A DFT Study of Aminophenol Stability

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The theoretical study of the acetaminophen acid biotransformation mechanism using quantum chemistry calculations at the B3LYP theory level, together with the 6-31 G * basis set were employed to obtain energy (E), ionization potential (IP), bond dissociation energy (BDE) and spin-density distribution. The unpaired electron remains is localized on the O 7 phenolic oxygen (39%), C 3 and C 5 carbon atoms at ortho positions (27% and 26%) and C 1 at para position (33%). A recombination reaction between a hydroxyl radical and the radicalized carbon atoms at ortho and para positions explain the formation of 3-hydroxy-acetaminophen (3HA) and p-benzoquinone (PBQ) plus acetamide as metabolites of PAR. IP showed that 3HA have more antioxidant properties and can be also responsible for its analgesic activity. LUMO value of PBQ is related with N-acetyl-pbenzoquinone-imine (NAPQI), as toxic metabolic.

“…5 These metabolism and reactivity can be compared with salicylates metabolism 26 and p-aminophenol oxidation. 27 …”

Section: Resultsmentioning

confidence: 99%

A Theoretical Study for Oxidative Metabolism of Acetaminophen

Borges¹,

Nascimento²,

Alves³

2010

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“…DFT calculations indicated that for MTZ an initial hydrogen abstraction is approximately 94.07 (5), 100.60 (8), and 101.88 kcal/mol (7) at the C 7 , C 9 , and C 8 positions, respectively. The OH bond dissociation energy shows a high value of 108.22 kcal/mol (9).…”

Section: Resultsmentioning

confidence: 99%

An Electronic Study for Metronidazole Metabolism

Silva¹,

Mendes²,

Vale³

et al. 2011

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The metronidazole metabolism has been explained by a mechanism involving single electron transfer using quantum chemistry calculations at the B3LYP theory level, together with the 6-31 + G(d, p) basis set. These methods were employed to obtain energy (E), ionization potential (IP), spin-density distribution, and LUMO and MEPs of the metronidazole. Our results using DFT/B3LYP/6-31+G(d, p) calculations show the ionization potential and spin densities of metronidazole can be used in oxidation or reduction prediction of its metabolism. The positive charge radical is stabilized by resonance. These properties were observed by spin density distribution. The bond dissociation energy is related with hydrogen abstraction and a possible hydroxylation via cytochrome P-450. An increase of spin distributions on C 7 < C 9 < C 8 < O 10 positions explain the azol ring participation in the stabilization.

“…Further, the stability of the compounds can be observed by spin densities distribution. [23][24][25][26][27][28][29][30] The calculated spin density to initial electron abstraction (see Fig. 5) shows more contribution from the oxygen of carbonyl moiety for the 4 derivative (0.29), followed of 1 and 2 derivatives (0.27 and 0.26), and 3 derivative (0.16).…”

Section: Resultsmentioning

confidence: 99%

Stability and Reactivity of Benzopyranones Derivatives

Lima¹,

Oliveira²,

Seabra³

et al. 2011

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The goal of this investigation is the stability and reactivity of benzopyranones derivatives using quantum chemistry calculations at the B3LYP level of theory, together with the 6-31G * basis set. Quantum chemistry was employed to obtain energy (E), HOMO and LUMO, ionization potential (IP), and spin-density distribution for benzopyranones derivatives. The gas phase structures are discussed based on thermodynamic values. Calculations of spin densities were performed for radical formed by electron abstraction. The results supported a relation between thermodynamic values and frequency of observation. The lowest HOMO and IP values are related with more reactive and minus stable compounds. These results are confirmed by spin densities distribution.