Enolisation Kinetics of m-Nitro Acetophenone

Malhotra, Swati; Jaspal, Dipika

doi:10.9767/bcrec.9.1.5258.16-22

Cited by 6 publications

(5 citation statements)

References 18 publications

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“…m-Methylacetophenone is a colorless liquid used as a reagent in organic synthesis. Amino acids too on the other hand have been tested for their catalytic activity on a number of substances (Malhotra and Jaspal, 2014;Rodina and Godson, 2006;Zhong et al, 2012;Vassilev et al, 2013). However no substantial work has been carried out in order to study the catalytic potential of these biomolecules in the enolisation of m-Methylacetophenone which remains the main motive of this research work.…”

Section: Introductionmentioning

confidence: 98%

Amino acids as catalysts for the enolisation study of m-Methylacetophenone

Malhotra¹,

Jaspal

Malviya

2019

Arabian Journal of Chemistry

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Amino acids have been used as catalysts for the study of kinetic of enolisation of m-Methylacetophenone, in which iodination has been the chosen method. Several parameters like effect of ketone concentration, effect of dielectric constant, effect of catalysts etc. have been investigated for their effect on enolisation kinetics. The study is focused on b-alanine, DL-alanine, L-alanine and Glycine for their effects on the rate. The order of the rate constants obtained has been found to be in the order of increasing dipole moments of the amino acids i.e. L-alanine < Glycine < DL-alanine < b-alanine. With an increase in the temperature from 323 K to 338 K, an increase in the rate was from 1.3 to 2.12 mol À1 min À1 . The ongoing reaction was found to be bimolecular in nature. The values of different thermodynamic parameters like Entropy (DS " ), Enthalpy (DH " ), Energy of activation (DEa) and Gibbs free energy (DF " ) were found to be 6.20 e.u., 24.74 cal mol À1 , 25.20 k cal mol À1 and 24.54 cal mol À1 respectively. ª 2014 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

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Section: Introductionmentioning

confidence: 98%

Amino acids as catalysts for the enolisation study of m-Methylacetophenone

Malhotra¹,

Jaspal

Malviya

2019

Arabian Journal of Chemistry

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“…The keto form is thermodynamically more stable than the enol form, but some factors, such as dielectric constant and hydrogen bond-forming ability of solvent, temperature, concentration, catalyst, and substituent groups, shift the equilibrium in favor of the enol form. For instance, more polar keto form in a polar solvent is the predominant tautomeric form due to the solvation effect [8, [15][16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

“…Recently, water was used as a catalyst to increase the rate of enolization reactions. It is found that free energy of activation of keto-enol tautomerization process decreases in the presence of one or two water molecules [16,17,21,28,31]. It also seems that water molecules control the pathway of aldol reaction by decreasing or increasing the formation rate of enol intermediate, in other words, the enol content of the carbonyl compound.…”

Section: Introductionmentioning

confidence: 99%

Theoretical study of the effect of water clusters on the enol content of acetone as a model for understanding the effect of water on enolization reaction

Nafe

Arshadi

2021

Struct Chem

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The enolization of simple carbonyl compounds is a key reaction for many chemical and biochemical processes. Numerous theoretical and experimental studies have been done to probe aspects of the mechanism of this reaction. In this work, the effect of small water clusters, (H 2 O) n : n=1-9, on the enol content of acetone is investigated by using density functional theory calculations at the M06 level of theory in the gas and solution phases. The calculations indicated that the formation of hydrogen-bonded assemblies between water clusters and both tautomers of acetone affect the enolization reaction. Among them, the trimeric water cluster has the highest binding energy difference (DE b ) in the solution phase and greatly shift the equilibrium in the favor of the enol form. The results also shown that under this condition, the enol content of acetone increased by decreasing the polarity of the solvent. The practical conclusion of this study is that the enol content of carbonyl compounds can be maximized only by addition a de ned amount of water.

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“…Over the years, there have been an extensive number of kinetic studies on the keto‐enol equilibrium mostly on acetophenone or acetyl heterocycle derivatives in water [11–18] with only a few studies on molecules similar to BnFTP [19,20] and an even more limited number in organic solvents [21] . Every kinetic study carried out on the enolization of carbonyls was assessed by either deuteration, racemization, or halogenation, [13] the latter one being the most used [11–18,22−24] . Here we use the racemization approach, conducted with a polarimeter set‐up that continuously samples the racemizing mixture to the polarimeter cell, using a recycle loop connected to the reactor in order to measure directly the enantiomeric excess of the compound during the racemization reaction.…”

Section: Introductionmentioning

confidence: 99%

Fungicide Precursor Racemization Kinetics for Deracemization in Complex Systems

et al. 2020

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In the racemization area, the keto-enol equilibrium is a major player when it comes to racemizing α-chiral carbonyl compounds. The racemization kinetics in the co-crystal induced deracemization of a fungicide precursor is complex as next to the racemization catalyst, which is a base, an acidic co-former is used to ensure the crystallization of the co-crystal. Here we show that understanding of the racemization kinetics of the target compound is of key importance for optimization of the co-crystallization based deracemization process. The racemization rates in solution as a function of solvent and base concentration were determined by measuring the decreasing enrichment of the chiral ketone due to racemization over time, using a polarimeter setup with a continuous recycling loop through the polarimeter cell. The established racemization kinetics model aligns with the experimental data giving access to the intrinsic racemization rate constant. The proposed mechanism is first order with respect to the enantiomeric excess of the target compound and the base-catalyst concentration. The solvent is shown to strongly affect the racemization constant, with protic solvents increasing this rate substantially due to hydrogen-bond stabilization of the enolate. Finally, we observed the presence of the chiral acid co-former to alter the reaction mechanism albeit remaining first order with respect to the enantiomeric excess. Though more complex, the mechanism still followed Arrhenius law, providing key information on the impact of temperature.

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Enolisation Kinetics of m-Nitro Acetophenone

Cited by 6 publications

References 18 publications

Amino acids as catalysts for the enolisation study of m-Methylacetophenone

Amino acids as catalysts for the enolisation study of m-Methylacetophenone

Theoretical study of the effect of water clusters on the enol content of acetone as a model for understanding the effect of water on enolization reaction

Fungicide Precursor Racemization Kinetics for Deracemization in Complex Systems

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