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Home , Brisance, Nitronium ion, Oxygen balance, RDX

Baran GM R.A. Rodriguez Chemistry of High Energy Materials 2012-08-18

History of High Energy Materials 7th century A.D.- "Greek Fire" petroleum distillate used by Byzantines of Constantinopole

13th century - black powder (aka ) Chinese alchemists

Explosives Non- 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 (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 () 1° Explosives 2° Explosives Propellants Pyrotechnics

[detonate by ignition] [need ] - Black powder - Fireworks late 19th century - chemistry on common materials (resins,cotton, etc.) - Lead azide - TNT - /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 - Introduction to high energy materials terminology Chair of inorganic chemistry : 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 comprised of an oxidant and fuel, which releases Detonation velocity (VoD): The velocity at which the shock wave front travels energy ( 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 balance (OB%): Expression used to indicate degree to which explosive can be oxidized. If explosive contains just enough oxygen to form from carbon, water from hydrogen 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 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- nitro-nitrate Br NO2 1. nBuLi - colorless liquid 2. N2O4 -78 °C S S 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 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. JOC 1988. 5353 N N N N 2 O N N N N OCN 85% 2 Baran GM R.A. Rodriguez Chemistry of High Energy Materials 2012-08-18

Initial Results: homocoupled product Routes to O-Nitro functionality - 1. 2 methoxypropene 1.cat. K3[Fe(CN)6] HO NO + 2 cat. H Me O O Na2S2O8 - Use of mixed acids (esterification) and oxides described for C-Nitraion Me N 2. NaOH H Key points: N HO OH O O N X 1. fuming (anhydrous) HNO3 prep: dry air bubbled through anhydrous HNO3 to H2N remove any oxides of nitrogen present, followed by addition of trace urea NO N N Me O 2 O N to remove any nitrous acid present. AKA "white " N N 2. Urea destruction of nitrous acid important to avoid violent fume-off Me Me NO O O O O Me O 2 NH 3. O- with mixed acids of "white nitric acid" above ambient temperatures N N O O Me NO2 Me NH is dangerous and has increase risk of explosion 4. anhydrous HNO /Ac O- Acetyl nitrate is generally a weak nitrating agent but 12% O 3 2 in the presence of a strong acid like HNO3, ionization to nitronium occurs O O O O NO2 NO2 NO2 Me Me O O O2NO ONO2 anh HNO3 HO OH 90% HNO HO ONO Me Me O O N 3 2 N Me O O Ac2O Ac O Me O O 2 activation Me Me Me Me O2NO ONO2 90% HO OH 70% O NO OH O O Me 2 - O O Me - CN N NO2 NO NO N O O 2 2 O O shock sensative NC CN NaO3S NC CN Fe Transfer nitration (neutral conditions - good for acid sensative alcohols) - O O NC Fe CN +CN NC OSO Na Me - Fe 3 NC CN -NaSO SO3Na 4 NC CN - BF4 Me NO2 NO Me N Me Olah G.A. et al JOC, 1965. 30, 3373 O NO ONO Me O 2 O m.p. 86 °C 2 2 1.HCl, MeOH OH ONO2 2 eq NO2 Det.Temp Me Me BF - + 4 works for 1 2 3 alcohols 140 C O NO ONO 2. Ac O/HNO MeCN Me N Me °, °, ° ° 2 NO 2 2 3 O O Me 2 NO2 OH quant yield ONO2 72% (2 steps) H 65% optimized in situ halide displacement with AgNO 3 Low yields for 2 ONO2 ° O2NO PPh3, I2 AgNO3 HgNO3 can be used for 2° and R OH R I R ONO2 3° alkyl halide displacements ONO2 O2NO decomposition of nitrocarbonates (very mild, rt or reflux MeCN) comparable O O stability to PETN AgNO3 -AgCl R ONO2 Py -CO 80% O2N NO2 RO Cl RO ONO2 2 N N ring opening of strained oxygen heterocycles H2O HO N N ONO2 20,164 MPH!! N2O4 ONO O2N NO2 O (or) ONO2 CHEETAH calculates CH2Cl2 [O] O2NO as powerful as HMX O ONO2 N2O5 Baran GM R.A. Rodriguez Chemistry of High Energy Materials 2012-08-18 selective O-nitrations 1 eq SOCl(NO ) 3 HO ONO2 -chloride ion catalysis 65% OH anhydrous ZnCl2, hydrochloride salt of amine, or dissolved HCl(g) can serve 2 eq SOCl(NO ) HO OH 3 O2NO ONO2 as a source of electropositive chloride under the oxidizing conditions of nitration OH 70% OH 2 HCl + 2HNO3 + 3Ac2O 2AcOCl + N2O3 + 4AcOH 3 eq SOCl(NO3) O2NO ONO2 100% ONO2 AcOCl + R2NH R2NCl + AcOH nitrodesilylation deamination R2NCl + HNO3 + Ac2O R2NNO2 + AcOCl + AcOH N2O5 NO2F RO SiR3 RO ONO2 + O2NO SiR3 CH Cl R NH2 R ONO2 Wright et al. Can. J. Res. 1948. 26B, 294 2 2 MeCN NO2 Routes to N-Nitro functionality HNO /Ac O NC N CN 3 2 NO2 R = Cl- (N+) 93% R N - Compounds resulting from nitration of nitrogen are of far less use for NC CN mainstream organic synthesis. However the N-NO group is an important HNO /Ac O 2 3 2 N HNO3/Ac2O 70% 'explosophore' and is present in many enrgetic materials (w/o chloride) NC CN R = H

- Direct nitration of a 1° amine to a nitramine using HNO3/mixed acids is not X possible due to instability of the tautomeric isonitramine in strongly acidic NO2 conditions. 2° amines are more stable and can undergo electrophilic nitration 2 HOCl HNO /Ac O NaHSO3 (aq) R NH R NCl 3 2 using HNO3/Ac2O 2 2 R N R NHNO2 NO2 2° w/ HNO3/Ac2O Cl O N NO2 OH + NO2 - Nitrolysis of fully substituted nitrogen HN N H N N N R OH + N2O NC N CN Me Me rupture of C−N bond leading to formation on N−NO2 R O R O 93% 22% 6% O N R A Path A 2 2 analines - must contain one or more nitro groups on the aromatic ring N R CO H O + 1 2 R How to get around this problem?? 2 R2 - synthesis via condensation chemistry (Mannich, 1,4 addition, etc) R1 N O

R2 Path B NO2 What about if need more direct method?? + R2 OH R1 N -non-acidic nitrating reagents (nucleophilic nitration) B R2 O + NO2 Nitramine formation via nitrolysis possible from: nBuLi Et H R ONO2 NH2 R NHLi R N N R NH -78 C R1 - carbamate ° + R1 O OLi NO2 N NO2 - urea N R2N NR2 R2N SiR3 R R1 2 - formamide R1 R1 N O + NO2 - acetamide 1. Na - H Ph R2N NO Ar NH2 + Ph R Ar NH2 Na Ar N N Ar NH 2 - sulfonamide 2. EtONO2 EtONO2 ONa Ease of alkyl nitrolysis depends on stability of the resulting cation: benzyl, tertiary (t-Bu), etc... Baran GM R.A. Rodriguez Chemistry of High Energy Materials 2012-08-18

Synthesis of Hexanitrohexaazaisowurtzitane (HNIW) Syntheses of some nitramine explosives

- Many nitramines are more powerful than aromatic C-nitro compounds and have 1. CrO3, AcOH NNs NNs NH2 NH2 NNs NNs high brisance and high chemical stability and low sensativity to impact and NsCl, 2. HOCH2CH2OH friction compared to nitrate ester explosives. This is why they are of interest to K2CO3 (aq) TsOH military applications. 95% 82% (2 steps) O O Bn Bn Bn OH OH Bn Bn O N N N NH2 N N MeCN/H2O Bn Bn H N N Br Br 76% + H + Ph cat. H N N N K2CO3 O N N NOH Bn 2 eq. Bn Bn Bn Bn O2N NO2 1. HNO /NH NO 1. O , CH Cl H2, 3 4 3 3 2 2 O + Ph [Pd] X NO2 urea, 33% 2. DMS [O] Ph Me X NNs NNs NNs NNs NNs O Ac2O NNs N 2. H2SO4 3. NH2OH/NaOAc N N 92% decomp. messy. Nitration 86% (3 steps) O O O O of aromatic rings O Ph O CrO3 Ph N N F2NSO3H, 90% HNF2, H2SO4, Ac NO2 O N NO O2N NO2 Bn Bn Ac O2N CFCl 2 2 N N 1. N2O4 N N 3 N N O N Bn Bn Ac Ac 2. HNO3/H2SO4 2 NO N N H2, Pd(OAc)2 N N N N 2 HNO3/SbF6 O N N N NO via nitroso Ns N N Ns 2 2 Ac2O, PhBr cat. CF3SO3H N N N N 93% N N Bn Bn 65% Bn Bn O2N NO2 H2, DANGER! F2N NF2 F2N NF2 NO 99% HNO3 O2N 2 [Pd] TNFX N N O2N Ac Ac (3,3 bis(difluoroamino)octahydro N N NO2 Ac Ac N N 1. HCO H N N 1,5,7,7 tetranitro 1,5 diazocine) Ac Ac 2 Ac Ac N N N N N N O N NO 2. Ph, Δ 2 2 NH2 + - Br HN NH -H2O OHCN NCHO NH3 Br 1. NaNO (aq) HNIW aka CL-20 HBr-AcOH NaOH, 80 °C 2 HO OH Br Br 2. HCl (aq) - explosive/propellant (low smoke-emission) 160 °C 60 mmHg - most powerful to date (better oxidizer-to-fuel than RDX/HMX) OH 72% 10% Br N - first prep by Nielsen 1987 Naval Air Warefare - pilot plant in 1990 for 200 kg in China Lake facility O2N NO2 - unmatched performance in specific impulse, O N CH Br 1. NaHCO3, NaI 2 2 O2N CH2Br burn rate, detonation velocity (9.38 km/s = 21,000 MPH!!) DMSO, 100 °C HNO3/TFAA - highest density than any other explosive (d = 2.044 g/cm3) N 2. NaNO2, NaOH N 81% N - thermally stable (250 -260 °C) but sensative to mechanical stress NO2 K3Fe(CN)6, K2S2O8 still greater stability than nitrocellulose, PETN and others. NO2 NO TNAZ 29% (2 steps) - 4 different polymprphs with different densities/properties Baran GM R.A. Rodriguez Chemistry of High Energy Materials 2012-08-18

No single nitrating agent is as diverse and versatile N O Preparation of N2O5 [Deville 1849] 2 5 It is considered as the future for energetic materials synthesis O AgNO + Cl (g) 3 2 N + AgNO3 N2O5 non-acidic nitrating reagents (neutral) O Cl 1° amines/nitramines leads to deamination and formation of nitrate ester Dehydration of nitric acid by-product but analines are successful. HNO3 + P2O5 N2O5 + H3PO4 O O nitronium nitrate salt O3 + - - adopts two structures Δ N O N O N2O5 N N [NO2 ][NO3 ] 2 4 2 5 O O O depending on condition - isolation by sublimation and collection trap at -78 °C sublime slightly above rt polar - stream of ozone needed to avoid collection on N2O4 - if don't care about acidity, can use HNO /P O mixture directly (no ozone stream) condition: chlorinated solvents condition: anhyd. HNO3 3 2 5 - clean and selective - powerful but acidic and non-selective - non-oxidizing &n non-acidic Process chemist at Defense and Evaluation Research Agency (DERA) in the UK Development of a flow process: Using commercial ozonizer to generate 5 - 10% - 1st prepared over 150 years ago but due to difficult prep and low thermal mix of ozone in oxygen and mixed in flow with N2O4. N2O5 is trapped in solid stability (require -60 °C long term storage) received little attention. condenser tubes (cooled by dry ice/acetone). - Environmental restrictions and push for green chemistry sparked interest Explosives in JACS: Sila explosives Klapotke T.M. JACS 2007. 129, 6908 Advantage: Rxns are very clean O2NO - faster and less exothermic (due to absence of oxidation byproducts) - Used in WW I - high yields - One of most high energy explosives known O2NO ONO2 - simple isolation - more shock sensative than TNT. used as booster mix - non-acidic conditions possible with this reagent (compared to mixed acids) - Europe marketed as lentonitrat (vasodilator) like NG PETN ONO2 rt Stable for 2 weeks at -20 °C N2O5 2 N O + O - Det. Velocity 8,400 m/s 2 4 2 Stable for up to 1 yr at -60 °C - d= 1.7 g/cm3 "The crystalline compound exploded on every synthesis of TNT under mild conditions Silicon analogue of PETN occasion upon contact with Teflon spatula... Me Solutions in diethyl ether exploded upon the slighest Me - VERY high e evaporation of the solvent." NO2 O2N NO2 O2NO dens N2O5/HNO3 No explosion hazard 32 C, O NO Si ONO ° 2 2 Si(CH2OAc)4 Si(CH2Cl)4 quant yield VERY NO2 NO 2 low e- dens ONO2 Why does Si-PETN have drastically increased sensativity? N-nitrations of ureas O2N O2N NO2 Theoretical: electrostatic potential: H H H 1. Surface electrostatic potential, in general, is related to the sensitivity of the bulk N N N N N N HNO3 HNO3 2. The more evenly distributed the electrostatic potential is over the surface of a O O O O O O H SO P O , the more stable it is to impact. N N 2 4 N N 2 5 N N H H H O NO O-nitrations of polyols NO2 O2N NO2 2 O ONO ONO N O OH OH 2 2 O2NO Si N2O5, CCl4 O OH ONO2 HO O2NO 0 °C O2NO OH OH quant yield ONO2 ONO2