Browsing by Author "Angappan, Mano Priya"

Now showing 1 - 9 of 9

COMPLEXES OF CRIEGEE INTERMEDIATE CH2OO WITH CO, CO2, H2O, SO2, NO2, CH3OH, HCOOH AND CH3CH3CO MOLECULES – A DFT STUDY ON BONDING, ENERGETICS AND SPECTRA
(Elsevier, 2021-09) Muraledharan, Shyama; Meera, Cheviri; Angappan, Mano Priya; Senthilkumar, Lakshmipathi
Using high-level quantum chemical methods like CBS-QB3, CCSD(T), PBEPBE, the bonding and energy of the criegee intermediate (CI) CH2OO complexes, with atmospherically abundant gas molecules like H2O, CO, CO2, SO2, NO2, HCOOH, CH3OH and CH3CH3CO are studied. The interaction of CIs with these molecules results in hydrogen-bonded reaction complexes due to the zwitterionic character of CIs. Our findings indicate that CIs interact strongly with HCOOH, CH3OH, H2O and are weakly bonded to CO and CO2. The bonded complex of CIs with SO2 results in heteroozonide adduct. Energy decomposition analysis (EDA) reveals that the weakest interaction of CI with CO differs by 14 kcal/mol from that of the strongest criegee-HCOOH complex. EDA results augment well with the nature of bonding and charge transfer mechanism. Notably, exchange–correlation (XC) energy contributes maximum towards the interaction. Our IR analysis results suggest that CH2 and Osingle bondO stretching frequencies of CIs are red-shifted with large charge transfers where distinct CH2 symmetric modes increase the rate in hydrogen-bonded criegee reaction complexes. The electronic transitions in UV absorption spectra show that the excitation wavelengths of CIs complexes with the atmospheric molecules is red-shifted.
A DENSITY FUNCTIONAL THEORY INVESTIGATION ON NOREPINEPHRINE INTERACTION WITH AMINO ACIDS AND ALCOHOLS
(Elsevier, 2023-07-05) Angappan, Mano Priya; Basheer, Aazaad; Divya, Mariyam Biju
Norepinephrine (NP) plays a key role in the behaviour of forebrain activities, acts as a hormone and neurotransmitter in the central nervous system releases from the neurons of locus coeruleus in the brain stem. NP produces many effects in the body which includes attention, cognitive function, stress reactions and pain reactions etc. In the current scenario, neurobehavioral disorder is increasing worldwide and great attention is paid to know the role of NP. In this work, we intend to mimic the active role of NP in the presence of amino acids and alcohols by means of hydrogen bond interaction. Conformational analysis and their hydrogen bond interaction of different conformers have been studied earlier, therefore herein we made an attempt to get the biological importance and their chemical behaviour of NP due to amino acids and alcohols. Hydrogen bond interaction of glycine, alanine, ethanol and methanol with NP have been studied and the most stable conformers have been identified. Alanine and methanol show strong interaction with NP than glycine and ethanol. From AIM analysis, electron density and the Laplacian of electron density increases with decrease in bond length and the NBO analysis shows that stabilization energy increases. From molecular orbital analysis, we found HOMO is spread over benzene ring with character due to p orbitals. Hence, this study tells the current scenario of a major challenging task and the impact of neurotransmitter in the presence of amino acids and alcohols.
A DENSITY FUNCTIONAL THEORY INVESTIGATION ON NOREPINEPHRINE INTERACTION WITH AMINO ACIDS AND ALCOHOLS
(Elsevier, 2023-07-05) Angappan, Mano Priya; Basheer, Aazaad; Divya, Mariyam Biju
Norepinephrine (NP) plays a key role in the behaviour of forebrain activities, acts as a hormone and neurotransmitter in the central nervous system releases from the neurons of locus coeruleus in the brain stem. NP produces many effects in the body which includes attention, cognitive function, stress reactions and pain reactions etc. In the current scenario, neurobehavioral disorder is increasing worldwide and great attention is paid to know the role of NP. In this work, we intend to mimic the active role of NP in the presence of amino acids and alcohols by means of hydrogen bond interaction. Conformational analysis and their hydrogen bond interaction of different conformers have been studied earlier, therefore herein we made an attempt to get the biological importance and their chemical behaviour of NP due to amino acids and alcohols. Hydrogen bond interaction of glycine, alanine, ethanol and methanol with NP have been studied and the most stable conformers have been identified. Alanine and methanol show strong interaction with NP than glycine and ethanol. From AIM analysis, electron density and the Laplacian of electron density increases with decrease in bond length and the NBO analysis shows that stabilization energy increases. From molecular orbital analysis, we found HOMO is spread over benzene ring with character due to p orbitals. Hence, this study tells the current scenario of a major challenging task and the impact of neurotransmitter in the presence of amino acids and alcohols.
ENVIRONMENTAL IMPLICATIONS OF OXALIC AND MALONIC ACIDS WITH TROPOSPHERIC OXIDANTS
(John Wiley and Sons Ltd, 2024-05-30) Basheer, Aazaad; Angappan, Mano Priya; Rubini, Subramani
Dicarboxylic acids (DCAs) are major players in the formation of secondary organic aerosols (SOAs) and climate change. DCAs have potential impact on human health and environmental issues ranging from local scale to global scale participate mainly in the cloud condensation. In this context, oxalic acid (OA) and malonic acid (MA) are the most dominant DCAs in the atmosphere. A full atmospheric degradation mechanism of OA and MA with the most reactive tropospheric oxidants, namely, OH, Cl and NO3 radicals, were studied using M06-2X, ωB97XD/cc-pVTZ and 6-311++G(2df,2p) level of theories. To evaluate the atmospheric influence, this study enables us to deep investigation of fate of OA and MA with respect to the mentioned radicals and their subsequent secondary reactions. The latter result in the formation of carbon dioxide (CO2), formic acid (HCOOH), which contributes to the formation of SOA and climate change. The reaction mechanism in this study was initiated through H-abstraction reaction, followed by dehydrogenation and decarboxylation reaction of both DCAs. The rate coefficients of OA, MA with OH, Cl and NO3 radicals are determined theoretically using variational transition state theory (VTST) with Eckart tunnelling method in the temperature range of 278–1000 K. At 298 K, the rate coefficient of OA with OH, Cl and NO3 are 2.48 × 10−15, 2.37 × 10−20, 6.16 × 10−23 in cm3 molecule−1 s−1, whereas MA with OH, Cl and NO3 are 9.76 × 10−14, 1.01 × 10−12 and 5.89 × 10−18 in cm3 molecule−1 s−1, respectively. Our present results shed light on the atmospheric implications of two DCAs and provide the significant insight for the atmospheric pathways.
INVESTIGATION OF THE GAS-PHASE REACTION OF NOPINONE WITH OH RADICALS: EXPERIMENTAL AND THEORETICAL STUDY
(MDPI, 2022-08-05) Gisèle, El Dib; Angappan, Mano Priya; Senthilkumar, Lakshmipathi
Monoterpenes are the most essential reactive biogenic volatile organic compounds. Their removal from the atmosphere leads to the formation of oxygenated compounds, such as nopinone (C9H14O), one of the most important first-generation β-pinene oxidation products that play a pivotal role in environmental and biological applications. In this study, experimental and theoretical rate coefficients were determined for the gas-phase reaction of nopinone with hydroxyl radicals (OH). The absolute rate coefficient was measured for the first time using a cryogenically cooled cell along with the pulsed laser photolysis–laser-induced fluorescence technique at 298 K and 7 Torr. The hydrogen abstraction pathways were found by using electronic structure calculations to determine the most favourable H-abstraction position. Pathway 5 (bridgehead position) was more favourable, with a small barrier height of −1.23 kcal/mol. The rate coefficients were calculated based on the canonical variational transition state theory with the small-curvature tunnelling method (CVT/SCT) as a function of temperature. The average experimental rate coefficient (1.74 × 10−11 cm3 molecule−1 s−1) was in good agreement with the theoretical value (2.2 × 10−11 cm3 molecule−1 s−1). Conclusively, the results of this study pave the way to understand the atmospheric chemistry of nopinone with OH radicals.
INVESTIGATION OF THE GAS-PHASE REACTION OF NOPINONE WITH OH RADICALS: EXPERIMENTAL AND THEORETICAL STUDY
(MDPI, 2022-08-05) Gisèle, El Dib; Angappan, Mano Priya; Senthilkumar, Lakshmipathi
Monoterpenes are the most essential reactive biogenic volatile organic compounds. Their removal from the atmosphere leads to the formation of oxygenated compounds, such as nopinone (C9H14O), one of the most important first-generation β-pinene oxidation products that play a pivotal role in environmental and biological applications. In this study, experimental and theoretical rate coefficients were determined for the gas-phase reaction of nopinone with hydroxyl radicals (OH). The absolute rate coefficient was measured for the first time using a cryogenically cooled cell along with the pulsed laser photolysis–laser-induced fluorescence technique at 298 K and 7 Torr. The hydrogen abstraction pathways were found by using electronic structure calculations to determine the most favourable H-abstraction position. Pathway 5 (bridgehead position) was more favourable, with a small barrier height of −1.23 kcal/mol. The rate coefficients were calculated based on the canonical variational transition state theory with the small-curvature tunnelling method (CVT/SCT) as a function of temperature. The average experimental rate coefficient (1.74 × 10−11 cm3 molecule−1 s−1) was in good agreement with the theoretical value (2.2 × 10−11 cm3 molecule−1 s−1). Conclusively, the results of this study pave the way to understand the atmospheric chemistry of nopinone with OH radicals.
MECHANISM AND KINETICS OF ATMOSPHERIC DEGRADATION OF MENTHOL INITIATED BY HYDROXYL RADICAL
(Royal Society of Chemistry, 2023-11-01) Angappan, Mano Priya; Basheer, Aazaad
Menthol is a naturally occurring compound belonging to the cyclic monoterpene family and is one of the main constituents of peppermint oil, recognized worldwide as a cooling agent. This study is the first report on the reaction mechanism of menthol with OH radical by exploring the hydrogen abstraction mechanism using theoretical methods like M06-2X and wB97X-D/6-311+G(d,p) level of theory. Menthol has three chiral centres with cyclohexane, isopropyl and methyl groups; all the reactive sites have been studied to identify the dominant route. The H atom abstracted from the isopropyl group of menthol is found to be more energetically favourable than the entire reactive site. The results acquired are compared with high level G3B3 for the most prominent pathway. Further, the rate coefficients of all initial reactions are calculated using canonical variational transition state theory (CVT) with Wigner tunnelling correction. The most favourable pathway shows the rate coefficient of 9.83 × 10−11 cm3 molecule−1 s−1 (298 K) at the M06-2X level of theory and the results are consistent with the experimental value (1.48 ± 0.31 × 10−11 cm3 molecule−1 s−1). The formation of a peroxy radical and its reaction with atmospheric species is analyzed theoretically. The stable product 2-(1-hydroperoxy-1-methyl-ethyl)-5-methyl-cyclohexanol is formed via reaction of the peroxy radical with HO2. The thermochemistry of the entire reaction channel shows both exothermic and exergonic nature. The atmospheric life time of menthol in the presence of OH radical is found to be 1.13 hours indicates the inevitable contribution of the present study at local scale.
REACTION MECHANISM AND KINETICS OF H AND CL ATOM ABSTRACTION IN DICHLOROMETHANE WITH OH RADICAL
(Elsevier, 2023-05) Angappan, Mano Priya; Basheer, Aazaad; Vasanth, Perumal Mythili; Senthilkumar, Lakshmipathi
Dichloromethane or methylene chloride (DCM, CH2Cl2) is a hazardous toxic pollutant that enters the stratosphere via reaction with OH radicals. The present study examines DCM's complete reaction mechanism with OH radicals via H and Cl atom abstraction using density functional theory (DFT) methods such as B3LYP, M06-2X level of theory with 6–311++G(d,p) and 6–311++G(3df,2p) basis sets. In addition to DFT results, ab initio and composite methods such as MP2, CCSD(T), G3B3, and CBS-QB3 level of theory are utilized to validate the results. The subsequent secondary reaction mechanism of peroxy radicals with HO2 and NO radicals was studied in both singlet and triplet states. H-atom abstraction is the most favorable with a small relative energy barrier of 2.70 kcal/mol. The rate constant calculated by canonical variational transition state theory with the small curvature tunneling method (CVT/SCT) at 298 K is 9.50 × 10-13 cm3 molecule-1 s−1, which agrees well with previous experimental studies, and the atmospheric lifetime of the reaction is 12.18 days at 298 K. Possible new intermediates and products, such as dichloromethyl peroxide, dichloromethyl nitrate, and formyl chloride, have been identified.
REACTION MECHANISM AND KINETICS OF H AND CL ATOM ABSTRACTION IN DICHLOROMETHANE WITH OH RADICAL
(Elsevier, 2023-05) Angappan, Mano Priya; Basheer, Aazaad; Vasanth, Perumal Mythili; Senthilkumar, Lakshmipathi
Dichloromethane or methylene chloride (DCM, CH2Cl2) is a hazardous toxic pollutant that enters the stratosphere via reaction with OH radicals. The present study examines DCM's complete reaction mechanism with OH radicals via H and Cl atom abstraction using density functional theory (DFT) methods such as B3LYP, M06-2X level of theory with 6–311++G(d,p) and 6–311++G(3df,2p) basis sets. In addition to DFT results, ab initio and composite methods such as MP2, CCSD(T), G3B3, and CBS-QB3 level of theory are utilized to validate the results. The subsequent secondary reaction mechanism of peroxy radicals with HO2 and NO radicals was studied in both singlet and triplet states. H-atom abstraction is the most favorable with a small relative energy barrier of 2.70 kcal/mol. The rate constant calculated by canonical variational transition state theory with the small curvature tunneling method (CVT/SCT) at 298 K is 9.50 × 10-13 cm3 molecule-1 s−1, which agrees well with previous experimental studies, and the atmospheric lifetime of the reaction is 12.18 days at 298 K. Possible new intermediates and products, such as dichloromethyl peroxide, dichloromethyl nitrate, and formyl chloride, have been identified