Explosions 10

Question 1

Why do we need new explosive materials?

Answer 1

• Many current explosives aren’t very ‘clean’ - give detonation products that arent environmentally friendly
• Can get more complicated products in true detonations
• Explosives with a higher nitrogen content generally reduce the production of CO/C

Question 2

What properties can we change to make different properties?

Answer 2

• Crsytal packing - can manipulate the sability by changing this
• Stability
• Detonation products
• Tagging - stop them being used in an illicit manner

Question 3

What are some examples of energetic groups and what do they do?

Answer 3

Give the explosive more power - more sensitive
* Nitro groups
* Azide groups
* Alkine groups
* High ring strain (lots of chemical energy)
* Aromatic ring with lots of nitrogens

Question 4

What are some examples of stabilising groups and what do they do?

Answer 4

Stabilise the explosive so that it doesnt detonate accidentally
* Benzene ring/aromatic rings
* Amine groups

Question 5

What is the PPE required for explosive reseach labs?

Answer 5

• Helmet
• Face Shield
• Leather coat
• Kevlar gloves
• Kevlar suit
• Blast shield

Question 6

Why is a small amount of explosive tested on in research labs and what is this amount?

Answer 6

< 500 mg of explosive
* Dont know how it will expload
* Dont know the detonation products

Question 7

Which of these analytical techniques would be the best to determine if the oxygen balance predicted products are correct?
a) FTIR
b) NMR
c) GC-MS
d) LC-MS
e) Ion Chromatography

Answer 7

FTIR in the gas phase because it looks at small molecules and can differentiate those (CO, H2O, CO2, N2)
* NMR - too complex preparation to use
* GC-MS - cant separate those types of products easily (MS is good for giving molecular ion but GC isnt)
* LC-MS - not useful when we are forming gases
* Ion Chromatography - not forming ions or in a condensed phase

Question 8

What can be seen from FTIR spectras about slightly reactants?

Answer 8

• Detonation products are more complex than modelled with the oxygen balance
• Correlation between less negative oxygen balances and a more clean decomposition
• Two compounds with identical oxygen balances have different products
• Further supporting that testing needs to be done to know the products and how they behave

Question 9

Influence of oxygen balance on stability

Answer 9

• Less negative oxygen balance the more sensitive
• Crystal packing (density) is also a factor as two compounds could have the same oxygen balance but if one is less dense it will be less sensitive
• Most sensitive has a higher density

Question 10

How does crystal packing affect stability?

Answer 10

• The use of explosive salts can control the crystal packing (hard to predict however)
• e.g. Ag+ can easily pack to make the compound more dense and so less sensitive
• However changing to a NH2+ salt creates loads of space (lower density) and much more sensitive
• XRD is useful to look at the crystal packing

Question 11

How does the stability of nitrogen containing compounds change?

Answer 11

• There is a limit to the stability achievable with nitrogen based explosives
• N-N are the least stable, then N=N and then N≡N being the most stable (enthalpically favourable)
• Want to maximise the number of N=N and N≡N but this is synthetically challenging
• Combination of kinetic and thermodynamic stability

Question 12

What is stereochemsitry and regiochemsitry?

Answer 12

Stereochemsitry: each of two or more compounds differing only in the spatial arrangement of their atoms.
Regiochemsitry: same molecular chemsitry but different connectivity

Question 13

How does Stereochemistry/Regiochemistry affect explosives?

Answer 13

• Changes the properties
• Have different sensitivites and melting points

Question 14

What are the desired properties for new explosives?

Answer 14

• Melting point
• Sensitivity
• Explosive power
• Tunability