things that go boom

THINGS THAT GO BOOMOXYGEN BALANCE, OXIDIZERS, PEROXIDES, PEROXIDE FORMERS

BOOM! SOME DEFINITIONS

• BLEVE

• EXPLOSION

• EXPLOSIVES

• DEFLAGRATION

• DETONATION

BLEVEBoiling Liquid Expanding Vapor Explosion

EXPLOSION & EXPLOSIVES• EXPLOSION - Sudden release of

energy and an increase in volume – may involve generation of high temperatures and release of gas

• EXPLOSIVES – any chemical compound, when heated, impacted, detonated or initiated that will undergo change evolving large amounts of gas

DEFLAGRATION VS DETONATION• Deflagration

• Low explosives• subsonic explosion driven by heat transfer • “slow burning”

• Detonation• High explosives• Supersonic explosion – breaks the sound barrier• Supersonic shock wave

WHAT CAUSES EXPLOSIONS?• Oxidizing agents/Oxidants

• Gases – Cl , F , N2O , O2 , O3- , Steam

• Liquids – Br , H2O2 , HNO3 , HClO4 , H2SO4 , ClO-

• Solids – BrO3- , ClO3

- , ClO2- , CrO4

2− , Cr2O72− , IO3

- , I2O5 , NO₃− , NO₂− , ClO₄ , O2

2- , MnO4− , Picrates

OXIDANTS/OXIDIZERS

• A substance that removes electrons from another reactant in a REDOX chemical reaction.

• Primary hazard of oxidants/oxidizers are their ability to combust or initiate combustion.

• “The dangerous materials definition of an oxidizing agent is a substance that is not necessarily combustible, but may, generally by yielding oxygen, cause or contribute to the combustion of other material”.

OXIDIZER HAZARDS• Incidents must be handled promptly

• Hazards of stored oxidizers:

Increase the burn rate of combustible materialscause spontaneous ignition of combustible materialscan decompose rapidlycan liberate hazardous gasescan undergo self-sustained decomposition which can result in explosion!can react explosively if mixed with incompatibles or in fire conditions

OXIDIZER CLASSES• Class 1: An oxidizer that does not moderately increase the burning rate of the

combustible materials with which it comes into contact

• Class 2: An oxidizer that causes a moderate increase in the burning rate of combustible materials with which it comes into contact

• Class 3: An oxidizer that causes a severe increase in the burning rate of combustible materials with which it comes into contact

• Class 4: An oxidizer that can undergo an explosive reaction due to contamination or exposure to thermal or physical shock and that causes a severe increase in the burning rate of combustible materials with which it comes into contact

OXYGEN BALANCE• Just how explosive is it?

• O.B. = -1600[(2x) + (y/2) + Met – z] M.W.

Where:X = # CarbonsY = # HydrogensZ = # OxygensMet = # metals (if no metal present then “0”)M.W. = Molecular Weight

• Compound must also contain a potentially reactive group• Empirical formula is used to determine # of C, H, O, Met

IT’S A POTENTIALLY EXPLOSIVE MOLECULE IF…

…it has enough oxygen to convert…

1) All of the carbon into carbon dioxide

2) All of the hydrogen into water

3) All of the metal into metal oxide

THEN it is said to have ZERO OXYGEN BALANCE

When MORE oxygen is present than is used it is said to have (+) oxygen balance.When LESS oxygen is present than can be used it is said to have (-) oxygen balance.

SENSITIVITY, STRENGTH, BRISANCE

• SENSITIVITY - is the degree to which an explosive can be initiated by impact, heat, or friction.

• STRENGTH - is the parameter determining the ability of the explosive to move the surrounding material. It is related to the total gas yield of the reaction, and the amount of heat produced.

• BRISANCE - is the shattering capability of a high explosive, determined mainly by its detonation pressure.

OXBAL & BOOM-ABILITY• SENSITIVITY, STRENGTH & BRISANCE

are ALL somewhat dependent upon Oxygen Balance (OxBal).Compounds approach optimum explosivity (BOOM-ability) as the OxBal approaches ZERO

• Though OxBal can be calculate remember….it is an ASSESSMENT tool onlyit is used to gauge the POTENTIAL to explode NOT as a predictor of explosivity.

• OxBal %’s between -200 and +200 have a higher chance of explosive potentialthe closer to “0” the “better” i.e. more explosive potential

ACETONE VS ACETONE DIPEROXIDE

Acetone Acetone diperoxide

C3H6O = MW = 58.08g/mol

OxBal = -220.38

Has no metals or potentially reactive groups

C6H12O4 Empirical formula = C3H6O2MW = 148.16g/mol

OxBal = -75.58

Has no metals but DOES have potentially reactive groups. i.e. Peroxides

SPEAKING OF PEROXIDES• Contain the O-O linkage which is inherently unstable

• Largest class of peroxides are the organic peroxides or hydroperoxides

R-O-O-R’ Organoperoxides R-O-O-H Hydroperoxides

• Prone to decompose violently from:• Shock weak O-O bond ~ 207 kJ/mole• Friction compared to C-C bond ~345 kJ/mole• Heat Dissociation products are free radicals and highly reactive

PEROXIDE USESMaking polymers – peroxides decompose and generate radicals that initiate

polymerization

• Very diluted peroxide initiators• heat of decomposition is easily absorbed in the surrounding matrix (like a

heat sink)

HOWEVER – in a pure, concentrated form, heat evolved from decomposition may not dissipate efficiently

As TEMP REACTION RATE

SELF-ACCELERATING DECOMPOSITION

AUTOXIDATION – FREE RADICAL CHAIN PROCESS

• 3 STAGES

• CHAIN INITIATION – some event initiates such as exposure to light or random interaction with O2 or an impurity is introduced and radicals are formed

• PROPAGATION – the cycle continues as new radicals act as initiators and propagate hydroperoxides

• TERMINATION – reactions occur where the free radicals collide and combine odd electrons to form new bonds…..

…Unless it EXPLODES!

AUTOXIDATION FREE RADICAL CHAIN PROCESS

HYDROPEROXIDE

this process will perpetuate as long as O2 is present or it explodes

PEROXIDE FORMERS• Are compounds that themselves are not peroxides, however, through free-

radical, autoxidation, H-abstraction process involving molecular oxygen peroxides are formed

• Initiated by light, a radical generator or a peroxide contaminant

• A cyclic process almost identical to peroxide decomposition autoxidation process however converts a NON-peroxide into a peroxide.

• The most common are organic compounds but there are some inorganic compounds.

METHYL ETHYL ETHER TO A HYDROPEROXIDE

PEROXIDE FORMING MOIETIESListed from “most” likely to “least” likely to form dangerous peroxides

TOP THREE PEROXIDE FORMING MOIETIES

Ethers & Acetals w/a-hydrogenHydrogen attached to an alpha carbon is called an alpha-hydrogen

Alkenes with allylichydrogen

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Allylic hydrogen is a hydrogen atom that is bonded to an allylic carbon in an organic molecule

Chloroalkenes &Fluoroalkenes

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MORE MOIETIES


Vinyl alkynes (vinylacetylene) with a- hydrogens


Alkylalkynes with a- hydrogens


Alkylarenes with tertiary a- hydrogens

Dienes (divinyls)

Alkanes and cycloalkanes with tertiary hydrogen

Acrylates & methylacrylates Secondary alcohols

Ketones with a- hydrogens

Aldehydes Ureas, amides and tactams with a- hydrogens on a carbon attached to a nitrogen.

CLASSES OF PEROXIDIZABLE COMPOUNDS

CLASS A

CLASS B

CLASS C

PEROXIDE FORMER INHIBITER


BHT- Butylhydroxytoluene, also a food preservative. Follows the same general “path” as an you see in the autoxidation of peroxide formers HOWEVER, after H-abstraction from the BHT to the radical the BHT radical ends the chain reaction due to stearic hindrance.

EVALUATING AND TESTING FOR PEROXIDES

EXAMINE FOR VISIBLE CRYSTALS

Crystals? DON’T TOUCH!

The crystals may cause an explosion if subjected to an impact or friction.

Never underestimate a peroxide formers ability to explode!

IS IT SAFE TO TEST FOR PEROXIDES?


Otherwise you may test if:

• Low peroxide hazard chemicals – previously opened container less than 2 years old or unopened less than 3 years old.

• Medium peroxide hazard chemicals – previously opened container less than 1 year old or unopened less than 2 years old

• High peroxide hazard chemicals – previously opened container less than 6 months old or unopened less than 1 year old.

NOTE: If it’s not safe to test due to crystals or <10% volume this is a BOMB SQUAD job.

If the contents have evaporated to less than 10% of original volume….DO NOT TEST!

TESTING FOR PEROXIDES• Color-metric test strips

• Detect inorganic and organic compounds that contain a peroxide or hydroperoxide group

• Suitable for routine testing of simple ethers such as Diethyl ether, THF, and p-dioxane.

• Iodine Test

• Suitable for testing ay peroxide forming chemical

• Test Mixture: A 1:100 part solution of potassium iodide and glacial acetic acid

• Test 1 ml of chemical with 1 ml of text mixture.

Pale yellow almost colorless ~ 0.001-0.005% peroxides

Bright yellow or brown ~ 0.01% or greater

STABALIZING PEROXIDE FORMERS

• ~ 0.001-0.005% peroxides in solution

• May be moved for stabilization

• 1g of BHT (Butylated hydroxytoluene) per liter of chemical.

• Date when stabilized on container

• ~ 0.01% or greater peroxides in solution

• DO NOT MOVE! Stabilize before moving.

• 1g of BHT per liter of chemical.

• Date when stabilized on container

Methods for destruction of peroxides for HAZARDOUS MATERIALS personnel*Which one you pick depends on knowing the chemical properties of the material and any possible incompatibilities with the materials used to treat the peroxides. Either of these two methods would be a good choice for diethyl ether, for example.

Ferrous sulfate reductionAdd 6 g of ferrous sulfate, FeSO4, and 6 mL of concentrated sulfuric acid, H2SO4, to 110 mL of water. Shake or mix well. Caution: always add acid to water, not vice-versa.Shake approximately 1 liter of the peroxide-contaminated material in a bottle or separatory funnel with 5-10 mL of your ferrous sulfate solution.Remove and discard the aqueous layer. Wash/shake your solution with distilled water and discard the aqueous layer. Repeat your peroxide test on your material. Repeat step 2 as necessary until the test is negative for peroxides.

Activated alumina adsorptionPass your contaminated material through a standard chromatography column packed with activated alumina (Al2O3). Allow approximately 80 g of alumina per 700 mL of material.Test the purified material. Repeat step 1 as necessary until you get a negative peroxide test.Caution: the peroxides will remain on the alumina in active form. Wash your alumina with the FeSO4 solution described in method A above before disposing or reusing your alumina. Do not combine it with other wastes if you (foolishly) decide not to treat the alumina before disposal.

Note that destruction of high level of peroxides is a procedure fraught with peril and risk of bodily injury, including death.

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