives.
1
2
3
4
5
6
C (C)(N)(PO)(H)
C (C)(CB)(N)(PO)
2[O (C)(PO)] + PO (O)2(H)
2[O (C)(PO)] + PO (C)(O)2
21.8a
13.4a
727.6b
756.9
25.1c
4.2d
The certain inconsistency between the calculated
and experimental enthalpies of vaporization for cyclic
derivatives III, VI, VIII, and XV is probably ex-
plained by features in measuring their H0vap. It is
known that the enthalpies of vaporization of cyclic
structures should be considered with caution es-
pecially when the termochemical characteristics are
obtained by the Solomonov equation [21, 22] on the
basis of solution data. As shown in [23], the transfer
of such compounds from condensed phase to solution
may involve conformational transformations with
5
6
a
Calculated from data of [16]: Carbon is substituted by P=O
b
group. Standard deviation is 2.47,
and
are correction
6
5
c
d
for rings.
Data of [16].
Data of [17].
Table 4. Group increments Xi for calculation of enthalpies
of vaporization, kJ mol , and standard deviations
1
1
energies of up to 10 15 kJ mol . This contribution
can misrepresent experimental enthalpies of vaporiza-
tion. Conformational transformations are also typical
of a tetramethyl-substituted five-membered cyclic
structure, resulting in that such compounds differ
significantly in reactivity andother properties from
other five-membered cyclic analogs [24, 25]. There-
fore, for cyclic organophosphorus derivatives III, VI,
VIII, and XV, the calculated enthalpies of vaporiza-
tion listed in Table 1 seem more reliable.
Run no.
Group
Xi
1
2
3
4
5
C (C)(N)(PO)(H)
C (C)(CB)(N)(PO)
2[O (C)(PO)] + PO (O)2(H) 26.8
2[O (C)(PO)] + PO (C)(O)2 26.8
1.0a
6.9a
0.43
0.30
=
6.4b 0.16
5
6
a
Calculated from data of [20]: Carbon is substituted by P=O
b
group,
and
are corrections for rings. Data of [20].
6
5
The applied approach allows the thermochemical
characteristics of new, model, and practically pros-
pective four-coordinate phosphorus derivatives to be
estimated with high accuracy in the absence of cor-
responding experimental data.
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