A Theoretical Study of the Enol Contents of Cyclohexanone, Cyclopentanone and Acetone

Al-Msiedeen, Ashraf; Al-Mazaideh, Ghassab M.; Khalil, Salim M.

doi:10.9734/acsj/2016/25048

Cited by 6 publications

(3 citation statements)

References 30 publications

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“…If the compound is a reaction product and the latter is occurring, perhaps DMSO is a more efficient reagent than acetone. Acetone exhibits keto/enol tautomerism where the keto structure is thermodynamically more stable and is favored in equilibrium [15]. It is possible that only one of the acetone structures is capable of this particular reaction with TCTNB causing the reaction rate to be slower.…”

Section: Resultsmentioning

confidence: 99%

1,3,5‐Trichloro‐2,4,6‐Trinitrobenzene: The Elusive Impurity Standard

Kelly

Brown

2021

Propellants Explo Pyrotec

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1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB) is an insensitive high explosive synthesized in two steps; 1,3,5‐trichloro‐2,4,6‐trinitrobenzene (TCTNB) is the only intermediate. Due to solubility limitations, TATB is often dissolved in dimethylsulfoxide (DMSO) for liquid chromatography‐mass spectrometry (LC–MS) analyses; however, DMSO is capable of participating in a wide variety of reactions. Intending to use it as an impurity standard, TCTNB was dissolved in DMSO. A stark color change from colorless to yellow accompanied by wavelength and ion chromatogram changes occurred over 24 hours. Three compounds were identified as causing the color change. All three were present in both acetone and DMSO solutions, but, overtime the absorbance spectra of the DMSO solution changed indicating an underlying reaction occurs between these compounds and DMSO. The chemical formulas of impurities present in the TCTNB sample as well as reaction products are identified via quadrupole time of flight mass spectrometry. The chemical structures are also proposed. The combination of the solvent system, ionization technique, and halogenated/nitrated aromatic ring structures resulted in substitutions of both the chlorine and nitro groups to hydroxyl groups. Three proposed structures were closely related to TCTNB, but only one was detected at a consistent mass and absorbance wavelength in both acetone and DMSO. This compound had undergone a chlorine to hydroxyl substitution and should be utilized for TCTNB detection.

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Section: Resultsmentioning

confidence: 99%

1,3,5‐Trichloro‐2,4,6‐Trinitrobenzene: The Elusive Impurity Standard

Kelly

Brown

2021

Propellants Explo Pyrotec

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“…We have used the DFT method for calculation studies of a series of tautomersims described in a previous report [16,17,18].In this study, the possible tautomers of formamide and fluoro-formamide and their transition states are elaborated using quantum mechanical density functional theory (DFT). DFT results are used to study the stability of all tautomers and transition states at both the carbonyl carbon and at the nitrogen position, as well as details of their relative energies.…”

Section: Introductionmentioning

confidence: 99%

DFT Comparative Study of the Formamide and Fluoro-FormamideTautomers and Their Corresponding Transition States

Al-Msiedeen

2021

Preprint

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Seventeen tautomers of formamide [NH3CO] and thirty one tautomers of fluoro-formamide [NH2FCO] were examined by density functional theory (DFT) calculations. Five methods of DFT (B3LYP/ 6-311++G, B3LYP/ 6-311++G(2df,2p), B3LYP/cc-pVTZ, wB97X-D/6-311++G(2df,2p) and wB97X-D/ cc-pVTZ) were used to calculate the energies and optimized geometries of formamide tautomers. B3LYP/cc-pVTZ method was determined as the best method and used to calculate relative energies, optimized geometries, mulliken charge distributions, Gibbs free energies and enthalpy of formations of all proposed fluoro-formamide/fluoro-formamidic acid tautomers. Ten transition states of formamide tautomers and nineteen transition states of fluoro-formamide tautomers were determined by vibrational frequency calculations (they have an imaginary value of frequency). Using B3LYP/cc-PVTZ, the relatively small energies of formamide (A1) and formamidic acid (A6) (-446246 and -446193kJ.mol -1 , respectively) participate to it being more stable than other formamide/formamidic acid tautomers, as well as for fluoro-formamide (C1) (-706947 kJ.mol -1 ) and fluoro-formamidic acid (C3) (-706855 kJ.mol -1 ). The stability of fluoro-formamide at carbonyl and at nitrogen was discussed using two thermodynamic calculations: Enthalpy of formation [∆H(298)] and Gibbs free energy (∆G) values, positive ∆G values (59 to 114 kJ mol-1) for fluoro-formamidetautomerism confirms the stability of fluoro-formamide at carbonyl.

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“…Enol content of carbonyl compounds has been traditionally determined by the Kurt-Meyer titration method but when the amount of enol form is less than 1 ppm this technique doesn't work well. In that case, spectroscopic methods, ash photolysis, thermochemical and kinetic methods can be used [6,7,14,[22][23][24][25][26]. Also, some theoretical studies have been carried out as well [27][28][29][30][31][32].…”

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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A Theoretical Study of the Enol Contents of Cyclohexanone, Cyclopentanone and Acetone

Cited by 6 publications

References 30 publications

1,3,5‐Trichloro‐2,4,6‐Trinitrobenzene: The Elusive Impurity Standard

1,3,5‐Trichloro‐2,4,6‐Trinitrobenzene: The Elusive Impurity Standard

DFT Comparative Study of the Formamide and Fluoro-FormamideTautomers and Their Corresponding Transition States

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

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