“…The experimentally determined p 0 (298 K) vary in a strongly nonmonotonic manner with N c ; vis., there is an “odd−even” dependence observed with respect to N c (Figure ). This odd−even alternation in p 0 (298 K) has previously been noted for the straight chain dicarboxylic acids. , This observation has been rationalized by analogy to measurements of the melting temperature, T m , of the diacids, where a strong odd−even dependence is observed; the odd diacids typically melt at lower temperatures than the even diacids. , We note, however, that p 0 (298 K) for the C 12 diacid is greater than that for the C 10 diacid, different to the variation observed between the smaller even carbon number diacids. 3 (a) Measured vapor pressures (Pa) for the straight-chain diacids for this work (·), Bilde et al (▵), Chattopadhyay and Ziemann 20 (□), Tao and McMurry 16 (×), da Silva et al (◇), and Davies and Thomas 13 (▿).…”
Section: Resultssupporting
confidence: 75%
“…17,20 This observation has been rationalized by analogy to measurements of the melting temperature, T m , of the diacids, 17 where a strong odd-even dependence is observed; the odd diacids typically melt at lower temperatures than the even diacids. 52,53 We note, however, that p 0 (298 K) for the C 12 diacid is greater than that for the C 10 diacid, different to the variation observed between the smaller even carbon number diacids.…”
A method for the measurement of evaporation rates and vapor pressures of low volatility compounds was developed and applied to the homologous series of C4-C10 and C12 dicarboxylic acids. Proton-transfer chemical ionization mass spectrometry was used to follow directly the temperature-dependent evaporation rates of aerosol samples collected on a cold plate that could be heated at a known rate. The vapor pressures of the deposited compounds were derived from observed evaporation rates through application of the Hertz-Knudsen equation. Temperature programmed desorption allowed for quantification of the enthalpy (DeltaHsub) and entropy (DeltaSsub) of sublimation of the diacids and is described. A strong odd-even dependence with respect to the total carbon number was observed in the derived diacid vapor pressures, consistent with previous measurements. However, the vapor pressures from this method were systematically lower than previous measurements. Though seen in the vapor pressure, no odd-even carbon chain length dependence was readily discernible in the measured values of DeltaHsub and DeltaSsub. Perhaps most importantly, these experimental results also suggest that residual solvent molecules (from the aerosol generation process) trapped in the diacid samples can have a considerable influence on the measured thermodynamic parameters and, if not properly accounted for, may give erroneous results.
“…The experimentally determined p 0 (298 K) vary in a strongly nonmonotonic manner with N c ; vis., there is an “odd−even” dependence observed with respect to N c (Figure ). This odd−even alternation in p 0 (298 K) has previously been noted for the straight chain dicarboxylic acids. , This observation has been rationalized by analogy to measurements of the melting temperature, T m , of the diacids, where a strong odd−even dependence is observed; the odd diacids typically melt at lower temperatures than the even diacids. , We note, however, that p 0 (298 K) for the C 12 diacid is greater than that for the C 10 diacid, different to the variation observed between the smaller even carbon number diacids. 3 (a) Measured vapor pressures (Pa) for the straight-chain diacids for this work (·), Bilde et al (▵), Chattopadhyay and Ziemann 20 (□), Tao and McMurry 16 (×), da Silva et al (◇), and Davies and Thomas 13 (▿).…”
Section: Resultssupporting
confidence: 75%
“…17,20 This observation has been rationalized by analogy to measurements of the melting temperature, T m , of the diacids, 17 where a strong odd-even dependence is observed; the odd diacids typically melt at lower temperatures than the even diacids. 52,53 We note, however, that p 0 (298 K) for the C 12 diacid is greater than that for the C 10 diacid, different to the variation observed between the smaller even carbon number diacids.…”
A method for the measurement of evaporation rates and vapor pressures of low volatility compounds was developed and applied to the homologous series of C4-C10 and C12 dicarboxylic acids. Proton-transfer chemical ionization mass spectrometry was used to follow directly the temperature-dependent evaporation rates of aerosol samples collected on a cold plate that could be heated at a known rate. The vapor pressures of the deposited compounds were derived from observed evaporation rates through application of the Hertz-Knudsen equation. Temperature programmed desorption allowed for quantification of the enthalpy (DeltaHsub) and entropy (DeltaSsub) of sublimation of the diacids and is described. A strong odd-even dependence with respect to the total carbon number was observed in the derived diacid vapor pressures, consistent with previous measurements. However, the vapor pressures from this method were systematically lower than previous measurements. Though seen in the vapor pressure, no odd-even carbon chain length dependence was readily discernible in the measured values of DeltaHsub and DeltaSsub. Perhaps most importantly, these experimental results also suggest that residual solvent molecules (from the aerosol generation process) trapped in the diacid samples can have a considerable influence on the measured thermodynamic parameters and, if not properly accounted for, may give erroneous results.
“…The modern view of the crystal structure of the saturated acids is that the crystal layers are made up of units of two molecules of acids, bound together by residual valences at the carboxyl groups (48,49,58,97,98,100,115). The tendency to form mixed crystals is the greater, the more nearly alike the fatty acids, and is marked with the higher saturated acids.…”
“…Attractive forces between atoms in crystals may be classified as follows: (1) valence forces, due to electron-pair bonds (or to one-electron or three-electron bonds (4)); (2) ionic forces, due to electrostatic forces between ions; (5) metallic forces,-those holding the atoms together in crystals of metals. (These probably are in part electrostatic attractions between the positively charged atom kernels and those valence electrons which are "free" or in other atoms, and in part attractions due to the interaction of valence forces similar to those producing electron-pair bonds in non-metallic crystals.…”
Section: Ionsmentioning
confidence: 99%
“…The ratios AB/BB for cubic, octahedral, and tetrahedral arrangements of B atoms around an A atom are 0.866, 0.707, and 0.613 respectively. If the ratio of the distance between A and B atoms for stable bonding (e.g., the sum of the A and B radii from table 1 for electron-pair binding or from table 2 for ionic binding, in appropriate structures) to the distance between two B atoms at which repulsion between them begins to be considerable (e.g., twice the B radius from table 2 if B is a negative ion or twice that from table 5 if B is an uncharged atom) is less than 0.866, the cubic arrangement is less stable than the octahedral, provided other factors can be neglected. If this ratio is less than 0.707, the octahedral arrangement is less stable than the tetrahedral.…”
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
