•Novel 5-styryl-2-(4-tolylsulfonamido)chalcones were synthesized and characterized•The geometry of a representative example was established using X-ray crystallography•The experimental data was ...complemented with density functional theory•The compounds were evaluated in vitro against α-glucosidase and α-amylase, and for antioxidant properties•Their mechanism of antioxidant effect was evaluated at theoretical level
Sulfonylation of the 5-styryl-2-aminochalcones with p-toluenesulfonyl chloride in pyridine afforded novel 5-styryl-2-sulfonamidochalcone hybrids. XRD analysis of a representative compound helped to confirm the presence of a six-membered N–H···O intramolecularly hydrogen bonded chair-like pseudo ring. Topology was determined through Hirshfeld surface analysis and the energy of frontier molecular orbitals was used to evaluate the stability of this compound. The inhibitory effect of the test compounds against α-glucosidase and α-amylase activities was evaluated in vitro through enzymatic assays, and their antioxidant properties also in vitro through the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (NO) radical scavenging assays. An in vitro cell-based antioxidant activity assay of the most active compounds, 2f and 2h, involving lipopolysaccharide (LPS) induced reactive oxygen species (ROS) production also confirmed their capability to scavenge free radicals. Molecular modelling was used to postulate ligand–enzyme interactions and to rationalize the mechanism of antioxidant effect of these compounds.
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In this work, a theoretical investigation of thermochemistry and kinetics of the oxidation of bifunctional 2-Methoxyethanol (2ME) biofuel using methyl radical was introduced. Potential-energy surface ...for various channels for the oxidation of 2ME was studied at density function theory (M06-2X) and ab initio CBS-QB3 levels of theory. H-atom abstraction reactions, which are essential processes occurring in the initial stages of the combustion or oxidation of organic compounds, from different sites of 2ME were examined. A similar study was conducted for the isoelectronic n-butanol to highlight the consequences of replacing the ϒ CH
group by an oxygen atom on the thermodynamic and kinetic parameters of the oxidation processes. Rate coefficients were calculated from the transition state theory. Our calculations show that energy barriers for n-butanol oxidation increase in the order of α ‹ O ‹ ϒ ‹ β ‹ ξ, which are consistent with previous data. However, for 2ME the energy barriers increase in the order α ‹ β ‹ ξ ‹ O. At elevated temperatures, a slightly high total abstraction rate is observed for the bifunctional 2ME (4 abstraction positions) over n-butanol (5 abstraction positions).
Unimolecular pyrolysis of isopropyl acetate (
IPA
) and isopropyl propanoate (
IPP)
esters as biodiesel surrogates has been carried out using density functional theory (DFT) at BMK/DZ, TZ level and ...CBS-QB3 ab initio calculations. Results were compared with isopropyl butanoate (
IPB)
. The rate constants for unimolecular decomposition reactions are calculated based on transition state theory (TST) and compared with the available experimental data. Derived reaction rates have been calculated at a wide range of temperatures relevant to the interest of atmospheric and combustion communities. Among all dissociation channels of
IPA
,
IPP
and
IPB,
acid/propene formation is the most favorable reaction path from kinetic and thermodynamic points of view. On the other side, formation of lower esters is obstructed by high activation energy barriers and is improbable to occur except at high temperature for
IPP
and
IPB
. Reaction channels involving simple bond scission require less energy than new esters formation.
Quantum chemical calculations were used to study the production of ethylene and keto/enol tautomers from ethoxyquinoline (2‐EQ) and ethoxyisoquinoline (1‐EisoQ and 3‐EisoQ) in the gas phase and ...ethanol at the MP2/6‐311++G(2d,2p)//BMK/6‐31+G(d,p) level. The obtained data indicate that the elimination of ethylene from 1‐EisoQ and 2‐EQ is slightly more favorable than from 3‐EisoQ. Formation of quinolone and isoquinolone (2‐EQO, 1‐EisoQO, and 3‐EisoQO) is kinetically favored compared to their enols. Decomposition of 2‐EQ and 1‐EisoQ to ethylene and keto forms is thermodynamically and kinetically preferable more stable than the corresponding enols. However, the hydroxy form of 3‐EisoQ is more stable than its keto tautomer in the gas phase and ethanol. The enol tautomers cost less energy when formed from their keto forms rather than from the parent ethoxyquinolone and ethoxyisoquinoline.
Oxidation of Methyl Propanoate by the OH Radical Mahmoud, Mohamed A. M.; El-Demerdash, Safinaz H.; Gogary, Tarek M. EL ...
Russian Journal of Physical Chemistry A,
12/2018, Letnik:
92, Številka:
12
Journal Article
Recenzirano
Odprti dostop
Atmospheric oxidation of methyl propanoate (MP) by the OH radical has been performed using density functional theory (BMK, BBIK) and ab initio (MP2, CBS-QB3) calculations. The thermodynamic and ...kinetic parameters are calculated. Three channels have been discussed. These reactions occur through low energy barriers of 3.2–4.3 kcal/mol. The energy barriers increase in the order α < µ < β at CBS–QB3. However, BMK shows slightly different order. Rate constants and branching ratios reveal that the H-abstraction from C
α
is as the dominant reaction over the whole temperature range of 200–300 K, with a competition from C
β
channel at lower temperature. The BB1K data reproduce the available experimental rate constant.
The kinetics of hydrogen atom abstraction from methyl propionate (
MePr
), a biodiesel model, by
•
H and
•
CH
3
radicals, have been studied. Here, we employ density functional theory (BB1K, BMK, ...M06-2X, M08-HX, and
ω
B97XD) and
ab initio
(MP2, CBS-QB3, and G3) calculations. Rate coefficients of each of six-bimolecular reaction pathways of
MePr
oxidation were calculated using the conventional transition state theory (TST) with Eckart (Eck) tunneling correction over a wide temperature range, 700-1600 K at pressure 1.0 atm. Branching ratios analysis of different reaction channels indicates that abstraction of H atom from C
α
is the most dominated route for
MePr
fuel consumption. However, rate constants of H-atom abstraction from the terminal methyl groups increase with rising of temperature for both
•
H and
•
CH
3
radicals.
•NBS-acetic acid mixture effected C-3 bromination of 2-hydroxy-6-methoxyacetophenone (1).•The MEP and Fukui function isosurface maps of 1 show that C-3 accommodates higher negative charge than ...C-5.•DFT predicted the 3-Br isomer 2 to be more stable and favoured in solution and gas phase than the 5-Br form.•The Hirshfeld surface analysis and 2D fingerprint diagrams were used to study the crystal packing and supramolecular features of 2.
In principle both position C-3 and C-5 of 2-hydroxy-6-methoxyacetophenone (1) should be able to react with N-bromosuccinimide (NBS), being jointly activated by the meta directing effect of the carbonyl group and strongly so by the ortho-para directing resonance effects of the hydroxyl and methoxy group, respectively. However, this acetophenone derivative reacted with NBS in acetic acid to afford 3-bromo-2-hydroxy-6-methoxyacetophenone (2), exclusively. Intramolecular hydrogen (CO…HO) bonding interaction in ortho-hydroxycarbonyl compounds result in a thermodynamically stable six-membered ring with the resultant complex resembling naphthalene. C-3 becomes the α-position of this naphthaneloid scaffold and therefore the most activated/nucleophilic for electrophilic attack by NBS. The molecular electrostatic potential (MEP) map of substrate 1 shows that C-3 accommodates higher negative charge than that on C-5 making the former centre more susceptible to electrophilic attack. Moreover, density functional theory (DFT) method also predicted the 3-Br isomer to be more stable and favoured than the 5-Br form in acetic acid solution and also in the gas phase. Single crystals of the monobrominated acetophenone 2 were obtained and the structure of this compound was accurately established with the aid of X-ray diffraction technique complemented with spectroscopic (NMR, FT-IR, Uv-Vis and HR-MS) and DFT methods. The intermolecular interaction pattern was studied by Hirshfeld surface analysis along with 2D fingerprint diagrams. The DFT calculations were also performed in the gas phase to correlate the experimental results with the simulated data.
•C-3 iodination of the 2‑hydroxy-6-methoxycarbonyl derivatives was achieved with NIS-acetic acid mixture.•Single X-ray diffraction, 1HNMR , FT-IR and DFT data support the presence of intramolecular ...OH⋯O hydrogen bond.•The steric effect caused the acetyl group of 2a to shift away from the methoxy group resulting in significantly reduced hydrogen bridge length.•Computational methods were used to study the intermolecular interactions of these compounds in a gas phase.•Iodine atom of 2a is involved in C–I⋯π interaction (0.7%), whereas both I⋯I (5.3%) and C–I⋯π (5.1%) are present in 2b.
The structures of 2‑hydroxy-3-iodo-6-methoxyacetophenone 2a and 2‑hydroxy-3-iodo-6-methoxybenzaldehyde 2b were elucidated using a combination of NMR, IR and UV–Vis spectroscopic techniques complemented with single crystal X-ray diffraction analysis. XRD confirmed the presence of thermodynamically more favourable six-membered intramolecular hydrogen bonding motif designated as S(6) in the graph-set assignments involving interaction between OH (donor) and an oxygen atom (acceptor) of the carbonyl group with hydrogen bond distance, O(2)-H(2)⋯O(1) of 2.463(2) Å and 2.606(2) Å for 2a and 2b, respectively. The halogen bonding affinity of the iodine atom of 2a as a representative model was investigated in the solution phase by 13CNMR spectroscopy in various deuterated solvents (CDCl3, DMSO‑d6, pyridine-d5 & benzene-d6) and also in benzene-d6 in the presence of triethylamine (Et3N) as a Lewis base. XRD analysis determined that the iodine atom of 2b is involved in two main types of halogen bonding, namely C–I⋯O and halogen-halogen (C–I⋯I–C) contacts. The C–I⋯π and intermolecular C–I⋯O–H contacts were observed in the case of 2a. The DFT calculations were also performed in the gas phase to correlate the experimental results with the simulated data.
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•Unimolecular mechanisms of DMM combustion were studied using DFT and CBS-QB3 methods.•Rate constants of complex (R1–R4) and simple bond fission (R5–R11) were calculated.•Results show ...comparable rates using TST and the RRKM theories for different reactions.•Pressure and temperature dependence on reaction mechanisms were investigated.•Branching ratio analysis shows domination of P5 with competition from P6/P7 channels.
Many recent studies have been considered dimethoxymethane (DMM) as a potent fuel additive which reduces soot production and nitrogen oxides (NOx) emissions of diesel and biodiesel fuel. This study reports thermo-kinetic investigation of DMM pyrolysis in temperature range 300–2000 K using M06-2X and ωB97XD density functional methods and modest cost ab initio/complete basis set-quadratic Becke3 (CBS-QB3) procedure. The energy profile has been constructed using possible unimolecular H-atom transfer reactions (R1–R4) and simple bond fission reactions (R5–R11). Rate constant calculations were conducted at high-pressure (HP) limit and in the fall-off regimes using classical transition state (TST) and the statistical Rice-Ramsperger-Kassel-Marcus (RRKM) theories, respectively. Based on CBS-QB3 energies, branching ratios analysis reveals unimportance of all H-atom transfer reactions at T ≥ 400 K, while the homolytic bond cleavage reaction R5 which produces CH3 and gauche– OCH2OCH3 fragments is considered the main dominated decomposition channel with high competition from R6 (CH3 and trans– CH3OCH2O) and R7 (CH3O and CH2OCH3) channels especially at elevated temperature.
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