Synthesis of two new gem-fluoronitro containing tetranitroadamantanes and property comparison with their nitro and gem-dinitro analogues.

Two new fluorinated tetranitroadamantanes, 2,6-difluoro-2,4,4,6-tetranitroadamantane and 2,4,6,8-tetrafluoro-2,4,6,8-tetranitroadamantane, were synthesized. 2,6-Difluoro-2,4,4,6-tetranitroadamantane was prepared from 4,4-dinitroadamantane-2,6-dione by a three-step route with an overall yield of 40%. It has a slightly higher crystal density (1.787 g cm-3) than its analogue 2,2,4,4,6,6-tetranitroadamantane (1.777 g cm-3). 2,4,6,8-Tetrafluoro-2,4,6,8-tetranitroadamantane was prepared from 4,8-dihydroxyadamantane-2,6-dione by an eight-step route with an overall yield of 8%. It is notable that the replacement of one nitro group in the gem-dinitro functionality with fluorine might slightly reduce the detonation performance but improve the density and inherent steric hindrance, which makes it possible to introduce more nitro functionalities on the adamantane backbone.