Virial Coefficients of Methanol from 150 to 300°C and Polymerization in the Vapor

Kell, G. S.; McLaurin, Graham E.

doi:10.1063/1.1671800

Cited by 88 publications

(32 citation statements)

References 32 publications

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“…The latter value is in good agreement with the experiment of Kell, McLaurin, and Whalley (performed at temperatures from 423 to 723 K) that the successive entropy of the trimer is -17 calmol ' K and the trimer has the linear structure [51,52]. Similarly We predicted the thermodynamic quantities of the water clusters.…”

Section: The Water-cluster Distributionsupporting

confidence: 90%

Water-cluster distribution with respect to pressure and temperature in the gas phase

1993

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In spite of decades of extensive studies of water, the experimental information of water clusters larger than the trimer is hardly available yet. To aid the better analysis of certain cluster properties in an experiment, we studied the small-water-cluster distribution (particularly for the minimum-energy structures) in the gas phase. Utilizing the thermodynamic information in the range from the water monomer to the octamer (except for the heptamer) by ab initio calculations, we investigated the mole fractions of the water clusters along the vapor pressure of the condensed phase. These mole fractions increase with increasing temperature or pressure, while the higher clusters increase still more. The entropy increment of the cyclic pentamer relative to the cyclic tetramer is particularly small; thus, the cyclic pentamer shows thermodynamically unusual characteristics. For the trimer, the cyclic structure is more stable than the linear structure at temperatures lower than -400 K, while above this temperature, the latter is more stable due to the entropy effect. Similar phenomena are also expected for the higher clusters. The mole fractions of the higher cyclic clusters are found to be very small in a vapor unless they are uncondensed with insufficient water molecules.PACS number(s): 36.40. +d, 31.20.Ej, 31.20.Tz, 36.90.+f

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Section: The Water-cluster Distributionsupporting

confidence: 90%

Water-cluster distribution with respect to pressure and temperature in the gas phase

1993

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“…Notice the agreement of E ass values to several water polymer association energies, as obtained by means of the virial coefficients [23].…”

Section: Resultssupporting

confidence: 65%

Multiple minima hypersurfaces of water clusters for calculations of association energy

Montero

Molina

Fabian

2000

Int. J. Quantum Chem.

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“…Given a temperature of 150°C and thermodynamic constants available from literature [39,40], the equilibrium constants are calculated as K 2 ϭ 0.011 (dimer/monomer) and K 3 ϭ 0.030 (trimer/monomer). The trimer is a cyclic structure and is relatively more stable than the dimer.…”

Section: Generation Of Solvent Ions From Methanol With Appimentioning

confidence: 99%

APPI-MS: Effects of mobile phases and VUV lamps on the detection of PAH compounds

Short¹,

Cai²,

Syage³

2007

J. Am. Soc. Mass Spectrom.

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The technique of atmospheric pressure photoionization (APPI) has several advantages over electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI), including efficient ionization of nonpolar or low charge affinity compounds, reduced susceptibility to ion suppression, high sensitivity, and large linear dynamic range. These benefits are greatest at low flow rates (i.e., Յ100 L/min), while at a higher flow, photon absorption and ion-molecule reactions become significant. Under certain circumstances, APPI signal and S/N have been observed to excel at higher flow, which may be due to a nonphotoionzation mechanism. To better understand APPI at higher flow rates, we have selected three lamps (Xe, Kr, and Ar) and four mobile phases typical for reverse-phase, high-pressure liquid chromatography: acetonitrile, methanol, (1:1) acetonitrile:water and (1:1) methanol:water. As test compounds, three polyaromatic hydrocarbons are studied: benzo[a]pyrene, indeno [1,2,3-c, d]pyrene and benz [a]anthracene. We find that solvent photoabsorption cross-section is not the only parameter in explaining relative signal intensity, but that solvent photo-ion chemistry can also play a significant role. Three conclusions from this investigation are: (1) [4,5]. Recent work has focused on the direct comparison of different sources (APPI, APCI, and ESI) with specific target compounds, e.g., polyaromatic hydrocarbons [6,7], hydrophobic peptides [8], pesticides [9,10], as well as fatty acids and lipids [4,5]. In many cases atmospheric pressure photoionization (APPI) [1,7] has demonstrated extended linear dynamic range [11], enhanced sensitivity and thus lower detection limits [6,9,[12][13][14][15], and reduced or no off-line sample cleanups [6,9] in comparison with direct APCI or ESI. Adding a dopant (dopant-assisted, DA) to the mobile phase in many cases can further increase sensitivity [2].A related analytical technique is atmospheric pressure laser ionization (APLI), which has shown excellent sensitivity for certain non-or low-polar compounds [3]. The enhanced sensitivity is a direct result of the high photon flux associated with a laser system, often several orders of magnitude higher than the noncoherent light sources, e.g., lamps used with APPI. The APLI source relies on one-color, two-photon (1 ϩ 1) resonantlyenhanced multiphoton ionization (REMPI), typically using a KrF excimer laser emitting light at 5.0 eV, efficiently ionizing nonpolar molecules. However, APLIis not yet widely used due to the large size, expense, and maintenance associated with the laser system. Furthermore, changing the wavelength of an excimer laser requires the replacement of the gas mixture and often re-tuning of the laser cavity, whereas with an APPI system, the wavelength can be changed by simply switching the lamp.To improve the capabilities of APPI for LC-MS, we have focused on the ion chemistry involved in and following the photoionization process. Although direct, single-photon ionization (SPI) of a compound [M] however, there is litt...

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Virial Coefficients of Methanol from 150 to 300°C and Polymerization in the Vapor

Cited by 88 publications

References 32 publications

Water-cluster distribution with respect to pressure and temperature in the gas phase

Water-cluster distribution with respect to pressure and temperature in the gas phase

Multiple minima hypersurfaces of water clusters for calculations of association energy

APPI-MS: Effects of mobile phases and VUV lamps on the detection of PAH compounds

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