Chemistry of High Energy MaterialsR.A. RodriguezBaran GM2012-08-18History of Explosives7th century A.D.- "Greek Fire" petroleum distillate used byByzantines of ConstantinopoleHigh Energy Materials13th century - black powder (aka gunpowder) Chinese alchemistsNon-explosive materialsExplosives18th century - black powder composition became standardized:KNO3/charcoal/sulfur (75/15/10 w/w)19th century - NH4NO3 replacement for KNO3 in black powder1846 - Italian Chemist Ascanio Sobrero invented nitroglycerin (NG)High ExplosivesLow Explosives[detonate]1 Explosives2 Explosives[detonate by ignition]- Lead azide- Tetrazene[need detonator]- TNT- RDX[deflagrate-burn rapidly]Propellants- Black powder- liquid/solidPyrotechnics- Fireworks- Color/flash/soundOrganic Chemistry of Explosives by J.P. Agrawal and R.D. HodgsonProf. Thomas Klapotke - Ludwig-Maximilians-Universität München - GermanyChair of inorganic chemistryDr. Michael A. Hiskey - Los Alamos National LaboratoryWhat makes an explosion?1863 - German chemist Julius Wilbrand invented 2,4,6-trinitrotoluene (TNT)originally used as a yellow dye. Potential as an explosive not appreciateddue to difficulty to detonate (insensative).1866 - Mixing of NG with silica (PBX) to make malleable paste (dynamite)late 19th century - nitration chemistry on common materials (resins,cotton, etc.)1910 - military use of TNT for artillery shells and armour-piercing shells1939-1945 - World War II - Research on explosives intesified (nitration chemistry)Developlment of cyclotrimethylenetrinitramine (RDX) andcyclotetramethylenetetranitramine (HMX).Introduction to high energy materials terminologyBrisance: Shattering capabiliy of explosive. Measure of rate an explosivedevelops its maximum pressure.Relative effectiveness factor (R.E. factor): Measurement of an explosive'spower for military purposese. It is used to compare an explosive'seffectiveness relative to TNT by weight (TNT equivalent/kg or TNTe/kg).Exothermic chemical reaction comprised of an oxidant and fuel, which releasesenergy (gas and heat) in a given time interval.Detonation velocity (VoD): The velocity at which the shock wave front travelsthrough a detonated explosive. Difficult to measure in practice so usegas theory to make prediction.Whats the difference between explosive, propellants and pyrotechnics?Specific impulse (Isp): The force with respect to the amount of propellant usedper 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 wavesOxygen balance (OB%): Expression used to indicate degree to which explosivecan be oxidized. If explosive contains just enough oxygen to form carbondioxide from carbon, water from hydrogen molecules and all metal oxides frommetals with no excess, the explosive is said to have zero oxygen balance.
Chemistry of High Energy MaterialsR.A. RodriguezChemical types/class of organic explosivesAromatic C-nitro compoundsAliphatic C-nitro compoundsNO2R11 nitroalkaneR22 nitroalkaneNO2high explosive withhigh thermal andchemical (LLM-116)O2NNNO2NNO2H2NNO2NNH2Opyridine N-oxideO2NH 2NNNONH2NO2NH2NNNOO2NNO2NNH2pyrazine N-oxide tetrazine N-oxideNO2ArF2 NbenzotriazolestetrazolesNH2NNHNNO21,2,4 i-PETNNNHONO2NO2O2NONNOO2Nnovel energetic nitrate NNOONO2O2NONNNRDX (VOD 8440 m/s) HMX (VOD 9110 m/s)ONO2O2NPentaerythritol tetranitrate(PETN) (VOD 8310 DNI)Aliphatic N-nitro compoundsNitroglycerin (VOD 7750 m/s)OONH2x 4poor ,3,5-trinitrobenzene 2,4,6-trinitrophenol(TNB)(picric acid)O2NOOH2NO2NTNTNO2O2NNO2Aliphatic O-nitro compoundsNitro derivatives of pyrroles, thiopenes, and furans are not practical explosives:1. heat of formation offers no benefits over standard arylene hydrocarbons2. during nitration, these heterocycles are much more prone to oxidation andacid cat. ring opening compared to arenesH-bondingreduction 3 nitroalkaneNO2R2NO2R1acidic lkaneR2R3R1RNO2NO2NO2NO2R2RBaran ohexaazaisowurtzitane(HNIW or CL-20)(VOD 9380 m/s)HNO2NArNNNONH3-nitro-1,2,4-triazol-5-one(NTO)
Chemistry of High Energy MaterialsR.A. RodriguezNitration chemistryTMSOAcTMSRoutes to C-Nitro eO2NONOO2NNMeMeMeMeOO2NONOMeMeMeMedinitroO2N ONO2nitro-nitrite1. NaHMDS2. N2O4O2NNO2PhOHDCE/ rtPh NO2Ph76%74%O2NNO22. N2O4 -78 C77%NItration selectivity on arene/heteroareneKakiuchi, et al. Synlett 1999. 901HHNaNO3 xs,CAN 2eqRRAcOH/CHCl380 - 90%HRNO2RHHRHRNO2RRRRHwu et al. J Chem Soc Chem Commun 1994. 1425Taniguchi et al. JOC 2010. 75, RClNO2RO2NNNHAcPhO2NCl80 - 90%NO2HMeCN, reflxNO2H2SO4traditional[NO2 ]44%NFe(NO3)3 9H2O RFeCl3O2NKNO3ClNO292%NO2S23%PhOAcNO2Al2O3Mukaiyama et al. Chem Lett 1995. 505OO2N1. nBuLiSNO2ONNO2O2NBr- colorless liquid1 atm NONO2ONNO2nitro-nitrateRadical methodsNefAcONO2OAcOMeMeMeMeNO2NO2 ONO2alkaline nitrationO2N ONitration with HNO3 is difficultNO2ONDirect nitration of aliphatic and alicyclic hydrocarbons possible in the vaporphase using HNO3 or NO2 (toxic redish-brown gas) at elevated temperatures.HOONO2[2 2]Borgardt et al. Chem Rev 1964. 64, 19 (polynitro functionality)NO2NO2NO2AcONO2The nitro gorup whether attached to aromatic or aliphatic carbon, is probablythe most widely studied of the functional groups and this is in part attributedto its use as an 'explosophore' in many energetic materials.Baran GM2012-08-18F3 COOOTBANCF3F3CONO2TFAA76%NNO2NCO2R* No rxn inpresence ofTEMPO
Chemistry of High Energy MaterialsR.A. Rodriguez1 and 2 nitro compoundsVictor Meyer rxn- alkyl chlorides too slow- only good for 1 (2 alkyl halide gives nitrate ester)- nitrate ester arises from desproportionation of silver nitrate acc. by heat/lightR XNONOHOetherROAgNO2 AgXRONO1.KOtBuamyl nitrate2. H 1. NBS2. [O]3. [H]ONaNO2DMSOfastXRRRNNO2 OR nitrite esterRH OHNO2HOOHphloroglucinolOONNORCO2HRHNO3F20 - 30%RNO2CO2HONO2MeO2CNH3 Cl-OAg NR2OOAcetone91%NH3 CC H3NNHDMDOAcetone/H2O85%O2NEaton et al. JOC 1988. 5353Ag0Ag AgO ONOO O-Ag0N OR1R2OR2ONN OR1retroaldolONONHOMevia amine thusH2O NNCO2. AgNO3NO2ONO2NO2NO2MeNO2NNO2O2NN ONO2ONO2Original Target/Route via modified Kaplan Shechter RxnOoxidation of isocyanatesOCNR1O NaDMDOC H3NNO2NNO2 O2NKaplanShechter Rxn1. NaNO2O OMeNO2OR2R1nitronateNMeNR2NO2oxidation of aminesONaOHNO2NO2HNO360 %NO2NOR1MeO2CH OChavez, D.E. et al. Angew. 2008, 47, 8307NO2NO2OO2NOR1NO2RNO2S2O8 2-Synthesis of an energetic nitrate esterKornblum et al. JACS 1956. 78, 1497gem-dinitros from acidsRonly usefuloxidantOHRORNO2NO2NO2 (or)NO2O2NNO2FNO2N(low yields)OFluorotrinitromethaneNO2OHRNO2slowORRRO NaNO2ONO2 O2NNO2NO2Hmodified VM (alkali metal nitrites e.g. NaNO2) time and solubility is VIMPRCF3CO3HBaran NHNHONHNNNRNHNNN
Chemistry of High Energy MaterialsR.A. RodriguezInitial Results: homocoupled productHO1. 2-methoxypropeneMecat. H NO2HOOHMe2. NaOHMeONOMeOONOOOMeMeOOMeONONCCN CN-CNCNO2NOm.p. 86 CDet.Temp140 CO2NO- Use of mixed acids (esterification) and nitrogen oxides described for C-NitraionKey points:HN1. fuming (anhydrous) HNO3 prep: dry air bubbled through anhydrous HNO3 toOONXH2Nremove any oxides of nitrogen present, followed by addition of trace ureaNNNO2toremove any nitrous acid present. AKA "white nitric acid"NONN2. Urea destruction of nitrous acid important to avoid violent fume-offMeNO2NH 3. O-nitrations with mixed acids of "white nitric acid" above ambient temperaturesMe OO Meis dangerous and has increase risk of explosionNO2NHMe4. anhydrous HNO3/Ac2O- Acetyl nitrate is generally a weak nitrating agent but12%Oin the presence of a strong acid like HNO3, ionization to nitronium ion occursOOMeO-NaSO4NO2NNCCNNC FeNCOO2NOONaO3SOOSO3NaOONO21.HCl, MeOHONO22. Ac2O/HNO3NO Me72% (2 steps)O2NOOHOOHONO2OHO Me65% optimizedONO2OHNO2OHNO2O2NOONO2comparablestability to PETNNNNNNO2MeMeNMe2 eq NO2Olah G.A. et al JOC, 1965. 30, 3373ONO2 MeCNquant yieldONO2MeNHBF4Mein situ halide displacement with AgNO3RO2NO2NOMeMeO2N70%ONO2Transfer nitration (neutral conditions - good for acid sensative alcohols)NO2OHOAc2Oshock sensativeFeO2NO20,164 MPH!!90%ONO2OH 90% HNO3BF4MeNO2anh HNO3 HOAc2ONO2OMeNO2ONO2SO3NaCNNO2OMeOO MeONOMeMeONC FeONMeCNNCRoutes to O-Nitro functionality1.cat. K3[Fe(CN)6]Na2S2O8NO2Meactivation-OMeOOBaran GM2012-08-18OHPPh3, I2RIAgNO3RCHEETAH calculatesas powerful as HMXLow yields for 2 HgNO3 can be used for 2 and3 alkyl halide displacementsONO2decomposition of nitrocarbonates (very mild, rt or reflux MeCN)OROOAgNO3PyClRO-AgClONO2-CO2ring opening of strained oxygen heterocyclesNO2works for 1 , 2 , 3 alcoholsN2O4O (or)CH2Cl2OONOONO2RONO280%H2O[O]N2O5HOO2NOONO2ONO2
Chemistry of High Energy MaterialsR.A. Rodriguezselective O-nitrations1 eq SOCl(NO3)65%ONO2OHnitrodesilylationanhydrous ZnCl2, hydrochloride salt of amine, or dissolved HCl(g) can serveas a source of electropositive chloride under the oxidizing conditions of nitrationONO2OH3 eq SOCl(NO3) O2NO100%RO SiR3-chloride ion catalysisOH2 eq SOCl(NO3) O2NO70%OHHOHO2 HClONO2ROCH2Cl2ONO2 O2NO SiR3R NH2R2NClNO2FRMeCNHNNRNONRNCNOCNMe93%22%How to get around this problem?- synthesis via condensation chemistry (Mannich, 1,4 addition, etc)NR NH2R NH2Ar NH2nBuLi-78 CR NHLi1. Na2. EtONO2EtONO2R NN-OAr NNONaHNO3Ac2OR2NNO2 4AcOHAcOH AcOCl AcOHNHNO3/Ac2OR Cl- (N )CNRNNCHNO3/Ac2OR HCNNO2NNC70%CNMe2 HOClR NCl2HNO3/Ac2OR NNO2 NaHSO (aq)3R NHNO2Cl6%APath AO2NOR1NR2N R1 CO2HR2R2OPath BR2BR1NO2N R2 OHR2Nitramine formation via nitrolysis possible from:NO2R NHR1OLiAr NH2Na EtONO2R2NClN2O3- Nitrolysis of fully substituted nitrogenrupture of C N bond leading to formation on N NO2What about if need more direct method?-non-acidic nitrating reagents (nucleophilic nitration)H R2NH Xanalines - must contain one or more nitro groups on the aromatic ringO2AcOClAcOCl 93%HNO3/Ac2O(w/o chloride)NO2NNO2R OH N2O3Ac2ONO2NC- Direct nitration of a 1 amine to a nitramine using HNO3/mixed acids is notpossible due to instability of the tautomeric isonitramine in strongly acidicconditions. 2 amines are more stable and can undergo electrophilic nitrationusing HNO3/Ac2ONO22 w/ HNO3/Ac2OH Wright et al. Can. J. Res. 1948. 26B, 294- Compounds resulting from nitration of nitrogen are of far less use formainstream organic synthesis. However the N-NO2 group is an important'explosophore' and is present in many enrgetic materialsOH2HNO3ONO2Routes to N-Nitro functionalityO ONO2deaminationN2O5Baran GM2012-08-18H NO2Ar NHR1NR1NO2 R1PhNNO2PhOR2NNR2R2N SiR3R2N NOR1- carbamate- ureaR2 - formamideN- acetamideR2- sulfonamideEase of alkyl nitrolysis depends on stability of the resulting cation:benzyl, tertiary (t-Bu), etc.
Chemistry of High Energy MaterialsR.A. RodriguezSynthesis of Hexanitrohexaazaisowurtzitane (HNIW)Syntheses of some nitramine explosives- Many nitramines are more powerful than aromatic C-nitro compounds and havehigh brisance and high chemical stability and low sensativity to impact andfriction compared to nitrate ester explosives. This is why they are of interest tomilitary applications.ONH2 Phcat. H eCN/H2OHH2 eq.BnBnNNNNO2NO2NNNNBnNN NO2NNO2NNsNsCl,K2CO3 (aq)95%OHBn1. CrO3, AcOH2. HOCH2CH2OHTsOHNNs82% (2 steps)OHBrBnX NO2 O2N1. HNO3/NH4NO3urea, 33%NNs2. H2SO492%NNs1. O3, CH2Cl22. DMSNNsOONNsNNsOO76%BrK2CO3NOHNO2NNsdecomp. messy. Nitrationof aromatic ringsNNs3. NH2OH/NaOAc86% (3 steps)ONNsOOPhAcO2N1. N2O4NOBnBn H , Pd(OAc)AcAc 2. HNO3/H2SO4 2NN22NNvia nitrosoAc2O, PhBr cat.NNNNN93%65%BnO2NBnBnBn DANGER!H2,99% HNO3NO2[Pd]O2NNNH2NNH2,[Pd] XNH2BnNNNBaran GM2012-08-18AcAcAcHNNNNAcNNNNAcNH1. HCO2H2. Ph, Δ-H2OAcAcOHCNHNIW aka CL-20- explosive/propellant (low smoke-emission)- most powerful to date (better oxidizer-to-fuel than RDX/HMX)- first prep by Nielsen 1987 Naval Air Warefare- pilot plant in 1990 for 200 kg in China Lake facility- unmatched performance in specific impulse,burn rate, detonation velocity (9.38 km/s 21,000 MPH!!)- highest density than any other explosive (d 2.044 g/cm3)- thermally stable (250 -260 C) but sensative to mechanical stressstill greater stability than nitrocellulose, PETN and others.- 4 different polymprphs with different densities/propertiesNO2NN NO2F2NSO3H,90% HNF2, H2SO4,CFCl3NsNNO2O2NNO2NNF2 NO2NHNO3/SbF6NsCF3SO3HNNNNO2NF2TNFX(3,3 bis(difluoroamino)octahydro1,5,7,7 tetranitro 1,5 diazocine)AcNCHONF2NNF2AcNNO2NNO2NH2OH HBr-AcOH BrHO160 C72%OHO2NNO2NNO2TNAZNH3 BrBrBrNaOH, 80 C60 mmHgBr1. NaHCO3, NaIDMSO, 100 CNO2N2. NaNO2, NaOHK3Fe(CN)6, K2S2O829% (2 steps)CH2Br1. NaNO2 (aq)2. HCl (aq)10%O2NCH2BrHNO3/TFAANNO281%NNO
Chemistry of High Energy MaterialsR.A. RodriguezN2O5No single nitrating agent is as diverse and versatileIt is considered as the future for energetic materials synthesisPreparation of N2O5 [Deville 1849] OAgNO3non-acidic nitrating reagents (neutral)1 amines/nitramines leads to deamination and formation of nitrate esterby-product but analines are successful.N2O5OOO nitronium nitrate saltNNO[NO2 ][NO3-]Ocondition: chlorinated solvents- clean and selective- non-oxidizing &n non-acidicHNO3- adopts two structuresdepending on conditioncondition: anhyd. HNO3- powerful but acidic and non-selective- 1st prepared over 150 years ago but due to difficult prep and low thermalstability (require -60 C long term storage) received little attention.- Environmental restrictions and push for green chemistry sparked interestAdvantage: Rxns are very clean- faster and less exothermic (due to absence of oxidation byproducts)- high yields- simple isolation- non-acidic conditions possible with this reagent (compared to mixed acids)rtStable for 2 weeks at -20 CN2O52 N2O4 O2Stable for up to 1 yr at -60 Csynthesis of TNT under mild itrations of polyolsOHOHOHHOOHOHO2NHNNNO2P2O5NNNNOOO2NNO2ONO2 ONO2N2O5, CCl40 Cquant yieldHNO3NO2ONO2 ONO2AgNO3N2O5H3PO4N2O4O3N2O5Process chemist at Defense and Evaluation Research Agency (DERA) in the UKDevelopment of a flow process: Using commercial ozonizer to generate 5 - 10%mix of ozone in oxygen and mixed in flow with N2O4. N2O5 is trapped in solidcondenser tubes (cooled by dry ice/acetone).Explosives in JACS: Sila explosivesO2NOO2NOONO2PETN- Det. Velocity 8,400 m/s- d 1.7 g/cm3VERY high edensSiKlapotke T.M. JACS 2007. 129, 6908- Used in WW I- One of most high energy explosives known- more shock sensative than TNT. used as booster mix- Europe marketed as lentonitrat (vasodilator) like NGONO2ONO2ONO2"The crystalline compound exploded on everyoccasion upon contact with Teflon spatula.Solutions in diethyl ether exploded upon the slighestevaporation of the solvent."Si(CH2OAc)4Si(CH2Cl)4Why does Si-PETN have drastically increased sensativity?Theoretical: electrostatic potential:1. Surface electrostatic potential, in general, is related to the sensitivity of the bulk2. The more evenly distributed the electrostatic potential is over the surface of amolecule, the more stable it is to impact.O2NOO2NOONO2O2NO - isolation by sublimation and collection trap at -78 C- stream of ozone needed to avoid collection on N2O4- if don't care about acidity, can use HNO3/P2O5 mixture directly (no ozone stream)VERYlow e- densONHN2O5ClΔO2NONO2NOP2O5O2NONo explosion hazardN-nitrations of ureasCl2 (g)Silicon analogue of PETN32 C,quant yieldNO2NH MeNO2HN Dehydration of nitric acidpolarsublime slightly above rtBaran GM2012-08-18O2NOOSiNOO
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 e