Theoretical Study of Covalently Bound Α-Cyclodextrin Associations

Anconi, Cléber P. A.; Nascimento, Clébio S.; Almeida, Wagner B. De; Santos, Hélio F. Dos

doi:10.1021/jp209244d

Cited by 12 publications

(11 citation statements)

References 39 publications

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“…According to the conformational analysis of cycloheptane, the lowest-energy conformer is the twist-chair conformer. − In the case of cycloheptoxy, the twist-chair comformers are still the most stable structures. The twist-chair structure of cycloheptane has a C 2 binary symmetry.…”

Section: Resultsmentioning

confidence: 99%

Conformation and Spectroscopy Study of Cycloheptoxy Radical

Lin

Fang

2010

J. Phys. Chem. A

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Alkoxy radicals are important intermediates in the formation of tropospheric ozone. The spectroscopic identification and characterization of these species are important for understanding their chemistry in the atmosphere. In this work, we report the observation of the laser induced fluorescence (LIF) excitation spectrum of cycloheptoxy radical. The spectrum was assigned preliminary to the lowest energy twist-chair conformer (TC-i) of cycloheptoxy. The whole picture of the interconversions at ground state between different conformers of cycloheptoxy radicals was described by density functional theory calculations. The results revealed that despite the ring strain, the seven-membered ring alkoxy radical could exist in the supersonic jet-cooled condition. The decomposition and the low energy barrier pseudorotation between twist-chair conformers might be the reason of the much quieter spectrum of cycloheptoxy compared with the LIF spectrum of cyclohexoxy.

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Section: Resultsmentioning

confidence: 99%

Conformation and Spectroscopy Study of Cycloheptoxy Radical

Lin

Fang

2010

J. Phys. Chem. A

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“…All calculations are performed using the Gaussian 03 and 09 suites of programs. , Geometry optimizations and frequency calculations for all reactants, products, and transition-state species are carried out using the CBS-Q, G2, and G4 composite methods. The geometries selected for the transition states are based on the cycloalkane model for H-migration reactions and the findings of Anconi et al, Franco et al, and Wilberg for the lowest energy conformations of cycloheptane through cyclononane. ,− In each case, the carbon that is chosen to serve as a model for the migrating hydrogen is selected on the basis of an attempt to reduce any gauche interactions. The CBS-Q, G2, and G4 composite methods are chosen for their high accuracies, having reported standard deviations of 1.1, 1.0, and 0.8 kcal mol −1 respectively .…”

Section: Computational Methodologymentioning

confidence: 99%

Ab Initio Study of Hydrogen Migration across n-Alkyl Radicals

Davis

Francisco

2011

J. Phys. Chem. A

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A thorough ab initio investigation is conducted on all possible hydrogen migration pathways for the 1-ethyl, 1-propyl, 1-butyl, 1-pentyl, 1-hexyl, 1-heptyl, and 1-octyl radicals in order to determine underlying trends in reaction enthalpies, activation energies, Arrhenius A-factors, tunneling, and rate coefficients. The G4, G2, and CBS-Q composite methods are used to determine the enthalpy of reaction and activation energy barrier for each reaction. Each method shows excellent agreement with eight experimental enthalpy of reaction values, with root mean squared values of 0.8, 0.9, and 0.6 kcal mol(-1) for CBS-Q, G2, and G4, respectively. Differences in barrier heights, A-factors, tunneling, and rate coefficients are observed for axial and equatorial arrangements as well as between secondary hydrogen migration sites, depending on the location of the secondary site relative to the terminal carbon. The validity of using cycloalkane model systems to estimate rate parameters is also assessed. The failure of two key assumptions inherent to the cycloalkane models, resulting in a breakdown in the accuracy of these methods for larger transition states, is discussed. This study has significant ramifications for future theoretical, experimental, and modeling studies involving the decomposition of n-alkanes.

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“…12 The isomers representing possible ways CD rims may face each other along the polymer chain have been reported as TT, HH and HT. 13 One therefore expects different types of CDs to have preferred orientation along the polymeric chain which in turn determines the size, crystallinity, and morphology of the supramolecular structure and other physical properties such as aggregation behaviour.…”

Section: Introductionmentioning

confidence: 99%

Self-assembly of cyclodextrin–oil inclusion complexes at the oil–water interface: a route to surfactant-free emulsions

Mathapa

Paunov

2013

J. Mater. Chem. A

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We investigated the self-assembly of cyclodextrin (CD) molecules at the tetradecane-aqueous solution interface through formation of inclusion complexes (ICs). We studied the surface activity of CDs at both the air-water and the oil-water interface. Although a-CD and b-CD are not surface active at the air-water interface, they form pseudo-surfactants as inclusion complexes with linear oil molecules at the oil-water interface. We discussed the factors affecting the formation of these ICs and their assembly into microcrystals at the oil-water interface. We discovered that the morphology and the size of the aggregates formed by these ICs are dependent on the type of CD and oil used. Lamella sheets and long microrods were obtained from a-CD molecules and tetradecane. In contrast, b-CD-tetradecane gave short microrods which assembled in microcrystals. We characterised the CD-tetradecane ICs using optical microscopy, SEM, TEM and FT-IR. The crystallinity of the ICs was assessed using cross-polarised light microscopy. We demonstrated the spontaneous formation of a dense layer of adsorbed CD-tetradecane IC microcrystals at the tetradecane-water interface. At large oil volume fractions, this phenomenon led to the formation of a Pickering type of oil-in-water emulsion stabilised by adsorbed CD-oil microcrystals while at low oil volume fractions it completely solubilises the oil in the form of IC microcrystals. This emulsion stabilisation mechanism with sustainable materials like CDs may find applications in surfactant free pharmaceutical and cosmetic formulations reducing the release of surfactants in the environment.

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Theoretical Study of Covalently Bound Α-Cyclodextrin Associations

Cited by 12 publications

References 39 publications

Conformation and Spectroscopy Study of Cycloheptoxy Radical

Conformation and Spectroscopy Study of Cycloheptoxy Radical

Ab Initio Study of Hydrogen Migration across n-Alkyl Radicals

Self-assembly of cyclodextrin–oil inclusion complexes at the oil–water interface: a route to surfactant-free emulsions

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