Ultraviolet-gas phase and -photocatalytic synthesis from CO and NH3

Abstract

The major photoproduct obtained on irradiation of gaseous NH3 and CO mixtures is ammonium cyanate; lesser amounts of urea, biurea, biuret semi-carbazide, formamide and cyanide were observed. The formation of the major gas phase photolysis product may be rationalized by the following reaction sequence: (see article). Urea is probably formed from NH4NCO in a thermal reaction while formamide may result from the disproportionation of NH2CO. Photocatalytic syntheses of 14C-urea, -formamide, and -formadehyde are effected by irradiation of 14CO and NH3 in the presence of Vycor, silica gel, or volcanic ash shale surfaces. These syntheses are catalyzed by ultraviolet wavelengths longer than those absorbed by the gaseous reactants. The syntheses are also effected when the surface material is first irradiated in the presence of CO followed by a dark incubation with NH3. Apparently, the initiating step is a light dependent formation of a reactive form of CO on the surface. A discussion is given on the possible contribution of these reactions to the abiotic synthesis of organic nitrogen compounds on Mars, on the primitive Earth and in interstellar space.

Some Insights Into Formamide Formation Through Gas-Phase Reactions in the Interstellar Medium

“…In a recent experimental work, Jones et al (2011) demonstrate that the formation of formamide in binary ice mixtures of CO and NH 3 is possible when subjected to irradiation by energetic particles such as electrons. This binary mixture has also been previously studied in the solid state (Grim et al 1989) and gas phase (Hubbard et al 1975). Garrod et al (2008) proposed a gas-grain chemical model where formamide is formed on grains at low temperature by hydrogenation of OCN.…”

On the Formation of Amide Polymers via Carbonyl–amino Group Linkages in Energetically Processed Ices of Astrophysical Relevance

“…Urea, for one, is considered a key prebiotic compound (Horneck & BaumstarkKhan 2012). An endogeneous formation (gas phase as well as liquid phase) of urea is discussed extensively and multiple pathways to form urea exist (Lowe et al 1963;Lohrmann 1972;Ferris et al 1974;Hubbard et al 1975;Sakurai & Yanagawa 1984;Miller 1993;Shapiro 1999). However, a purely endogeneous formation is under debate, due to the seemingly low concentration of cyanates in the oceans of early Earth (Miller 1993) and a limited stability of cyanates at pH values lower than six; at this pH cyanates can hydrolyze to hydrogen cyanide at timescales of geological range (Miller & Orgel 1974).…”

Search for methylamine in high mass hot cores

“…It is known that NH 2 CHO is formed in CO:NH 3 mixtures after UV and electron irradiation (Grim et al 1989;Demyk et al 1998;Jones et al 2011) and it has also been proposed that it can form from H-and N-atom addition to solid CO (Tielens & Charnley 1997). Gasphase formation from CO and NH 3 is viable as well (Hubbard et al 1975), although these experiments were conducted under high-pressure conditions, not the low pressures applicable in the ISM. Further quantification of both gas-phase and solid phase routes through laboratory experiments is needed.…”