Anchal Gahlaut

Bio: Anchal Gahlaut is an academic researcher from Indian Institute of Technology, Jodhpur. The author has contributed to research in topics: Dissociation (chemistry) & Formose reaction. The author has an hindex of 2, co-authored 3 publications receiving 11 citations.

Unimolecular decomposition of formamide via direct chemical dynamics simulations.

Abstract: Formamide (NH2CHO), being the simplest organic molecule containing an amide functional group, serves as a prototype to study protein and peptide chemistry. Formamide has been found in Comets and interstellar media and its decomposition results in smaller molecules such as NH3, CO, HCN, HNCO, etc. These smaller molecules are considered to have been potential precursors for the formation of complex biological molecules, such as nucleic acids and nucleobases, in the early Earth. Several experimental and theoretical investigations of formamide decomposition have been reported in the literature. In the present work, unimolecular decomposition of formamide in the electronic ground state was investigated by classical direct chemical dynamics simulations. The calculations were performed at three different energies using the density functional B3LYP/aug-cc-pVDZ level of electronic structure theory. The major dissociation products observed were NH3, CO, H2, HNCO, H2O, HCN, and HNC along with products of a few minor dissociation channels. Reactivity, atomic level mechanisms, and product branching ratios were investigated as a function of total energy.

Theoretical investigation of the dissociation chemistry of formyl halides in the gas phase.

Abstract: Halogen substituted analogues of formaldehyde, HXCO (X = F, Cl, Br, and I), play a crucial role in the degradation of stratospheric ozone. Several spectroscopic and quantum chemistry investigations of the dissociation chemistry of formyl halides have been reported in the literature. Due to their importance in combustion and atmospheric chemistry, we investigated the gas phase dissociation of formyl halides using electronic structure theory, direct chemical dynamics simulations, and Rice–Ramsperger–Kassel–Marcus rate constant calculations. Chemical dynamics simulations were performed using density functional B3LYP/6-31G* theory with suitable effective core potentials for the halogen atoms. Simulations showed multiple pathways and mechanisms for the dissociation of formyl halides. The major reaction products were HX + CO which formed via direct and indirect pathways. Trajectory lifetime distribution calculations indicated non-statistical dissociation dynamics.

Global Emissions of Refrigerants HCFC-22 and HFC-134a: Unforeseen Seasonal Contributions

Abstract: Significance HCFC-22 (CHClF2) and HFC-134a (CH2FCF3) are two major gases currently used worldwide in domestic and commercial refrigeration and air conditioning. HCFC-22 contributes to stratospheric ozone depletion, and both species are potent greenhouse gases. We find pronounced seasonal variations of global emissions for these two major refrigerants, with summer emissions two to three times higher than in winter. Thus results suggest that global emissions of these potent greenhouse gases might be mitigated by improved design and engineering of refrigeration systems and/or by reinforcing system service regulations. HCFC-22 (CHClF2) and HFC-134a (CH2FCF3) are two major gases currently used worldwide in domestic and commercial refrigeration and air conditioning. HCFC-22 contributes to stratospheric ozone depletion, and both species are potent greenhouse gases. In this work, we study in situ observations of HCFC-22 and HFC-134a taken from research aircraft over the Pacific Ocean in a 3-y span [HIaper-Pole-to-Pole Observations (HIPPO) 2009–2011] and combine these data with long-term ground observations from global surface sites [National Oceanic and Atmospheric Administration (NOAA) and Advanced Global Atmospheric Gases Experiment (AGAGE) networks]. We find the global annual emissions of HCFC-22 and HFC-134a have increased substantially over the past two decades. Emissions of HFC-134a are consistently higher compared with the United Nations Framework Convention on Climate Change (UNFCCC) inventory since 2000, by 60% more in recent years (2009–2012). Apart from these decadal emission constraints, we also quantify recent seasonal emission patterns showing that summertime emissions of HCFC-22 and HFC-134a are two to three times higher than wintertime emissions. This unforeseen large seasonal variation indicates that unaccounted mechanisms controlling refrigerant gas emissions are missing in the existing inventory estimates. Possible mechanisms enhancing refrigerant losses in summer are (i) higher vapor pressure in the sealed compartment of the system at summer high temperatures and (ii) more frequent use and service of refrigerators and air conditioners in summer months. Our results suggest that engineering (e.g., better temperature/vibration-resistant system sealing and new system design of more compact/efficient components) and regulatory (e.g., reinforcing system service regulations) steps to improve containment of these gases from working devices could effectively reduce their release to the atmosphere.

Reaction between NH3 (X̌1A1) and CO (X1Σ+): A Computational Insight into the Reaction Mechanism of Formamide (H2N-CHO) Formation.

Abstract: Formamide (NH2CHO) is the smallest molecular unit that contains the basic peptide linkage and thus has recently attracted a great amount of interest in the field of astrochemistry. In this work usi...

Formation of Formamide from HCN + H2O: A Computational Study on the Roles of a Second H2O as a Catalyst, as a Spectator, and as a Reactant.

Abstract: Formamide (NH2CHO), being the smallest and fundamental building block of life (with a peptide linkage), has recently been able to attract much interests, in the field of astrochemistry, astrophysic...

Aminohydroxymethylene (H2N-C̈-OH), the Simplest Aminooxycarbene.

Abstract: We generated and isolated hitherto unreported aminohydroxymethylene (1, aminohydroxycarbene) in solid Ar via pyrolysis of oxalic acid monoamide (2). Astrochemically relevant carbene 1 is persistent under cryogenic conditions and only decomposes to HNCO + H2 and NH3 + CO upon irradiation of the matrix at 254 nm. This photoreactivity is contrary to other hydroxycarbenes and aminomethylene, which undergo [1,2]H shifts to the corresponding carbonyls or imine. The experimental data are well supported by the results of CCSD(T)/cc-pVTZ and B3LYP/6-311++G(3df,3pd) computations.