Tetranitromethane, a colorless to pale yellow, oily liquid, is prepared by nitration of acetic anhydride with anhydrous nitric acid. It is sensitive to heat, friction and shock and is highly explosive in the presence of impurities. It is mainly used as an oxidizer in rocket propellants and explosives.
Despite these "unfavourable" properties a sample of neat tetranitromethane was prepared for a NMR analysis: Whereas for 15N a sharp singlet was measured at 46.8ppm (relative to nitromethane), we were astonished to obtain a nice multiplet built up of nine lines for 13C (see below), centred at 119.6 ppm (relative to TMS/CDCl3). This fine structure must be attributed to the 14N-13C coupling, which is normally not observed due to efficient quadrupolar 14N (spin 1 nucleus) relaxation. Obviously quadrupolar relaxation is slow in this case, most probably due to a small or even vanishing electric field gradient at the 14N sites.
This work was carried out in the group of Prof. Peter Bigler (firstname.lastname@example.org), see also http://nmr.dcbp.unibe.ch/.