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Chemistry of High Energy Materials 2012-08-18 Baran GM R.A. Rodriguez Chemistry of High Energy Materials 2012-08-18 History of Explosives High Energy Materials 7th century A.D.- "Greek Fire" petroleum distillate used by Byzantines of Constantinopole 13th century - black powder (aka gunpowder) Chinese alchemists Explosives Non-explosive materials 18th century - black powder composition became standardized: KNO3/charcoal/sulfur (75/15/10 w/w) 19th century - NH4NO3 replacement for KNO3 in black powder 1846 - Italian Chemist Ascanio Sobrero invented nitroglycerin (NG) High Explosives Low Explosives 1863 - German chemist Julius Wilbrand invented 2,4,6-trinitrotoluene (TNT) [detonate] [deflagrate-burn rapidly] originally used as a yellow dye. Potential as an explosive not appreciated due to difficulty to detonate (insensative). 1866 - Mixing of NG with silica (PBX) to make malleable paste (dynamite) 1° Explosives 2° Explosives Propellants Pyrotechnics [detonate by ignition] [need detonator] - Black powder - Fireworks late 19th century - nitration chemistry on common materials (resins,cotton, etc.) - Lead azide - TNT - liquid/solid - Color/flash/sound - Tetrazene - RDX 1910 - military use of TNT for artillery shells and armour-piercing shells 1939-1945 - World War II - Research on explosives intesified (nitration chemistry) Developlment of cyclotrimethylenetrinitramine (RDX) and Organic Chemistry of Explosives by J.P. Agrawal and R.D. Hodgson cyclotetramethylenetetranitramine (HMX). Prof. Thomas Klapotke - Ludwig-Maximilians-Universität München - Germany Introduction to high energy materials terminology Chair of inorganic chemistry Brisance: Shattering capabiliy of explosive. Measure of rate an explosive develops its maximum pressure. Dr. Michael A. Hiskey - Los Alamos National Laboratory Relative effectiveness factor (R.E. factor): Measurement of an explosive's power for military purposese. It is used to compare an explosive's What makes an explosion? effectiveness relative to TNT by weight (TNT equivalent/kg or TNTe/kg). Exothermic chemical reaction comprised of an oxidant and fuel, which releases Detonation velocity (VoD): The velocity at which the shock wave front travels energy (gas and heat) in a given time interval. through a detonated explosive. Difficult to measure in practice so use gas theory to make prediction. Whats the difference between explosive, propellants and pyrotechnics? Specific impulse (Isp): The force with respect to the amount of propellant used per unit time. Used to calculate propulsion performance. Rate at which it burns (Flamming gummy bear vs. rocket booster vs. TNT) Speed of reaction will determine subsonic vs. supersonic blast pressure waves Oxygen balance (OB%): Expression used to indicate degree to which explosive can be oxidized. If explosive contains just enough oxygen to form carbon dioxide from carbon, water from hydrogen molecules and all metal oxides from metals with no excess, the explosive is said to have zero oxygen balance. Baran GM R.A. Rodriguez Chemistry of High Energy Materials 2012-08-18 Chemical types/class of organic explosives Aromatic C-nitro compounds Aliphatic C-nitro compounds NO2 NO2 NO2 R2 NO2 Me HO acidic protons (NO2)x R NO2 R1 NO2 R NO2 (condensation NO NO x ≥ 4 chemistry) O N NO O2N 2 O2N 2 1° nitroalkane 2° nitroalkane Terminal 2 2 poor chemical TNT 1,3,5-trinitrobenzene 2,4,6-trinitrophenol gem-dinitroalkane stability (TNB) (picric acid) R 2 NO2 R R 3 NO 2 R2 2 high explosive with Aliphatic O-nitro compounds Aliphatic N-nitro compounds R1 R NO NO 1 2 high thermal and R1 NO2 2 NO2 chemical stability Internal NO O N NO 3° nitroalkane Trinitromethyl O2NO ONO2 2 2 2 gem-dinitroalkane N N ONO2 N NO2 Nitroglycerin (VOD=7750 m/s) heterocycles O2NN NNO2 N N N N ONO NO2 2 O2N NO2 O N NO O NO 2 2 2 RDX (VOD=8440 m/s) HMX (VOD=9110 m/s) O O N NO O2NN NNO2 2 2 ONO2 NO2 N O NO O2N NO2 N H S O 2 N N Pentaerythritol tetranitrate H H H N NH Nitro derivatives of pyrroles, thiopenes, and furans are not practical explosives: (PETN) (VOD=8310 m/s) N,N'-dinitrourea 2 2 1. heat of formation offers no benefits over standard arylene hydrocarbons (DNU) nitroguanadine NO2 2. during nitration, these heterocycles are much more prone to oxidation and O2NO ONO2 acid cat. ring opening compared to arenes O2N NO2 O N 2 NO2 O2N O O2NO ONO2 N N H-bonding H2N NO2 NO 2 O2N NO2 reduction in O2NN NNO N N novel energetic nitrate eseter 2 sensativity N NH N N N N O2N N O ONO2 F2N NF2 O2N NO H O2NO 2 NO2 N 3,3-bis(difluoroamino) 4-amino-3,5-dinitropyrazole 2,4-dinitroimidazole furazans/benzofurazans Si Hexanitrohexa- octahydro-1,5,7,7- (LLM-116) (2,4-DNI) furoxans/benzofuroxans ONO azaisowurtzitane 2 tetranitro-1,5-diazocine O2NO (HNIW or CL-20) NH O 2 NH2 (TNFX) O2N N Si-PETN (VOD=9380 m/s) O2N NO2 O O2N N NO2 N N N H N H N H 2 2 N N N N O N O N N N N 2 H N N NH 2 2 H2N N NH2 O Ar Ar Ar NO2 N N N O N NH NO2 NH2 N N O O benzotriazoles H H 1,3,4-oxadiazoles 3-nitro-1,2,4-triazol-5-one pyridine N-oxide pyrazine N-oxide tetrazine N-oxide tetrazoles 1,2,4 triazoles (NTO) Baran GM R.A. Rodriguez Chemistry of High Energy Materials 2012-08-18 Nitration chemistry NO2 TMS NO AcONO2 2 NO2 O The nitro gorup whether attached to aromatic or aliphatic carbon, is probably the most widely studied of the functional groups and this is in part attributed to its use as an 'explosophore' in many energetic materials. ONO2 ONO2 [2+2] Borgardt et al. Chem Rev 1964. 64, 19 (polynitro functionality) _ OAc Nef _ OAc AcONO2 TMS NO NO Routes to C-Nitro functionality O 2 O 2 NO + O N 2 N Direct nitration of aliphatic and alicyclic hydrocarbons possible in the vapor N O O O OAc phase using HNO3 or NO2 (toxic redish-brown gas) at elevated temperatures. H NO2 O2N NO2 HNO3 alkaline nitration NO Nitration with HNO3 is difficult 25% H 2 NO Me Me Me Me 2 NO2 NO2 NO2 O2N 1. NaHMDS O2N O2N O2N NO2 N2O4 2. N2O4 Me Me O2N NO2 O2N ONO O N ONO 2 2 O2N O N O N O N NO2 2 NO 2 NO 2 NO O O + + 74% 2 2 2 Me Me Me Me Me Me Me Me N N Me Me Me Me Me Me O O dinitro nitro-nitrite nitro-nitrate Br NO2 1. nBuLi - colorless liquid 2. N2O4 -78 °C S S Radical methods 77% OH O2N Cl 1 atm NO NItration selectivity on arene/heteroarene NO2 NO + 2 Ph Ph Ph Kakiuchi, et al. Synlett 1999. 901 N DCE/ rt KNO 76% 23% 3 Al2O3 H2SO4 Cl traditional N NO2 + Mukaiyama et al. Chem Lett 1995. 505 Ph [NO2 ] CO2R 92% N 44% NaNO xs, H H 3 Fe(NO ) 9H O CAN 2eq H NO2 R 3 3 2 R Cl FeCl3 Cl AcOH/CHCl R R 3 R R MeCN, reflx N R R NO2 N 80 - 90% CO R TBAN NO 80 - 90% 2 2 H NO2 H NO2 TFAA NO2BF4 NHAc O O TBAN O * No rxn in H Ph 76% presence of H NO N R R R R MeCN NO2 2 TEMPO Ph F3C O CF3 F3C O CO R Hwu et al. J Chem Soc Chem Commun 1994. 1425 84% 2 Taniguchi et al. JOC 2010. 75, 8126 Baran GM R.A. Rodriguez Chemistry of High Energy Materials 2012-08-18 1° and 2° nitro compounds O NOH NO2 CF3CO3H O OH Victor Meyer rxn N only useful - alkyl chlorides too slow 1.KOtBu oxidant - only good for 1° (2° alkyl halide gives nitrate ester) 1. NBS amyl nitrate + - nitrate ester arises from desproportionation of silver nitrate acc. by heat/light 2. [O] NO2 2. H+ S O 2- 3. [H] 2 8 O O2N NO N ether + 2 + + AgX NO O O O H R X R NO R O O2N NO2 OAg 2 NO2 N NO2H + NO2 O2N NO2 modified VM (alkali metal nitrites e.g. NaNO2) time and solubility is VIMP (low yields) Kaplan R NaNO2 R R N O R NO R Shechter Rxn DMSO NaNO2 X NO2 + O NO2 OH fast slow NO2 R R R nitrite ester R R Synthesis of an energetic nitrate ester O2NO ONO2 O H+ OH O N Chavez, D.E. et al. Angew. 2008, 47, 8307 OR O2NO ONO2 R NO2 NO2 HO OH O O O O 0 R phloroglucinol NO NaOH N 1. NaNO O N NO Ag Kornblum et al. JACS 1956. 78, 1497 2 2 2 2 Fluorotrinitromethane 2. AgNO + 3 R1 R2 Ag R1 R2 R1 R2 NO2 nitronate NO2 NO 2 NO2 + Ag NO (or) NO O O Ag 2 2 O O 0 O O O N NO N O O -Ag 2 2 F NO2 F NO2 N N O O O N N O O N N O R R gem-dinitros from acids 1 2 R R O 1 2 R1 R2 N R1 R2 R R HNO NO2 NO2 CO H 3 HNO3 O Na 2 MeO C CO H Original Target/Route via modified Kaplan Shechter Rxn 20 - 30% 2 2 60 % R R NO2 MeO2C NO2 NO retro Me O 2 Me O O oxidation of amines aldol Me O NO2 Me NH Me N NH +Cl- Me 3 NO2 -CH2O O NH O O O OH DMDO N N Acetone N C+H3N O2N Fe NH3+C 91% NO2 C+H3N O2N O O O O O O N activation N [O] N oxidation of isocyanates Me O Me O R Me NH Me NH NH NCO NO2 via amine thus O NH R DMDO H2O essential O NH NH N N Acetone/H O Eaton et al.
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