r.a. rodriguez chemistry of high energy materials · explosives non-explosive materials ... 1°...

Chemistry of High Energy Materials R.A. Rodriguez Baran GM2012-08-18

High Energy Materials

Explosives Non-explosive materials

High Explosives Low Explosives

1° Explosives 2° Explosives Propellants Pyrotechnics

- Fireworks- Color/flash/sound

[detonate by ignition]- Lead azide- Tetrazene

[need detonator]- TNT- RDX

- Black powder- liquid/solid

Organic Chemistry of Explosives by J.P. Agrawal and R.D. Hodgson

Prof. Thomas Klapotke - Ludwig-Maximilians-Universität München - Germany Chair of inorganic chemistry

Dr. Michael A. Hiskey - Los Alamos National Laboratory

History of Explosives

What makes an explosion?

Exothermic chemical reaction comprised of an oxidant and fuel, which releasesenergy (gas and heat) in a given time interval.

Whats the difference between explosive, propellants and pyrotechnics?

Rate at which it burns (Flamming gummy bear vs. rocket booster vs. TNT)Speed of reaction will determine subsonic vs. supersonic blast pressure waves

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

13th century - black powder (aka gunpowder) Chinese alchemists

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)

1863 - German chemist Julius Wilbrand invented 2,4,6-trinitrotoluene (TNT) 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)

late 19th century - nitration chemistry on common materials (resins,cotton, etc.)

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 cyclotetramethylenetetranitramine (HMX).

[detonate] [deflagrate-burn rapidly]

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).

Detonation velocity (VoD): The velocity at which the shock wave front travelsthrough a detonated explosive. Difficult to measure in practice so use gas theory to make prediction.

Specific impulse (Isp): The force with respect to the amount of propellant usedper unit time. Used to calculate propulsion performance.

Oxygen 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.


N N

NNO2N

O2N

NO2

NO2

Aliphatic C-nitro compounds

R NO2 R1 NO2

R2

R1 NO2

R3R2

R NO2

NO2

R1 NO2

NO2R2

1° nitroalkane 2° nitroalkane

3° nitroalkane

Terminalgem-dinitroalkane

Internalgem-dinitroalkane

acidic protons(condensation

chemistry)

high explosive withhigh thermal andchemical stability

R1

R2

NO2

NO2NO2

Trinitromethyl ONO2

Me

O2N NO2

NO2

N N

N

NO2

O2N NO2

ONO2

O2NO

TNT

Nitroglycerin (VOD=7750 m/s)

RDX (VOD=8440 m/s)

Chemical types/class of organic explosives

NO2

NO2

O2N NO2

O2NN NNO2

O2NN NNO2

O2NN NNO2

O2N NO2

NF2F2N

N NN N

NN

NO2

NO2

O2N

O2N

O2N NO2

ONO2

ONO2

O2NO

O2NO

NO2

NO2

ONO2

SiONO2

O2NO

O2NO

ONO2

ONO2O2NO

O2NO

Pentaerythritol tetranitrate(PETN) (VOD=8310 m/s)

Aromatic C-nitro compounds

Aliphatic O-nitro compounds

HMX (VOD=9110 m/s)

O2N NO2

NO2

O2N NO2

NO2

HO(NO2)x

x ≥ 4poor chemical

stability

Aliphatic N-nitro compounds

NH

O

NH

NO2

H2N

N

NH2

NO2

N,N'-dinitrourea(DNU) nitroguanadine

1,3,5-trinitrobenzene(TNB)

2,4,6-trinitrophenol(picric acid)

O2NNH

Nitro 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 and acid cat. ring opening compared to arenes

S O

heterocycles

NNH

NO2H2N

O2N

4-amino-3,5-dinitropyrazole(LLM-116)

NHN

O2N

NO22,4-dinitroimidazole

(2,4-DNI)

N

NO

furazans/benzofurazansfuroxans/benzofuroxans

O

Hexanitrohexa-azaisowurtzitane(HNIW or CL-20)(VOD=9380 m/s)Si-PETN

novel energetic nitrate eseter

3,3-bis(difluoroamino)octahydro-1,5,7,7-

tetranitro-1,5-diazocine(TNFX)

NN

NH

H2N

NO2N

HN

NH

O2N ONN

N

Ar

N N

O ArAr

1,3,4-oxadiazoles 3-nitro-1,2,4-triazol-5-one(NTO)

O2N

NO2

benzotriazolesN

NN

NH

H2N

N

O2N

H2N

NO2

NH2

NH2 N

NO2N

H2N

NO2

NH2

O O

O

N

N N

N

NH2

NH2

O

O

tetrazoles 1,2,4 triazolespyridine N-oxide tetrazine N-oxidepyrazine N-oxide

H-bondingreduction insensativity


Routes to C-Nitro functionality

Nitration chemistry

Borgardt et al. Chem Rev 1964. 64, 19 (polynitro functionality)

The 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.

Direct nitration of aliphatic and alicyclic hydrocarbons possible in the vaporphase using HNO3 or NO2 (toxic redish-brown gas) at elevated temperatures.

Me

NO2H

Me

HNO3

25% Me

NO2

MeNitration with HNO3 is difficult

Me

MeMe

Me

N2O4

N NO

OO

O

+

O2N

NO2H

Me

NO2

Me

O2N

MeMeMe

ONO

Me

O2N

MeMeMe

ONO2

Me

O2N

MeMe

nitro-nitratenitro-nitritedinitro

+

- colorless liquid

Radical methods

Ph1 atm NO

DCE/ rtPh

NO2Ph

NO2

OH

76% 23%

+

Mukaiyama et al. Chem Lett 1995. 505

Al2O3

PhNO2

92%

R

HH

R

R

NO2H

RH

R

NO2H

RH

R

NO2H

R80 - 90%

NaNO3 xs,CAN 2eq

AcOH/CHCl3

Hwu et al. J Chem Soc Chem Commun 1994. 1425Taniguchi et al. JOC 2010. 75, 8126

R

R

R NO2

ClRFe(NO3)3 9H2OFeCl3

MeCN, reflx

N

Cl

N

CO2R

KNO3

H2SO4

TBAN

Ph MeCNNO2BF4

Ph

NHAc

NO2

84%

80 - 90%

S

Br1. nBuLi2. N2O4 -78 °C

S

NO2

TMS AcONO2 NO2

NO2O2N

O2N NO2

1. NaHMDS2. N2O4

NO2O2N

O2N NO2

NO2O2N

O2N NO2

NO2O2N

O2N NO2

NO2

N

Cl

N

CO2R

N

Cl

N

CO2R

NO2

O2N

traditional[NO2

+]

F3C O

O

CF3

OTFAA

F3C O

O

NO2

TBAN * No rxn inpresence ofTEMPO

TMS

O

NO

[2+2]_ OAc

NO2+

NO2

O

NO

_ OAcNO2

ON

O

OAc

Nef

O

ONO2

AcONO2

ONO2

NO2NO2

alkaline nitration

NItration selectivity on arene/heteroarene

76%

44%

77%

Kakiuchi, et al. Synlett 1999. 901

74%


Victor 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/light

modified VM (alkali metal nitrites e.g. NaNO2) time and solubility is VIMP

Kornblum et al. JACS 1956. 78, 1497

NO2

R

RO

R

R+

NaNO2 NO2

R

ROH

R

RNO

OH

HO OHphloroglucinol

N O

nitrite ester

1° and 2° nitro compounds

oxidation of isocyanates

O NOH

ONO2H

1.KOtBuamyl nitrate2. H+

1. NBS2. [O]3. [H]

NO2

CF3CO3HN

O OHNO2

O2N NO2S2O8 2-

H+

NO2O2NNO2+

C+H3N

C+H3NNH3+C

NH3+Cl-

NCO

OCN

NO2

O2N

O2N

O2NNO2

NO2

F NO2

NO2NO2

O2N NO2

NO2NO2 (or)

NO2

F NO2

NO2

CO2HR

R

HNO3

20 - 30%

R

R

NO2

NO2MeO2C CO2H

HNO3

60 % MeO2C NO2

NO2

oxidation of amines

Synthesis of an energetic nitrate ester ONO2

ONO2

O2NO

O2NO

NO2

NO2Chavez, D.E. et al. Angew. 2008, 47, 8307

Original Target/Route via modified Kaplan Shechter Rxn

NHO

O

NO2

MeMe

NN

N

NHN

O

OMe

Me

O

O O

OMe

Me NO2

OH

R1 R2

NO2 N

R1 R2

OONaOH 1. NaNO2

2. AgNO3 R1 R2

NO2O2N

N

R1 R2

OO

NO

O Na

R1 R2

NN O

O

O

OAg+

R1 R2

NN O

O

O

OAg

R1 R2

NN O

O

O

O-Ag0

Ag0

Ag+

nitronate

-CH2O

retroaldol

NO O

NHO

O

N

MeMe

NN

N

NH

OO

NHO

O

N

MeMe

NN

N

NH

OO

Fe

activation [O]NH

R

R

N

NN

N

NH

OO

DMDOAcetone/H2O

85%

DMDOAcetone

91%

gem-dinitros from acids

Fluorotrinitromethane

R XN

O

OAg+ ether

R NO2 R ONO+ AgX

O O

O NO

OR

slowXR

R

fast

NaNO2DMSO

NO2

R

RH+

Eaton et al. JOC 1988. 5353

NO2O2N

NO2+

(low yields) KaplanShechter Rxn

via amine thusH2O essential

only usefuloxidant


+

Routes to O-Nitro functionalityInitial Results: homocoupled product

HO

HO

NO2

OHH2N

N N

NHN

1.cat. K3[Fe(CN)6] Na2S2O8

1. 2-methoxypropene cat. H+

X

O

O

NO2

MeMe

O

O

NO2

MeMe

O

O

NO2

MeMe

12%NH

NN

N

NH

2. NaOH NO

OMe

Me

O

O

N

O O

MeMe

OON

O O

MeMe

OO

O

O

N

MeMe

OO

NO O

Fe

O

O

N

MeMe

O O

O

O

N

MeMe

OO

O

OMe

Me

activation

O OSO3Na

NaO3S

FeNC

CN

CN

OSO3Na

NC

NC

-NaSO4-

+CN-FeNC

CN

CN

CN

NC

NC

- CN-

O

O

NO2

MeMe

O

O

NO2

MeMe

65% optimized

1.HCl, MeOH

2. Ac2O/HNO3

O2NO

O2NO

NO2

ONO2

ONO2

NO272% (2 steps)

- Use of mixed acids (esterification) and nitrogen oxides described for C-NitraionKey points:1. fuming (anhydrous) HNO3 prep: dry air bubbled through anhydrous HNO3 to remove any oxides of nitrogen present, followed by addition of trace urea to remove any nitrous acid present. AKA "white nitric acid"2. Urea destruction of nitrous acid important to avoid violent fume-off3. O-nitrations with mixed acids of "white nitric acid" above ambient temperatures is dangerous and has increase risk of explosion4. anhydrous HNO3/Ac2O- Acetyl nitrate is generally a weak nitrating agent but in the presence of a strong acid like HNO3, ionization to nitronium ion occurs

NO2

HO

HO

NO2

OH

OHanh HNO3Ac2O

90% HNO3Ac2O

NO2

HO

O2NO

NO2

OH

ONO2

NO2

O2NO

O2NO

NO2

ONO2

ONO2

70%90%

shock sensative

Transfer nitration (neutral conditions - good for acid sensative alcohols)

OH

OH

N

Me

Me MeNO2

ONO2

ONO2N

Me

Me MeH

BF4-

BF4-2 eq

Olah G.A. et al JOC, 1965. 30, 3373

works for 1°, 2°, 3° alcohols

in situ halide displacement with AgNO3

R OHPPh3, I2

R IAgNO3

R ONO2

Low yields for 2°HgNO3 can be used for 2° and3° alkyl halide displacements

decomposition of nitrocarbonates (very mild, rt or reflux MeCN)

RO

O

Cl RO

O

ONO2

AgNO3

PyR ONO2

-AgCl

-CO2

O

O

(or)

ring opening of strained oxygen heterocycles

N2O4

CH2Cl2ONO

ONO2[O]

H2O HOONO2

O2NOONO2

20,164 MPH!!

ONO2

ONO2O2NO

O2NO

comparable stability to PETN

N N

NNO2N

O2N

NO2

NO2

N2O5

CHEETAH calculates as powerful as HMX

m.p. 86 °CDet.Temp

140 °C MeCNquant yield

80%


Routes to N-Nitro functionality

nitrodesilylation deamination

R NH2 R ONO2

NO2F

MeCNRO SiR3 RO ONO2

N2O5

CH2Cl2+ O2NO SiR3

- Compounds resulting from nitration of nitrogen are of far less use for mainstream organic synthesis. However the N-NO2 group is an important 'explosophore' and is present in many enrgetic materials

selective O-nitrations

HO

OH

OH

1 eq SOCl(NO3)

2 eq SOCl(NO3)

3 eq SOCl(NO3) O2NO

ONO2

ONO2

O2NO

OH

ONO2

HO

OH

ONO265%

70%

100%

HN NO

O

H+R OH + N2O

- Direct nitration of a 1° amine to a nitramine using HNO3/mixed acids is not possible due to instability of the tautomeric isonitramine in strongly acidic conditions. 2° amines are more stable and can undergo electrophilic nitration using HNO3/Ac2O

R

2° w/ HNO3/Ac2O

N CNNC

N

MeN

Me

NO2NO2

NO2

93% 22% 6%analines - must contain one or more nitro groups on the aromatic ring

How to get around this problem??- synthesis via condensation chemistry (Mannich, 1,4 addition, etc)

What about if need more direct method??-non-acidic nitrating reagents (nucleophilic nitration)

-chloride ion catalysis

- Nitrolysis of fully substituted nitrogen

R NH2nBuLi-78 °C R NHLi

Et ONO2R N N

OLi

H+R NH

NO2

Ar NH21. Na2. EtONO2

Ar NH2 Ar N NONa

H+Ar NH

NO2

EtONO2Na+-

anhydrous ZnCl2, hydrochloride salt of amine, or dissolved HCl(g) can serveas a source of electropositive chloride under the oxidizing conditions of nitration

2 HCl + 2HNO3 + 3Ac2O 2AcOCl + N2O3 + 4AcOH

AcOCl + R2NH R2NCl + AcOH

R2NCl + HNO3 + Ac2O R2NNO2 + AcOCl + AcOH

Wright et al. Can. J. Res. 1948. 26B, 294

HNO3/Ac2O(w/o chloride)

N CNNC

NO2

93%N

NC CNX

HNO3/Ac2OR = H

NNC CN

HNO3/Ac2OR = Cl- (N+)

R

NO2

70%

Ease of alkyl nitrolysis depends on stability of the resulting cation:benzyl, tertiary (t-Bu), etc...

R NH22 HOCl R NCl2

HNO3/Ac2OR N

NO2

ClR NHNO2

NaHSO3 (aq)

rupture of C−N bond leading to formation on N−NO2

R1 N

O

R2

R2

A

B

Path A

Path B

R1 CO2HNR2

R2

O2N+

R1 N

O

NO2

R2

R2 OH+

Nitramine formation via nitrolysis possible from:

R1N

R1

Ph

R2N NR2R1 N

O

R2

R2

- carbamate- urea- formamide- acetamide- sulfonamide

R1N

R1

Ph

NO2NO2

+

R2N SiR3

R2N NO

O

O

N NOH

OR


Synthesis of Hexanitrohexaazaisowurtzitane (HNIW)

- Many nitramines are more powerful than aromatic C-nitro compounds and have high brisance and high chemical stability and low sensativity to impact and friction compared to nitrate ester explosives. This is why they are of interest to military applications.

Syntheses of some nitramine explosives

OH OHO O

NNs NNs

O O

NNs NNs

NOH

O O

NNs NNs

O

N N NsNs

NO2O2N

F2N NF2

NO2O2N

N N NO2O2N

F2N NF2

NO2O2N

TNFX(3,3 bis(difluoroamino)octahydro1,5,7,7 tetranitro 1,5 diazocine)

NH2

HO OH

OH

NH3+Br-

Br Br

Br N

Br

N

NO

CH2BrO2N

N

NO2

CH2BrO2N

N

NO2

NO2O2N

HBr-AcOH160 °C72%

NaOH, 80 °C60 mmHg

1. NaNO2 (aq)2. HCl (aq)

10%

HNO3/TFAA

81%

1. NaHCO3, NaI DMSO, 100 °C

2. NaNO2, NaOHK3Fe(CN)6, K2S2O8

29% (2 steps)TNAZ

NsCl,K2CO3 (aq)

95%

1. CrO3, AcOH2. HOCH2CH2OH TsOH

82% (2 steps)

NH2 NH2 NNs NNs NNs NNs

Br BrK2CO3

76%

1. O3, CH2Cl22. DMS

3. NH2OH/NaOAc86% (3 steps)

1. HNO3/NH4NO3 urea, 33%

2. H2SO492%

F2NSO3H,HNF2, H2SO4,CFCl3

90%

HNO3/SbF6

CF3SO3H

NH2

Ph H

O

O

H+

2 eq.

MeCN/H2Ocat. H+

N

N

N

NN

N

Bn Bn Bn

BnBnBn

N NN N

NN

BnBn

Bn

Bn

Bn Bn

NO2+

messy. Nitration of aromatic rings

XN

Ph[O]

N

PhO Ac2O

N

MeO

N

PhCrO3

N

PhO

H2,[Pd]

decomp.

X

N NN N

NN

BnBn

Bn

Bn

Bn Bn

H2, Pd(OAc)2

Ac2O, PhBr cat.

N NN N

NN

Ac

Ac

Ac

Ac

Bn Bn65%

N NN N

NN

NO2

NO2

O2NO2N

O2N NO2

1. N2O42. HNO3/H2SO4

via nitroso93%

H2,[Pd]

N NN N

NHHN

Ac

Ac

Ac

Ac

DANGER!

1. HCO2H

2. Ph, Δ -H2O

N NN N

NCHOOHCN

Ac

Ac

Ac

Ac

99% HNO3N N

N N

NN

NO2

NO2

O2NO2N

O2N NO2

HNIW 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 stress still greater stability than nitrocellulose, PETN and others.- 4 different polymprphs with different densities/properties


N2O5

N2O5O

NN

O

O

O

O[NO2

+][NO3-] - adopts two structures

depending on conditionpolarsublime slightly above rt

non-acidic nitrating reagents (neutral)1° amines/nitramines leads to deamination and formation of nitrate esterby-product but analines are successful.

- 1st prepared over 150 years ago but due to difficult prep and low thermal stability (require -60 °C long term storage) received little attention.- Environmental restrictions and push for green chemistry sparked interest

Advantage: 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)

condition: anhyd. HNO3- powerful but acidic and non-selective

condition: chlorinated solvents- clean and selective- non-oxidizing &n non-acidic

N2O5 2 N2O4 + O2rt Stable for 2 weeks at -20 °C

Stable for up to 1 yr at -60 °C

nitronium nitrate salt

No single nitrating agent is as diverse and versatileIt is considered as the future for energetic materials synthesis

Preparation of N2O5 [Deville 1849]AgNO3 + Cl2 (g)

ON

Cl

O+ AgNO3 N2O5

Dehydration of nitric acidHNO3 + P2O5 N2O5 + H3PO4

- 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)

O3N2O4Δ N2O5

Process 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).

Me

NO2

NO2

N2O5/HNO3

32 °C,quant yield

Me

NO2

NO2

O2N

No explosion hazard

NH

HN

HN

NH

OON

HNN

NH

OO

O2N

NO2

N

NN

NOO

O2N

NO2

NO2

O2N

HNO3

P2O5

HNO3

H2SO4

N-nitrations of ureas

HO

OH

OH

OH

OH

OHN2O5, CCl4

0 °Cquant yield

O2NO

ONO2

ONO2

ONO2

ONO2

ONO2

synthesis of TNT under mild conditions

O-nitrations of polyols

Klapotke T.M. JACS 2007. 129, 6908

O2NO ONO2

O2NO

ONO2PETN- Det. Velocity 8,400 m/s- d= 1.7 g/cm3

- 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 NG

SiO2NO ONO2

O2NO

ONO2

Silicon analogue of PETN

Si(CH2OAc)4 Si(CH2Cl)4

"The crystalline compound exploded on everyoccasion upon contact with Teflon spatula...Solutions in diethyl ether exploded upon the slighestevaporation of the solvent."

Explosives in JACS: Sila explosives

Why 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 a molecule, the more stable it is to impact.

Si ON

O

O2NO

O2NO

O2NO O

VERYlow e- dens

VERY high e- dens

r.a. rodriguez chemistry of high energy materials · explosives non-explosive materials ... 1°...

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