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1. Mechanistical study on the formation of hydroxyacetone (CH 3 COCH 2 OH), methyl acetate (CH 3 COOCH 3 ), and 3-hydroxypropanal (HCOCH 2 CH 2 OH) along with their enol tautomers (prop-1-ene-1,2-diol (CH 3 C(OH)CHOH), prop-2-ene-1,2-diol (CH 2 C(OH)CH 2 OH), 1-methoxyethen-1-ol (CH 3 OC(OH)CH 2 ) and prop-1-ene-1,3-diol (HOCH 2 CHCHOH)) in interstellar ice analogs

   https://doi.org/10.1039/d2cp03543j  

   Wang, Jia ; Marks, Joshua H. ; Turner, Andrew M. ; Nikolayev, Anatoliy A. ; Azyazov, Valeriy ; Mebel, Alexander M. ; Kaiser, Ralf I. ( January 2023 , Physical Chemistry Chemical Physics)

   We unravel, for the very first time, the formation pathways of hydroxyacetone (CH 3 COCH 2 OH), methyl acetate (CH 3 COOCH 3 ), and 3-hydroxypropanal (HCOCH 2 CH 2 OH), as well as their enol tautomers within mixed ices of methanol (CH 3 OH) and acetaldehyde (CH 3 CHO) analogous to interstellar ices in the ISM exposed to ionizing radiation at ultralow temperatures of 5 K. Exploiting photoionization reflectron time-of-flight mass spectrometry (PI-ReToF-MS) and isotopically labeled ices, the reaction products were selectively photoionized allowing for isomer discrimination during the temperature-programmed desorption phase. Based on the distinct mass-to-charge ratios and ionization energies of the identified species, we reveal the formation pathways of hydroxyacetone (CH 3 COCH 2 OH), methyl acetate (CH 3 COOCH 3 ), and 3-hydroxypropanal (HCOCH 2 CH 2 OH) via radical–radical recombination reactions and of their enol tautomers (prop-1-ene-1,2-diol (CH 3 C(OH)CHOH), prop-2-ene-1,2-diol (CH 2 C(OH)CH 2 OH), 1-methoxyethen-1-ol (CH 3 OC(OH)CH 2 ) and prop-1-ene-1,3-diol (HOCH 2 CHCHOH)) via keto-enol tautomerization. To the best of our knowledge, 1-methoxyethen-1-ol (CH 3 OC(OH)CH 2 ) and prop-1-ene-1,3-diol (HOCH 2 CHCHOH) are experimentally identified for the first time. Our findings help to constrain the formation mechanism of hydroxyacetone and methyl acetate detected within star-forming regions and suggest that the hitherto astronomically unobserved isomer 3-hydroxypropanal and its enol tautomers represent promising candidates for future astronomical searches. These enol tautomers may contribute to the molecular synthesis of biologically relevant molecules in deep space due to their nucleophilic character and high reactivity. 

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2. The Prototypical Transition Metal Carbenes, (CO) 5 Cr=CH 2 , (CO) 4 Fe=CH 2 , (CO) 3 Ni=CH 2 , (CO) 5 Mo=CH 2 , (CO) 4 Ru=CH 2 , (CO) 3 Pd=CH 2 , (CO) 5 W=CH 2 , (CO) 4 Os=CH 2 , and (CO) 3 Pt=CH 2 : Challenge to Experiment

   https://doi.org/10.1021/acs.jpca.8b05394  

   Weidman, Jared D. ; Estep, Marissa L. ; Schaefer, Henry F. ( July 2018 , The Journal of Physical Chemistry A)
3. A Mechanistic Study on the Formation of Acetone (CH 3 COCH 3 ), Propanal (CH 3 CH 2 CHO), Propylene Oxide (c-CH 3 CHOCH 2 ) along with Their Propenol Enols (CH 3 CHCHOH/CH 3 C(OH)CH 2 ) in Interstellar Analog Ices

   https://doi.org/10.3847/1538-4357/ac8c92  

   Singh, Santosh K. ; Fabian Kleimeier, N. ; Eckhardt, André K. ; Kaiser, Ralf I. ( December 2022 , The Astrophysical Journal)

   Carbonyl-bearing complex organic molecules (COMs) in the interstellar medium (ISM) are of significant importance due to their role as potential precursors to biomolecules. Simple aldehydes and ketones like acetaldehyde, acetone, and propanal have been recognized as fundamental molecular building blocks and tracers of chemical processes involved in the formation of distinct COMs in molecular clouds and star-forming regions. Although previous laboratory simulation experiments and modeling established the potential formation pathways of interstellar acetaldehyde and propanal, the underlying formation routes to the simplest ketone—acetone—in the ISM are still elusive. Herein, we performed a systematic study to unravel the synthesis of acetone, its propanal and propylene oxide isomers, as well as the propenol tautomers in interstellar analog ices composed of methane and acetaldehyde along with isotopic-substitution studies to trace the reaction pathways of the reactive intermediates. Chemical processes in the ices were triggered at 5.0 K upon exposure to proxies of Galactic cosmic rays in the form of energetic electrons. The products were detected isomer-selectively via vacuum ultraviolet (VUV) photoionization reflectron time-of-flight mass spectrometry. In our experiments, the branching ratio of acetone (CH₃COCH₃):propylene oxide (c-CH₃CHOCH₂):propanal (CH₃CH₂CHO) was determined to be (4.82 ± 0.05):(2.86 ± 0.13):1. The radical–radical recombination reaction leading to acetone emerged as the dominant channel. The propenols appeared only at a higher radiation dose via keto–enol tautomerization. The current study provides mechanistic information on the fundamental nonequilibrium pathways that may be responsible for the formation of acetone and its (enol) isomers inside the interstellar icy grains.

    

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4. On the formation and the isomer specific detection of methylacetylene (CH 3 CCH), propene (CH 3 CHCH 2 ), cyclopropane (c-C 3 H 6 ), vinylacetylene (CH 2 CHCCH), and 1,3-butadiene (CH 2 CHCHCH 2 ) from interstellar methane ice analogues

   https://doi.org/10.1039/C8CP03921F  

   Abplanalp, Matthew J. ; Góbi, Sándor ; Kaiser, Ralf I. ( March 2019 , Physical Chemistry Chemical Physics)

   Pure methane (CH 4 ) ices processed by energetic electrons under ultra-high vacuum conditions to simulate secondary electrons formed via galactic cosmic rays (GCRs) penetrating interstellar ice mantles have been shown to produce an array of complex hydrocarbons with the general formulae: C n H 2n+2 ( n = 4–8), C n H 2n ( n = 3–9), C n H 2n−2 ( n = 3–9), C n H 2n−4 ( n = 4–9), and C n H 2n−6 ( n = 6–7). By monitoring the in situ chemical evolution of the ice combined with temperature programmed desorption (TPD) studies and tunable single photon ionization coupled to a reflectron time-of-flight mass spectrometer, specific isomers of C 3 H 4 , C 3 H 6 , C 4 H 4 , and C 4 H 6 were probed. These experiments confirmed the synthesis of methylacetylene (CH 3 CCH), propene (CH 3 CHCH 2 ), cyclopropane (c-C 3 H 6 ), vinylacetylene (CH 2 CHCCH), 1-butyne (HCCC 2 H 5 ), 2-butyne (CH 3 CCCH 3 ), 1,2-butadiene (H 2 CCCH(CH 3 )), and 1,3-butadiene (CH 2 CHCHCH 2 ) with yields of 2.17 ± 0.95 × 10 −4 , 3.7 ± 1.5 × 10 −3 , 1.23 ± 0.77 × 10 −4 , 1.28 ± 0.65 × 10 −4 , 4.01 ± 1.98 × 10 −5 , 1.97 ± 0.98 × 10 −4 , 1.90 ± 0.84 × 10 −5 , and 1.41 ± 0.72 × 10 −4 molecules eV −1 , respectively. Mechanistic studies exploring the formation routes of methylacetylene, propene, and vinylacetylene were also conducted, and revealed the additional formation of the 1,2,3-butatriene isomer. Several of the above isomers, methylacetylene, propene, vinylacetylene, and 1,3-butadiene, have repeatedly been shown to be important precursors in the formation of polycyclic aromatic hydrocarbons (PAHs), but until now their interstellar synthesis has remained elusive. 

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5. Disproportionation of Sn(II){CH(SiMe 3 ) 2 } 2 to ·Sn(III){CH(SiMe 3 ) 2 } 3 and ·Sn(I){CH(SiMe 3 ) 2 }: Characterization of the Sn(I) Product

   https://doi.org/10.1039/d3cc01542d  

   Mears, Kristian ; Nguyen, Gia-Ann ; Ruiz, Bronson ; Zou, Wenxing ; Fettinger, James C ; Power, Philip P ( May 2023 , Chemical Communications)

   Half a century since the photocatalytic disproportionation of Lappert's dialkyl stannylene SnR 2 , R = CH(SiMe 3 ) 2 (1) gave the persistent trivalent radical [·SnR 3 ], the characterization of the corresponding Sn(I) product, ·SnR is now described. It was isolated as the hexastannaprismane Sn 6 R 6 (2), from the reduction of 1 by the Mg(I)-reagent, Mg(BDI Dip ) 2 , (BDI = (DipNCMe) 2 CH, Dip + 2,6-diisopropylphenyl). 

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