Reactivity of Amines with CO2 on the Surface of Titan

Titan possesses many of the basic elements of habitability, including a rich organic chemistry. However, the thick atmosphere of Titan shields the surface from radiation, which makes the incorporation of oxygen into organic compounds difficult, due to a reducing environment and low temperatures that slow chemical reactions. These obstacles may be overcome by impacts or cryovolcanic heating of ice, which would mix organics with liquid water and allow chemical reactions that can incorporate oxygen. However, reactions involving oxygen can occur on Titan without invoking such unusual conditions. We show that the reaction of carbon dioxide with amines can lead to oxygenated organics at Titan's surface without the need for external energy input, via the carbamation reaction: R-NH2 + CO2 → R-NH-COOH. Using a combination of micro-Raman spectroscopy and UHV FTIR spectroscopy, we examine the reaction products and kinetics of the carbamation reaction for methylamine, dimethylamine, pyrrolidine and trimethylamine. All four amines react with CO2 at cryogenic temperatures. This indicates that primary, secondary, and tertiary amines can undergo carbamation at low temperatures. Reaction was observed with methylamine as low as 40 K, demonstrating that carbamation is fast at Titan surface temperatures. We will present data on the kinetics of the carbamation reaction for of the four amines, as well as estimates of the quantity of carbamic acids that may be produced on Titan's surface and in the atmosphere.