Kinetics of IO radicals with ethyl formate and ethyl acetate: a study using cavity ring-down spectroscopy and theoretical methods.

The gas-phase kinetics of the reactions of IO radicals with ethyl formate (EF) and ethyl acetate (EA) were investigated experimentally using cavity ring-down spectroscopy (CRDS). IO radicals were generated in situ in the CRD reaction zone by photolyzing a mixture of (CH3I + O3 + N2) at 248 nm and thereby probed at 445.04 nm. The rate coefficients for the reactions (IO + EF) and (IO + EA) were measured at a total pressure of 65 Torr of N2 in the temperature range of 258-358 and 260-360 K, respectively. The rate coefficients for the reactions (IO + EF) and (IO + EA) were measured experimentally at room temperature to be kExpt,298KIO+EF = (3.38 ± 0.67) × 10-14 and kExpt,298KIO+EA = (1.56 ± 0.30) × 10-13 cm3 molecule-1 s-1, respectively. The effects of pressure and photolysis laser fluence on the kinetics of test reactions were found to be negligible within the experimental uncertainties for the studied range. To complement our experimental findings, the kinetics of the title reactions were investigated theoretically using canonical variational transition state theory (CVT) with small curvature tunnelling (SCT) at the CCSD(T)//M06-2X/def2-SV(P) level of theory in temperatures between 200 and 400 K. Very good agreement was observed between the experimentally measured and theoretically calculated rate coefficients for both the reactions at 298 K. The thermochemical parameters as well as the branching ratios for the title reactions are also discussed in this study.

A Combined Experimental and Theoretical Study to Determine the Kinetics of 2-Ethoxy Ethanol with OH Radical in the Gas Phase.

The reactivity of 2-ethoxy ethanol with OH radicals was experimentally measured in the temperature range of 278-363 K using the pulsed laser photolysis-laser-induced fluorescence (PLP-LIF) technique. The rate coefficient at room temperature was measured to be (1.14 ± 0.03) × 10-11 cm3 molecule-1 s-1, and the Arrhenius expression was derived to be kexpt278-363K = (1.61 ± 0.35) × 10-13 exp{(1256 ± 236)/T} cm3 molecule-1 s-1. Computational calculations were performed to compute the kinetics of the titled reaction in the temperature range of 200-400 K using advanced methods incorporated with tunneling correction at the CCSD(T)/aug-cc-pVTZ//M06-2X/6-31+G(d,p) level of theory. The Arrhenius expression derived from the computationally calculated rate coefficients is ktheo200-400K = (1.59 ± 0.35) × 10-13exp{(1389 ± 62)/T} cm3 molecule-1 s-1. The feasibility of each reaction pathway was also determined using the calculated thermochemical parameters. Atmospheric implication parameters such as cumulative atmospheric lifetime and photochemical ozone creation potential were calculated and are discussed in this paper.

Experimental and Computational Investigations of the Tropospheric Photooxidation Reactions of 1,1,1,3,3,3-Hexafluoro-2-Methyl-2-Propanol Initiated by OH Radicals and Cl Atoms.

The gas-phase kinetics for the reactions of OH radicals and Cl atoms with 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol (HF2M2P) were measured at temperatures between 268 and 363 K using the relative rate experimental technique. Methane and acetonitrile were used as reference compounds to measure the rate coefficients of the title reactions. For the reactions of HF2M2P with OH radicals and Cl atoms, the rate coefficients were measured to be (7.07 ± 1.21) × 10-15 and (2.85 ± 0.54) × 10-14 cm3 molecule-1 s-1, respectively, at 298 K. The obtained Arrhenius expressions for the reactions of HF2M2P with OH radicals and Cl atoms are kHF2M2P + OHExp - (268 - 363 K) = (7.84 ± 0.75) × 10-14 exp [-(717 ± 59)/T] and kHF2M2P + ClExp - (268 - 363 K) = (3.21 ± 0.45) × 10-12 exp [-(1395 ± 83)/T] cm3 molecule-1 s-1. In addition to the experimental measurements, computational kinetic calculations were also performed for the title reactions at the M06-2X/MG3S//M06-2X/6-31 + G(d,p) level of theory using advanced methods such as the canonical variational transition-state theory coupled with small curvature tunneling corrections at temperatures between 200 and 400 K. Theoretical calculations reveal that the H-abstraction from the CH3 group is a more favorable reaction channel than that from the OH group. Thermochemistry, branching ratios, cumulative atmospheric lifetime, global warming potential, acidification potential, and photochemical ozone creation potential of HF2M2P were calculated in the present investigation.

Dissociative nature of C(sp2)-N(sp3) bonds of carbazole based materials via conical intersection: simple method to predict the exciton stability of host materials for blue OLEDs: a computational study.

In this work, the origin of the singlet and triplet exciton-induced degradation of host materials with C(sp2)-N(sp3) bonds around nitrogen (carbazoles, acridines, etc.), connecting donor and acceptor units, was unravelled using DFT and CASSCF methods. The results reveal that molecules (employed in OLEDs) with basic units containing C(sp2)-N(sp3) bonds (nitrogen connected to carbon in a triangular fashion) have a natural tendency to fragment at the C-N bond through an S1/S0 conical intersection (CI). The calculation of barrier heights, to reach a dissociation point, indicates that degradation via triplet states is kinetically less feasible (ΔGT1-TS* > 25 kcal mol-1) compared to that via the first singlet excited state (ΔGS1-TS* ∼7-30 kcal mol-1). However, the long lifetime of triplets (as compared to singlets) aids in the reverse intersystem crossing from triplet to singlet state for subsequent degradation. From the results and inference, ΔGS1-TS* and ΔES1-T1 are proposed to be the controlling factors for exciton-induced degradation of host materials with C(sp2)-N(sp3) bonds. Furthermore, multiple functionalization of carbazole moieties reveals that polycyclic aromatic systems employed as acceptor units of host materials are best suited for PhOLEDs as they will increase their lifetime due to the larger ΔGS1-TS* and ΔES1-T1. For TADF-based devices, materials with fused ring systems (with N(sp3) at the centre) in the donor unit are the most recommended ones based on the findings of this work, as they avoid the dissociative channel altogether. A negative linear correlation between ΔGS1-TS* and HOMO-LUMO gap is observed, which provides an indirect way to predict the kinetic stability of these materials in excitonic states. These initial results are promising for the future development of the QSAR-type approach for the smart design of host materials for long-life blue OLEDs.

Cl Atom-Initiated Photo-Oxidation Reactions of Vinyl Trifluoroacetate and Allyl Trifluoroacetate in Tropospheric Conditions.

Relative rate (RR) technique coupled with gas chromatography (GC) was used to investigate the kinetics of the reactions of two hydrofluoroesters (allyl trifluoroacetate (CF3C(O)OCH2CH═CH2, ATFA) and vinyl trifluoroacetate (CF3C(O)OCH═CH2, VTFA)) with Cl atoms between 268 and 363 K and at 760 Torr of N2 (or air). The temperature-dependent Arrhenius expressions for the title reactions were obtained to be k268-363KVTFA+Cl = [(7.83 ± 2.26) × 10-12 exp((974 ± 89)/T)] cm3 molecule-1 s-1 and k268-363KATFA+Cl = [(9.03 ± 1.92) × 10-12 exp((883 ± 65)/T)] cm3 molecule-1 s-1, respectively. A negative temperature dependency was observed for both the reactions. In addition to this, the kinetics of the studied reactions was evaluated computationally at the CCSD(T)/cc-pVTZ//MP2/6-311++G(d,p) level of theory in the temperature range of 200-400 K using canonical variational transition (CVT) state theory in conjunction with small curvature tunneling (SCT) corrections and interpolated single point energy (ISPE) methods. The product analysis of the reactions of VTFA and ATFA with Cl atoms in the presence of O2 was also investigated using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-infrared spectroscopy (GC-IR). The plausible oxidation mechanism of the title reactions was proposed based on the product analyses. Further, to comprehend the impact of these molecules on the troposphere, atmospheric lifetimes, lifetime-corrected radiative forcing (RF), and global warming potential (GWP) were estimated and are presented in this manuscript.

Cl-Initiated Photo-oxidation Studies of Methyl Valerate and Methyl Isovalerate under Tropospherically Relevant Conditions.

Rate coefficients for the reactions of methyl valerate (MV) and methyl isovalerate (MIV) were investigated using the relative rate (RR) technique in the temperature range of 268-363 K and at 760 Torr of N2. The rate coefficients at 298 ± 2 K were measured to be kMV+Cl = (1.69 ± 0.40) × 10-10 cm3 molecule-1 s-1 and kMIV+Cl = (1.06 ± 0.23) × 10-10 cm3 molecule-1 s-1. To comprehend the experimentally measured rate coefficients, kinetic parameters for the title reactions were computed at the CCSD(T)/cc-pVTZ//BHandHLYP/6-311+G(d,p) level of theory over the temperature range of 200-400 K using canonical variational transition (CVT) state theory in conjunction with small curvature tunneling (SCT) corrections and the interpolated single-point energy (ISPE) method. Additionally, the degradation mechanisms were proposed based on the analyzed products. Moreover, to further understand the atmospheric fate of these molecules in the troposphere, atmospheric lifetimes, radiative forcings (RFs), and global warming potentials (GWPs) were calculated.

Kinetic Investigations of the Reaction of Phenyl Radicals with Ethyl Acetate in the Gas Phase: An Experimental and Computational Study.

Cavity ring-down spectroscopy (CRDS) was employed to investigate the kinetics of the reaction between phenyl radicals (C6H5•) and ethyl acetate (EtOAc) in the gas phase. Nitrosobenzene (C6H5NO) was used as the radical precursor to generate C6H5• at 248 nm, and the generated radicals were subsequently probed at 504.8 nm. The rate coefficients were investigated experimentally in the temperature range of 258-358 K with an interval of 20 K and at a total pressure of 55 Torr in the nitrogen atmosphere. The obtained Arrhenius expression for the title reaction (C6H5• + EtOAc) in the temperature range of 258-358 K was kphenyl + EtOAcExpt - (258 - 358 K) = (9.33 ± 0.11) × 10-16 exp[(883.7 ± 181.0)/T] cm3 molecule-1 s-1, and the rate coefficient at room temperature (298 K) was kphenyl + EtOAcExpt - 298 K = (2.20 ± 0.12) × 10-14 cm3 molecule-1 s-1. Negligible effects of pressure and photolysis laser fluence were found on the experimentally measured rate coefficients. To complement our experimental findings, rate coefficients of the title reaction were computationally investigated employing the canonical variational transition-state theory with small curvature tunnelling (CVT/SCT) at the CCSD(T)/cc-pVDZ//B3LYP/6-31+G(d,p) level of theory in the temperature range of 200-400 K. The temperature-dependent rate coefficient in the studied temperature range was obtained to be kphenyl + EtOAcTheory - (200 - 400 K) = (7.68 ± 0.12) × 10-17 exp[(1731.6 ± 216.0)/T] cm3 molecule-1 s-1, and the rate coefficient at 298 K was obtained as kphenyl + EtOAcTheory - 298 K = 2.45 × 10-14 cm3 molecule-1 s-1. Both the experimentally measured and computed rate coefficients show good agreement at 298 K. A negative temperature dependency was observed for both the experimentally measured and computed rate coefficients. A detailed discussion of the thermochemical parameters and branching ratios of the title reaction are also presented in this Article.

Photooxidation Reactions of Ethyl 2-Methylpropionate (E2MP) and Ethyl 2,2-Dimethylpropionate (E22DMP) Initiated by OH Radicals: An Experimental and Computational Study.

The relative rate (RR) technique was used for the measurement of OH-initiated photooxidation reactions of ethyl 2-methylpropionate (E2MP) and ethyl 2,2-dimethylpropionate (E22DMP) in the temperature range of 268-363 K at 760 Torr. In addition to this, the thermodynamic and kinetic parameters for the title reactions were theoretically investigated using CCSD(T)/cc-pVTZ//M06-2X/6-311++G(2d,2p) level of theory in the temperature range of 200-400 K using canonical variational transition state theory (CVT) in combination with small curvature tunneling (SCT) method. The rate coefficients at (298 ± 2) K were measured to be kE2MP+OH = (2.71 ± 0.79) × 10-12 cm3 molecule-1 s-1 and kE22DMP+OH = (2.58 ± 0.80) × 10-12 cm3 molecule-1 s-1. The degradation mechanisms for the title reactions were investigated in the presence of O2 using gas chromatography with mass spectrometry (GC-MS) and gas chromatography with infrared spectroscopy (GC-IR). From the recognized products, the possible product degradation mechanisms were predicted. In addition to this, the atmospheric lifetimes (ALs), lifetime-corrected radiative forcing (RF), global warming potential (GWPs) and photochemical ozone creation potentials (POCPs) were calculated to further understand the environmental impact of these molecules on the Earth's troposphere.

Kinetics and Mechanistic Study for Gas Phase Tropospheric Photo-oxidation Reactions of 2,2,2-Trifluoroethyl Methacrylate with OH Radicals and Cl Atoms: An Experimental and Computational Approach.

The photo-oxidation reactions of 2,2,2-trifluoroethyl methacrylate (TFEMA) initiated by OH radicals and Cl atoms were investigated via experimental as well as computational methodologies. The rate coefficients for these reactions were investigated using the relative rate technique (RR) at temperatures between 268 and 363 K. The rate coefficients for the reaction of OH radicals with TFEMA were measured with reference to diethyl ether and propylene. Propane and propylene were used in the kinetic measurements as reference compounds. At 298 K, experimentally obtained rate coefficients for the reaction of TFEMA with OH radicals and Cl atoms are kTFEMA+OHexp-298K = (2.81 ± 0.54) × 10-11 and kTFEMA+Clexp-298K = (1.91 ± 0.44) × 10-10 cm3 molecule-1 s-1, respectively. The Arrhenius expression obtained for the respective reactions are kTFEMA+OHexp-(268-363K) = (7.32 ± 0.62) × 10-12 exp[(400 ± 53) and kTFEMA+Clexp-(268-363K) = (4.10 ± 0.78) × 10-12  exp[(1228 ± 115)/T]. To further complement our experimental findings, rate coefficients were also calculated computationally for the reactions of OH radicals and Cl atoms with TFEMA at CCSD(T)/cc-pVDZ//M062X/6-31+G(d,p) and CCSD(T)/cc-pVDZ//MP2/6-31+G(d,p) levels of theory using canonical variational transition state theory (CVT) with small curvature tunneling (SCT) over the temperature range 200-400 K. Moreover, to analyze the end products formed during the title reactions, qualitative analyses were performed using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-infrared spectroscopy (GC-IR) as analytical tools and degradation mechanisms were proposed for the title reactions. Branching ratios, thermochemical parameters of these reactions, and their impact on the troposphere were discussed.

Photo-Oxidation Reaction Kinetics and Mechanistics of 4-Hydroxy-2-butanone with Cl Atoms and OH Radicals in the Gas Phase.

The temperature-dependent rate coefficients for the gas-phase reaction of 4-hydroxy-2-butanone (4H2BN) with Cl atoms and OH radicals were explored experimentally using relative rate technique and computational methods. The concentrations of the reactants as well as products were followed using gas chromatography (GC) with the flame ionization detector, GC/mass spectrometry, and GC/infrared spectroscopy as analytical techniques. Formaldehyde was obtained as the major product during the title reaction. The kinetics of 4H2BN with Cl atoms and OH radicals were measured over the temperature range of 298-363 K at 760 Torr in the N2 atmosphere using C3H8, C2H4, isopropanol, and n-propanol as reference compounds. The temperature-dependent rate coefficients for the reaction of 4H2BN with Cl atoms and OH radicals were obtained as kExpt( T) = [(1.52 ± 0.86) × 10-26] T5 exp[(2474 ± 450)/ T] cm3 molecule-1 s-1 and kexpt( T) = [(2.09 ± 0.24) × 10-12] exp[-(409 ± 15)/ T] cm3 molecule-1 s-1, respectively. Theoretical calculations were carried out at the M062X/6-31G(d,p) and M06-2X/6-31+G(d,p) level of theories, and the rate coefficients for H abstraction reactions were evaluated using the canonical variational transition state theory with the inclusion of small-curvature tunneling correction over the temperature range of 200-400 K. The rate coefficients obtained over the studied temperature range were used to fit the data, and the Arrhenius expression was obtained to be kCl(Theory) (200-400 K) = (6.10 × 10-25) T4.42 exp(2397/ T) cm3 molecule-1 s-1, kOH(Theory) (200-400 K) = (1.13 × 10-19) T2.27 exp(1505/ T) cm3 molecule-1 s-1, respectively, for the reactions of Cl atoms and OH radicals with 4H2BN. The possible reaction mechanism proposed based on the obtained products for the title reaction, thermochemistry, branching ratios, and atmospheric implications and cumulative lifetime of 4H2BN were also explored in this study.

Gas Phase Kinetics and Mechanistic Insights for the Reactions of Cl atoms with Isopropyl Formate and Isobutyl Formate.

Rate coefficients for the reactions of Cl atoms with isopropyl formate (IPF) and isobutyl formate (IBF) were measured experimentally over the temperature range of 268-363 K and at 760 Torr of nitrogen using relative rate method. Ethyl acetate and ethyl formate were used as reference compounds for the measurement of rate coefficients for the reaction of IPF with Cl atoms. Ethane and ethylene were used as reference compounds for the measurement of rate coefficients for the reaction of IBF with Cl atoms. The obtained rate coefficients for the reactions of IPF and IBF with Cl atoms at 298 K are (1.56 ± 0.47) × 10-11 and (7.60 ± 1.10) × 10-11 cm3 molecule-1 s-1 respectively. The derived temperature dependent Arrhenius expression for the reactions of IPF and IBF with Cl atoms are kR1(268-363K)Experimental = (3.87 ± 0.88) × 10-12 exp [(418 ± 70)/T] and kR2(268-363K)Experimental = (1.83 ± 0.45) × 10-11 exp [(421 ± 70)/T] cm3 molecule-1 s-1 respectively. A qualitative analysis of the products formed during the reactions of Cl atoms with IPF and IBF were carried out using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-infrared spectroscopy (GC-IR) as analytical tools, and the degradation mechanisms were proposed on the basis of end products. To rationalize our experimentally obtained results, computational calculations were performed to calculate the temperature dependent rate coefficients for these reactions over the temperature range of 200-400 K at CCSD(T)/cc-pVDZ//MP2/6-31+G(d, p) level of theory using canonical variational transition state theory (CVT) with small curvature tunneling (SCT). Detailed discussions on the thermochemistry of the reactions, branching ratios, and atmospheric implications are discussed in the manuscript.

Cl-Atom-Initiated Atmospheric Degradation of Saturated Cyclic Hydrocarbons: Kinetic and Mechanistic Investigation.

The temperature-dependent reaction kinetics of methyl cyclohexane (MCH) and methyl cyclopentane (MCP) with Cl atoms were experimentally explored via the relative rate technique. Gas chromatography coupled with a flame ionization detector was employed to follow the reactant as well as the reference compound concentrations during the course of reaction. Gas chromatography coupled with mass spectrometry and gas chromatography coupled with infrared spectroscopy were used as the diagnostic tools for the detection and identification of the products in the title reaction. The rate coefficients for the reaction of Cl atoms with methyl cyclohexane and methyl cyclopentane were measured in the temperature range of 283-363 K at 760 Torr using isoprene and propylene as reference compounds. To support the experimental results, computational calculations were performed over the temperature range of 200-400 K using canonical variational transition state theory coupled with small curvature tunneling (CVT/SCT), conventional transition state theory (CTST) coupled with Wigner tunneling corrections, and CVT coupled with Wigner tunneling methods using the MP2 level of theory with 6-31G(d,p) as the basis set. The temperature-dependent rate coefficients were measured for the reaction of methyl cyclohexane and methyl cyclopentane with Cl atoms to be k(MCH) = [(4.48 ± 0.75) × 10-11]exp[(604 ± 25)/T] cm3 molecule-1 s-1 and k(MCP) = [(5.71 ± 0.66) × 10-12]exp[(1819 ± 669)/T] cm3 molecule-1 s-1, respectively. The measured rate coefficients at 298 K for the reactions of Cl atoms with methyl cyclohexane and methyl cyclopentane are k298 KMCH = (3.36 ± 0.34) × 10-10 cm3 molecule-1 s-1 and k298 KMCP = (2.25 ± 0.24) × 10-10 cm3 molecule-1 s-1, respectively. The conceivable atmospheric degradation mechanism for the reaction of methyl cyclohexane as well as methyl cyclopentane with Cl atoms was projected based on the products obtained during the reaction. Atmospheric implications, cumulative atmospheric lifetimes, thermochemistry, ozone formation potentials, and branching ratios of these molecules were also calculated and have been reported in this article.

Cl Atom Initiated Photo-oxidation of Mono-chlorinated Propanes To Form Carbonyl Compounds: A Kinetic and Mechanistic Approach.

Cl atom initiated photo-oxidation of monochlorinated propanes to form the carbonyl compounds was investigated. Propionaldehyde and acetone were identified to be major products in the oxidation of 1-chloropropane and 2-chloropropane, respectively. The complete product analyses were carried out using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-infrared spectroscopy (GC-IR) as analytical tools, and an appropriate oxidation mechanism was proposed on the basis of the product analyses. The temperature dependent rate coefficients for the reactions of Cl atoms with 1-chloropropane (1-CP) and 2-chloropropane (2-CP) were measured experimentally in the gas phase, using the relative rate method in the temperature range 268-363 K and at 1 atm pressure. Ethane, ethylene, and ethyl acetate were used as reference compounds. The obtained rate coefficients for the reactions of Cl atoms with 1-CP and 2-CP at room temperature (298 K) and at 1 atm pressure were (4.64 ± 0.70) × 10-11 and (2.57 ± 0.44) × 10-11 cm3 molecule-1 s-1, respectively. Furthermore, to complement our experimentally obtained results, computational calculations were performed for these reactions using canonical variational transition state theory (CVT) with small curvature tunneling (SCT) in combination with the CCSD/cc-pVDZ//MP2/6-31+G(d,p) level of theory. Detailed discussion on feasibility of the reactions, branching ratios, degradation mechanism, and atmospheric implications are discussed in this manuscript.

Investigation of the Absorption Cross Section of Phenyl Radical and Its Kinetics with Methanol in the Gas Phase Using Cavity Ring-Down Spectroscopy and Theoretical Methodologies.

Cavity ring-down spectroscopy (CRDS) was used to measure the absorption cross section of phenyl radicals (C6H5•) at 504.8 nm (2B1 ← 2A1 transition) in the nitrogen atmosphere at 40 Torr total pressure and 298 K using nitrosobenzene (C6H5NO) as the radical precursor. At 504.8 nm, the absorption cross section was measured to be σphenyl504.8 nm = (5.7 ± 1.4) × 10-19 cm2 molecule-1. The absorption cross section was independent of the total pressure range (40-200 Torr) over which it was studied with a precursor concentration of (4-5) × 1013 molecules cm-3. In addition to this, the absolute rate coefficients for the reaction of phenyl radicals with methanol were measured over the temperature range of 263-298 K and at 40 Torr pressure with N2 using CRDS. The temperature-dependent rate coefficient for the title reaction over the studied temperature range was obtained to be k263-298 Kexperiment (T) = (1.38 ± 0.60) × 10-11 exp [-(1764 ± 321)/T] cm3 molecule-1 s-1 with a rate coefficient of k(T) = (3.50 ± 0.32) × 10-14 cm3 molecule-1 s-1 at 298 K. The effect of pressure and laser fluence was found to be negligible within the experimental uncertainties in the studied range. In addition, to complement our experimental findings, the T-dependent rate coefficients for the title reaction were investigated using computational methods. The B3LYP/6-311 + G(d,p) level of theory was used in combination with canonical variational transition-state theory with small-curvature tunneling to calculate the rate coefficients. The T-dependent rate coefficient in the range of 200-400 K was obtained as k200-400 Ktheory (T) = 2.43 × 10-13 exp[-(478.38/T)] cm3 molecule-1 s-1 with a room-temperature (298 K) rate coefficient of 4.67 × 10-14 cm3 molecule-1 s-1.

Excited state C-N bond dissociation and cyclization of tri-aryl amine-based OLED materials: a theoretical investigation.

Tri-aryl amines (TAA) such as triphenylamine (TPA) are widely used for designing chromophores for dye-sensitized solar cells (DSSC) and organic light-emitting diodes (OLED). These materials degrade over time and hence result in reduced performance. Therefore, exploring the associated mechanistic pathways and factors controlling the degradation is necessary for future development of durable TAA-based devices. Hence, in this study, the complete active space self-consistent-field (CASSCF) method coupled with second order N-electron valence perturbation theory (NEVPT2) calculations was carried out to understand the excited state phenomena occurring in TAA using TPA and N,N-diphenyl-2-naphthylamine (DPNA) as model systems. The results indicated the presence of a conical intersection between ground and first excited singlet states with C-N bond dissociation, which acts as a channel for the excited molecules to dissociate and form radical fragments (phenyl/naphthyl). This occurrence is unusual for non-saturated bonds with delocalization. The resulting radical fragments formed intra-molecular products and subsequently yielded five- and six-membered cyclized products depending on the type of aryl groups. The significant findings from this study throw light on the photostability of TAA-based OLED devices as well as on the possible route to synthesize cyclic amines such as carbazoles.

Temperature-Dependent Kinetics of the Reaction of a Criegee Intermediate with Propionaldehyde: A Computational Investigation.

The temperature-dependent kinetics for the reaction of a Criegee intermediate (CH2OO) with propionaldehyde (CH3CH2CHO) was investigated using canonical variational transition state theory (CVT) in conjunction with the small curvature tunneling (SCT) method and the interpolated single point energy (ISPE) method at the CCSD(T)/AUG-cc-pVTZ//B3LYP/6-311G(d,p) level of theory. A rich chemistry was depicted by the title reaction, though the contributions of all of the reaction pathways were limited to atmospheric pressure conditions. The reaction of CH2OO with CH3CH2CHO was identified to proceed via the formation of secondary ozonide (SOZ), which then underwent a sequence of unimolecular isomerization and decomposition reactions to form a variety of products. The obtained rate coefficient for the formation of SOZ at 298 K was determined to be k = 2.44 × 10-12 cm3 molecule-1 s-1. At low temperature, collisionally stabilized SOZ was found to be the more stable product. Contrarily, at high temperature, SOZ degraded to HCHO, and CH3CH2COOH was found to be the major product. The complete degradation mechanism and thermochemistry for the reaction of CH2OO with CH3CH2CHO along with their rate coefficients over the temperature range of 200-1000 K are reported.

Photo Oxidation Reaction Kinetics of Ethyl Propionate with Cl Atom and Formation of Propionic Acid.

Temperature-dependent rate coefficients for the photo oxidation reaction of ethyl propionate with Cl atom were investigated experimentally using the relative rate technique. Gas chromatography with flame ionization detector (GC-FID), gas chromatography-mass spectrometry (GC-MS), and GC-infrared spectroscopy (GC-IR) were used to follow the concentrations and identification of reactants and products. The kinetics of ethyl propionate with Cl atoms was investigated over the temperature range of 263-363 K at atmospheric pressure, relative to C2H6 and C2H4. Theoretical calculations were also performed at CCSD(T)/6-311++G(d,p)//BHandHLYP/6-311G(d,p) level of theory, and the rate coefficients for H-abstraction reactions were calculated using canonical variational transition state theory (CVT) with interpolated single point energies (ISPE) method over the temperature range of 200-800 K. The temperature-dependent rate coefficients for the reaction of ethyl propionate with Cl atom were obtained both experimentally as well as theoretically and are kExpt( T) = [(6.88 ± 1.65) × 10-24] T4.5 exp[(1108 ± 87)/ T] cm3 molecule-1 s-1 and kTheory( T) = (6.73 × 10-19) T2.74 exp[(571)/ T] cm3 molecule-1 s-1, respectively. On the basis of product analysis on the title reaction and the computational studies, we have proposed the atmospheric degradation mechanism and various pathways for Cl atom-initiated photo oxidation of EP. Propionic acid is identified as the major product in the degradation of ethyl propionate on reaction with Cl atom. The thermochemistry, branching ratios, and cumulative lifetime of ethyl propionate are calculated and presented in this Article.

Thermochemistry and Kinetic Studies on the Autoignition of 2-Butanone: A Computational Study.

Unimolecular reactions of alkylperoxy(ROO•), hydroperoxyalkyl(•QOOH), and hydroperoxyalkylperoxy(•OOQOOH) radicals of 2-butanone, which is a potential biofuel molecule, have been studied computationally. These radicals are responsible for the chain branching at low temperature oxidation and play a significant role in modeling the autoignition. The composite CBS-QB3 method was used to study the thermochemistry and energetics of all the species involved. Intrinsic reaction coordinate (IRC) calculations were carried out for all the transition states along various reaction pathways. All the possible reactions like H-migration, •OH elimination, and HO•2 elimination reactions were studied for these radicals. It was found that, the isomerization of •OOQOOH to HOOQOO• is the most favorable channel, which involves 8- and 9-membered cyclic transition states. However, the decomposition pathway involves the H-migration from carbon to oxygen. The mechanism for the decomposition of all •OOQOOH radicals with their potential energy level diagrams are reported. The temperature dependent rate coefficients were also studied using Canonical Variational Transition state theory (CVT) with small curvature tunneling (SCT) in the temperature range of 400-1500 K, which is relevant to the combustion. Thermodynamic parameters for all the reactions involved were calculated. The high barrier (1,3 H-migration) reactions were found to be exothermic and spontaneous, which is unexpected.

Experimental and Theoretical Investigations on the Reaction of 1,3-Butadiene with Cl Atom in the Gas Phase.

Temperature dependent rate coefficients for the reaction of Cl atom with 1,3-butadiene were measured over the temperature range 269-363 K relative to its reaction with isoprene and 1-pentene. Theoretical calculations were performed for the title reaction using CVT/SCT in combination with CCSD(T)/6-31+G (d,p)//MP2/6-311+G(2df,2p) level of theory, to complement our experimental measurements. The test molecule would survive for 1 h in the atmosphere, and therefore, it can be considered as a very short-lived compound. 1,3-Butadience cannot contribute to global warming as it is very short-lived. However, 4 ppm of ozone is estimated to be formed by the test molecule, which can be considered to be reasonably significant.

An Exprimental and Computational Study on the Cl Atom Initiated Photo-Oxidization Reactions of Butenes in the Gas Phase.

Temperature-dependent rate coefficients for the reactions of Cl atoms with trans-2-butene and isobutene were measured over the temperature range of 263-363 K using relative rate technique with reference to 1,3-butadiene, isoprene, and 1-pentene. The measured rate coefficients for the reactions of Cl atoms with isobutene and trans-2-butene are kR1298K= (3.43 ± 0.11) × 10-10 and kR2298K = (3.20 ± 0.04) × 10-10 cm3 molecule-1 s-1, respectively, at 298 K and 760 torr. Measured rate coefficients were used to fit the Arrhenius equations, which are obtained to be kR1-Exp269-363K = (4.99 ± 0.42) × 10-11 exp[(584 ± 26)/T] and kR2-Exp269-363K = (1.11 ± 0.3) × 10-10 exp[(291 ± 88)/T] cm3 molecule-1 s-1 for isobutene and trans-2-butene, respectively. To understand the reaction mechanism, estimate the contribution of each reaction site, and to complement our experimental results, computational studies were also performed. Canonical variational transition state theory with small curvature tunneling in combination with MP2/6-31G(d), MP2/6-31G(d,p), MP2/6-31+G(d,p), CCSD(T)/cc-pvdz, and QCISD(T)/cc-pvdz level of theories were used to calculate the temperature-dependent rate coefficients over the temperature range of 200-400 K. The effective lifetimes, thermodynamic parameters, and atmospheric implications of the test molecules were also estimated.