ChemInform Abstract: Computational Methods in Ion Chemistry. Applications to Unimolecular and Bimolecular Reactions of Protonated Organic Molecules

ChemInform ◽  
2010 ◽  
Vol 27 (29) ◽  
pp. no-no
Author(s):  
E. UGGERUD
Keyword(s):  
Computational Methods ◽  
Organic Molecules ◽  
Ion Chemistry ◽  
Bimolecular Reactions

A comparative ion chemistry study of acetone, diacetone alcohol, and mesityl oxide

1986 ◽  
Vol 64 (10) ◽  
pp. 1979-1988 ◽  
Author(s):  
Afaf Kamar ◽  
Alexander Baldwin Young ◽  
Raymond Evans March
Keyword(s):  
Infrared Multiphoton Dissociation ◽  
Mesityl Oxide ◽  
Alternative Form ◽  
Dehydration Process ◽  
Ion Chemistry ◽  
Bimolecular Reactions ◽  
Common Structure ◽  
Diacetone Alcohol ◽  
Multiphoton Dissociation ◽  
Ion Species

The evolution of ion species by unimolecular and bimolecular reactions, both concurrent and sequential, has been investigated for each of 2-propanone, d6-2-propanone, 4-hydroxy-4-methyl-2-pentanone, and 4-methyl-3-penten-2-one. Infrared multiphoton dissociation (IRMPD) has been used in order to differentiate between gaseous ionic isomers. It is concluded that the isomeric species, protonated 2-propanone dimer and protonated 4-hydroxy-4-methyl-2-pentanone, both of m/z 117, are of different structures. The ion species C6H11O+ of m/z 99, and its perdeuterated analogue, which is observed in all three systems, may exist in two forms, one of which is unique to 2-propanone while an alternative form appears to be common to 4-hydroxy-4-methyl-2-pentanone and 4-methyl-3-penten-2-one. The ion species of m/z 83 (C5H7O+) which is observed only in the latter two systems only could not be differentiated and may have a common structure. In the protonated dimers of 2-propanone and 4-hydroxy-4-methyl-2-pentanone, evidence obtained by IRMPD indicates that the activation energy for dedimerization (134 kJ mol−1) is less than that for the dehydration process.

scholarly journals Benchmarking computational methods to calculate the octanol/water partition coefficients of a diverse set of organic molecules

2021 ◽  
Author(s):  
Alondra López-Colón ◽  
Mariela E. Santiago-Mercado ◽  
Jonathan I. Aguirre-Santiago ◽  
Ariana de Jesús-Hernández ◽  
Jenlyan Negrón-Hernández ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Computational Methods ◽  
Partition Coefficients ◽  
Density Functional ◽  
Organic Molecules ◽  
Correlation Coefficients ◽  
New Drugs ◽  
Functional Theory ◽  
Lower Correlation ◽  
Hybrid Density Functional

In the discovery process of new drugs and the development of novel therapies in medicine, computational modeling is a complementary tool for the design of new molecules by predicting for example their solubility in different solvents. Here, we benchmarked several computational methods to calculate the partition coefficients of a diverse set of 161 organic molecules with experimental logP values obtained from the literature. In general, density functional theory methods yielded the best correlations and lower average deviations. Although results are obtained faster with semiempirical and molecular mechanics methodologies, these methods yielded higher average deviations and lower correlation coefficients than hybrid density functional theory methods. We recommend the use of an empirical formula to correct the calculated values with each methodology tested.

scholarly journals Assessment of approximate computational methods for conical intersections and branching plane vectors in organic molecules

2014 ◽  
Vol 141 (12) ◽  
pp. 124122 ◽  
Author(s):  
Alexander Nikiforov ◽  
Jose A. Gamez ◽  
Walter Thiel ◽  
Miquel Huix-Rotllant ◽  
Michael Filatov
Keyword(s):  
Computational Methods ◽  
Organic Molecules ◽  
Conical Intersections

High Resolution Replication of Organoclay Surfaces

1982 ◽  
Vol 40 ◽  
pp. 576-577
Author(s):  
W. W. Barker ◽  
W. E. Rigsby ◽  
V. J. Hurst ◽  
W. J. Humphreys
Keyword(s):  
Clay Mineral ◽  
Organic Molecule ◽  
Organic Molecules ◽  
X Ray Diffraction ◽  
Xrd Pattern ◽  
X Ray ◽  
Naturally Occurring ◽  
Silicate Layers ◽  
Mineral Identification

Experimental clay mineral-organic molecule complexes long have been known and some of them have been extensively studied by X-ray diffraction methods. The organic molecules are adsorbed onto the surfaces of the clay minerals, or intercalated between the silicate layers. Natural organo-clays also are widely recognized but generally have not been well characterized. Widely used techniques for clay mineral identification involve treatment of the sample with H2 O2 or other oxidant to destroy any associated organics. This generally simplifies and intensifies the XRD pattern of the clay residue, but helps little with the characterization of the original organoclay. Adequate techniques for the direct observation of synthetic and naturally occurring organoclays are yet to be developed.

Direct phase determination in electron crystallography: small organic molecules

1992 ◽  
Vol 50 (2) ◽  
pp. 1166-1167
Author(s):  
Douglas L. Dorset
Keyword(s):  
Organic Molecules ◽  
Data Sets ◽  
Temperature Structure ◽  
3D Analysis ◽  
Intensity Data ◽  
Electron Crystallography ◽  
Phase Determination ◽  
Measured Intensity ◽  
3D Data

The quantitative use of electron diffraction intensity data for the determination of crystal structures represents the pioneering achievement in the electron crystallography of organic molecules, an effort largely begun by B. K. Vainshtein and his co-workers. However, despite numerous representative structure analyses yielding results consistent with X-ray determination, this entire effort was viewed with considerable mistrust by many crystallographers. This was no doubt due to the rather high crystallographic R-factors reported for some structures and, more importantly, the failure to convince many skeptics that the measured intensity data were adequate for ab initio structure determinations.We have recently demonstrated the utility of these data sets for structure analyses by direct phase determination based on the probabilistic estimate of three- and four-phase structure invariant sums. Examples include the structure of diketopiperazine using Vainshtein's 3D data, a similar 3D analysis of the room temperature structure of thiourea, and a zonal determination of the urea structure, the latter also based on data collected by the Moscow group.

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