Activation Energy and NBO Interaction Approaches to the Determination of the Relative Resonance Acceptor Strengths of CN, NO, COMe, CHO and NO2 Groups from the Ring-Opening of 1,2-Benzo-3-Carbomethoxycyclobutenes

2019 ◽  
Author(s):  
Veejendra Yadav ◽  
Arpita Yadav
Keyword(s):  
Activation Energy ◽  
Interaction Energy ◽  
Ring Opening ◽  
Activation Energies ◽  
Interaction Energies ◽  
Differential Activation ◽  
Transition Structures

<p>The relative resonance-acceptor ability based on the activation energies for the outward ring-openings of 1,2-benzo-3-carbomethoxycyclobutenes bearing CN, NO, COMe, CHO and NO<sub>2</sub> as C6 and C7 substituents is different from that based on the s<sub>C3C4</sub>-p*<sub>C1C2</sub> interactions in the inward opening transition structures. The differential activation energy (∆G<sup>‡</sup>) predicts outward ring-opening and, in contrast, the differential s<sub>C3C4</sub>-p*<sub>C1C2</sub> interaction energy predicts inward opening, throughout. The relative resonance-acceptor ability estimated from the s<sub>C3C4</sub>-p*<sub>C1C2</sub> interaction energies is more realistic than that from the activation energies.</p>

scholarly journals Activation Energy and NBO Interaction Approaches to the Determination of the Relative Resonance Acceptor Strengths of CN, NO, COMe, CHO and NO2 Groups from the Ring-Opening of 1,2-Benzo-3-Carbomethoxycyclobutenes

2019 ◽  
Author(s):  
Veejendra Yadav ◽  
Arpita Yadav
Keyword(s):  
Activation Energy ◽  
Interaction Energy ◽  
Ring Opening ◽  
Activation Energies ◽  
Interaction Energies ◽  
Differential Activation ◽  
Transition Structures

<p>The relative resonance-acceptor ability based on the activation energies for the outward ring-openings of 1,2-benzo-3-carbomethoxycyclobutenes bearing CN, NO, COMe, CHO and NO<sub>2</sub> as C6 and C7 substituents is different from that based on the s<sub>C3C4</sub>-p*<sub>C1C2</sub> interactions in the inward opening transition structures. The differential activation energy (∆G<sup>‡</sup>) predicts outward ring-opening and, in contrast, the differential s<sub>C3C4</sub>-p*<sub>C1C2</sub> interaction energy predicts inward opening, throughout. The relative resonance-acceptor ability estimated from the s<sub>C3C4</sub>-p*<sub>C1C2</sub> interaction energies is more realistic than that from the activation energies.</p>

scholarly journals Differential Activation Energy and NBO Interaction Approaches to Torquoselectivity and Its Dependence on the Conformational Profile of the Substituent

2021 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Activation Energy ◽  
Ring Opening ◽  
Energy Approach ◽  
Differential Activation ◽  
Distinct Level ◽  
Lower Activation ◽  
Secondary Reactions ◽  
The Subject ◽  
Interaction Approach ◽  
Lower Activation Energy

The torquoselectivity of ring opening of 3-CF<sub>3</sub>-cyclobutene, 3-CHF<sub>2</sub>-cyclobutene, 3-CH<sub>2</sub>F-cyclobutene, 3-CF<sub>3</sub>-oxetene and perfluoro-3-CH<sub>3</sub>-cyclobutene have been studied at the MP2/cc-pVTZ level of theory and the results analysed by using the differential activation energy approach and also differential NBO interactions of the breaking ring bond with the substituent bonds. The outward or inward ring opening that has lower activation energy in the differential activation energy approach or larger interaction in the differential NBO interaction approach constitutes the preferred mode. The predictions from the two approaches are largely found to be contradicting each other, specifically when the substituent is electron-deficient. The CHF<sub>2</sub> and CH<sub>2</sub>F substituents on cyclobutene and oxetene can adopt three distinct conformations with respect to the cleaving ring bond. It has been discovered that each conformer exhibits a distinct level of torquoselectivity and some may even contribute to the overall selectivity substantially. The conformational profile of the substituent, therefore, is recommended to be taken into account in any serious treatment of the subject. The experimental torquoselectivity, if otherwise, is a likely consequence of secondary reactions, specifically equilibration through reaction reversal while honouring the relative thermodynamic stabilities of the ring opened products.

scholarly journals Stereochemical Effect of the Small Ring Unit in 7-R-3,4-Cyclopropano- and 7-R-3,4-Epoxy-bicyclo[4.2.0]octan-1,5-Dienes on Conrotatory Ring Opening Torquoselectivity

2021 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Activation Energy ◽  
Ring Opening ◽  
Energy Approach ◽  
The Other ◽  
Small Ring ◽  
Formyl Group ◽  
Differential Activation ◽  
Interaction Approach ◽  
Relationship Of

Application of the differential activation energy approach suggests that the strong inward opening tendency of the formyl group in 3,4-cyclopropano-7-formyl-bicyclo[4.2.0]octan-1,5-diene and also 3,4-epoxy-7-formyl-bicyclo[4.2.0]octan-1,5-diene is either counter balanced to a level that the reaction turns torquo-neutral or it rotates outward, depending upon the stereo-relationship of the small ring unit with the formyl substituent. The NBO interaction approach, however, predicts inward selectivity throughout. These molecules, therefore, can be used as excellent test examples to judge the validity of one approach over the other.

scholarly journals Differential Activation Energy and NBO Interaction Approaches to Torquoselectivity and Its Dependence on the Conformational Profile of the Substituent

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Activation Energy ◽  
Ring Opening ◽  
Energy Approach ◽  
Differential Activation ◽  
Distinct Level ◽  
Lower Activation ◽  
Secondary Reactions ◽  
The Subject ◽  
Interaction Approach ◽  
Lower Activation Energy

The torquoselectivity of ring opening of 3-CF<sub>3</sub>-cyclobutene, 3-CHF<sub>2</sub>-cyclobutene, 3-CH<sub>2</sub>F-cyclobutene, 3-CF<sub>3</sub>-oxetene and perfluoro-3-CH<sub>3</sub>-cyclobutene have been studied at the MP2/cc-pVTZ level of theory and the results analysed by using the differential activation energy approach and also differential NBO interactions of the breaking ring bond with the substituent bonds. The outward or inward ring opening that has lower activation energy in the differential activation energy approach or larger interaction in the differential NBO interaction approach constitutes the preferred mode. The predictions from the two approaches are largely found to be contradicting each other, specifically when the substituent is electron-deficient. The CHF<sub>2</sub> and CH<sub>2</sub>F substituents on cyclobutene and oxetene can adopt three distinct conformations with respect to the cleaving ring bond. It has been discovered that each conformer exhibits a distinct level of torquoselectivity and some may even contribute to the overall selectivity substantially. The conformational profile of the substituent, therefore, is recommended to be taken into account in any serious treatment of the subject. The experimental torquoselectivity, if otherwise, is a likely consequence of secondary reactions, specifically equilibration through reaction reversal while honouring the relative thermodynamic stabilities of the ring opened products.

Determination of Activation Energy of the Iron Acceptor Pair Association and Dissociation Reaction

2015 ◽  
Vol 242 ◽  
pp. 230-235
Author(s):  
Kevin Lauer ◽  
Christian Möller ◽  
D. Debbih ◽  
Manuel Auge ◽  
Dirk Schulze
Keyword(s):  
Activation Energy ◽  
Iron Content ◽  
Reaction Rates ◽  
Activation Energies ◽  
Illumination Intensity ◽  
Dissociation Reaction ◽  
Acceptor Pair ◽  
Association Reaction

A method to measure the reaction rates of the iron acceptor pair association and dissociation is presented and applied. The activation energies of the dissociation and association reaction are determined for the acceptors boron, aluminum, gallium and indium. Additionally, the activation energies are reported for different illumination intensities. It is found that the activation energy of the association reaction varies for the investigated acceptors and that the activation energy of the dissociation reaction depends strongly on the illumination intensity. It is shown that neglecting of the dissociation reaction in the evaluation of relative interstitial iron content decrease causes a considerable overestimation of the activation energy of the iron acceptor association.

The Determination of Kinetic Parameters of Transformer Oil and its Blends by Thermal Analysis

2012 ◽  
Vol 13 (4) ◽  
Author(s):  
Veresha Dukhi ◽  
Ajay Bissessur ◽  
Catherine Jane Ngila ◽  
Nelson Mutatina Ijumba
Keyword(s):  
Activation Energy ◽  
Weight Loss ◽  
Kinetic Parameters ◽  
Breakdown Voltage ◽  
Activation Energies ◽  
Transformer Oil ◽  
Dielectric Fluid ◽  
Differential Scanning Calorimetric ◽  
Significant Difference

Abstract The insulation of transformer oil comprise of two practices: paper and dielectric fluid (such as mineral transformer oil). Ageing of these oils occur mainly by thermal, electrical and oxidative stresses. This paper describes the determination of kinetic parameters of a naphthenic based transformer oil and its blends based on the Ozawa, Flynn and Wall (OFW) and Kissinger models using data obtained from thermogravimetric analysis (TGA) and differential scanning calorimetric (DSC), plots. Virgin oil and its blends were analysed from an initial temperature range of 20-25 ºC to 300 ºC at temperature ramps of 1, 2, 4, 6, 8 and 10 ºC min-1. The OFW method in conjunction with TGA data was used to calculate the apparent decomposition activation energies at each of the selected weight loss (% conversion or α) values. The activation energies at 10% weight loss were found to be 57.0, 63.7 and 69.3 kJ mol-1 for BHT-B (virgin oil-2,6-di-tert-butyl-4-methylphenol blends), DBP-B (virgin oil-2,6-di-tert-butylphenol blends) and VO (virgin transformer oil), respectively. However using this method the activation energy (Ea) of the oils showed no significant difference between virgin oil and its blends. DSC curves revealed that the decomposition reaction was exothermic in nature. From DSC data the activation energy was determined using two separate models: OFW and Kissinger models. Decomposition activation energy obtained from DSC data showed no significant difference when applied to these two models. Dissipation factor tests showed superior results for the blends when compared to those of virgin transformer oil. However, the blends showed substantial reductions in their dielectric breakdown voltage. The implication of the reduced breakdown voltage is that the blends show poorer dielectric strength in comparison to virgin transformer oil.

scholarly journals Assay of β-N-acetylhexosaminidase isoenzymes in different biological specimens by means of determination of their activation energies

1998 ◽  
Vol 44 (2) ◽  
pp. 226-231 ◽  
Author(s):  
Luis F Pérez ◽  
J Carlos Tutor
Keyword(s):  
Activation Energy ◽  
Cerebrospinal Fluid ◽  
Catalytic Activity ◽  
Seminal Plasma ◽  
Activation Energies ◽  
Thermodynamic Method ◽  
Heat Inactivation ◽  
Specific Substrate ◽  
Isoenzyme Composition

Abstract The activation energy (Ea) of β-N-acetylhexosaminidase (Hex, EC 3.2.1.52) was determined with 3,3′-dichlorophenylsulfonphthaleinyl-N-acetyl-β-d-glucosaminide as substrate, with a much higher value being found for the Hex B isoenzyme (Ea = 75.1 kJ/mol) than for the Hex A isoenzyme (Ea = 41.8 kJ/mol). This fact allowed for the development of a fast and reliable thermodynamic method to determine the isoenzyme composition of Hex in different biological specimens (serum/plasma, saliva, cerebrospinal fluid, seminal plasma, urine, and leukocyte lysates). The results in serum given by the proposed method may be superimposed upon those obtained by the heat inactivation assay of O’Brien et al. (N Engl J Med 1970;273:15–20), and the catalytic activity calculated for Hex A offers a good correlation with that obtained by using the specific substrate 4-methylumbelliferyl-N-acetyl-β-d-glucosaminide-6 sulfate (n = 25, r = 0.953).

scholarly journals Differential Activation Energy and NBO Interaction Approaches to Torquoselectivity and Its Dependence on the Conformational Profile of the Substituent

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Activation Energy ◽  
Ring Opening ◽  
Energy Approach ◽  
Differential Activation ◽  
Distinct Level ◽  
Lower Activation ◽  
Secondary Reactions ◽  
The Subject ◽  
Interaction Approach ◽  
Lower Activation Energy

The torquoselectivity of ring opening of 3-CF<sub>3</sub>-cyclobutene, 3-CHF<sub>2</sub>-cyclobutene, 3-CH<sub>2</sub>F-cyclobutene, 3-CF<sub>3</sub>-oxetene and perfluoro-3-CH<sub>3</sub>-cyclobutene have been studied at the MP2/cc-pVTZ level of theory and the results analysed by using the differential activation energy approach and also differential NBO interactions of the breaking ring bond with the substituent bonds. The outward or inward ring opening that has lower activation energy in the differential activation energy approach or larger interaction in the differential NBO interaction approach constitutes the preferred mode. The predictions from the two approaches are largely found to be contradicting each other, specifically when the substituent is electron-deficient. The CHF<sub>2</sub> and CH<sub>2</sub>F substituents on cyclobutene and oxetene can adopt three distinct conformations with respect to the cleaving ring bond. It has been discovered that each conformer exhibits a distinct level of torquoselectivity and some may even contribute to the overall selectivity substantially. The conformational profile of the substituent, therefore, is recommended to be taken into account in any serious treatment of the subject. The experimental torquoselectivity, if otherwise, is a likely consequence of secondary reactions, specifically equilibration through reaction reversal while honouring the relative thermodynamic stabilities of the ring opened products.

Annealing Kinetics of Neutron?Irradiated Aluminium and Copper

1960 ◽  
Vol 13 (2) ◽  
pp. 347 ◽  
Author(s):  
TH Blewitt ◽  
RR Coltman ◽  
CE Klabunde
Keyword(s):  
Activation Energy ◽  
Activation Energies ◽  
Slope Method ◽  
Measured Activation Energy ◽  
Measured Activation ◽  
Kinetics Of ◽  
Constant Activation Energy

Activation energies for the annealing of copper and aluminium following reactor bombardment near 4 OK have been measured in the range from 10 to 40 OK. Both the change in slope method and the isothermal technique method were utilized with the assumption that a constant activation energy existed. Computations of the number of jumps involved from the measured activation energy result in an impossibly small number. It is obvious that the method for determination of the activation energies is not applicable, probably because of the non-uniqueness of the activation energy.

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