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Enthalpy of combustion of 4-diethylaminonitrosobenzene
J. Chem. Thermodynamics 1998, 30, 271]274
NOTE
Enthalpy of combustion of 4-diethylaminonitrosobenzene Maria D. M. C. Ribeiro da Silva, a M. Agostinha R. Matos, Centro de In¨ estigac ¸ao Departamento de Quımica, ˜ em Quımica, ´ ´ Faculdade de Ciencias, Uni¨ ersidade do Porto, Rua do Campo Alegre, 687, ˆ P-4150 Porto, Portugal
G. Pilcher, and Department of Chemistry, Uni¨ ersity of Manchester, Manchester M13 9PL, U.K.
W. E. Acree, Jr. Department of Chemistry, Uni¨ ersity of North Texas, Denton, TX 76203-5070, U.S.A.
Crystalline aromatic C-nitroso compounds are white when dimeric and green when monomeric. In this note we report the enthalpies of combustion and sublimation of 4-diethylaminonitrosobenzene and show the thermochemical results to be consistent with this green compound being monomeric in the solid state. A commercial sample ŽTCI America Chemical Company. was recrystallized five times from hexane and then sublimed in ¨ acuo. The elemental analysis results were in agreement with the corresponding calculated values. The experimentally determined mass fractions for C 10 H 14 N2 O were: C, 0.6745; H, 0.0785; N, 0.1569; and the calculated values were: C, 0.6739; H, 0.0792; N, 0.1572. The mean value for the ratio of the mass of carbon dioxide produced by the sample rrŽg . cmy3 . s 1.404 in the combustion experiments to that calculated from its mass was Ž1.0000 " 0.0004.. The bomb calorimeter has been described elsewhere.Ž1,2. The energy equivalent was determined from the combustion of benzoic acid ŽBureau of Analysed Samples 190-p., and the resulting value from nine calibrations was « Žcalor.rŽJ . Ky1 . s Ž15911.2 " 1.5. for an average mass of water added to the calorimeter of 3119.6 g. Samples in pellet form were ignited at T s Ž298.150 " 0.001. K in 3.04 MPa of oxygen with 1 cm3 of water added to the bomb. The energy for electrical ignition, combustion of the cotton fuse, and the corrections for nitric acid formation were determined as previously described.Ž1,2. The energy of combustion of the auxiliary aid, hexadecane, was determined in separate a
To whom correspondence should be addressed.
0021]9614r98r020271 q 04 $25.00r0rct970315
Q 1998 Academic Press Limited
272
M. D. M. C. Ribeiro da Silva et al.
measurements, yD c u 0rŽJ . gy1 . s Ž47156.9 " 1.2.. The amount of substance used was determined in the first four experiments from the mass of carbon dioxide produced, and for the other experiments from the sample mass. The D c u 0 was calculated by the procedure of Hubbard et al.Ž3. The combustion results are given in table 1. The mean value of the standard massic energy of combustion, yD c u 0rŽJ . gy1 . s Ž33522.4 " 9.4.; with molar mass 178.2334 g . moly1 , y1 . y1 . Ž . Ž . Ž . Ž . yD c HT s Ž5979.8 " 3.6.; D f HT s Ž43.9 " 3.8. m cr r kJ mol m cr r kJ mol with uncertainties of twice the standard deviation of the mean. The enthalpy of sublimation was measured by the ‘‘¨ acuum sublimation’’ drop microcalorimetric method as previously described,Ž4. with the Calvet HighT K Temperature microcalorimeter held at T s 378 K. The observed D g,cr,378 298.15 K Hm T K Ž . was corrected to T s 298.15 K using D378 298.15 K Hm g estimated from the values of T Ž5. g y1 . . Ž Ž Stull et al. The D cr Hm r kJ mol s 107.9 " 3.7. was determined from five y1 . Ž . Ž . experiments, thus enabling the calculation of D f HT s Ž151.8 " 5.3.. m g r kJ mol It has been shownŽ6. that 4-dimethylaminonitrosobenzene is stabilized additionally relative to nitrosobenzene by 20 kJ . moly1 , and this is also the case for 4-diethylaminonitrosobenzene because the following gaseous reaction is thermoneutral. 4-Me 2 NC 6 H 4 NO q Et 2 NC 6 H 5 ª 4-Et 2 NC 6 H 4 NO q Me 2 NC 6 H 5 .
Ž 1.
y1. Ž . Ž . With D f HT for 4-Me 2 NC 6 H 4 NO s Ž185.0 " 2.3.;Ž6. for m g r kJ mol Ž6. Ž . Me 2 NC 6 H 5 s Ž100.5 " 4.7.; and for Et 2 NC 6 H 5 s Ž62.1 " 7.6.,Ž7. D r HT m g r y1 ŽkJ . mol . s Ž5.2 " 10.6. for reaction Ž1.. DŽN s N. in the nitrosobenzene dimer was assessed as Ž91.1 " 1.5. kJ . moly1 ;Ž8. the additional stabilization would reduce DŽN s N. to c. 51 kJ . moly1 . From comparison with other aromatic nitroso dimers, it seems reasonable to assume the enthalpy of sublimation of the hypothetical dimer of 4-Et 2 NC 6 H 4 NO to be less than 130 kJ . moly1 . By consideration of the simple cycle:
y51
6
2 Monomer Ž g . 6 216
130 q35
6
2 Monomer Ž cr .
Dimer Ž g . 6
Dimer Ž cr .
it becomes apparent that the dimerization of 4-Et 2 NC 6 H 4 NO in the solid state would be endothermic so that the thermochemical results are consistent with this compound being monomeric in the crystalline state and, therefore, green. ao Cientıfica e Tecnologica, Thanks are due to Junta Nacional de Investigac¸˜ ´ ´ JNICT, for financial support through Centro de Investigac¸˜ ao em Quımica da ´ Universidade do Porto ŽLinha 5. and for the research project PRAXIS XXI Žproject 2r2.1rQUIr54r94..
1.54678 0.17287 0.35799 0.00414 1.43026 16.5 0.2 22780.8 22.9 1.1 7.5 16881.9 67.2 33558.7
3.30206 0.60013 0.58365 0.00325 2.99777 19.2 0.2 47757.1 58.3 1.1 20.8 27523.3 52.8 33495.9
2.03261 0.43597 0.30551 0.00377 1.82979 17.2 0.0 29144.5 43.3 1.1 12.1 14406.8 61.2 33536.9
1.77402 0.30860 0.32316 0.00439 1.61358 16.7 0.2 25701.2 32.2 1.1 9.8 15239.2 71.3 33534.3 0.38265 0.24393 0.00358 1.53404 16.5 0.5 24435.9 37.2 1.0 10.1 11503.1 58.1 33522.5
0.34085 0.20410 0.00299 1.32737 16.5 0.0 21140.9 32.5 1.1 8.6 9624.9 48.6 33523.0
0.32995 0.28051 0.00325 1.53035 16.8 0.0 24374.3 35.6 1.1 9.5 13227.9 52.8 33485.4
m s mass; cpd s compound; DTad s corrected temperature riservariation of adiabatic temperature; « f s energy equivalent of the contents in the final state; D mŽH 2 O. s deviation of the mass of the water added to the calorimeter from 3119.6 g; DUŽIBP. s energy change for the isothermal combustion reaction under actual bomb conditions; DUŽHNO3 . s energy correction for the nitric acid formation; DUŽign. s energy of ignition; DUS s standard state correction or Žsum of corrections for the standard state.; m D c u 0 Žhex. s energy of combustion of n-hexadecane Žcombustion auxiliary.; m D c u 0 Žfuse. s energy of combustion of the fuse Žcotton.; D c u 0 Žcpd. s massic energy of combustion of the compound; DUŽIBP. s y « Žcalor. q c p ŽH 2 O, l. D mŽH 2 O. q « f 4 DTad q DUŽign..
mŽCO 2 , total.rg mŽcpd.rg mŽhex.rg mŽfuse.rg DTad rK « frŽJ . Ky1 . D mŽH 2 O.rg yDUŽIBP.rJ DUŽHNO3 .rJ DUŽign.rJ DUS rJ ym D c u 0 Žhex.rJ ym D c u 0 Žfuse.rJ yD c u 0 Žcpd.rŽJ . gy1 .
TABLE 1. Combustion results for 4-diethylaminonitrosobenzene Ž p 0 s 0.1 MPa.
Ž . D c HT m 4-diethylaminonitrosobenzene
273
274
M. D. M. C. Ribeiro da Silva et al.
REFERENCES 1. Ribeiro da Silva, M. A. V.; Ribeiro da Silva, M. D. M. C.; Pilcher, G. Re¨ . Port. Quım. ´ 1984, 26, 163]172. 2. Ribeiro da Silva, M. D. M. C.; Ribeiro da Silva, M. A. V.; Pilcher, G. J. Chem. Thermodynamics 1984, 16, 1149]1155. 3. Hubbard, W. N.; Scott, D. W.; Waddington, G. Experimental Thermochemistry, Vol. 1. Rossini, F. D.; editor. Interscience: New York. 1956, Chap. 5. 4. Adedeji, F. A.; Brown, D. L. S.; Connor, J. A.; Leung, M.; Paz Andrade, M. I.; Skinner, H. A. J. Organometallic Chem. 1975, 97, 221]228. 5. Stull, D. R.; Westrum, E. F.; Sinke, G. C. The Chemical Thermodynamics of Organic Compounds. Wiley: New York. 1969. 6. Acree, W. E. Jr; Tucker, S. A.; Pilcher, G.; Toole, G. J. Chem. Thermodynamics 1994, 26, 85]90. 7. Ribeiro da Silva, M. A. V.; Ribeiro da Silva, M. D. M. C.; Monteiro, M. F. B. M.; Gomes, M. L. A. C. N.; Chickos, J. S.; Smith, A. P.; Liebman, J. F. Structural Chemistry 1996, 7, 367]373. 8. Acree, W. E. Jr.; Tucker, S. A.; Chowdhary, A.; Pilcher, G.; Ribeiro da Silva, M. D. M. C.; Monte, M. J. S. J. Chem. Thermodynamics 1993, 25, 1253]1261.
(Recei¨ ed 19 May 1997; in final form 21 October 1997)
WA-97r039
NOTE
Enthalpy of combustion of 4-diethylaminonitrosobenzene Maria D. M. C. Ribeiro da Silva, a M. Agostinha R. Matos, Centro de In¨ estigac ¸ao Departamento de Quımica, ˜ em Quımica, ´ ´ Faculdade de Ciencias, Uni¨ ersidade do Porto, Rua do Campo Alegre, 687, ˆ P-4150 Porto, Portugal
G. Pilcher, and Department of Chemistry, Uni¨ ersity of Manchester, Manchester M13 9PL, U.K.
W. E. Acree, Jr. Department of Chemistry, Uni¨ ersity of North Texas, Denton, TX 76203-5070, U.S.A.
Crystalline aromatic C-nitroso compounds are white when dimeric and green when monomeric. In this note we report the enthalpies of combustion and sublimation of 4-diethylaminonitrosobenzene and show the thermochemical results to be consistent with this green compound being monomeric in the solid state. A commercial sample ŽTCI America Chemical Company. was recrystallized five times from hexane and then sublimed in ¨ acuo. The elemental analysis results were in agreement with the corresponding calculated values. The experimentally determined mass fractions for C 10 H 14 N2 O were: C, 0.6745; H, 0.0785; N, 0.1569; and the calculated values were: C, 0.6739; H, 0.0792; N, 0.1572. The mean value for the ratio of the mass of carbon dioxide produced by the sample rrŽg . cmy3 . s 1.404 in the combustion experiments to that calculated from its mass was Ž1.0000 " 0.0004.. The bomb calorimeter has been described elsewhere.Ž1,2. The energy equivalent was determined from the combustion of benzoic acid ŽBureau of Analysed Samples 190-p., and the resulting value from nine calibrations was « Žcalor.rŽJ . Ky1 . s Ž15911.2 " 1.5. for an average mass of water added to the calorimeter of 3119.6 g. Samples in pellet form were ignited at T s Ž298.150 " 0.001. K in 3.04 MPa of oxygen with 1 cm3 of water added to the bomb. The energy for electrical ignition, combustion of the cotton fuse, and the corrections for nitric acid formation were determined as previously described.Ž1,2. The energy of combustion of the auxiliary aid, hexadecane, was determined in separate a
To whom correspondence should be addressed.
0021]9614r98r020271 q 04 $25.00r0rct970315
Q 1998 Academic Press Limited
272
M. D. M. C. Ribeiro da Silva et al.
measurements, yD c u 0rŽJ . gy1 . s Ž47156.9 " 1.2.. The amount of substance used was determined in the first four experiments from the mass of carbon dioxide produced, and for the other experiments from the sample mass. The D c u 0 was calculated by the procedure of Hubbard et al.Ž3. The combustion results are given in table 1. The mean value of the standard massic energy of combustion, yD c u 0rŽJ . gy1 . s Ž33522.4 " 9.4.; with molar mass 178.2334 g . moly1 , y1 . y1 . Ž . Ž . Ž . Ž . yD c HT s Ž5979.8 " 3.6.; D f HT s Ž43.9 " 3.8. m cr r kJ mol m cr r kJ mol with uncertainties of twice the standard deviation of the mean. The enthalpy of sublimation was measured by the ‘‘¨ acuum sublimation’’ drop microcalorimetric method as previously described,Ž4. with the Calvet HighT K Temperature microcalorimeter held at T s 378 K. The observed D g,cr,378 298.15 K Hm T K Ž . was corrected to T s 298.15 K using D378 298.15 K Hm g estimated from the values of T Ž5. g y1 . . Ž Ž Stull et al. The D cr Hm r kJ mol s 107.9 " 3.7. was determined from five y1 . Ž . Ž . experiments, thus enabling the calculation of D f HT s Ž151.8 " 5.3.. m g r kJ mol It has been shownŽ6. that 4-dimethylaminonitrosobenzene is stabilized additionally relative to nitrosobenzene by 20 kJ . moly1 , and this is also the case for 4-diethylaminonitrosobenzene because the following gaseous reaction is thermoneutral. 4-Me 2 NC 6 H 4 NO q Et 2 NC 6 H 5 ª 4-Et 2 NC 6 H 4 NO q Me 2 NC 6 H 5 .
Ž 1.
y1. Ž . Ž . With D f HT for 4-Me 2 NC 6 H 4 NO s Ž185.0 " 2.3.;Ž6. for m g r kJ mol Ž6. Ž . Me 2 NC 6 H 5 s Ž100.5 " 4.7.; and for Et 2 NC 6 H 5 s Ž62.1 " 7.6.,Ž7. D r HT m g r y1 ŽkJ . mol . s Ž5.2 " 10.6. for reaction Ž1.. DŽN s N. in the nitrosobenzene dimer was assessed as Ž91.1 " 1.5. kJ . moly1 ;Ž8. the additional stabilization would reduce DŽN s N. to c. 51 kJ . moly1 . From comparison with other aromatic nitroso dimers, it seems reasonable to assume the enthalpy of sublimation of the hypothetical dimer of 4-Et 2 NC 6 H 4 NO to be less than 130 kJ . moly1 . By consideration of the simple cycle:
y51
6
2 Monomer Ž g . 6 216
130 q35
6
2 Monomer Ž cr .
Dimer Ž g . 6
Dimer Ž cr .
it becomes apparent that the dimerization of 4-Et 2 NC 6 H 4 NO in the solid state would be endothermic so that the thermochemical results are consistent with this compound being monomeric in the crystalline state and, therefore, green. ao Cientıfica e Tecnologica, Thanks are due to Junta Nacional de Investigac¸˜ ´ ´ JNICT, for financial support through Centro de Investigac¸˜ ao em Quımica da ´ Universidade do Porto ŽLinha 5. and for the research project PRAXIS XXI Žproject 2r2.1rQUIr54r94..
1.54678 0.17287 0.35799 0.00414 1.43026 16.5 0.2 22780.8 22.9 1.1 7.5 16881.9 67.2 33558.7
3.30206 0.60013 0.58365 0.00325 2.99777 19.2 0.2 47757.1 58.3 1.1 20.8 27523.3 52.8 33495.9
2.03261 0.43597 0.30551 0.00377 1.82979 17.2 0.0 29144.5 43.3 1.1 12.1 14406.8 61.2 33536.9
1.77402 0.30860 0.32316 0.00439 1.61358 16.7 0.2 25701.2 32.2 1.1 9.8 15239.2 71.3 33534.3 0.38265 0.24393 0.00358 1.53404 16.5 0.5 24435.9 37.2 1.0 10.1 11503.1 58.1 33522.5
0.34085 0.20410 0.00299 1.32737 16.5 0.0 21140.9 32.5 1.1 8.6 9624.9 48.6 33523.0
0.32995 0.28051 0.00325 1.53035 16.8 0.0 24374.3 35.6 1.1 9.5 13227.9 52.8 33485.4
m s mass; cpd s compound; DTad s corrected temperature riservariation of adiabatic temperature; « f s energy equivalent of the contents in the final state; D mŽH 2 O. s deviation of the mass of the water added to the calorimeter from 3119.6 g; DUŽIBP. s energy change for the isothermal combustion reaction under actual bomb conditions; DUŽHNO3 . s energy correction for the nitric acid formation; DUŽign. s energy of ignition; DUS s standard state correction or Žsum of corrections for the standard state.; m D c u 0 Žhex. s energy of combustion of n-hexadecane Žcombustion auxiliary.; m D c u 0 Žfuse. s energy of combustion of the fuse Žcotton.; D c u 0 Žcpd. s massic energy of combustion of the compound; DUŽIBP. s y « Žcalor. q c p ŽH 2 O, l. D mŽH 2 O. q « f 4 DTad q DUŽign..
mŽCO 2 , total.rg mŽcpd.rg mŽhex.rg mŽfuse.rg DTad rK « frŽJ . Ky1 . D mŽH 2 O.rg yDUŽIBP.rJ DUŽHNO3 .rJ DUŽign.rJ DUS rJ ym D c u 0 Žhex.rJ ym D c u 0 Žfuse.rJ yD c u 0 Žcpd.rŽJ . gy1 .
TABLE 1. Combustion results for 4-diethylaminonitrosobenzene Ž p 0 s 0.1 MPa.
Ž . D c HT m 4-diethylaminonitrosobenzene
273
274
M. D. M. C. Ribeiro da Silva et al.
REFERENCES 1. Ribeiro da Silva, M. A. V.; Ribeiro da Silva, M. D. M. C.; Pilcher, G. Re¨ . Port. Quım. ´ 1984, 26, 163]172. 2. Ribeiro da Silva, M. D. M. C.; Ribeiro da Silva, M. A. V.; Pilcher, G. J. Chem. Thermodynamics 1984, 16, 1149]1155. 3. Hubbard, W. N.; Scott, D. W.; Waddington, G. Experimental Thermochemistry, Vol. 1. Rossini, F. D.; editor. Interscience: New York. 1956, Chap. 5. 4. Adedeji, F. A.; Brown, D. L. S.; Connor, J. A.; Leung, M.; Paz Andrade, M. I.; Skinner, H. A. J. Organometallic Chem. 1975, 97, 221]228. 5. Stull, D. R.; Westrum, E. F.; Sinke, G. C. The Chemical Thermodynamics of Organic Compounds. Wiley: New York. 1969. 6. Acree, W. E. Jr; Tucker, S. A.; Pilcher, G.; Toole, G. J. Chem. Thermodynamics 1994, 26, 85]90. 7. Ribeiro da Silva, M. A. V.; Ribeiro da Silva, M. D. M. C.; Monteiro, M. F. B. M.; Gomes, M. L. A. C. N.; Chickos, J. S.; Smith, A. P.; Liebman, J. F. Structural Chemistry 1996, 7, 367]373. 8. Acree, W. E. Jr.; Tucker, S. A.; Chowdhary, A.; Pilcher, G.; Ribeiro da Silva, M. D. M. C.; Monte, M. J. S. J. Chem. Thermodynamics 1993, 25, 1253]1261.
(Recei¨ ed 19 May 1997; in final form 21 October 1997)
WA-97r039