Theoretical study of substituent effects. Analysis of steric repulsion by means of paired interacting orbitals

Fujimoto, Hiroshi; Mizutani, Yoshitaka; Endo, Jun; Jinbu, Yasuhisa

doi:10.1021/jo00272a021

Cited by 18 publications

(14 citation statements)

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“…This is because as the alkyl chain in the alcohol increases in size, the steric effect also increases. The steric effect is one of the main factors directly affecting the rates of reactions 36. In addition, by testing the ability of the P‐H, E–R, L–H, and P‐P models to correlate the experimental data for the three esterification systems, we found that the same model (P‐P model) can represent the data accurately with total average error less than 3% (Tables III–V and Figs.…”

Section: Resultsmentioning

confidence: 85%

Kinetics of catalytic esterification of propionic acid with different alcohols over Amberlyst 15

Ali

2009

Int J of Chemical Kinetics

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The kinetics of the esterification reaction between propionic acid and methanol, ethanol, and 1-butanol over the ion exchange resin, Amberlyst 15, was investigated. Experiments were conducted using a fixed-bed plug flow reactor over the temperature range of 298-328 K. Acid to alcohol molar ratios of 3:1, 1:1, and 1:3 were employed. For each esterification system, the equilibrium conversion of propionic acid was found to increase with increasing reaction temperature. Several kinetic models were tested to correlate the collected data under kinetically controlled conditions; the pseudo-homogeneous (P-H), Eley-Rideal (E-R), Langmuir-Hinshelwood (L-H), and Pöpken (P-P) models. In all cases, the activity coefficients were estimated using the UNIFAC model to account for the nonideal thermodynamic behavior of the reactants and products. The P-P model was found to best represent the kinetic data of the investigated esterification systems with a total average error of less than 3%. The increase of alcohol chain length had a negative impact on the conversion of propionic acid due to steric hindrance. The activation energy of the esterification reaction is influenced by the chain length of the alcohol used. The adsorption equilibrium constants estimated by the P-P model and the solubility parameters reported by AICHE DIPPER ® followed the same trend; ester < acid < alcohol < water.

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Section: Resultsmentioning

confidence: 85%

Kinetics of catalytic esterification of propionic acid with different alcohols over Amberlyst 15

Ali

2009

Int J of Chemical Kinetics

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“…The steric component affecting the carboxylic acid reactivity is perhaps the decisive factor for catalysed esterification. [17][18][19] Steric hindrance increases with increasing molecular size, inducing electronic repulsion between non-bonded atoms of reacting molecules. As the alkyl chain in the carboxylic acid increases in size, its steric effect increases as well.…”

Section: Effect Of the Fatty Acid Composition On The Biodiesel Convermentioning

confidence: 99%

“…This repulsive hindrance lowers the electron density in the intermolecular region and disturbs the bonding interactions. 19 Kirschenbauer 20 has reported that the reaction of paraffinic chains such as stearic acids which occur in saturated fatty acids are relatively inert, i.e. they are attacked by oxygen only under very severe conditions.…”

Section: Effect Of the Fatty Acid Composition On The Biodiesel Convermentioning

confidence: 99%

Effects of the properties and the structural configurations of fatty acid methyl esters on the properties of biodiesel fuel: a review

Gopinath

Krishnamurthy

Velraj

et al. 2014

Proceedings of the Institution of Mechanical Engineers, Part D:

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Biodiesel is a renewable fuel that is suitable for both stationary and automotive engines. It consists of fatty acid methyl esters and fatty acid ethyl esters when vegetable oils are transesterified with methanol and ethanol respectively. The structural configuration and properties of individual fatty acid methyl esters can significantly influence the biodiesel properties. The purpose of the present work is to review the effects of the properties and the structural configurations of fatty acid methyl esters on various biodiesel properties. The structural configuration includes the molecular structure, the chain length, the saturated or unsaturated nature, the degree of unsaturation and the position of double bonds. Important properties of fatty acid methyl esters are reviewed, and a large number of data consisting of their reported values are given. The viscosity, the cetane number, the heat of combustion, the density, the bulk modulus and compressibility, the iodine value, the oxidative stability, the low-temperature properties, the boiling point, the lubricity, the saponification value, the surface tension, the specific heat, the latent heat of vaporization and the flash point are reviewed in the present study. The reported mathematical equations for estimating the properties of fatty acid compounds and biodiesel are presented. A few studies that recommend enrichment of a particular fatty acid (or acids) which is possible through genetic modification to improve the overall biodiesel properties are also cited. The contribution of a particular fatty acid (or acids) favours some properties while it has an undesirable effect on other properties. Hence the specification of one particular fatty acid profile to improve all the properties of biodiesel is not possible. Considering the low-temperature properties and the oxidative stability, a combination of both saturated fatty acids and unsaturated fatty acids is necessary. Therefore, it is important to decide whether a biodiesel should contain a larger amount of saturated fatty acid esters or unsaturated fatty acid esters in order to obtain better fuel properties. The inherent genetic modification of the fatty acid profile could be the best possibility for addressing several fuel property issues simultaneously.

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“…The second effect, i.e., the steric hindrance, increases when the alkyl chain in the carboxylic acid increases. This effect is originated by electronic repulsion between non-bonded atoms of reactants that decreases the electron density in the intermolecular region and disturbs bonding interactions [42] . The steric component affecting carboxylic acid reactivity should certainly be examined for acidcatalyzed esterification [41,43] specially when using solid acid catalysts.…”

Section: Influence Of the Chain Length Of The Carboxylic Acidmentioning

confidence: 99%

Preparation of Glycerol Carbonate Esters by using Hybrid Nafion–Silica Catalyst

et al. 2013

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Glycerol carbonate esters (GCEs) which are valuable biomass derivative compounds have been prepared by direct esterification starting from glycerol carbonate and long organic acids with different chain length, in absence of solvent and using acid organic resins, zeolites and hybrid organic-inorganic acid catalysts as heterogeneous catalysts.The best results in terms of activity and selectivity to glycerol carbonate esters have been obtained using a Nafion-silica composite. A full reaction scheme has been established and it has been found that an undesired competing reaction is the generation of glycerol and esters derived from a secondary hydrolysis of the endocyclic ester group due to water formed during the esterification reaction. The influence of temperature, substrates ratio, catalyst to substrate ratio and use of solvent has been studied and, under optimized reaction conditions and the adequated catalyst, it is possible to achieve 95% selectivity to the desired product at 98% conversion. It was found that reaction rate decreased as the number of carbons in the linear alkyl chain of the carboxylic acid increases for both p-toluenesulfonic acid and Nafion SAC-13. Fitting experimental data to a mechanistically based kinetic model, the reaction kinetic parameters for Nafion SAC-13 catalysis were determined and compared when reacting different carboxylic acids. A kinetic study showed that the lower reactivity of the carboxylic acid when increasing the chain length can be explained by inductive as well as steric effects.2

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Theoretical study of substituent effects. Analysis of steric repulsion by means of paired interacting orbitals

Cited by 18 publications

References 0 publications

Kinetics of catalytic esterification of propionic acid with different alcohols over Amberlyst 15

Kinetics of catalytic esterification of propionic acid with different alcohols over Amberlyst 15

Effects of the properties and the structural configurations of fatty acid methyl esters on the properties of biodiesel fuel: a review

Preparation of Glycerol Carbonate Esters by using Hybrid Nafion–Silica Catalyst

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