1093230-99-9Relevant academic research and scientific papers
Amphidynamic crystals of a steroidal bicyclo[2.2.2]octane rotor: A high symmetry group that rotates faster than smaller methyl and methoxy groups
Rodriguez-Molina, Braulio,Perez-Estrada, Salvador,Garcia-Garibay, Miguel A.
, p. 10388 - 10395 (2013)
The synthesis, crystallization, single crystal X-ray structure, and solid state dynamics of molecular rotor 3 provided with a high symmetry order and relatively cylindrical bicyclo[2.2.2]octane (BCO) rotator linked to mestranol fragments were investigated in this work. By use of solid state 13C NMR, three rotating fragments were identified within the molecule: the BCO, the C19 methoxy and the C18 methyl groups. To determine the dynamics of the BCO group in crystals of 3 by variable temperature 1H spin-lattice relaxation (VT 1H T1), we determined the 1H T1 contributions from the methoxy group C19 by carrying out measurements with the methoxy-deuterated isotopologue rotor 3-d6. The contributions from the quaternary methyl group C18 were estimated by considering the differences between the VT 1H T1 of mestranol 8 and methoxy-deuterated mestranol 8-d3. From these studies it was determined that the BCO rotator in 3 has an activation energy of only 1.15 kcal mol-1, with a barrier for site exchange that is smaller than those of methyl (Ea = 1.35 kcal mol-1) and methoxy groups (Ea = 1.92 kcal mol-1), despite their smaller moments of inertia and surface areas.
