Vapour Pressure Determination for Dibenzo-p-dioxin, Dibenzofuran, Octachlorodibenzo-p-dioxin and Octachlorodibenzofuran Using a Knudsen Effusion Method
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A new apparatus with Knudsen effusion method especially designed for the vapour pressure measurements of dioxin congeners and other POPs is described. Crystalline benzoic acid and anthracene were first used to test the new designed apparatus. The vapour pressure and enthalpy results of the two reference compounds were found in good agreement with accepted literature data. The vapour pressure and enthalpy results of crystalline DD, DF, OCDD and OCDF determined with the new apparatus are presented, and compared with the literature data measured with other methods.Keywords:
Dibenzofuran
The vapor pressure of zinc has been measured using Knudsen's effusion method. The temperature-vapor pressure relation was found to be log10pmm=(−6688/T)+8.888 in the range 300°—360°C. These results are about 20 percent higher than those previously reported. It is suggested that this difference may be attributed principally to the omission of a probability factor by earlier workers.
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Dibenzofuran
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A twin Knudsen apparatus for the measurement of vapor pressures is described. The apparatus has been employed in the temperature range 1140–1412°K, using approximately one milligram samples of PuF3, AmF3 and Am metal. Radiometric assay of condensed effusates yielded vapor pressure data in the range ∼5×10−7 mm to ∼2×10−3 mm that were internally consistent within a mean deviation of ±5 percent. The apparatus is particularly suitable for the determination of small differences in vapor pressure of similar substances.
Knudsen flow
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Sublimation
Torr
Enthalpy of sublimation
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Sublimation
Benzoic acid
Enthalpy of sublimation
Knudsen flow
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Short syntheses of the natural dibenzofuran, ruscodibenzofuran (1) from readily available phenols are described. The key steps involve initial formation of a 2-isopropenylbenzofuran by reaction of an ortho-halogenophenol with cuprous isopropenylacetylide followed by cycloaddition of methyl propiolate, to provide a functionalized dibenzofuran.
Dibenzofuran
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A novel design for thermally activated delayed fluorescence (TADF) emitters was developed by decorating dibenzofuran with four carbazole type electron donors and two CN electron withdrawing units. The four carbazole type donors were attached to one side of the dibenzofuran, and two CN units were introduced on the other side of the dibenzofuran for highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) separation. The HOMO and LUMO were largely separated, and they were overlapped in the dibenzofuran due to aromatic nature of dibenzofuran. Two TADF emitters, DBFCzCN and DBFtCzCN, were built on the design platform decorating the dibenzofuran, and they showed high EQEs of 25.2% and 17.4% in the vacuum deposited TADF devices. Additionally, the DBFtCzCN emitter showed a high EQE of 13.9% in the solution processed TADF devices.
Dibenzofuran
Carbazole
HOMO/LUMO
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A new apparatus with Knudsen effusion method especially designed for the vapour pressure measurements of dioxin congeners and other POPs is described. Crystalline benzoic acid and anthracene were first used to test the new designed apparatus. The vapour pressure and enthalpy results of the two reference compounds were found in good agreement with accepted literature data. The vapour pressure and enthalpy results of crystalline DD, DF, OCDD and OCDF determined with the new apparatus are presented, and compared with the literature data measured with other methods.
Dibenzofuran
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Abstract Solid ZnSe is evaporated from a Knudsen cell in vacuum. The effective molecular weight of the ZnSe vapor is directly determined by weighing the cell with and without effusion taking place. The rate of effusion is adjusted by a moveable furnace. An effective molecular weight of 135 ± 5 g/mol is found for temperatures between 1190 and 1310 K. The weight indicates the complete dissociation of the sublimed ZnSe into Zn and Se 2 vapor. In that temperature range, the total equilibrium vapor pressure of solid ZnSe is estimated from the recoil force according to \documentclass{article}\pagestyle{empty}\begin{document}$ \log _{10} (P/{\rm kPa}) = - (12896 \pm 96){\rm K}/T + (9.19 \pm 0.08). $\end{document}
Atmospheric temperature range
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Volatilisation
Sulfonylurea
Saturation (graph theory)
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