User:Georgezhou1/sandbox

In February 2016, Lineberger published a paper titled “Experimental and Theoretical Studies of the Reactivity and Thermochemistry of Dicyanamide: N(CN)” Dicyanamide N(CN) in the Journal of Physical Chemistry. Lineberger and his lab determined dicyanamide to be a very stable species, with an experimental electron-binding energy of 4.135 ± 0.010 eV. In order to characterize dicyanamide’s reactivity, they explored its reactivity with whole gamut of molecular species. Nitric acid was the only neutral reagent that reacted rapidly enough to be detected by selected ion flow tube (SIFT) measurements. The reaction of dicyanamide with nitric acid proceeded with a bimolecular reaction rate constant of 2.7x 10-10 cm3/s at a pressure of 0.45 Torr. Based on this lack of reactivity of dicyanamide, Lineberger and his laboratory hypothesize that dicyanamide exists in molecular clouds of interstellar medium. This has been corroborated by spacecraft Cassini’s voyage to Saturn’s moon Titan. Cassini collected mass spectra of Titan’s nitrogen- and methane- rich atmosphere, and the mass spectrum showed a strong peak corresponding to 66 m/z. This strongly suggest the presence of dicyanamide in Titan’s atmosphere. Measurements of the microwave spectrum for this anion would allow astronomers to search for this molecule in astrochemical environments. Moreover, the mixing of nitric acid with ionic liquids containing dicyanamide resulted in hypergolic behaviour. This suggests that dicyanamide can be used possibly as a next-generation bipropellant hypergolic fuels, facilitating the current effort to replace hydrazine fuels, which are dangerous because of their toxic, volatile, and corrosive nature. Previous studies conducted by Chambreau and co-workers determined that dicyanamide reacts with two nitric acid molecules to form deprotonated 1,5-dinitrobiuret. Lineberger and his lab characterized this mechanism. A key step in the formation of 1,5-dinitrobiuret is the proton transfer from nitric acid to dicyanamide. Computational modeling showed that dicyanamide has two protonation sites: a terminal nitrile and a central nitrogen. Computational and experimental studies showed that it is more favorable to protonate dicyanamide on the terminal nitrile than on the central nitrogen. Computational studies also indicate that the association of dicyanamide with nitric acid is exothermic by 25 kcal/mol. It is this energy that Lineberger suspects to be responsible for the hypergolic behavior upon mixing nitric acid with ionic liquids containing dicyanamide.