Poly Methoxy Phenols in Solution:  O−H Bond Dissociation Enthalpies, Structures, and Hydrogen Bonding

Heer, Martine I. de; Korth, ‡ and Hans-Gert; Mulder, Peter

doi:10.1021/jo9901485

Cited by 168 publications

(169 citation statements)

References 37 publications

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“…Several DFT functionals have been used to describe this interaction in substituted phenols. [40][41][42] The M06-2X functional has been developed to improve the description of medium-range correlation, [43][44][45] which is important to compute hydrogen bonding. Hydrogen bonding has been accurately described by M06-2X in several systems, [43,[46][47][48][49][50][51] and the addition of dispersion changes the M06-2X results by less than 1.6 kcal mol À1 , [47][48][49] making it unnecessary to include dispersion in this work.…”

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confidence: 99%

Computational Study of Bond Dissociation Enthalpies for Substituted β‐O‐4 Lignin Model Compounds

2011

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The biopolymer lignin is a potential source of valuable chemicals. Phenethyl phenyl ether (PPE) is representative of the dominant β-O-4 ether linkage. DFT is used to calculate the Boltzmann-weighted carbon-oxygen and carbon-carbon bond dissociation enthalpies (BDEs) of substituted PPE. These values are important for understanding lignin decomposition. Exclusion of all conformers that have distributions of less than 5% at 298 K impacts the BDE by less than 1 kcal mol(-1). We find that aliphatic hydroxyl/methylhydroxyl substituents introduce only small changes to the BDEs (0-3 kcal mol(-1)). Substitution on the phenyl ring at the ortho position substantially lowers the C-O BDE, except in combination with the hydroxyl/methylhydroxyl substituents, for which the effect of methoxy substitution is reduced by hydrogen bonding. Hydrogen bonding between the aliphatic substituents and the ether oxygen in the PPE derivatives has a significant influence on the BDE. CCSD(T)-calculated BDEs and hydrogen-bond strengths of ortho-substituted anisoles, when compared with M06-2X values, confirm that the latter method is sufficient to describe the molecules studied and provide an important benchmark for lignin model compounds.

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confidence: 99%

Computational Study of Bond Dissociation Enthalpies for Substituted β‐O‐4 Lignin Model Compounds

2011

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“…Electron donating groups have an opposite effect. 15,39,84,85 The present calculated PA for the Magnolol reached 51 kJ mol -1 in water. For Magnolols substituted in meta-and ortho-positions, computed PAs and ΔPAs in the water are reported in Table 4.…”

Section: 104mentioning

confidence: 52%

“…These results are in accordance with data published for substituent phenols. 41,47,[82][83][84][85] The computed IPs using above mentioned calculated Δ hydr H(e -) value 81 in the water for molecules substituted in meta-and ortho-positions are reported in Table 2. Table 2 summarizes ΔIP values, too.…”

Section: 36mentioning

confidence: 99%

“…Knowledge of BDEs has been accumulating substantially for the past 15-20 years owing to the development of both experimental and quantum chemical techniques. 38,39,41,45,47,69,70,[82][83][84][85][86][87][88][89][90][91][92][93][94] In this study, all conformers have been optimized and the conformer with higher stability has been used in each case. The calculated BDE for the basic structure, Magnolol, in gas-phase reached 375 kJ mol .…”

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confidence: 99%

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DFT/B3LYP Study of the Substituent Effects on the Reaction Enthalpies of the Antioxidant Mechanisms of Magnolol Derivatives in the Gas-Phase and Water

Najafi¹,

Najafi²,

Najafi³

2012

Bulletin of the Korean Chemical Society

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In this paper, the study of various ortho-and meta-substituted Magnolol derivatives is presented. The reaction enthalpies related to three antioxidant action mechanisms HAT, SET-PT and SPLET for substituted Magnolols have been calculated using DFT/B3LYP method in gas-phase and water. Calculated results show that electronwithdrawing substituents increase the bond dissociation enthalpy (BDE), ionization potential (IP) and oxidation/ reduction enthalpy (O/RE), while electron-donating ones cause a rise in the proton dissociation enthalpy (PDE) and proton affinity (PA). In ortho-position, substituents show larger effect on reaction enthalpies than in metaposition. In comparison to gas-phase, water attenuates the substituent effect on all reaction enthalpies. In gasphase, BDEs are lower than PAs and IPs, i.e. HAT represents the thermodynamically preferred pathway. On the other hand, SPLET mechanism represents the thermodynamically favored process in water. Results show that calculated enthalpies can be successfully correlated with Hammett constants (σ m ) of the substituted Magnolols. Furthermore, calculated IP and PA values for substituted Magnolols show linear dependence on the energy of the highest occupied molecular orbital (E HOMO ).

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“…However, both geometries should be taken into consideration for structural, chemical and biological studies regarding hydroxycinnamic acids since they are the most populated ones at room temperature. In di-and tri substituted compounds a stabilising intramolecular H-bond is formed, which is known to be energetically favourable in this kind of phenolic systems [44][45][46][47][48][49]57], and is therefore essential for the interpretation of their structure-activity relationships (SAR's).…”

Section: Discussionmentioning

confidence: 99%

Conformational behaviour of biologically active ferulic acid derivatives

Calheiros¹,

Borges²,

Marques³

2009

Journal of Molecular Structure: THEOCHEM

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a b s t r a c tThe conformational behaviour of several biologically relevant hydroxycinnamic systems -ferulic acid and its methyl, ethyl, propyl and butyl esters -was studied by quantum mechanical calculations, at the DFT level. A full geometry optimisation was carried out, as well as a Fourier analysis of the main internal rotations within these molecules. The geometrical preferences of these compounds result from a balance between the stabilising resonance and hydrogen bonding effects and the destabilising non-bonding repulsions, the most stable conformers displaying an s-cis conformation and hydroxyl/methoxyl substituent groups coplanar to the aromatic ring. The results thus obtained allow a better understanding of the well recognised in vitro and in vivo antioxidant and growth-inhibiting properties of this type of phenolic systems.

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Poly Methoxy Phenols in Solution: O−H Bond Dissociation Enthalpies, Structures, and Hydrogen Bonding

Cited by 168 publications

References 37 publications

Computational Study of Bond Dissociation Enthalpies for Substituted β‐O‐4 Lignin Model Compounds

Computational Study of Bond Dissociation Enthalpies for Substituted β‐O‐4 Lignin Model Compounds

DFT/B3LYP Study of the Substituent Effects on the Reaction Enthalpies of the Antioxidant Mechanisms of Magnolol Derivatives in the Gas-Phase and Water

Conformational behaviour of biologically active ferulic acid derivatives

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