Detection and Confirmation of Interstellar Acetic Acid

Mehringer, David M.; Snyder, L. E.; Miao, Yanti; Lovas, F. J.

doi:10.1086/310612

Cited by 204 publications

(173 citation statements)

References 12 publications

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“…Acetic acid has been observed to be between 1/10 to 1/100 less abundant than methyl formate (Mehringer et al 1997;Remijan et al 2002Remijan et al , 2003Cazaux et al 2003), whereas the abundance of ethanol has been found to be between 0.3 and 3 times that of dimethyl ether (Millar et al 1988;Ikeda et al 2001;Nummelin et al 1998a;White et al 2003). The contradiction with the MEP comes from the relative stabilities of these isomers.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Differential adsorption of complex organic molecules isomers at interstellar ice surfaces

Lattelais

Bertin

Mokrane

et al. 2011

A&A

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Context. Over 20 of the ∼150 different species detected in the interstellar and circumstellar media have also been identified in icy environments. For most of the species observed so far in the interstellar medium (ISM), the most abundant isomer of a given generic chemical formula is the most stable one (minimum energy principle -MEP) with few exceptions such as, for example, CH 3 COOH/HCOOCH 3 and CH 3 CH 2 OH/CH 3 OCH 3 , whose formation is thought to occur on the icy mantles of interstellar grains. Aims. We investigate whether differences found in the compositions of molecular ices and the surrounding gas phase could originate from differences between the adsorption of one isomer from that of another at the ice surface. Methods. We performed a coherent and concerted theoretical/experimental study of the adsorption energies of the four molecules mentioned above, i.e. acetic acid (AA)/methyl formate (MF) and ethanol (EtOH)/dimethyl ether (DME) on the surface of water ice at low temperature. The question was first addressed theoretically at LCT using solid state periodic density functional theory (DFT) to represent the organized solid support. The experimental determination of the ice/molecule interaction energies was then carried out independently by two teams at LPMAA and LERMA/LAMAp using temperature programmed desorption (TPD) under an ultra-high vacuum (UHV) between 70 and 160 K. Results. For each pair of isomers, theory and experiments both agree that the most stable isomer (AA or EtOH) interacts more efficiently with the water ice than the higher energy isomer (MF or DME). This differential adsorption can be clearly seen in the different desorption temperatures of the isomers. It is not related to their intrinsic stability but instead to both AA and EtOH producing more and stronger hydrogen bonds with the ice surface. Conclusions. We show that hydrogen bonding may play an important role in the release of organic species from grains and propose that, depending on the environment, differential adsorption should not be rejected as a possible way of interpreting MEP exceptions.

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Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Differential adsorption of complex organic molecules isomers at interstellar ice surfaces

Lattelais

Bertin

Mokrane

et al. 2011

A&A

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“…This source, dubbed the "Large Molecule Heimat" by Snyder et al (1994), is extraordinary for its rich molecular content: most complex organic molecules such as, e.g., acetic acid (CH 3 COOH, Mehringer et al 1997), glycolaldehyde (CH 2 (OH)CHO, Hollis et al 2000), acetamide (CH 3 CONH 2 , Hollis et al 2006), and aminoacetonitrile (NH 2 CH 2 CN, Belloche et al 2008a,b), were first discovered in Sgr B2(N). This hot core is located in the very massive and extremely active region of high-mass star formation Sagittarius B2, at a projected distance of ∼100 pc from the Galactic center, whose distance is 8.0 ± 0.5 kpc from the Sun (Reid 1993).…”

Section: Introductionmentioning

confidence: 99%

Increased complexity in interstellar chemistry: detection and chemical modeling of ethyl formate andn-propyl cyanide in Sagittarius B2(N)

Беллоче

Garrod

Müller

et al. 2009

A&A

242

300

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Context. In recent years, organic molecules of increasing complexity have been found toward the prolific Galactic center source Sagittarius B2. Aims. We wish to explore the degree of complexity that the interstellar chemistry can reach in star-forming regions. Methods. We carried out a complete line survey of the hot cores Sgr B2(N) and (M) with the IRAM 30 m telescope in the 3 mm range, plus partial surveys at 2 and 1.3 mm. We analyzed this spectral survey in the local thermodynamical equilibrium approximation. We modeled the emission of all known molecules simultaneously, which allows us to search for less abundant, more complex molecules. We compared the derived column densities with the predictions of a coupled gas-phase and grain-surface chemical code.Results. We report the first detection in space of ethyl formate (C 2 H 5 OCHO) and n-propyl cyanide (C 3 H 7 CN) toward Sgr B2(N). The detection of n-propyl cyanide is based on refined spectroscopic parameters derived from combined analyses of available laboratory spectroscopic data. For each molecule, we identified spectral features at the predicted frequencies having intensities compatible with a unique rotation temperature. For an assumed source size of 3 , our modeling yields a column density of 5.4 × 10 16 cm −2 , a temperature of 100 K, and a linewidth of 7 km s −1 for ethyl formate. n-Propyl cyanide is detected with two velocity components having column densities of 1.5 × 10 16 cm −2 and 6.6 × 10 15 cm −2 , respectively, for a source size of 3 , a temperature of 150 K, and a linewidth of 7 km s −1 . The abundances of ethyl formate and n-propyl cyanide relative to H 2 are estimated to be 3.6 × 10 −9 and 1.0 × 10 −9 , respectively. We derived column density ratios of 0.8/15/1 for the related species t-HCOOH/CH 3 OCHO/C 2 H 5 OCHO and 108/80/1 for CH 3 CN/C 2 H 5 CN/C 3 H 7 CN. Our chemical modeling reproduces these ratios reasonably well. It suggests that the sequential, piecewise construction of ethyl and n-propyl cyanide from their constituent functional groups on the grain surfaces is their most likely formation route. Ethyl formate is primarily formed on the grains by adding CH 3 to functional-group radicals derived from methyl formate, although ethanol may also be a precursor. Conclusions. The detection in Sgr B2(N) of the next stage of complexity in two classes of complex molecule, esters and alkyl cyanides, suggests that greater complexity in other classes of molecule may be present in the interstellar medium.

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“…All the species studied in this work are astrochemically-relevant and have been identied in the ISM: water was rst detected in 1969 in Sgr B2, Orion, and W49; 41 carbon monoxide was detected in 1970 in Orion; 42 methanol was rst detected in 1970 in Sgr B2; 43 formic acid was detected in 1971 in Sgr B2; 44 acetaldehyde was detected in 1973 in Sgr B2; 45,46 acetic acid was rst detected in 1997 in Sgr B2; 47 and acetone was detected in 1987 in Sgr B2. 48 The astrochemical origin of the species studied here is only well understood in some cases.…”

Section: Astrophysical Implicationsmentioning

confidence: 91%

THz and mid-IR spectroscopy of interstellar ice analogs: methyl and carboxylic acid groups

et al. 2014

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A fundamental problem in astrochemistry concerns the synthesis and survival of complex organic molecules (COMs) throughout the process of star and planet formation. While it is generally accepted that most complex molecules and prebiotic species form in the solid phase on icy grain particles, a complete understanding of the formation pathways is still largely lacking. To take full advantage of the enormous number of available THz observations (e.g., Herschel Space Observatory, SOFIA, and ALMA), laboratory analogs must be studied systematically. Here, we present the THz (0.3-7.5 THz; 10-250 cm À1 ) and mid-IR (400-4000 cm À1 ) spectra of astrophysically-relevant species that share the same functional groups, including formic acid (HCOOH) and acetic acid (CH 3 COOH), and acetaldehyde (CH 3 CHO) and acetone ((CH 3 ) 2 CO), compared to more abundant interstellar molecules such as water (H 2 O), methanol (CH 3 OH), and carbon monoxide (CO). A suite of pure and mixed binary ices are discussed. The effects on the spectra due to the composition and the structure of the ice at different temperatures are shown. Our results demonstrate that THz spectra are sensitive to reversible and irreversible transformations within the ice caused by thermal processing, suggesting that THz spectra can be used to study the composition, structure, and thermal history of interstellar ices.Moreover, the THz spectrum of an individual species depends on the functional group(s) within that molecule. Thus, future THz studies of different functional groups will help in characterizing the chemistry and physics of the interstellar medium (ISM).

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Detection and Confirmation of Interstellar Acetic Acid

Cited by 204 publications

References 12 publications

Differential adsorption of complex organic molecules isomers at interstellar ice surfaces

Differential adsorption of complex organic molecules isomers at interstellar ice surfaces

Increased complexity in interstellar chemistry: detection and chemical modeling of ethyl formate andn-propyl cyanide in Sagittarius B2(N)

THz and mid-IR spectroscopy of interstellar ice analogs: methyl and carboxylic acid groups

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