Conformational Studies in Organic Liquids

Teixeira‐Dias, J. J. C.; Carvalho, Luís A. E. Batista de; Ribeiro‐Claro, Paulo J. A.

doi:10.1007/978-94-011-2832-2_7

Cited by 2 publications

(1 citation statement)

References 10 publications

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“…[1][2][3] The development of suitable computer simulation methods have made it feasible to investigate a great number of liquid state properties that would not be possible, or difficult to access, with other theoretic or experimental techniques. 4,5 However, the success of the investigations using computational methodologies depends strongly on the availability of potential functions capable of describing the intermolecular interactions adequately.…”

Section: Introductionmentioning

confidence: 99%

Structure and weak hydrogen bonds in liquid acetaldehyde

Cordeiro¹,

Cordeiro²

2004

J. Braz. Chem. Soc.

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Investigaram-se a estrutura e formação de pontes de hidrogênio no acetaldeído líquido por simulações de Monte Carlo. Um modelo para acetaldeído com todos os átomos explicitados foi otimizado no presente trabalho. Os valores teóricos obtidos para a entalpia de vaporização e a densidade do líquido mostram boa concordância com os dados experimentais. Os gráficos de função de distribuição radial (rdf) indicam um líquido bem estruturado comparado com outros líquidos orgânicos dipolares semelhantes. A minimização usando mecânica molecular em fase gasosa produz um trímero com uma estrutura muito estável. A geometria deste complexo apresenta boa concordância com os gráficos de rdf. A correlação sítio-sítio mais próxima observada é entre o oxigênio e o hidrogênio da carbonila, sugerindo que esta correlação possui um importante papel na estrutura do líquido e suas propriedades. A distância média O⋅⋅⋅H e o ângulo C-H⋅⋅⋅O obtidos são característicos de pontes de hidrogênio fracas.Monte Carlo simulations have been performed to investigate the structure and hydrogen bonds formation in liquid acetaldehyde. An all atom model for the acetaldehyde have been optimized in the present work. Theoretical values obtained for heat of vaporisation and density of the liquid are in good agreement with experimental data. Graphics of radial distribution function indicate a well structured liquid compared to other similar dipolar organic liquids. Molecular mechanics minimization in gas phase leads to a trimer of very stable structure. The geometry of this complex is in very good agreement with the rdf. The shortest site-site correlation is between oxygen and the carbonyl hydrogen, suggesting that this correlation play a important role in the liquid structure and properties. The O⋅⋅⋅H average distance and the C-H⋅⋅⋅O angle obtained are characteristic of weak hydrogen bonds. Keywords:Monte Carlo simulation, acetaldehyde, liquid structure, weak hydrogen bond IntroductionIn recent years, theoretical investigation of liquid state properties has become a challenging subject for theoretical chemists and physicists, since fast and high memory capability computers have become available at relatively low cost.1-3 The development of suitable computer simulation methods have made it feasible to investigate a great number of liquid state properties that would not be possible, or difficult to access, with other theoretic or experimental techniques. 4,5 However, the success of the investigations using computational methodologies depends strongly on the availability of potential functions capable of describing the intermolecular interactions adequately.6-9 Therefore, the optimisation of meaningful intermolecular potential functions is of fundamental importance for the investigation of liquid state properties using theoretical methods. This optimisation is not simple, however, due to the complexity of the liquid intermolecular interactions, and some criteria, such as pairwise additivity and consideration of dipolar interaction exclusively, have been used to s...

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Section: Introductionmentioning

confidence: 99%

Structure and weak hydrogen bonds in liquid acetaldehyde

Cordeiro¹,

Cordeiro²

2004

J. Braz. Chem. Soc.

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Raman spectra, conformational stability and normal coordinate analysis of ethylmethylamine

Carvalho

Teixeira‐Dias

1995

J Raman Spectroscopy

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Raman spectra of ethylmethylamine and ethylmethylamine-N-d, both in the liquid phase, at different temperatures, and in the solid phase were recorded. Additionally, Fourier transform IR (4000-400 cm-') spectra of these compounds in the liquid phase were also obtained. Normal coordinate calculations were performed for each conformer (T, G and G ) , using an optimized local symmetry force field for secondary amines. These calculations allowed the assignment of the vibrational spectra, in good agreement with the experimental evidence. Whereas in the liquid phase all the three possible conformers were detected, in the solid phase only the bands ascribed to the T conformer were observed From the temperature dependence study of the Raman spectrum of the liquid, the entbalpy differences between conformers were determined, yielding the values 4.6 f 0.3 kJ mol-' for 3.6 & 0.3 kJ mol-' for AHG-T and 1.1 f 0.3 kJ mol-' for AH,.-G. These were compared with ub SCF-MO results, for the isolated molecule, in order to assess the relative importance of intra-and intermolecular effects on conformational equilibria.

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Conformational Studies in Organic Liquids

Cited by 2 publications

References 10 publications

Structure and weak hydrogen bonds in liquid acetaldehyde

Structure and weak hydrogen bonds in liquid acetaldehyde

Raman spectra, conformational stability and normal coordinate analysis of ethylmethylamine

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