Carbynes in meteorites - Detection, low-temperature origin, and implications for interstellar molecules

Carbon from the Allende meteorite is not graphite but carbyne (triply bonded elemental carbon), inasmuch as on heating to 250° to 330°C it releases mainly triply bonded fragments: –(C≡C) n ,– with n = 1 to 5, and –(C≡C) n –CN, with n = 1 to 3. Although carbynes have been known to form only by condensation of carbon vapor above 2600 K or by explosive shock of > 600 kilobars, it is found that they also form metastably by the reaction 2CO → CO 2 + C (solid) at 300° to 400°C in the presence of a chromite catalyst. Such low-temperature formation by surface catalysis may be the dominant source of carbynes on the earth and in meteorites, and a major source of interstellar carbynes and cyanopolyacetylenes.