Chemical and radiative transfer modeling of propylene oxide

Abstract

Context. The recent identification of the first complex chiral molecule, propylene oxide (PrO) in space opens up a new window to further study the origin of homochirality on the Earth. There are some recent studies to explain the formation of PrO however additional studies on the formation of this species are needed for better understanding.Aims. We seek to prepare a complete reaction network to study the formation of propylene oxide in the astrophysically relevant conditions. Based on our results, a detailed radiative transfer modeling has been carried out to propose some more transitions which would potentially be targeted in the millimeter wave domain.Methods. Gas-grain chemical network was used to explain the observed abundance of PrO in a cold shell surrounding the high-mass star-forming region of Sgr B2. Quantum chemical calculations were employed to study various reaction parameters and to compute multiple vibrational frequencies of PrO. Results. To model the formation of PrO in the observed region, we considered a dark cloud model. Additionally, we used a model to check the feasibility of forming PrO in the hot core region. Some potential transitions in the millimeter wave domain are predicted which could be useful for the future astronomical detection. Radiative transfer modeling has been utilized to extract the physical condition which might be useful to know the properties of the source in detail. Moreover, vibrational transitions of PrO has been provided which could be very useful for the future detection of PrO by the upcoming James Webb Space Telescope (JWST).

Adsorption of Propylene Oxide on Amorphous Ice under Interstellar Conditions. A Grand Canonical Monte Carlo Simulation Study

“…Furthermore, Bergantini et al revealed that PO can be synthesized within the (few hundred nanometers wide) ice-phase coating interstellar grain in molecular clouds at 10 K, followed by sublimation once the temperature of the grains increases with the birth of the central star . This astrochemical model predicting the fractional abundances of PO in cold material in front of Sgr B2­(N) agreed with the observed astronomical abundances in Sgr B2­(N) along with the error limits ( n PO / n H 2 = 10 –12 –10 –10 ), which might be converted into the PO concentration of 10 –26 –10 –24 mol/dm 3 by using the H 2 number density value of 10 7 molecules/cm 3 . , In addition, the typical water abundance is about (1.2–8) × 10 6 relative to H 2 , which is about 4–6 orders of magnitude larger than that of PO …”

“…Having the adsorption isotherms calculated, we try to address the question whether the adsorption of PO on amorphous ice is a relevant process under interstellar conditions, in other words, whether the typical concentration of propylene oxide in the ISM corresponds to a non-negligible surface coverage at the temperatures considered. The typical concentration of PO in Sgr B2­(N) is thought to be in the range 0.01–1 molecules/dm 3 . − Estimating, on the other hand, the gas phase concentration of PO that corresponds to a certain surface coverage requires knowing the saturated vapor pressure at the temperature considered. The temperature dependence of p 0 can be estimated through the Antoine equation, i.e. where the value of p 0 is in kPa units, and A , B , and C are the Antoine parameters, having the values of A = 6.09921, B = 1066.383 K, and C = −46.846 K for PO .…”

“…Icy grains of the interstellar medium (ISM) are covered predominantly by low-density amorphous (LDA) ice, , which, besides water, contains also a number of diverse organic molecules . Among them, the formation of PO under astrophysically relevant conditions was investigated both in the gas phase and in grain surface reactions by using the quantum chemical approach (B3LYP/6-311++G­(d,p) level of theory) to map out the chemical reaction network, including a detailed radiative transfer modeling . Furthermore, Bergantini et al revealed that PO can be synthesized within the (few hundred nanometers wide) ice-phase coating interstellar grain in molecular clouds at 10 K, followed by sublimation once the temperature of the grains increases with the birth of the central star .…”

Collisional excitation and non-LTE modelling of interstellar chiral propylene oxide

“…At higher densities, opacities become so low that the lines would be undetectable. Finally, we note that a non-LTE model for propylene oxide was presented recently by Das et al (2019). In their work, the authors employed the collisional rate coefficients of CH 3 OH with H 2 , which is obviously a crude approximation to mimic the CH 3 CHCH 2 O−H 2 system.…”

Identification of pre-biotic molecules containing Peptide-like bond in a hot molecular core, G10.47+0.03

“…Among them several ankan.das@gmail.com prasanta.astro@gmail.com species are marked as the precursor to biomolecules. Study of the pre-biotic molecules is always fascinating as they involved in the formation of amino acids, proteins, and the basic building blocks of life (Chakrabarti & Chakrabarti 2000a,b;Das et al 2008;Garrod 2013;Chakrabarti et al 2015;Majumdar et al 2015;Das et al 2019). Protein synthesis occurs through peptide bond formation (Goldman et al 2010).…”