The lock-in phase in the urotropine-sebacic acid system

The 1,10-decanedioic acid-1,3,5,7-tetraazatricyclo[3.3.1.1(3,7)]decane (1/1 ) system, C10H18O4.C6H12N4, was studied at 215 (2) K. Its analysis provides important information with regard to the long-standing acid-carboxylate co ntroversy in the urotropine-alkanedioic acid system. In the present structu re, all the chain end-groups display a clear acid character. The asymmetric unit of this commensurate modulated phase contains two molecules of diacid as well as two molecules of urotropine. Furthermore, the chain packing sug gests a possible order parameter for the lock-in transition.