Carbon dioxide chemistry at low temperatures

Abstract

We show that the reaction of carbon dioxide with primary and secondary amines can lead to oxygenated orgs. at low temps. without the need for external energy input, via the carbamation reaction: R-NH_2 + CO_2 → R-NHCOOH. Using a combination of micro-Raman spectroscopy and UHV FTIR spectroscopy, we examine the reaction products and kinetics of the carbamation reaction for a variety of primary and secondary amines. We have obsd. carbamic acid formation in mixts. of methylamine, ethylamine, dimethylamine and pyrrolidine with CO_2 at cryogenic temps. This indicates that both primary and secondary amines can undergo carbamation at low temps. Reaction was obsd. with methylamine as low as 40 K, and with ethylamine at 100 K. These temps. are low enough to enable this reaction to occur on a variety of Solar System bodies where CO_2 and amines may be present in surface ices, such as Titan, Triton, Pluto and comets. We will present data on the kinetics of the carbamation reaction for a variety of amines, as well as ests. of the quantity of carbamic acids that may be produced on Titan's surface and in the atm.