The preparation and characterisation of some polynitro derivatives of 2,4,6,-trinitrophenyl substituted naphthalenes

In the present stUdy, the nitration of a number of 2,4,6-trinitrophenyl (picryl) substituted naphthalenes has been conducted. These compounds are: (a) 1-picrylnaphthalene; (b) 2-picrylnaphtha1ene; (c) 1,4- and 1,5-dipicrylnaphthalene; and (d) 1-methyl-4-picrylnaphthalene, all these compound being produced by Ullmann reaction between picryl chloride and the halogen substituted naphthalenes. A large number- of nitro-derivatives have been isolated and the structures assigned on the basis of nmr and mass spectral data. Some nitro -derivatives were also assigned on the basis of unequivocal synthesis from known compounds. The,most highly nitrated compounds isolated were from the nitration of 1,4- and 1,5-dipicrylnaphthalenes, where it was found that by using extremely vigourous conditions, three more nitro-groups could be introduced into the naphthalene moiety, making the total number of nitro-groups on the four rings, nine in all. The stability of these highly nitrated compounds to oxidation is in accord with an incomplete previous study of 1-picrylnaphthalene. The nitration of picrylbenzene has been previously studied, and a mechanism was proposed to explain the proportion of each isomer in the product mixture. This mechanism involved the stabilization of the p-nitropicrylbenzene (the predominant isomer) by a field effect involving the oxygen atoms of the ortho-nitro-groups. This mechanism is commented upon with particular reference to the nitration of picryl substituted naphthalenes of the present study.