Sila-Substitution of Alkyl Nitrates: Synthesis, Structural Characterization, and Sensitivity Studies of Highly Explosive (Nitratomethyl)-, Bis(nitratomethyl)-, and Tris(nitratomethyl)silanes and Their Corresponding Carbon Analogues

Abstract

A series of analogous nitratomethyl compounds of carbon and silicon of the formula types Me(3)ElCH(2)ONO(2) (1a/1b), Me(2)El(CH(2)ONO(2))(2) (2a/2b), MeEl(CH(2)ONO(2))(3) (3a/3b), (CH(2))(4)El(CH(2)ONO(2))(2) (4a/4b), and (CH(2))(5)El(CH(2)ONO(2))(2) (5a/5b) were synthesized [El = C (a), Si (b); (CH(2))(4)El = (sila)cyclopentane-1,1-diyl; (CH(2))(5)El = (sila)cyclohexane-1,1-diyl]. All compounds were characterized by using NMR, IR, and Raman spectroscopy and mass spectrometry. In addition, the crystal structures of Me(2)C(CH(2)ONO(2))(2) (2a), (CH(2))(4)C(CH(2)ONO(2))(2) (4a), Me(2)Si(CH(2)ONO(2))(2) (2b), and (CH(2))(5)Si(CH(2)ONO(2))(2) (5b) were determined by single-crystal X-ray diffraction. The gas-phase structures of the C/Si analogues 1a and 1b were determined by electron diffraction and compared with the results of quantum chemical calculations at different levels of theory. The thermal stabilities of the C/Si pairs 1a/1b-5a/5b were investigated by using DSC. In addition, their friction and impact sensitivities were measured with standard BAM methods. The extreme sensitivities of the silicon compounds 1b-5b compared to those of the corresponding carbon analogues 1a-5a were discussed in terms of the structures of the C/Si analogues and possible geminal Si...O interactions.