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Standard enthalpies of formation and of sublimation of 2,6-dimethylquinoline and 2,7-dimethylquinoline
M-3151 J. Chem. Thermodynamics 1995, 27, 1141–1145
Standard enthalpies of formation and of sublimation of 2,6-dimethylquinoline and 2,7-dimethylquinoline Manuel A. V. Ribeiro da Silva, M. Agostinha R. Matos, and Luı´ sa M. P. F. Amaral Centro de Investigac¸a˜o em Quı´ mica, Department of Chemistry, Faculty of Science, University of Porto, P-4050 Porto, Portugal
(Received 24 April 1995) The standard (p° = 0.1 MPa) molar enthalpies of formation for crystalline 2,6-dimethylquinoline, 2,6-(CH3 )2 –C9 H5 N, and 2,7-dimethylquinoline, 2,7-(CH3 )2 –C9 H5 N, at the temperature T=298.15 K, were derived from the standard molar energies of combustion, in oxygen, measured by static-bomb calorimetry. The standard molar enthalpies of sublimation, at T=298.15 K, were measured by microcalorimetry. 2,6-dimethylquinoline, 2,6-(CH3 )2 –C9 H5 N 2,6-dimethylquinoline, 2,7-(CH3 )2 –C9 H5 N
Df H°m(cr)/(kJ·mol−1 ) 36.422.5 34.322.6
DgcrH°m /(kJ·mol−1 ) 84.521.5 87.521.5
7 1995 Academic Press Limited
1. Introduction In a previous paper(1) we have reported the standard molar enthalpies of formation of 2-, 4-, 6-, and 8-methylquinoline in the gaseous state. In the present work we have measured the standard molar enthalpies of combustion and of sublimation for each of the crystalline isomers 2,6-, and 2,7-dimethylquinoline, at the temperature T=298.15 K. From these values, the standard molar enthalpies of formation for both compounds, in the gaseous state, at T=298.15 K, were derived, in order to analyse the enthalpic effects due to the simultaneous methyl substitution in the benzenic and in the pyridinic rings of quinoline.
2. Experimental The dimethylquinolines (Aldrich Chemical Co.), were purified by repeated vacuum sublimation until the combustion results were consistent and the carbon-dioxide recovery ratios were satisfactory. The CO2 recoveries from the combustion measurements, together with the standard deviations of the mean, were: 2,6-dimethylquinoline, (100.03 2 0.04) per cent; 2,7-dimethylquinoline, (100.0520.05) per cent. The static bomb calorimeter, subsidiary apparatus, 0021–9614/95/101141+05 $12.00/0
7 1995 Academic Press Limited
1142
M. A. V. Ribeiro da Silva, M. A. R. Matos, and L. M. P. F. Amaral
and technique have been described.(2, 3) For all experiments, ignition was made at T=(298.15020.001) K. Combustion experiments were made in oxygen at the pressure 3.04 MPa, with a volume 1 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 energy equivalent o(calor) of the calorimeter was determined from the combustion of benzoic acid (Bureau of Analysed Samples, Thermochemical Standard, BCS-CRM-190 p) having a massic energy of combustion, under standardizing conditions, of −(26431.8 2 3.7) J·g−1 . From eight calibration experiments, o(calor) = (16013.9 2 1.7) J·K−1 , where the uncertainty quoted is the standard deviation of the mean. This result corresponds to the average mass of water added to the calorimeter of 3119.6 g. The crystalline dimethylquinolines were burned in pellet form. The amount of substance used in each experiment was determined from the mass of carbon dioxide produced after allowance for that formed from the cotton-thread fuse and that lost due to carbon formation. For the cotton-thread fuse, empirical formula CH1.686O0.843 , Dc u° = − 16250 J·g−1 .(4) The corrections for nitric-acid formation were based on −59.7 kJ·mol−1 , for the molar energy of formation of HNO3(aq, c=0.1 mol·dm−3 ) from N2 , O2 , and H2O(l).(5) Corrections for carbon formation were based on Dc u°=−33 kJ·g−1 .(5) The density of hydroxyquinoline, r=1.093 g·cm−3 ,(6) was assumed for both the dimethylquinolines. An estimated pressure coefficient of massic energy: (1u/1p)T=−0.2 J·g−1 ·MPa−1 at T=298.15 K, a typical value for most organic compounds, was assumed. For each compound, Dc u° was calculated by the procedure given by Hubbard et al.(4) The molar masses used for the elements were those recommended by the IUPAC in 1991.(7) The standard molar enthalpies of sublimation of the compounds were determined by microcalorimetry, using the vacuum-sublimation drop-microcalorimetric method.(8) A sample of each crystalline dimethylquinoline (3 to 4) mg, contained in a small thin glass capillary tube sealed at one end, was dropped at room temperature into the hot reaction vessel in the Calvet High-Temperature Microcalorimeter (Setaram, Lyon, France) held at T=(372 to 373) K, and then removed from the
TABLE 1. Typical combustion experiments for x,y-dimethylquinolines at T=298.15 K x,y m(CO2 ,total)/g m'(cpd)/g m0(fuse)/g DTad /K of /(J·K−1 ) Dm(H2O)/g −DU(IBP)/J DU(HNO3 )/J DU(ign.)/J DUS /J −DU(fuse)/J −Dc u°/(J·g−1 )
2,6
2,7
2.21380 0.71731 0.00371 1.69528 16.04 −0.1 27173.35 39.76 1.18 15.54 60.25 37721.21
2.24300 0.72675 0.00380 1.71752 16.07 0.0 27530.61 38.98 1.18 15.77 61.71 37721.57
1143
Enthalpies of formation of dimethylquinolines TABLE 2. Values of −Dc u°/(J·g−1 ) for x,y-dimethylquinolines at T=298.15 K x,y:
2,6
2,7
37732.33 37719.50 37719.38 37734.46 37721.21 37744.18
37705.88 37721.57 37701.25 37729.76 37711.64 37722.96 −Dc u°/(J·g−1 )
37728.524.1
37715.524.5
hot zone by vacuum sublimation. The thermal corrections for the glass capillary tubes were determined in separate experiments, and were reduced as far as possible by dropping tubes of nearly equal mass, to within 210 mg, into each of the twin calorimeter cells. The calorimeter was calibrated in situ for these experiments by making use of the reported enthalpy of sublimation of naphthalene.(9) The experimental results, Dg,cr,T298.15 KH°m , were corrected to T=298.15 K using T D298.15 m(g) estimated by a group method, i.e. from {naphthalene+2-picoline + KH° toluene−2benzene}, based on the values of Stull et al.(9)
3. Results Results for a typical combustion experiment of each compound are given in table 1, where Dm(H2O) is the deviation of the mass of water added to the calorimeter from 3119.6 g, and DUS is the correction to the standard state. The remaining quantities are as previously described.(4) As samples were ignited at T=298.15 K, DU(IBP)=−{o(calor)+Dm(H2O)cp (H2O,l)+of }DTad+DUign . The individual results of all combustion experiments, together with the mean value and its standard deviation for each compound, are given in table 2. Table 3 lists the derived standard molar energies and enthalpies of combustion and the standard molar enthalpies of formation for the two crystaline dimethylquinolines at T = 298.15 K. In accordance with normal thermochemical practice, the uncertainties assigned to the standard molar enthalpies of combustion are in each case twice the overall standard deviation of the mean and include the uncertainties in calibration(10) and in the values of auxiliary quantities. To derive Df H°m(cr) TABLE 3. Derived standard (p°=0.1 MPa) molar values for 2,6-dimethylquinoline, 2,6-(CH3 )2 –C9 H5 N, and 2,7-dimethylquinoline, 2,7-(CH3 )2 –C9 H5 N, in the crystalline state at T=298.15 K
2,6-(CH3 )2 –C9 H5 N 2,7-(CH3 )2 –C9 H5 N
−DcU°m(cr)/(kJ·mol−1 )
−Dc H°m(cr)/(kJ·mol−1 )
Df H°m(cr)/(kJ·mol−1 )
5931.522.0 5929.422.1
5937.122.0 5935.022.1
36.422.5 34.322.6
1144
M. A. V. Ribeiro da Silva, M. A. R. Matos, and L. M. P. F. Amaral
TABLE 4. Standard (p° = 0.1) MPa) molar enthalpies of sublimation of dimethylquinolines at T=298.15 K
2,6-(CH3 )2 –C9 H5 N 2,7-(CH3 )2 –C9 H5 N
No. of expts
T K
Dg,cr,T298.15 KH°m kJ·mol−1
DT298.15 KH°m(g) kJ·mol−1
Dgcr H°m(298.15 K) kJ·mol−1
5 6
373 372
99.621.5 102.421.5
15.1 14.9
84.521.5 87.521.5
from Dc H°m(cr) the standard molar enthalpies of formation of H2O(l) and CO2(g), at T = 298.15 K, respectively, −(285.83020.042) kJ·mol−1 ,(11) and −(393.5120.13) kJ·mol−1 ,(11) were used. In table 4 the microcalorimetric determined enthalpies of sublimation are presented for both dimethylquinolines as well as the respective uncertainties, as twice the standard deviations of the mean. For the dimethylquinolines, the derived standard molar enthalpies of formation in the solid state, standard molar enthalpies of sublimation, and standard molar enthalpies of formation in the gaseous state at T=298.15 K, are summarized in table 5.
4. Discussion Previously we reported the standard molar enthalpies of formation in the gaseous state of 2-, 4-, 6-, and 8-methylquinoline,(1) and concluded that the increment in the molar enthalpy of formation for methyl substitution into the pyridinic ring of quinoline is equal to that for pyridine whereas that for methyl substitution into the benzenic ring is equal to that for the benzene. From the enthalpies of formation listed in table 6, the standard molar enthalpies of formation of both 2,6- and 2,7-dimethylquinoline in the gaseous state, can be estimated from the standard molar enthalpy of gaseous quinoline,(12) by adding the values for the increments in enthalpy of formation for methyl substitution into benzene: −(32.221.0) kJ·mol−1 , and for methyl substitution into the ortho-position in pyridine: −(41.221.1) kJ·mol−1 , to yield, for both isomers, an estimated Df H°m(g)=(127.121.8) kJ·mol−1 . These estimates are within 10 kJ·mol−1 of the experimental values which constitutes satisfactory agreement for such a method of estimation.
TABLE 5. Derived standard (p°=0.1 MPa) molar values of dimethylquinolines at T=298.15 K
2,6-(CH3 )2 –C9 H5 N 2,7-(CH3 )2 –C9 H5 N
Df H°m(cr)/(kJ·mol−1 )
Dgcr H°m /(kJ·mol−1 )
Df H°m(g)/(kJ·mol−1 )
36.422.5 34.322.6
84.521.5 87.521.5
120.922.9 121.823.0
Enthalpies of formation of dimethylquinolines
1145
TABLE 6. Standard molar enthalpies of formation of some compounds in the gaseous state, at T=298.15 K Compound Benzene, C6 H6 Toluene, CH3 –C6 H5 Pyridine, C6 H5 N 2-Methylpyridine, 2-CH3 –C5 H4 N Quinoline, C9 H7 N 2-Methylquinoline, 2-CH3 –C9 H6 N 6-Methylquinoline, 6-CH3 –C9 H6 N 2,6-Dimethylquinoline, 2,6-(CH3 )2 –C9 H5 N 2,7-Dimethylquinoline, 2,7-(CH3 )2 –C9 H5 N
Df H°m(g)/(kJ·mol−1 )
Reference
82.620.7 50.420.6 140.420.7 99.220.8 200.520.9 159.123.1 161.023.0 120.922.9 121.823.0
13 13 13 13 12 1 1 This work This work
Thanks are due to Junta Nacional de Investigac¸a˜o Cientı´ fica e Tecnolo´gica (JNICT) for financial support to Faculty of Science of Porto University (Project PBIC/C/CEN/10119/92) as well as to Centro de Investigac¸a˜o em Quı´ mica, University of Porto (Q.P./1-L.5). One of us (L.M.P.F.A.) thanks JNICT for the award of a research grant under Programa Cieˆncia (research grant no. BD/2277/92-RM). REFERENCES 1. Ribeiro da Silva, M. A. V.; Matos, M. A. R.; Amaral, L. M. P. F. J. Chem. Thermodynamics 1995, 27, 565–574. 2. Ribeiro da Silva, M. A. V.; Ribeiro da Silva, M. D. M. C.; Pilcher, G. Rev. Port. Quim. 1984, 26, 163. 3. Ribeiro da Silva, M. A. V.; Ribeiro da Silva, M. D. M. C.; Pilcher, G. J. Chem. Thermodynamics 1984, 16, 1149. 4. Hubbard, W. N.; Scott, D. W.; Waddington, G. Experimental Thermochemistry. Vol. 1, Chap. 5. Rossini, F. D.: editor. Interscience: New York. 1956. 5. J. Phys. Chem. Ref. Data 1982, Supplement no. 2. 6. Handbook of Chemistry and Physics. Weast, R. C.: editor. 70th edn. C.R.C. Press, Inc.: U.S.A. 1989. 7. IUPAC J. Phys. Chem. Ref. Data 1993, 22, 1571. 8. 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. 9. Stull, D. R.; Westrum, E. F.; Sinke, G. C. The Chemical Thermodynamics of Organic Compounds. Wiley: New York. 1969. 10. Rossini, F. D. Experimental Thermochemistry. Vol 1, Chap. 14. Rossini, F. D.: editor. Interscience: New York. 1956. 11. J. Chem. Thermodynamics 1978, 10, 903. 12. Steele, W. V.; Archer, D. V.; Chirico, R. D.; Collier, W. B.; Hossenlopp, I. A.; Nguyen, A.; Smith, N. K.; Gammon, B. E. J. Chem. Thermodynamics 1988, 20, 1233. 13. Pedley, J. B.; Naylor, R. D.; Kirby, S. B. Thermochemical Data of Organic Compounds. Chapman and Hall: London. 1986.
Standard enthalpies of formation and of sublimation of 2,6-dimethylquinoline and 2,7-dimethylquinoline Manuel A. V. Ribeiro da Silva, M. Agostinha R. Matos, and Luı´ sa M. P. F. Amaral Centro de Investigac¸a˜o em Quı´ mica, Department of Chemistry, Faculty of Science, University of Porto, P-4050 Porto, Portugal
(Received 24 April 1995) The standard (p° = 0.1 MPa) molar enthalpies of formation for crystalline 2,6-dimethylquinoline, 2,6-(CH3 )2 –C9 H5 N, and 2,7-dimethylquinoline, 2,7-(CH3 )2 –C9 H5 N, at the temperature T=298.15 K, were derived from the standard molar energies of combustion, in oxygen, measured by static-bomb calorimetry. The standard molar enthalpies of sublimation, at T=298.15 K, were measured by microcalorimetry. 2,6-dimethylquinoline, 2,6-(CH3 )2 –C9 H5 N 2,6-dimethylquinoline, 2,7-(CH3 )2 –C9 H5 N
Df H°m(cr)/(kJ·mol−1 ) 36.422.5 34.322.6
DgcrH°m /(kJ·mol−1 ) 84.521.5 87.521.5
7 1995 Academic Press Limited
1. Introduction In a previous paper(1) we have reported the standard molar enthalpies of formation of 2-, 4-, 6-, and 8-methylquinoline in the gaseous state. In the present work we have measured the standard molar enthalpies of combustion and of sublimation for each of the crystalline isomers 2,6-, and 2,7-dimethylquinoline, at the temperature T=298.15 K. From these values, the standard molar enthalpies of formation for both compounds, in the gaseous state, at T=298.15 K, were derived, in order to analyse the enthalpic effects due to the simultaneous methyl substitution in the benzenic and in the pyridinic rings of quinoline.
2. Experimental The dimethylquinolines (Aldrich Chemical Co.), were purified by repeated vacuum sublimation until the combustion results were consistent and the carbon-dioxide recovery ratios were satisfactory. The CO2 recoveries from the combustion measurements, together with the standard deviations of the mean, were: 2,6-dimethylquinoline, (100.03 2 0.04) per cent; 2,7-dimethylquinoline, (100.0520.05) per cent. The static bomb calorimeter, subsidiary apparatus, 0021–9614/95/101141+05 $12.00/0
7 1995 Academic Press Limited
1142
M. A. V. Ribeiro da Silva, M. A. R. Matos, and L. M. P. F. Amaral
and technique have been described.(2, 3) For all experiments, ignition was made at T=(298.15020.001) K. Combustion experiments were made in oxygen at the pressure 3.04 MPa, with a volume 1 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 energy equivalent o(calor) of the calorimeter was determined from the combustion of benzoic acid (Bureau of Analysed Samples, Thermochemical Standard, BCS-CRM-190 p) having a massic energy of combustion, under standardizing conditions, of −(26431.8 2 3.7) J·g−1 . From eight calibration experiments, o(calor) = (16013.9 2 1.7) J·K−1 , where the uncertainty quoted is the standard deviation of the mean. This result corresponds to the average mass of water added to the calorimeter of 3119.6 g. The crystalline dimethylquinolines were burned in pellet form. The amount of substance used in each experiment was determined from the mass of carbon dioxide produced after allowance for that formed from the cotton-thread fuse and that lost due to carbon formation. For the cotton-thread fuse, empirical formula CH1.686O0.843 , Dc u° = − 16250 J·g−1 .(4) The corrections for nitric-acid formation were based on −59.7 kJ·mol−1 , for the molar energy of formation of HNO3(aq, c=0.1 mol·dm−3 ) from N2 , O2 , and H2O(l).(5) Corrections for carbon formation were based on Dc u°=−33 kJ·g−1 .(5) The density of hydroxyquinoline, r=1.093 g·cm−3 ,(6) was assumed for both the dimethylquinolines. An estimated pressure coefficient of massic energy: (1u/1p)T=−0.2 J·g−1 ·MPa−1 at T=298.15 K, a typical value for most organic compounds, was assumed. For each compound, Dc u° was calculated by the procedure given by Hubbard et al.(4) The molar masses used for the elements were those recommended by the IUPAC in 1991.(7) The standard molar enthalpies of sublimation of the compounds were determined by microcalorimetry, using the vacuum-sublimation drop-microcalorimetric method.(8) A sample of each crystalline dimethylquinoline (3 to 4) mg, contained in a small thin glass capillary tube sealed at one end, was dropped at room temperature into the hot reaction vessel in the Calvet High-Temperature Microcalorimeter (Setaram, Lyon, France) held at T=(372 to 373) K, and then removed from the
TABLE 1. Typical combustion experiments for x,y-dimethylquinolines at T=298.15 K x,y m(CO2 ,total)/g m'(cpd)/g m0(fuse)/g DTad /K of /(J·K−1 ) Dm(H2O)/g −DU(IBP)/J DU(HNO3 )/J DU(ign.)/J DUS /J −DU(fuse)/J −Dc u°/(J·g−1 )
2,6
2,7
2.21380 0.71731 0.00371 1.69528 16.04 −0.1 27173.35 39.76 1.18 15.54 60.25 37721.21
2.24300 0.72675 0.00380 1.71752 16.07 0.0 27530.61 38.98 1.18 15.77 61.71 37721.57
1143
Enthalpies of formation of dimethylquinolines TABLE 2. Values of −Dc u°/(J·g−1 ) for x,y-dimethylquinolines at T=298.15 K x,y:
2,6
2,7
37732.33 37719.50 37719.38 37734.46 37721.21 37744.18
37705.88 37721.57 37701.25 37729.76 37711.64 37722.96 −Dc u°/(J·g−1 )
37728.524.1
37715.524.5
hot zone by vacuum sublimation. The thermal corrections for the glass capillary tubes were determined in separate experiments, and were reduced as far as possible by dropping tubes of nearly equal mass, to within 210 mg, into each of the twin calorimeter cells. The calorimeter was calibrated in situ for these experiments by making use of the reported enthalpy of sublimation of naphthalene.(9) The experimental results, Dg,cr,T298.15 KH°m , were corrected to T=298.15 K using T D298.15 m(g) estimated by a group method, i.e. from {naphthalene+2-picoline + KH° toluene−2benzene}, based on the values of Stull et al.(9)
3. Results Results for a typical combustion experiment of each compound are given in table 1, where Dm(H2O) is the deviation of the mass of water added to the calorimeter from 3119.6 g, and DUS is the correction to the standard state. The remaining quantities are as previously described.(4) As samples were ignited at T=298.15 K, DU(IBP)=−{o(calor)+Dm(H2O)cp (H2O,l)+of }DTad+DUign . The individual results of all combustion experiments, together with the mean value and its standard deviation for each compound, are given in table 2. Table 3 lists the derived standard molar energies and enthalpies of combustion and the standard molar enthalpies of formation for the two crystaline dimethylquinolines at T = 298.15 K. In accordance with normal thermochemical practice, the uncertainties assigned to the standard molar enthalpies of combustion are in each case twice the overall standard deviation of the mean and include the uncertainties in calibration(10) and in the values of auxiliary quantities. To derive Df H°m(cr) TABLE 3. Derived standard (p°=0.1 MPa) molar values for 2,6-dimethylquinoline, 2,6-(CH3 )2 –C9 H5 N, and 2,7-dimethylquinoline, 2,7-(CH3 )2 –C9 H5 N, in the crystalline state at T=298.15 K
2,6-(CH3 )2 –C9 H5 N 2,7-(CH3 )2 –C9 H5 N
−DcU°m(cr)/(kJ·mol−1 )
−Dc H°m(cr)/(kJ·mol−1 )
Df H°m(cr)/(kJ·mol−1 )
5931.522.0 5929.422.1
5937.122.0 5935.022.1
36.422.5 34.322.6
1144
M. A. V. Ribeiro da Silva, M. A. R. Matos, and L. M. P. F. Amaral
TABLE 4. Standard (p° = 0.1) MPa) molar enthalpies of sublimation of dimethylquinolines at T=298.15 K
2,6-(CH3 )2 –C9 H5 N 2,7-(CH3 )2 –C9 H5 N
No. of expts
T K
Dg,cr,T298.15 KH°m kJ·mol−1
DT298.15 KH°m(g) kJ·mol−1
Dgcr H°m(298.15 K) kJ·mol−1
5 6
373 372
99.621.5 102.421.5
15.1 14.9
84.521.5 87.521.5
from Dc H°m(cr) the standard molar enthalpies of formation of H2O(l) and CO2(g), at T = 298.15 K, respectively, −(285.83020.042) kJ·mol−1 ,(11) and −(393.5120.13) kJ·mol−1 ,(11) were used. In table 4 the microcalorimetric determined enthalpies of sublimation are presented for both dimethylquinolines as well as the respective uncertainties, as twice the standard deviations of the mean. For the dimethylquinolines, the derived standard molar enthalpies of formation in the solid state, standard molar enthalpies of sublimation, and standard molar enthalpies of formation in the gaseous state at T=298.15 K, are summarized in table 5.
4. Discussion Previously we reported the standard molar enthalpies of formation in the gaseous state of 2-, 4-, 6-, and 8-methylquinoline,(1) and concluded that the increment in the molar enthalpy of formation for methyl substitution into the pyridinic ring of quinoline is equal to that for pyridine whereas that for methyl substitution into the benzenic ring is equal to that for the benzene. From the enthalpies of formation listed in table 6, the standard molar enthalpies of formation of both 2,6- and 2,7-dimethylquinoline in the gaseous state, can be estimated from the standard molar enthalpy of gaseous quinoline,(12) by adding the values for the increments in enthalpy of formation for methyl substitution into benzene: −(32.221.0) kJ·mol−1 , and for methyl substitution into the ortho-position in pyridine: −(41.221.1) kJ·mol−1 , to yield, for both isomers, an estimated Df H°m(g)=(127.121.8) kJ·mol−1 . These estimates are within 10 kJ·mol−1 of the experimental values which constitutes satisfactory agreement for such a method of estimation.
TABLE 5. Derived standard (p°=0.1 MPa) molar values of dimethylquinolines at T=298.15 K
2,6-(CH3 )2 –C9 H5 N 2,7-(CH3 )2 –C9 H5 N
Df H°m(cr)/(kJ·mol−1 )
Dgcr H°m /(kJ·mol−1 )
Df H°m(g)/(kJ·mol−1 )
36.422.5 34.322.6
84.521.5 87.521.5
120.922.9 121.823.0
Enthalpies of formation of dimethylquinolines
1145
TABLE 6. Standard molar enthalpies of formation of some compounds in the gaseous state, at T=298.15 K Compound Benzene, C6 H6 Toluene, CH3 –C6 H5 Pyridine, C6 H5 N 2-Methylpyridine, 2-CH3 –C5 H4 N Quinoline, C9 H7 N 2-Methylquinoline, 2-CH3 –C9 H6 N 6-Methylquinoline, 6-CH3 –C9 H6 N 2,6-Dimethylquinoline, 2,6-(CH3 )2 –C9 H5 N 2,7-Dimethylquinoline, 2,7-(CH3 )2 –C9 H5 N
Df H°m(g)/(kJ·mol−1 )
Reference
82.620.7 50.420.6 140.420.7 99.220.8 200.520.9 159.123.1 161.023.0 120.922.9 121.823.0
13 13 13 13 12 1 1 This work This work
Thanks are due to Junta Nacional de Investigac¸a˜o Cientı´ fica e Tecnolo´gica (JNICT) for financial support to Faculty of Science of Porto University (Project PBIC/C/CEN/10119/92) as well as to Centro de Investigac¸a˜o em Quı´ mica, University of Porto (Q.P./1-L.5). One of us (L.M.P.F.A.) thanks JNICT for the award of a research grant under Programa Cieˆncia (research grant no. BD/2277/92-RM). REFERENCES 1. Ribeiro da Silva, M. A. V.; Matos, M. A. R.; Amaral, L. M. P. F. J. Chem. Thermodynamics 1995, 27, 565–574. 2. Ribeiro da Silva, M. A. V.; Ribeiro da Silva, M. D. M. C.; Pilcher, G. Rev. Port. Quim. 1984, 26, 163. 3. Ribeiro da Silva, M. A. V.; Ribeiro da Silva, M. D. M. C.; Pilcher, G. J. Chem. Thermodynamics 1984, 16, 1149. 4. Hubbard, W. N.; Scott, D. W.; Waddington, G. Experimental Thermochemistry. Vol. 1, Chap. 5. Rossini, F. D.: editor. Interscience: New York. 1956. 5. J. Phys. Chem. Ref. Data 1982, Supplement no. 2. 6. Handbook of Chemistry and Physics. Weast, R. C.: editor. 70th edn. C.R.C. Press, Inc.: U.S.A. 1989. 7. IUPAC J. Phys. Chem. Ref. Data 1993, 22, 1571. 8. 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. 9. Stull, D. R.; Westrum, E. F.; Sinke, G. C. The Chemical Thermodynamics of Organic Compounds. Wiley: New York. 1969. 10. Rossini, F. D. Experimental Thermochemistry. Vol 1, Chap. 14. Rossini, F. D.: editor. Interscience: New York. 1956. 11. J. Chem. Thermodynamics 1978, 10, 903. 12. Steele, W. V.; Archer, D. V.; Chirico, R. D.; Collier, W. B.; Hossenlopp, I. A.; Nguyen, A.; Smith, N. K.; Gammon, B. E. J. Chem. Thermodynamics 1988, 20, 1233. 13. Pedley, J. B.; Naylor, R. D.; Kirby, S. B. Thermochemical Data of Organic Compounds. Chapman and Hall: London. 1986.