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Solubilities of a gas in a crown ether
M-1746(N) J
Chem. Thermodwamics 1985, 17, 701-702
Solubilities
R. G. LINFORD
of a gas in a crown
ether
and D. G. T. THORNHILL
School of Chemistry,
Leicester Polytechnic,
P.O. Box 143, Leicester LEI 9BH, U.K.
(Received IO July 1984; in revised form 30 January 1985)
Crown ethers are macrocylic polyethers containing a central cavity enclosed by a flexible framework.‘” They are much used as “phase-transfer catalysts” in organic synthesis, analytical chemistry, and membrane studies because, by their use, inorganic salts can be dissolved in aprotic solvents. (2-4) The cation resides in the central cavity, forming a stable complex with the soluble crown ether, and the salt anion is left in a very exposed position which facilitates nucleophilic reaction. In general crown ethers are solids at room temperature but the two with the lowest molar masses are liquids. The purpose of this study was to determine whether the solubilities of gases of different molecular sizes were a function of the size of the cavity in a crown ether, and additionally whether the solubilities of oxygen and nitrogen were sufficiently different to provide the basis for a separation process. The solubilities of oxygen, nitrogen, carbon dioxide, and hydrogen sulphide were measured in the two liquid crown ethers: 1,4,7,10-tetraoxacyclododecane (Chemical Abstracts registry number 294-93-9; trivial name 12-crown-4) and 1,4,7,10,13-pentaoxacyclopentadecane (registry number 33100-27-5; trivial name 15-crown-5). In addition, the solubilities of the first three gases were determined in a solution of 1,4,7.10,13,16-hexaoxacyclooctadecane (registry number 17455-13-9; trivial name 1S-crown-6) in benzene. The solubility of argon in 1,4,7,10-tetraoxacyclododecane was also measured. The solubilities of hydrogen sulphide were measured using a mass method, closely based on that of Gerrard, (‘) full details of which will be reported elsewhere. The apparatus used for the other determinations was the same as that used for a study of the solubilities of ethane and sulphur hexafluoride in liquid mixtures.‘6) The crown ethers were from Borregaard, Sarpsburg, Norway and were supplied by Trafford Chemicals, Altringham, near Manchester; they were described as g.l.c.-pure, and were used as received. The gases were supplied by the British Oxygen Company (02,‘N2, CO,) and by Cambrian Chemicals (H,S, Ar) and had stated purities: O,, 99.5 moles per cent; N,, 99.9 moles per cent; CO,, 99.9 moles per cent; H,S, 99.6 moles per cent; Ar, 99.9 moles per cent. The results in table 1 are in the form of the mole fractions x of gas dissolved under a partial pressure of 101325 Pa at a specified temperature. It can be seen that the solubility of oxygen increases considerably with time. This might indicate a chemical reaction between the crown ether and oxygen. In consequence, it is not thought that a useful process 0071-9614/85/070701+02
%02.00/O
!Q 1985 Academic Press Inc. (London) Limited
702
NOTES
TABLE 1. Mole-fraction solubilities .Y of N,(g) or O,(g) or CO,(g) or Ar(g) or H,S(g) at the parttal _prc :ssure 101325 Pa in a liquid crown ether or in a solution of a crown ether in benzene as a function of equilibration time t and temperature 7 Solute -__
10%
tlh
T/K ..-.~
10% _._ solvent:
7.1 8.2 5.9 140 300 9.2 3100
1.5 1.5 0.1 0.1 15.0 2.0 0.2
303.5 303.6 316.5 302.8 302.8 302.8 295.2
8.2 1.4 7.0 0.8 29 30.4 390 217.0 180 1.4 3300 0.2
308.5 308.0 308.0 308.0 308.3 295.2
6.9 44 8.8 170
solvent:
15 20 130 a This solvent
7.0 21.5 20.0
solvent: 308.1 308.8 308.4
t/h ~..
lO‘+x
T/K ~~~
t,‘h
TIK
10%
t/h
7‘iK
25.5 1.2 0.4
303.6 316.5 302.8
97 14 250
41.0 1.6 0.8
303.6 316.5 302.8
7.8 168.5
308.0 308.0
3:;
25.5 196.0
308.0 308.0
47 150
168.0 309.0
308.4 308.3
at 298.15
K.
1,4.7,10-tetraoxacyclododecane 1.5 17.0 0.5 9.2
316.5 303.6 316.5 302.8
61 12 210
1,4,7,10,13-pentaoxacyclopentadecane 8.2 45
240 3200
1.7 46.5
308.0 308.0
18.0 24.0
308.3 295.2
11 270
1,4,7,10,13,16-hexaoxacyclooctadecane 28 135
was 46.7 g of the crown
75.0 51.0
308.7 308.4
ether
dissolved
in benzene 32 140
95.0 123.5
308.7 308.4
in 101.5 cm3 of solution
*
for separating the constituents of (nitrogen + oxygen) gas mixtures such as air could be based on dissolution of the mixtures in crown ethers. There was a similar change in solubility with time for carbon dioxide but not for the other gases. For nitrogen and oxygen in 1,4,7,10-tetraoxacyclododecane, solubilities were studied at two temperatures. Little difference was detected for nitrogen but for oxygen the solubility after 90 min at 316.65 K was nearly twice as high as the value of 303.65 K. The variation of solubility with time was greater at 316.65 K than at 303.65 K. REFERENCES 1. Pedersen, C. J. J. Am. Chem. Sot. 1967, 89, 7017. 2. Christensen, J. J.; Eatough, D. J.; Izatt, R. M. Chem. Rev. 1974, 74, 351. 3. Vogtle, F.; Weber, E. The Chemistry of Functional Groups: Supplement E: the Chemistry of Ethers, Crown Ethers, Hydroxyl Groups and their Sulphur Analogues: Part 1. Patai, S.: editor, Wiley Interscience: New York. 1980, ch. 2, p. 59. 4. Knipe, A. C. J. Chem. Educ. 1976, 53, 618. 5. Gerrard, W. J. Appl. Chem. Biotechnol. 1972, 22, 623. 6. Armitage, D. A.; Linford, R. G.; Thornhill, D. G. T. J. Chem. Thermodynamics 1983, 15, 225.
Chem. Thermodwamics 1985, 17, 701-702
Solubilities
R. G. LINFORD
of a gas in a crown
ether
and D. G. T. THORNHILL
School of Chemistry,
Leicester Polytechnic,
P.O. Box 143, Leicester LEI 9BH, U.K.
(Received IO July 1984; in revised form 30 January 1985)
Crown ethers are macrocylic polyethers containing a central cavity enclosed by a flexible framework.‘” They are much used as “phase-transfer catalysts” in organic synthesis, analytical chemistry, and membrane studies because, by their use, inorganic salts can be dissolved in aprotic solvents. (2-4) The cation resides in the central cavity, forming a stable complex with the soluble crown ether, and the salt anion is left in a very exposed position which facilitates nucleophilic reaction. In general crown ethers are solids at room temperature but the two with the lowest molar masses are liquids. The purpose of this study was to determine whether the solubilities of gases of different molecular sizes were a function of the size of the cavity in a crown ether, and additionally whether the solubilities of oxygen and nitrogen were sufficiently different to provide the basis for a separation process. The solubilities of oxygen, nitrogen, carbon dioxide, and hydrogen sulphide were measured in the two liquid crown ethers: 1,4,7,10-tetraoxacyclododecane (Chemical Abstracts registry number 294-93-9; trivial name 12-crown-4) and 1,4,7,10,13-pentaoxacyclopentadecane (registry number 33100-27-5; trivial name 15-crown-5). In addition, the solubilities of the first three gases were determined in a solution of 1,4,7.10,13,16-hexaoxacyclooctadecane (registry number 17455-13-9; trivial name 1S-crown-6) in benzene. The solubility of argon in 1,4,7,10-tetraoxacyclododecane was also measured. The solubilities of hydrogen sulphide were measured using a mass method, closely based on that of Gerrard, (‘) full details of which will be reported elsewhere. The apparatus used for the other determinations was the same as that used for a study of the solubilities of ethane and sulphur hexafluoride in liquid mixtures.‘6) The crown ethers were from Borregaard, Sarpsburg, Norway and were supplied by Trafford Chemicals, Altringham, near Manchester; they were described as g.l.c.-pure, and were used as received. The gases were supplied by the British Oxygen Company (02,‘N2, CO,) and by Cambrian Chemicals (H,S, Ar) and had stated purities: O,, 99.5 moles per cent; N,, 99.9 moles per cent; CO,, 99.9 moles per cent; H,S, 99.6 moles per cent; Ar, 99.9 moles per cent. The results in table 1 are in the form of the mole fractions x of gas dissolved under a partial pressure of 101325 Pa at a specified temperature. It can be seen that the solubility of oxygen increases considerably with time. This might indicate a chemical reaction between the crown ether and oxygen. In consequence, it is not thought that a useful process 0071-9614/85/070701+02
%02.00/O
!Q 1985 Academic Press Inc. (London) Limited
702
NOTES
TABLE 1. Mole-fraction solubilities .Y of N,(g) or O,(g) or CO,(g) or Ar(g) or H,S(g) at the parttal _prc :ssure 101325 Pa in a liquid crown ether or in a solution of a crown ether in benzene as a function of equilibration time t and temperature 7 Solute -__
10%
tlh
T/K ..-.~
10% _._ solvent:
7.1 8.2 5.9 140 300 9.2 3100
1.5 1.5 0.1 0.1 15.0 2.0 0.2
303.5 303.6 316.5 302.8 302.8 302.8 295.2
8.2 1.4 7.0 0.8 29 30.4 390 217.0 180 1.4 3300 0.2
308.5 308.0 308.0 308.0 308.3 295.2
6.9 44 8.8 170
solvent:
15 20 130 a This solvent
7.0 21.5 20.0
solvent: 308.1 308.8 308.4
t/h ~..
lO‘+x
T/K ~~~
t,‘h
TIK
10%
t/h
7‘iK
25.5 1.2 0.4
303.6 316.5 302.8
97 14 250
41.0 1.6 0.8
303.6 316.5 302.8
7.8 168.5
308.0 308.0
3:;
25.5 196.0
308.0 308.0
47 150
168.0 309.0
308.4 308.3
at 298.15
K.
1,4.7,10-tetraoxacyclododecane 1.5 17.0 0.5 9.2
316.5 303.6 316.5 302.8
61 12 210
1,4,7,10,13-pentaoxacyclopentadecane 8.2 45
240 3200
1.7 46.5
308.0 308.0
18.0 24.0
308.3 295.2
11 270
1,4,7,10,13,16-hexaoxacyclooctadecane 28 135
was 46.7 g of the crown
75.0 51.0
308.7 308.4
ether
dissolved
in benzene 32 140
95.0 123.5
308.7 308.4
in 101.5 cm3 of solution
*
for separating the constituents of (nitrogen + oxygen) gas mixtures such as air could be based on dissolution of the mixtures in crown ethers. There was a similar change in solubility with time for carbon dioxide but not for the other gases. For nitrogen and oxygen in 1,4,7,10-tetraoxacyclododecane, solubilities were studied at two temperatures. Little difference was detected for nitrogen but for oxygen the solubility after 90 min at 316.65 K was nearly twice as high as the value of 303.65 K. The variation of solubility with time was greater at 316.65 K than at 303.65 K. REFERENCES 1. Pedersen, C. J. J. Am. Chem. Sot. 1967, 89, 7017. 2. Christensen, J. J.; Eatough, D. J.; Izatt, R. M. Chem. Rev. 1974, 74, 351. 3. Vogtle, F.; Weber, E. The Chemistry of Functional Groups: Supplement E: the Chemistry of Ethers, Crown Ethers, Hydroxyl Groups and their Sulphur Analogues: Part 1. Patai, S.: editor, Wiley Interscience: New York. 1980, ch. 2, p. 59. 4. Knipe, A. C. J. Chem. Educ. 1976, 53, 618. 5. Gerrard, W. J. Appl. Chem. Biotechnol. 1972, 22, 623. 6. Armitage, D. A.; Linford, R. G.; Thornhill, D. G. T. J. Chem. Thermodynamics 1983, 15, 225.