The Sila-Explosives Si(CH₂N₃)₄ and Si(CH₂ONO₂)₄:  Silicon Analogues of the Common Explosives Pentaerythrityl Tetraazide, C(CH₂N₃)₄, and Pentaerythritol Tetranitrate, C(CH₂ONO₂)₄

Abstract

Abstract:The reaction of tetrakis(chloromethyl)silane, Si(CH2Cl)4, with sodium azide afforded tetrakis-(azidomethyl)silane (sila-pentaerythrityl tetraazide, Si(CH2N3)4 (1b)). Nitration of tetrakis(hydroxymethyl)-silane, Si(CH2OH)4, with nitric acid resulted in the formation of tetrakis(nitratomethyl)silane (sila-pentaerythritol tetranitrate, Si(CH2ONO2)4 (2b)). Compounds 1b and 2b are extremely shock-sensitive materials and very difficult to handle. Spectroscopic data were obtained as good as sensitivity and safety allowed for umambiguous identification. Quantum chemical calculations (DFT) of the C/Si pairs C(CH2OH)4/Si(CH2-OH)4, 1a/1b, and 2a/2b regarding the structures and electronic populations were performed.

Reaction mechanisms and sensitivity of silicon nitrocarbamate and related systems from quantum mechanics reaction dynamics

“…Experimental measurements 23,27,28 collected in Table 4 for the four EMs suggest that  thermal stability (Tdec) decreases as PETNC > Si-PETNC ≥ PETN > Si-PETN,  impact sensitivity (IS) increases as PETNC < PETN ≤ Si-PETNC < Si-PETN, and  friction sensitivity (FS) increases as PETNC < Si-PETNC < PETN < Si-PETN.…”

“…[23][24][25] δ-and β-HMX have the same molecular composition but different geometry configurations, and the former is more sensitive than the latter. 26 Thus even for single crystals the relation between sensitivity and material characteristics is complex and not understood.…”

“…27,28,47 Although the experimental crystal structure for Si-PETN is unavailable, we assume that it is also the case since the molecular structures for Si-PETN and PETN are nearly the same besides the central atom. 23 The molecular and crystal structures for the four EMs are shown in Fig. 1.…”

ReaxFF reactive molecular dynamics on silicon pentaerythritol tetranitrate crystal validates the mechanism for the colossal sensitivity

“…Recently, its silicon analogue, silicon-pentaerythritol tetranitrate (Si-PETN, Si-(CH 2 -O-NO 2 ) 4 ), was synthesized by the nitration of tetrakis (hydroxymethyl) silane with excess nitric acid (100%) in 1,2-dichloroethane at 0 1C. 18 Si-PETN has a molecular structure isomorphic with PETN, with the central carbon atom replaced by a silicon atom. Unexpectedly, it exhibits a dramatically enhanced sensitivity, exploding upon every contact with a Teflon spatula, 18 making it extremely dangerous and difficult to study, particularly by experiments.…”

“…18 Si-PETN has a molecular structure isomorphic with PETN, with the central carbon atom replaced by a silicon atom. Unexpectedly, it exhibits a dramatically enhanced sensitivity, exploding upon every contact with a Teflon spatula, 18 making it extremely dangerous and difficult to study, particularly by experiments. On one occasion a crystalline material was selected for X-ray diffraction studies, but it exploded under the microscope.…”