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Ind. Eng. Chem. Res. 1992,31, 2042-2046
Mahapatra, A.; Sharma, M. M. New strategies in separation of close-boiling (solid) mixtures: Extraction into micellar and microemulaion media. Solvent Ertr. Zon Erch. 1987,5(4), 781-788. Schlosberg, R. H.; Scouten, C. G. Organic Chemistry of calcium. Formation and pyrolysis of hydroxy calcium phenoxides. Energy Fuels 1988,2,582. Scouten, C. G.; Dougherty, H. W. Organic chemistry of calcium. 3. Steam stripping of metal phenoxides liberates phenol and regenerates the metal hydroxide. Ind. Eng. Chem. Res. 1990, 29, 1721-1725. Wadekar, V. V.; Sharma, M. M. Separation of close boiling substi-
tuted phenols by dissociation-extraction. J. Chem. Technol. BiotechnoL 1981, 31, 279.
Pradip I(.Pahari, Man Mohan Sharma* Department of Chemical Technology University of Bombay Matunga, Bombay 400 019, India Received for review July 26, 1991 Revised manuscript received April 28, 1992 Accepted May 12, 1992
Modified Joback Group Contribution Method for Normal Boiling Point of Aliphatic Halogenated Compoundst For the screening of alternatives of chlorofluorocarbons (CFCs), one of the limitations encountered is the nonavailability of primary data including normal boiling point and critical temperature. The Joback method, which was proposed for the prediction of boiling point from molecular structure of an organic compound, when tested for an aliphatic halogenated compound, was inadequate in accuracy. It appears that halogens have to be treated differently from other functionalgroups because of halogem-halogen and halogen-hydrogen nonbonded interactions. A modified Joback method, with an improved capability, is proposed with a reestimate of the group contribution by F and also with an addition of some groups and corrections for perfluorination, partial fluorination (with or without other halogens), perhalogenation (with or without F), and partial halogenation (without F). Introduction Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are being extensively used as refrigerants, blowing agents, and propellants and as solvents. Only bromochlorofluorocarbons (BCFCs) are used as fire extinguishing agents. CFCs possess most of the desirable characteristics but for their damaging effect on the stratospheric ozone layer and for their part in global warming by green house effect. The ozone layer depletion has become an international issue. “Montreal Protocol” prescribes curtailing the production and phasing out the use of CFCs on a global scale. There is a likely convention on the compounds contributing to greenhouse effect. Obviously, alternatives to CFCs have to be identified and developed. This has attracted the attention of scientists from many disciplines. Thermodynamic Screening from Normal Boiling Point The earliest screening by Midgley (1937) concluded that the potential refrigerants should be made up of some combinations carbon, hydrogen, nitrogen, oxygen, sulfur, fluorine, chlorine, and bromine. Ultimately the choice was for CFCs. Subsequently,CFCs found their way into many other industrial sectors. Now scientists and technologists are faced with a dilemma of identifying compounds which, as long as they are within the system, perform satisfactorily, perhaps even better than the currently used CFCs, but, when they leak out, should be harmless to human health and benign to the environment. Therefore, any alternative has to have a low or preferably zero ozone depletion potential (ODP) and also with relatively low global warming potential ( G W ) . These constraints limit the number of alternatives. One can screen various compounds using the desired thermodynamic criteria and find suitable alternatives. For an exhaustive thermodynamic screening, one has to consider compounds for which even fundamental thermodynamic data are not readily available. Recently McLinden and Didion (1988), using various constraints for screening, concluded that the potential refrigerants could consist of the elements carbon, fluorine, hydrogen, and oxygen.
HFC134a was proposed as a potential substitute for CFC12. According to many comparative analyses, including the one by Devotta and Gopichand (1992), HFC134a and HFC152a are considered to be the most potential substitutes for CFC12. Still the question of alternative does not appear to be over. There are also some unresolved issues like the global warming potential, toxicity, compatibility, energy efficiency, etc. The other possible compounds from the combinations of H, F, C, and 0 are fluorinated carboxylic acids, alcohols, aldehydes, ethers, and ketones. A recent, thermodynamic assessment of some fluorinated ethers and amines by Devotta et al. (1992) has indicated that tetrafluorodimethyl ether (CHF20CHF2)is another potential alternative to CFC12. In all the above screenings, the starting point for screening among a family of compounds is the normal boiling point. Knowing the boiling point, one could proceed in predicting the required thermodynamic property, from the molecular structure of the compound using well-established group contribution methods, corresponding state methods, and a few correlations. Devotta et al. (1992) have used this approach in their analysis. The limitation of such a screening is that the normal boiling point of a compound should be known. If there is some way of predicting the properties only from the molecular structure, this limitation can also be dispensed. Prediction of Normal Boiling Point by Joback Met hod There are a few methods proposed for the estimation of normal boiling point. These have been reviewed by Lyman et al. (1982) and Reid et al. (1988). These methods require, besides molecular structure, some extra parameters, like critical temperature, molar refraction, ionization potential, etc. It is very unlikely that these parameters will be known for a compound when ita boiling point is not known. Although some of these parameters can be estimated through group contribution methods, the propagation of error through such a route would be fairly high, and some of these methods are not comprehensive enough
0SS8-5885/92/263~-2042$03.O0/0 0 1992 American Chemical Society
Ind. Eng. Chem. Res., Vol. 31, No. 8, 1992 2043
to cover multiple substitutions of functional groups. The only method which can be used from the molecular structure was proposed by Joback (1984). Joback (1984) used the same groups used by Lydersen (1955) for critical properties, added some additional functional groups, and evaluated the contributions of those groups for normal boiling point. The equation was given as TBJ = 198.0 +
cs;
(1)
where Tar is in kelvin. The contribution 6; of the various groups are listed in Reid et al. (1988). The average absolute error and the standard deviation error were reported to be 12.9 and 17.9 K, respectively, while the average of the absolute percent error was 3.6%. Reid et al. (1988) have recommended the Joback method only as a guide to estimate TBwhen no experimental value is available. From recognition of the limitation of the Joback method, an assessment was carried out for a variety of fluorinated compounds, including many well-known refrigeranta and fire extinguishants. The normal boiling point data were taken mostly from published sources. As far as possible, the data were compiled from Ambrose (1980), Adcock et al. (1990), and Reid et al. (1988). Data for some less common fluids were taken from Siegemund et al. (1988). The list of compounds along with experimental and predicted boiling point values are presented in Table I. The boiling points of the compounds chosen are in the range 145-543 K. The functional groups are well represented, and the molecular weight range is also significant. The functional groups include aldehyde, amine, carboxylic acid, ether, ketone, and simple alkanes. Cyclic compounds were not included in the analysis. For the Joback method, the root mean square deviation for the compounds studied was 26.81 K. The maximum absolute deviation was -71.03 K for CFI. The average error in kelvin was 11.94%. The error band is fairly high. A study of the perfluorinated alkanes indicates that the error gradually decreases from -71.03 K for CF, to reach a minimum value of 0.5 K for C4FI0and again increases. This clearly indicates that the increment for C-F was not properly weighted by Joback. In general, the method is inadequate for fluorinated compounds, and the method mostly overestimates the boiling point. The error band tends to decrease for partially fluorinated and chlorinated compounds. The prediction for oxygenated compounds with the aliphatic functional groups such as aldehyde, ketone, and acids is rather poor, and the method usually overestimates the boiling point. The error is also high for bromofluoro compounds.
Modified Joback Method Both Ambrose (1980) and Fedors (1982) have distinguished fluorinated compounds in their group contribution method for critical temperatures. A unique provision was also given for a perfluoro condition. Fedors (1982) had assigned an extra allocation for polysubstitution of chlorine. Ambrose (1980) had included fluorinated functional groups like 4 F 3 , >CF2, and >CF- in the case of highly fluorinated aliphatic compounds. No such considerations were given by Joback (1984). No explanation has been offered 80 far for this anomalous behavior of halogenated, particularly fluorinated, compounds. However, it appears that halogens (may be restricted to F, C1, and Br in this discussion) have to be treated differently from other functional groups. The halogen atoms are relatively big and have high electronegativity. When multiple halogens and hydrogen are attached to a carbon, nonbonded halogen-halogen
hydrogen-*halogeninteractions are involved (Desiraju and Parthasarathy, 1989). Desiraju and Parthasarathy (1989) from their study on halogenated hydrocarbon crystals have concluded that intermolecular contacts from F to F, to H, to C are distinct from other halogen contacts. Also, F-H, which is strongly dipolar, has higher interactions relative to Fa-F. Therefore, F-F interactions play a less stabilizing role than other interactions. Extending this to liquids, one could perhaps state that the weak F-aF interactions result in lower boiling points for fluorinated compounds compared to other halogenated compounds. Therefore, it appears that partially and fully fluorinated and partially and fully halogenated (other than F) compounds require independent corrections. Similarly polysubstitutions of F when C is non-hydrogen bonded also have to be treated independently. In view of the aforementioned, some additional nonhydrogen bonded functional groups 4 F 3 , >CF2,and >CFwere introduced. Additional corrections were considered for (i) perfluorinated compounds, e.g., CF, and CF,COCF,; (ii) perhalogenated compounds (fully halogenated with or without fluorine), e.g., CBrCIFz and CCl,; (iii) partially fluorinated compounds (with or without other halogens), e.g., CH3F, CHC12CF3,and CHF20CHF2;and (iv) partially halogenated compounds (without fluorine), e.g., C2H3C13 and CH3Br. The other functional groups proposed by Joback (1984) were not disturbed, and their contributions could be directly read from Reid et al. (1988). However, for the sake of completion, the contributions of newly introduced groups and reestimated value for F along with other Joback’s functional groups are presented in Table 11. Some examples to illustrate the proposed method are presented in the Appendix. The improvement on the Joback method was rather striking, as can be seen from Table I. The root mean square deviation vas 6.36% with the mean of the absolute error of 13.94 K. Here also the errors are relatively high for CF4and CCl, with a maximum error of -43.95 K for CFI. The Joback method is inadequate in d i s m isomers, e.g., CHC12CF3and CHC12. The modified method proposed in this work is able to differentiate such isomers. It is interesting to note that the contribution of F has been revised to a fairly high value compared to the value suggested by Joback. The corrections suggested in the modified method account for the anomalous behavior of fluorinated compounds. The correction for partially halogenated compounds without fluorine is the only one with positive value, obviously to account for the increase in boiling point either with C1 or with Br as well as when the compound is partially halogenated. The presence of F tends to decrease the boiling points, hence the negative corrections.
Conclusion The prediction of normal boiling point from only the knowledge of the molecular structure appears to be extremely difficult. The only method by Joback (1984),when tested for aliphatic halogenated compounds, was grossly inadequate. It appears that halogens have to be treated differently from other functional groups because of halogewhalogen and halogen-.hydrogen nonbonded interactions. A reevaluation of the functional group F and the introduction of additional functional groups, with some corrections for perfluorination, partial fluorination (with or without other halogens), perhalogenation (with or without fluorine), and partial halogenation (without fluorine) improved the estimation significantly. There is further scope for reevaluating the contributions of oxygenated function groups, such as aldehyde, carboxylic acid, and ketone. There is still some need to improve the pre-
2044
Ind. Eng. Chem. Rea., Vol, 31, No. 8, 1992
Table I. no. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77
Comparison between the Joback and Modified Joback Methods formula reference Ti3 TRI 145.10 216.13 Reid et al. (1988) CF, 194.90 234.32 Reid et al. (1988) CZF6 Reid et al. (1988) 236.50 252.51 C3F8 271.20 270.70 Reid et al. (1988) CPIO 302.40 288.89 Reid et al. (1988) C6FlZ 329.80 307.08 Reid et al. (1988) C6F14 355.60 325.27 Reid et al. (1988) CTFI6 191.00 219.65 Reid et al. (1988) CHFS 221.50 220.82 Reid et al. (1988) CHZFZ 194.70 221.55 Reid et al. (1988) CH3F 253.45 241.36 Allied (1989) CHFzCHFz 246.93 239.01 McLinden (1991) CF3CHzF 248.20 242.56 Reid et al. (1988) CHlCHFz 225.60 239.74 Reid et al. (1988) CF3CH3 235.50 244.43 Reid et al. (1988) CHBCHZF 255.70 263.07 Reid et al. (1988) CHFzCHFCHF2 296.95 330.61 Reid et al. (1988) CClSF 245.20 292.45 Reid et al. (1988) CClzF2 193.20 254.29 Reid et al. (1988) CClF3 276.20 310.64 Reid et al. (1988) CClFiCClFz 235.20 272.48 Reid et al. (1988) CClFzCF3 320.80 348.80 Reid et al. (1988) CC13CF3 366.00 386.96 Reid et al. (1988) CC12FCClZF 301.10 314.16 McLinden (1991) CHClZCF3 303.09 314.16 Allied (1989) CHClFCClFz 263.00 276.00 McLinden (1991) CHFClCF3 224.60 237.84 Alled (1989) CHFzCFB 281.95 295.97 Reid et al. (1988) CHClzF 232.39 257.81 Reid et al. (1988) CHClFz 263.40 277.90 Reid et al. (1988) CH3CClFZ 263.40 280.69 Reid et al. (1988) CHzFCHClF 305.00 315.36 McLinden (1991) CH3CFClz Siegemund et al. (1988) 280.15 277.17 CzHzFSCl 349.90 368.77 Reid et al. (1988) CCl, 334.30 334.13 Reid et al. (1988) CHCL 249.10 259.71 Reid et al. (1988) CH3Ci 330.50 320.72 CHSCHClz Reid et al. (1988) 356.70 320.02 Reid et al. (1988) CHzClCHzCl 285.50 282.59 Reid et al. (1988) CHSCHZCl 342.46 369.50 Reid et al. (1988) CH2C1CH2CH 2C1 305.47 320.40 Reid et al. (1988) CZH&HzCl 313.00 297.14 Reid et al. (1988) CHzClz 419.40 394.00 Reid et al. (1988) CHClzCHClz 386.70 357.01 CHzCICHClz Reid et al. (1988) 354.22 347.20 Reid et al. (1988) CHSCC13 435.00 428.64 CHClzCCl3 Reid et al. (1988) 215.30 283.02 Reid et al. (1988) CBrF, 298.00 349.91 Reid et al. (1988) CBr2e2 Siegemund et al. (1988) 379.15 416.80 CBr3F 269.00 321.18 Reid et al. (1988) CBrCIFz Siegemund et al. (1988) 353.15 388.07 CBr2ClF 366.00 388.01 Reid et al. (1988) CFSCBr2C1F 320.40 368.10 Reid et al. (1988) CF3CFBrz 276.60 288.44 Reid et al. (1988) CH3Br 370.00 354.60 Reid et al. (1988) CHzBrz 311.50 311.32 Reid et al. (1988) CH&H2Br 404.70 377.48 Reid et al. (1988) CHzBrCH2Br Siegemund et al. (1988) 323.35 342.89 CF3CHBrCl 268.35 278.45 Adcock et al. (1990) CF3CHFOCF3 279.35 263.78 Adcock et al. (1990) CHFZOCHFZ 263.35 297.35 Adcock et al. (1990) CF30CFZOCF3 CFSCOCHS Siegemund et al. (1988) 295.15 316.49 CHFZCOCHFZ Siegemund et al. (1988) 331.15 318.11 Siegemund et al. (1988) 245.75 311.07 CF3COCF3 Siegemund et el. (1988) 280.95 349.23 CClF2C0CF 3 cclF,cocclF, Siegemund et al. (1988) 318.35 387.39 Siegemund et al. (1988) 357.65 425.55 cc1,ec0cclF; Siegemund et al. (1988) 397.05 463.71 CClzFCOCClzF CClSCOCClZF Siegemund et al. (1988) 436.85 501.87 cc1,cocc1, Siegemund et al. (1988) 476.75 540.03 CFSkOCHzeOCH3 Siegemund et al. (1988) 379.15 416.12 CFSCOOH Siegemund et al. (1988) 345.55 385.25 CzF8COOH Siegemund et al. (1988) 369.15 403.44 C,F,COOH Siegemund et al. (1988) 393.15 421.63 CAFaCOOH Sieaemund et al. (1988) 403.15 439.82 C$&OOH Siegemund et al. (1988) 430.15 458.01 C,F&OOH Siegemund et al. (1988) 448.15 476.20
TRI -71.03 -39.42 -16.01 50
13.51 22.72 30.33 -28.65 .68 -26.85 12.09 7.92 5.64 -14.14 -8.93 -7.37 -33.66 -47.25 -61.09 -34.44 -37.28 -28.00 -20.96 -13.06 -11.07 -13.00 -13.24 -14.02 -25.42 -14.50 -17.29 -10.36 2.98 -18.87 .17 -10.61 9.78 36.68 2.91 27.04 14.93 15.86 25.40 29.69 -7.02 6.36 -67.72 -51.91 -37.65 -52.18 -34.92 -22.01 -47.70 -11.84 15.40 .18 27.22 -19.54 -10.10 15.57 -34.00 -21.34 13.04 -65.32 -68.28 -69.04 -67.90 -66.66 -65.02 -63.28 -36.97 -39.70 -34.29 -28.48 -36.67 -27.86 -28.05
ERJ, % -48.95 -20.23 -6.77 .18 4.47 6.89 8.53 -15.00 .31 -13.79 4.77 3.21 2.27 -6.27 -3.79 -2.88 -11.34 -19.27 -31.62 -12.47 -15.85 -8.73 -5.73 -4.34 -3.65 -4.94 -5.89 -4.97 -10.94 -5.50 -6.56 -3.40 1.06 -5.39 .05 -4.26 2.96 10.28 1.02 7.32 4.66 5.07 6.06 7.68 -2.02 1.46 -31.45 -17.42 -9.93 -19.40 -9.89 -6.01 -14.89 -4.28 4.16 .06
6.73 -6.04 -3.76 5.57 -12.91 -7.23 3.94 -26.58 -24.30 -21.69 -18.99 -16.79 -14.88 -13.27 -9.75 -11.49 -9.29 -7.24 -9.10 -6.48 -6.26
TRMJ 188.70 212.35 232.52 252.70 272.87 293.04 313.22 213.68 208.51 202.90 241.72 232.16 230.95 226.54 225.78 269.79 282.78 240.88 212.54 261.06 232.71 307.05 344.85 300.96 297.49 269.15 237.33 277.32 245.50 254.89 268.38 296.79 260.50 315.22 345.56 271.14 331.01 331.45 294.02 354.33 316.90 308.57 405.43 368.44 365.65 440.07 241.27 298.34 368.97 269.61 340.24 364.51 332.07 299.87 366.03 322.75 388.91 329.69 283.40 264.16 277.36 303.29 318.49 289.10 309.46 337.81 379.70 421.60 454.04 486.48 402.92 351.48 371.65 391.83 412.00 432.17 452.35
TRM.1
-43.60 -17.45 3.98 18.50 29.63 36.76 42.38 -22.68 12.99 -8.20 11.73 14.77 17.25 -.94 9.72 -14.09 14.17 4.32 -19.34 15.14 2.49 13.75 21.15 .14 5.60 -6.15 -12.73 4.63 -13.11 8.51 -4.98 8.21 19.65 34.68 -11.26 -22.04 -51 25.25 -8.52 15.17 3.50 4.43 13.97 18.26 -18.45 -5.07 -25.97 -.34 10.18 -.61 12.91 1.49 -11.67 -23.27 3.97 -11.25 15.79 -6.34 -15.05 15.19 -14.01 -8.14 12.66 -43.35 -28.51 -19.46 -22.05 -24.55 -17.19 -9.73 -23.77 -5.93 -2.50 1.32 -8.85 -2.02 -4.20
ERlu.1, % -30.05 -8.95 1.68 6.82 9.77 11.14 11.92 -11.88 5.86 -4.21 4.63 5.98 6.95 -.42 4.13 -5.51 4.77 1.76 -10.01 5.48 1.06 4.29 5.78 .04 1.85 -2.34 -5.67 1.64 -5.64 3.23 -1.89 2.69 7.01 9.91 -3.37 -8.85
-.E 7.08 -2.98 4.11 1.09 1.42 3.33 4.72 -5.31 -1.17 -12.06 -.11 2.68 -.23 3.66 .41 -3.64 -8.41 1.07 -3.61 3.90 -1.96 -5.61 5.44 -5.32 -2.76 3.82 -17.64 -10.15 -6.11 -6.17 -6.18 -3.94 -2.04 -6.27 -1.72 -.68 .34 -2.20 -.47 -.94
Ind. Eng. Chem. Res., Vol. 31, No. 8, 1992 2045 Table I (Continued) formula no. C7FlsCOOH 78 79 Cl,,F21COOH CllFzsCOOH 80 CC13CHO 81 CClzFCHO 82 CCIFzCHO 83 84 N(CFJ3 85 N(C2Fsh 86 N(C$'7)3 87 N(C,F& 88 N(CSF11)S 89 N(CBF13)3
~
reference Siegemund et al. (1988) Siegemund et al. (1988) Siegemund et al. (1988) Siegemund et al. (1988) Siegemund et al. (1988) Siegemund et al. (1988) Siegemund et al. (1988) Siegemund et al. (1988) Siegemund et al. (1988) Siegemund et al. (1988) Siegemund et al. (1988) Siegemund et al. (1988)
TB
462.15 518.15 543.15 370.95 329.15 290.95 263.15 342.15 403.15 451.15 488.15 529.15
Table 11. Group Contributions for the Modified Joback Method group 6 Nonring Incrementa 23.58 22.88 21.74 18.25 18.18 24.96 24.14 26.15 9.20 27.38
4H3 >CH2 >CH>C< =CH2
=CH-
=c< =c= 4 H
4-
Ring Incrementa 4H2>CH>C< =cH-
27.15 21.78 21.32 26.73 31.01
=c
C = O (nonring) > C = O (ring) O=CH- (aldehyde) 4 O O H (acid) 400- (ester) =O (except as above) 1 .
92.88 76.34 22.42 31.22 762
7K
,".I"
94.97 72.24 169.09 81.10 -10.50
Nitrogen Incrementa
-NH2 >NH (nonring) >NH (ring) >N- (nonring) -N= (nonring) -N= (ring) -CN -NO,
73.23 50.17 52.82 11.74 74.60 57.55 125.66 152.54 63.56 68.78 52.10
Non-Hydrogen Bonded Incrementa 4F3 >CFZ >CF-
TaJ -32.24 -30.81 -24.00 -31.93 -35.57 -35.61 -1.07 23.36 29.79 23.22 5.65 -7.92
ERj, % -6.98 -5.95 -4.42 -8.61 -10.81 -12.24 -.41 6.83 7.39 5.15 1.16 -1.50
TBMJ
TBMJ
472.52 533.05 553.22 349.33 316.89 274.99 254.05 314.57 375.09 435.62 496.14 556.66
-10.37 -14.90 -10.07 21.62 12.26 15.96 9.10 27.58 28.06 15.53 -7.99 -27.51
ERMJ, % -2.24 -2.87 -1.85 5.83 3.72 5.48 3.46 8.06 6.96 3.44 -1.64 -5.20
dictive capabilities for isomeric halogenated compounds.
Acknowledgment We thank Dr. R. Vetrivel of the Physical Chemistry Division, National Chemical Laboratory, Pune, for his valuable discussions while revising this paper.
Nomenclature ERj = percentage error between TBand Tu, % ERMj = percentage error between TB and TBMj, % TB = normal boiling point, K Tar = normal boiling point by the Joback Method, K TBMJ= normal b o i i point by the modified Joback Method,
K
6i = incremental contribution for the ith group
Appendix Some examples to illustrate the prediction of normal boiling point using the modified Joback method are presented below. The values for the various groups are taken from Table II and then substituted in eq 1to obtain the normal boiling point in kelvin. (1) Tetrafluoromethane (CF,). It is an aliphatic perfluoro compound containing one non-hydrogen bonded -CF3 group and one fluorine atom. In addition there is a correction for perfluorination. TB = 198.0 + 1(-CFJ + 1(-F) + perfluorinated = 198.0
+ 29.96 + 6.31 + (-45.57) = 188.70 K
(2) l,l$$-Tetrafluoroethane (CHF2CHF2). It is an aliphatic partially fluorinated compound containing two >CH- groups and four F atoms. There is a correction for partial fluorination. It should be noted that >CF2 groups should not be considered for this compound as these are not non-hydrogen bonded. TB = 198.0 + 2(>CH-) + 4(-F) + partially fluorinated = 198.0
+ 2(21.74) + 4(6.31) + (-25.0) = 241.72 K
Sulfur Incrementa -SH -S- (nonring) -S- (ring)
Tar 494.39 548.96 567.15 402.88 364.72 326.56 264.22 318.79 373.36 427.93 482.50 537.07
29.96 20.17 23.94
Corrections for Halogenated Compounds perfluorinated -45.57 partially fluorinated with or without other halogens -25.00 partially halogenated without fluorine 11.43 -53.65 perhalogenated with or without fluorine
(3) Perfluorotrimethylamine ((CF,),N). It is a completely fluorinated aliphatic compound containing three non-hydrogen bonded CF3groups and one nitrogen atom. There is also a correction for perfluorination. TB = 198.0 + 3(-CF3) + 1(-N) + perfluorinated = 198.0 + 3(29.96)
+ 11.74 + (-45.57)
= 254.05 K (4) l,l,l-Trifluorochlorbromoethane(CF,CEBrCl). Although this compound contains C1 and Br besides F,it
Ind. Eng. Chem. Res. 1992,31, 2046-2050
2046
is still considered as a partially fluorinated aliphatic compound. It has one non-hydrogen bonded -CF3group, one >CH- group, one chlorine atom, and one bromine atom. There is also a correction for partial fluorination. TB = 198.0 + l(-CF3) + l(>CH-) + l(-Br) + l(-Cl) + partially fluorinated = 198.0
+ 29.96 + 21.74 + 66.86 + 38.13 + (-25.0) = 329.69 K
(5) Trifluorochloromethane (CF3Cl). It is a perhalogenated aliphatic compound containing one non-hydrogen bonded -CF3 and one C1 atom. There is also a correction for perhalogenation. TB = 198.0 + l(-CF3) + l(-Cl) + perhalogenated = 198.0
+ 29.96 + 38.13 + (-53.55) = 212.54 K
(6) l,l,l-Trichloroethane (CH3CC13). It is a partially halogenated aliphatic compound containing one -CH3 group, one >C< group, and three C1 atoms but no F. There is also a correction for partial halogenation. TB = 198.0 + l(-CH3) + 1(>C
