scholarly journals Determination of ΔHf2980(C12F10,g) from studies of the combustion of decafluorobiphenyl in oxygen and calculation of D(C6F5—C6F5)

1979 ◽  
Vol 57 (12) ◽  
pp. 1468-1470 ◽  
Author(s):  
Stanley James W. Price ◽  
Henry J. Sapiano
Keyword(s):  
Material Balance ◽  
Combustion Method ◽  
Heat Of Formation ◽  
Direct Combustion ◽  
Related Compounds ◽  
Fold Excess

The heat of formation of decafluorobiphenyl has been determined by the direct combustion method previously developed and used for hexafluorobenzene and related compounds. As in the hexafluorobenzene case the combustion of decafluorobiphenyl in oxygen yields CO2, CF4, and F2. With a ten-fold excess of oxygen the CO2 to CF4 ratio is 5.85 ± 0.08. A full material balance was obtained. The value of ΔHf2980(C12F10,g) = −1263.2 ± 5.1 kJ mol−1 may be combined with ΔHf2980(C6F5,g) = −387.4 ± 12.0 kJ mol−1 to give D(C6F5—C6F5) = 488.4 ± 24.5 kJ mol−1. Also with ΔHf2980(C6F6,g) = −945.6 ± 8.0 kJ mol−1 ΔH2980 for reaction [3][Formula: see text]is calculated to be −628.0 ± 16.8 kJ mol−1.

Determination of the Heat of Formation of Octafluorotoluene and Calculation of D[C6F5—F] – D[C6F5—CF3]

1973 ◽  
Vol 51 (22) ◽  
pp. 3662-3664 ◽  
Author(s):  
Michael J. Krech ◽  
Stanley James W. Price ◽  
Wayne F. Yared
Keyword(s):  
Material Balance ◽  
Combustion Method ◽  
Heat Of Formation ◽  
Enthalpies Of Formation ◽  
Direct Combustion ◽  
Fold Excess

The heat of formation of octafluorotoluene has been determined using the direct combustion method previously developed for hexafluorobenzene. As in the hexafluorobenzene case the combustion of octafluorotoluene in oxygen yields CO2, CF4, and F2. With a ten-fold excess of oxygen the CO2 to CF4 ratio is 3.85 ± 0.06. A full material balance was obtained. The value of ΔHf2980(C6F5CF3,g) = −303.2 ± 1.8 kcal mol−1 may be combined with the enthalpies of formation of C6F6, CF3, and F to give D[C6F5—F] – D[C6F5—CF3] = 55.7 ± 4.0 kcal mol−1.

Determination of ΔHf2980(C6F5Br, g) from studies of the combustion of bromopentafluorobenzene in oxygen and calculation of D[C6F5 — Br]

1977 ◽  
Vol 55 (24) ◽  
pp. 4222-4226 ◽  
Author(s):  
Michael J. Krech ◽  
Stanley James W. Price ◽  
Henry J. Sapiano
Keyword(s):  
Material Balance ◽  
Combustion Method ◽  
Heat Of Formation ◽  
Molar Ratio ◽  
Direct Combustion ◽  
A Value ◽  
Fold Excess

The heat of formation of bromopentafluorobenzene has been determined through the use of the direct combustion method which has been applied to hexafluorobenzene, octafluorotoluene, and iodopentafluorobenzene. While a platinum lined bomb is normally used for these types of compounds a steel bomb had to be adopted in this work. The combustion of bromopentafluorobenzene in the steel bomb yields CO2, CF4, F2, Br2, and BrF3. With a ten-fold excess of oxygen, the average CO2 to CF4 molar ratio is 7.29 ± 0.07. A material balance was obtained for carbon, fluorine, and bromine. The value of ΔHf2980(C6F5Br, g) = −711.6 ± 16.7 kJ mol−1 (−170.1 ± 4.0 kcal mol−1) has been combined with ΔHf2980(C6F5, g) = −387.4 kJ mol−1 (−92.6 kcal mol−1) and ΔHf2980(Br, g) = 111.7 kJ mol−1 (26.7 kcal mol−1) to obtain a value for D[C6F5—Br] of 435.9 kJ mol−1 (104.2 kcal mol−1).

Determination of ΔH0f298(C6F10,g) and ΔH0f298(C6F12,g) from studies of the combustion of decafluorocyclohexene and dodecafluorocyclohexane in oxygen and calculation of the resonance energy of hexafluorobenzene

1979 ◽  
Vol 57 (6) ◽  
pp. 685-688 ◽  
Author(s):  
Stanley James W. Price ◽  
Henry J. Sapiano
Keyword(s):  
Material Balance ◽  
Resonance Energy ◽  
Combustion Method ◽  
Heats Of Formation ◽  
Reaction Products ◽  
Molar Ratios ◽  
Direct Combustion ◽  
Related Compounds ◽  
Fold Excess

The heats of formation of decafluorocyclohexene and dodecafluorocyclohexane have been determined by the direct combustion method previously developed and used for hexafluorobenzene and related compounds. The combustion of decafluorocyclohexene and dodecafluorocyclohexane formed the reaction products CO2, CF4, and F2. In both cases a portion of the compound remained unburned. The unburned material was collected and quantitatively determined gravimetrically. A material balance was obtained for carbon and fluorine on the basis of CO2, CF4, and F2 and the amount of unburned compound. With a ten-fold excess of oxygen, the average CO2-to-CF4 molar ratios for C6F10 and C6F12 are 2.03 ± 0.01 and 1.35 ± 0.01, respectively. The values obtained for the heats of formation are ΔH0f298(C6F10,g) = −1906.6 ± 7.2 kJ mol−1 and ΔH0f298(C6F12,g) = −2368.9 ± 7.6 kJ mol−1. ΔH0f298 for the reaction C6F10(g) + F2(g) → C6F12(g) was calculated to be −462.3 ± 14.8 kJ mol−1 and the 'resonance energy' of C6F6 is estimated at −36.4 kJ mol−1.

Determination of ΔHf2980(C6F5I,g) from Studies of the Combustion of Iodopentafluorobenzene in Oxygen and Calculation of D(C6F5—X) Bond Dissociation Energies

1974 ◽  
Vol 52 (15) ◽  
pp. 2673-2678 ◽  
Author(s):  
Michael J. Krech ◽  
Stanley James W. Price ◽  
Wayne F. Yared
Keyword(s):  
Material Balance ◽  
Combustion Method ◽  
Heat Of Formation ◽  
Molar Ratio ◽  
Bond Dissociation Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Direct Combustion ◽  
Tenfold Excess

The heat of formation of iodopentafluorobenzene has been determined using the direct combustion method previously developed and used for hexafluorobenzene and octafluorotoluene. The combustion with oxygen yields CO2, CF4, F2, I2, and IF5. With a tenfold excess of oxygen the average CO2 to CF4 molar ratio is 11.08 ± 0.028. A material balance was obtained for carbon and fluorine. An apparent shortfall of about 30% in iodine has been related to the formation of IO2(OH) during analysis. The value of ΔHf2980 (C6F5I,g) = −133.2 ± 3.0 kcal mol−1 has been combined with D(C6F5—I) and ΔHf2980(I, g) to obtain ΔHf2980(C6F5,g) = −92.6 kcal mol−1 Using this value and the appropriate values of ΔHf2980 (C6F5X,g) and ΔHf2980(X, g), values of D(C6F5—X) have been calculated for X = OH, H, F, Cl, I, CH3, and CF3.

Determination of the Heat of Formation of Hexafluorobenzene

1972 ◽  
Vol 50 (18) ◽  
pp. 2935-2938 ◽  
Author(s):  
M. Krech ◽  
S. J. W. Price ◽  
W. F. Yared
Keyword(s):  
Aromatic Compounds ◽  
Visual Inspection ◽  
Material Balance ◽  
Heat Of Formation ◽  
Heat Of Combustion ◽  
New Method ◽  
Complete Combustion ◽  
Auxiliary Substance ◽  
Hydrocarbon Oil

A new method has been developed for determining the heat of combustion of perfluoro aromatic compounds. The basic differences from previous methods are that no auxiliary substance is used and no water is present in the bomb. The combustion of hexafluorobenzene in a platinum lined bomb yields CO2, CF4, and F2. Visual inspection and the material balance indicate that complete combustion is obtained. The value of [Formula: see text] obtained by this method is −224.0 ± 2.0 kcal/mol. Recalculation of the result of Cox etal. (1, 2) obtained from combustion of C6F6 in mylar bags in the presence of hydrocarbon oil and water leads to[Formula: see text]

The fluorimetric determination of cerium and terbium

1989 ◽  
Vol 54 (3) ◽  
pp. 616-621 ◽  
Author(s):  
Záviš Holzbecher
Keyword(s):  
Rare Earth ◽  
Detection Limit ◽  
Rare Earth Elements ◽  
Fluorimetric Determination ◽  
Fluorescence Maximum ◽  
Relative Standard ◽  
And Shifts ◽  
Hcl Medium ◽  
Fold Excess

It has been found that phosphoric acid decreases the first excitation maximum of Ce(III) at 256 nm, increases the second excitation maximum at 297 nm and shifts the fluorescence maximum from 350 to 346 nm. Under optimum conditions, with λexc = 297 nm and λem = 346 nm, Ce(III) can be determined fluorimetrically with a detection limit of 1.2 ng ml-1 in 12M-H3PO4 medium. No interference was observed from a 20-200 fold excess of HCl, H2SO4, Na, K, NH4+, Al and the rare earth elements. HNO3 interferes and Ce(IV) and Fe(III) interfere strongly. It follows from the stereofluorograms of Ce and Tb that the spectra of the two elements are practically independent. The detection limit for Tb(III) in 0.02-2.5M-H2SO4 medium for λexc = 222 nm and λem = 494 nm is 33 ng ml-1. No interference was observed from a 5-20 fold excess of Al3+ and the other rare earth elements. The determination is slightly less sensitive in H3PO4 or HCl medium. The relative standard deviation of the measurement for 10 ng ml-1 Ce(III) or 50 ng ml-1 Tb(III) is about 3%.

Liquid Chromatographic Determination of Amiodarone Hydrochloride and Related Compounds in Raw Materials and Tablets

1994 ◽  
Vol 77 (6) ◽  
pp. 1447-1453 ◽  
Author(s):  
Pauline M Lacrok ◽  
Norman M Curran ◽  
Wing-Wah Sy ◽  
Dennis K J Goreck ◽  
Pierre Thibault ◽  
...  
Keyword(s):  
Raw Materials ◽  
Chromatographic Determination ◽  
Raw Material ◽  
Liquid Chromatographic Method ◽  
Limit Of Quantitation ◽  
Liquid Chromatographic Determination ◽  
Liquid Chromatographic ◽  
Amiodarone Hydrochloride ◽  
Related Compounds

Abstract A liquid chromatographic method for the determination of amiodarone hydrochloride and 10 related compounds in drug raw material and for assay of drug in tablets was developed. The method specifies a 3 jxm Hypersil nitrile column (150 × 4.6 mm), a mobile phase of 1 + 1 acetonitrile–ammonium acetate buffer (0.1 M adjusted to pH 6.0 with 0.1 M acetic acid), a flow rate of 1 mL/min, and detection at 240 nm. The lower limit of quantitation of the related compounds is 0.02% or less. Drug contents in 2 raw material samples were 100.1 and 99.9% and ranged from 98.2 to 99.4% in 3 tablet formulations. Impurity levels in 2 samples of raw material from different manufacturers were ca 0.4%. The presence of 3 of the known related compounds in these samples was confirmed by liquid chromatographymass spectrometry. The method applied to raw materials was evaluated by a second laboratory and found to be satisfactory.

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