lecture topic 5: inorganic chemistry and industry ref: “inorganic chemistry: an industrial and...

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Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise: Inorganic chemistry is extremely important for many industries, but there are a handful of reactions which are of primary importance to the Chemical Industry. Goal: Students should be able to 1) describe recovery processes and uses of the most common elements 2) discuss the chemistry of atmospheric pollution

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Page 1: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Lecture Topic 5:Inorganic Chemistry and Industry

Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle

Premise: Inorganic chemistry is extremely important for many industries, but there are a handful of reactions which are of primary importance to the Chemical Industry.

Goal: Students should be able to

1) describe recovery processes and uses of the most common elements

2) discuss the chemistry of atmospheric pollution

3) discuss the chemistry of pulp and paper processing

4) describe the synthesis of NH3 and H2SO4.

Page 2: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Most Abundant Elements in the Earth’s Crust

Element Atom % Weight % Element Atom % Weight %

O 62.6 46.6 Ti 0.20 0.44

Si 21.2 27.7 F 0.091 0.080

Al 6.47 8.1 P 0.083 0.12

Na 2.64 2.8 C 0.057 0.032

Ca 1.95 3.6 Mn 0.038 0.10

Fe 1.94 5.0 S 0.034 0.052

Mg 1.84 2.1 Cl 0.030 0.048

K 1.42 2.6 Li 0.021 0.007

Page 3: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

OxygenOccurrence • large amounts in Earth’s crust (oxides of other elements)• 21% of atmosphere (as O2 and O3)

Recovery• by fractional distillation of air

Industrial Uses

1) Sewage Treatment: In the “activated sludge process”, sludge is oxygenated and biodegraded by aerobic bacteria.

2) Steelmaking: Impurities are removed by blowing O2 over molten iron to generate “slag”, a layer of oxides that floats atop the Fe(l).In the U.S., ~3million metric tons of O2 are used annually for this.

Page 4: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

NitrogenOccurrence • most abundant element in the atmosphere (N2)• very low abundance in Earth’s crustal rocks

Recovery• by fractional distillation of air

Industrial Uses• fertilizers (nitrates, ammonia, ammonium salts, and urea)• propellants and explosives (nitro-organics, nitrates, hydrazines)

Most Important Industrial Reaction• the Haber process for the production of ammonia (NH3)

Page 5: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Nitrogen for Fertilizers

Ammonia (NH3) prepared using the Haber process is

1) transported in liquid form by truck, barge and pipeline

2) often injected directly into soil (15-30 cm deep)

3) corrosive to the flesh

4) explosive with air at a 16-25% NH3 concentration

5) commonly converted to ammonium sulfate (NH4)2SO4, ammonium nitrate NH4NO3, or

urea (H2N)2CO for safe shipment, storage and use.

The relatively inert N2 of the atmosphere must be “fixed” as soluble reactive compounds….bioavailable compounds.

Page 6: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Nitrogen for FertilizersUrea :

1) is made by reaction of ammonia and the CO2 by-product of the water-gas shift reaction.

2) can be produced in forms that release nitrogen slowly to the soil:

a) “SCU” fertilizers are urea pellets coated with ~2% paraffin wax containing S8 that oxidizes away slowly in the soil.

b) Urea-formaldehyde (UF) polymers decompose slowly in the ground.

CO2 + 2NH3 NH4[CO2NH2]

urea

150 bars200C

+ H2O

ammonium carbamate

O

H2N NH2

Ammonium sulfate:

is a safe form of ammonia for shipping, storage and use.

2NH3(g) + H2SO4(aq) [NH4]2[SO4]

ammonium sulfate

Page 7: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Nitrogen for FertilizersNitric Acid and Ammonium Nitrate :

1) The catalytic oxidation of ammonia by air over Pt gauze at ~900°C gives nitric oxide (NO2) which is then converted to nitric

acid by air and H2O(l) to give the net reaction:

2) Nitric acid is converted on-site to ammonium nitrate :

3) NH4NO3 is potentially explosive!!

4) Calcium carbonate CaCO3 (chalk, limestone) can be added to solid NH4NO3 to form a non-explosive product.

5) NH4NO3 can be stored safely as a dilute aqueous solution.

6) 3% clay can be added as a drying agent to prevent caking (34-0-0)

NH3 + 2O2 HNO3 + H2O(l)nitric acid

HNO3 + NH3nitric acid

[NH4][NO3]ammonium nitrate

Page 8: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Nitrogen for Explosives and PropellantsExplosives and propellants are an important industrial technology for:

• safety projects (airbags, ejector seats, avalanche control)• civil engineering projects (highways, dams, waterways, etc.)• mining and quarrying• aerospace projects (launch technology)

There are 2 requirements for a material to be an explosive:

1. Decomposition or combustion must be highly exothermic.2. Hot reaction products must be gaseous.

The high bond energy of the NN triple bond explains the tendency of N-containing compounds to decompose exothermically to N2(g).

Airport security units use Neutron Activation Analysis to detect high nitrogen content.

Page 9: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Nitrogen for Explosives and Propellants

Ammonium Nitrate :

1) is the most commonly used blasting explosive

2) gentle heating to its melting point (170°C) gives nitrous oxide:

3) @ T>250°C, or when shocked, violent decomposition to N2 :

4) is commonly mixed with an oxidizable substance (fuel oil) for legitimate use as a relatively safe and inexpensive explosive.

NH4NO3 N2 + 2H2O + 0.5O2 explosive!

NH4NO3 N2O + 2H2O

nitrous oxide (laughing gas)

Page 10: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Nitrogen for Explosives and Propellants

Potassium Nitrate, KNO3 (Saltpeter) :

Used for black powder : (41% KNO3, 29.5% C, 29.5% S): for firearms (before guncotton)

(75% KNO3 15% C, 10% S): for fireworks, time fuses etc.

Hydrazine, H2NNH2, and dimethylhydrazine, (CH3)2NNH2 :

Used for rocket propellants : The hydrazine is oxidized by H2O2, O2(l), or F2(l).

Page 11: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Nitrogen for Explosives and PropellantsNitro-containing organic compounds : R-NO2

1) are the most common commercial high explosives

2) Nitro groups can oxidize the C content to CO or CO2 and the H content to H2O….increases exothermicity and gas volume.

CH3

NO2

NO2O2N

trinitrotoluene (TNT)

NO2

O2N NO2

trinitrocyclohexane(RDX or cyclonite)

O

O

O

O

NO2

O2N

NO2

NO2

pentaerythritol tetranitrate (PETN)

O

O

NO2

ONO2

O2N

nitroglycerine

HNNH NO2O2N

ethylene dinitramine (EDNA or haleite)

NO2

O2N NO2

O OPb2+

lead styphnate

Page 12: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

A Word on Nitrogen OxidesNitrogen oxides are widely implicated as air pollutants.

Nitrous oxide, N2O :

1) is a colourless, odourless, non-toxic gas

2) is produced: a) by degradation of nitrate fertilizers

b) as a by-product of nylon production

3) is used as an anaesthetic (laughing gas) and as a propellant (whipped-cream spray cans)

4) is implicated in greenhouse warming….has a residence time in the atmosphere of 150 years and could contribute up to 10% of the anticipated greenhouse warming.

5) in the stratosphere, reacts with the 1D excited state of atomic oxygen to generate nitric oxide. N2O + O(1D) 2NO

Page 13: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

A Word on Nitrogen Oxides“NOx” : NO, NO2, N2O4

1) NO….Nitric oxide is a toxic, colourless gas.

Very endothermic (ΔH° = +180.6 kJ/mol), BUT equilibrium rapidly established.

When air is heated to very high T, small amount of NO is made. If it is then quenched to T<1000K, the NO is “frozen in”. This is what happens in combustion engines!

2) NO2….Nitrogen dioxide is a toxic, brown gas.

NO reacts rapidly with O2 from air.

3) N2O4….Dinitrogen tetroxide is a yellow liquid (b.p. = 21°C @1bar)

Dimerization of NO2.

N2 + O2 2NO

2NO + O2 2NO2

NO + O3 NO2 + O2

2NO2 N2O4

Page 14: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

A Word on Nitrogen Oxides“NOx” : NO, NO2, N2O4

4) Acid precipiation: NO2 in the troposphere reacts with hydroxyl radicals (•OH, produced indirectly from ozone pollution) to form nitric acid.

5) Photochemical smog: a white aerosol that is intensely irritating to eyes and mucous membranes.

The chemistry of photochemical smog is complex (>50 rxns!)Involves photochemical reaction of NOx with unburned hydrocarbons to generate peroxyacyl nitratrate (PAN), aldehydes, hydroperoxides and peroxynitrates.

6) How to reduce NOx emissions….i) reduce combustion T (by lowering compression ratio)ii) lower post-combustion conc. of O2 (fuel-rich mixtures)iii) use catalytic converter to remove NO and unburnt fuel

NO2 + OH HNO3

Page 15: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

SiliconOccurrence • most important element in igneous and many sedimentary rocks• SiO2 (quartz, silica), aluminosilicates (feldspar, etc.), ….

Recovery• reduction of silica sand with coke (furnace) crude Si• chlorination of silica and reduction with Mg high purity Si

Industrial Uses• ferrosilicon alloys for acid-resistant metal (chemical reactors)• organosiloxane (“silicone”) polymers • electronic “chips”• SiO2 (fiber optics)

SiO2(g) + 2C(s) + 2Cl2(g) SiCl4(g) + 2CO(s)

SiCl4(distilled) + 2Mg(pure) Si(s) + 2MgCl2

Page 16: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Organopolysiloxanes (“Silicones”)1) ….are made by the hydrolysis of organochlorosilanes RnSiCl4-n:

Rochow process

Inclusion of RSiCl3 will Inclusion of R3SiCl will lead to chain branching. cause chain termination.

2) ….can be oils, waxes, rubbers

3) ….have high thermal stabilities, resistance to oxidation, electrical insulation, water repellency, good biocompatibility, low chemical reactivity.

RCl(g) + Si(s)heat

Cu catalyst RnSiCl4-n (n = 1-3)

nR2SiCl2 + nH2O Si O

R

R

Si O

R

R

Si O

R

R

+ 2nHCl

RSi

R

O SiR

R

RSi

O

OO

Si

SiSi

Page 17: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

AluminumOccurrence • in combination with Si and O as aluminosilicates in rocks• or as its ore, bauxite: essentially AlO(OH) with Fe contaminants

Recovery• Al(III) is “leached” out from bauxite using NaOH(aq) and the resulting gibbsite [α-Al(OH)3] is dehydrated to α-Al2O3.

• α-Al2O3 is dissolved in molten Na3AlF6 / CaF2 (9:1) and reduced electrolytically using graphite electrodes (consumed).

Industrial Uses• Al(m) is used in vehicles, aircraft, packaging, construction, etc.• Aluminosilicates are used as catalysts (e.g., zeolites)

2Al2O3 + 3C(g) 4Al(l) + 3CO2(g)

AlO(OH)(s) + OH(aq) + H2O Al(OH)4(aq) Al(OH)3 + OH(aq)

Page 18: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

SulfurOccurrence • native, i.e., elemental sulfur (S8 and other allotropes)• sulfates (SO4

2-) and sulfides (S2-)• hydrogen sulfide (H2S)

Recovery• elemental S used to be mined using the Frasch process• now, so much H2S is recovered as a by-product from natural gas and refinery operations that mining is obsolete!• Highly toxic H2S is converted to solid S by the Claus process

Industrial Uses• H2SO4 is the #1 synthetic chemical in terms of tonnage• H2SO4 used mostly to make fertilizers, but also for ClO2 • Kraft and Sulfite processes for wood pulping (paper)

Page 19: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Sulfur from H2S: Claus Process

Hydrogen Sulfide H2S :

1) is a highly toxic gas that occurs in Albertan “sour” natural gas (>30% H2S content)

2) H2S is “scrubbed” out of natural gas by absorption in aqueous

monoethanolamine (MEA, HOCH2CH2NH2) or diethanolamine

(DEA, (HOCH2CH2)2NH). The aqueous base is then stripped off

to recover the H2S.

3) Claus Process: H2S is burnt partially to SO2 in air

unburnt H2S and SO2 react (catalyzed by Fe2O3 or γ-Al2O3)

2H2S + 3O2 2SO2 + 2H2O

2H2S + SO2 3S + 2H2O

Page 20: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Sulfuric Acid

Sulfuric acid H2SO4 :

1) generally is produced by the contact process:a) exothermic air oxidation of SO2 (V2O5 or Pt catalyst)

b) SO3 is absorbed into 100% H2SO4 to give a mixture disulfuric and sulfuric acids, known as oleum

c) oleum is hydrolyzed to H2SO4

SO3 + S

O

O

OH

OH S

O

O

OH

O S

OH

O

O

2SO2 + O2Pt orV2O5

2SO3

H2S2O7 + H2O 2H2SO4

Page 21: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Sulfuric Acid2) 90% of the sulfur produced industrially is converted to H2SO4!!

3) 2/3 of the H2SO4 produced is consumed in fertilizer manufacture, to make ammonium sulfate: (NH4)2SO4 or superphosphate: 32% CaHPO4/Ca(H2PO4)2•H2O 3% H3PO4

50% CaSO4

or potassium sulfate: K2SO4 (Mannheim process)

4) H2SO4 is also used to make chlorine dioxide ClO2 for bleaching paper pulp and for sterilizing water. i) Mathieson process:

ii) Solvay process:

2NaClO3 + SO2 + H2SO4(aq) 2ClO2(g) + 2NaHSO4(aq)

6NaClO3 + CH3OH + 6H2SO4(aq) 6ClO2 + CO2 + 6NaHSO4 + 5H2O

Page 22: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Sulfur Chemicals: Pulp & Paper Industry

Kraft Process (or Sulfate process)1) An alkaline process resulting in strong, brown, “acid-free” paper.

2) Wood chips are digested at 800°C (800 kPa) for 1 to3 hours in aqueous NaOH/Na2S/Na2CO3 converting the lignin to soluble alcohols, anions, mercaptans (RSH) and organic sulfides (R2S).

3) Once the pulp is collected, tall oil (for soaps) is removed from the spent aqueous solution by centrifugation, then the water is removed and the remaining residue is ignited, converting the organic content to C. Finally, the NaOH, Na2S, Na2CO3 are regenerated by the addition of Na2SO4 and Ca(OH)2.

Wood pulping is a process in which lignin is broken down without excessive damage to the cellulose.

The the Kraft and Sulfite processes are chemical pulping processes.

Page 23: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Sulfur Chemicals: Pulp & Paper Industry

Sulfite Process

1) An acidic process yielding weaker, white paper.

2) Uses a buffered aqueous sulfurous acid solution (HSO3¯/H2SO3).

3) SO2 is passed over wet limestone CaCO3 to produce the solution.

4) This solution is used to digest wood chips at 130°C for 24h.

5) SO2 is recovered from relief gases and CaSO3 is recovered by evaporation of the spent liquor and addition of slaked lime Ca(OH)2.

SO2(g) + H2O(l) H2SO3(aq)CaCO3 Ca(HSO3)2(aq) + CO2(g)

Page 24: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Sulfur Compounds and Air Pollution

Sulfur dioxide SO2 :

1) is a moderately toxic, pungent, colourless gas (b.p. -10°C)

2) is produced in large amounts by burning fossil fuels (coal!), roasting sulfide ores (pyrite, FeS2), pulp & paper mill discharges,

and natural volcanic activity: [2:1 anthropogenic to natural]

3) Acid Precipitation: • mostly H2SO4 from:

wet clouds

or dry air

• also some H2SO3 from:

H2O + SO2 + 1/2O2 (or 1/3O3 or H2O2) H2SO4(l) (aerosol)

SO2 + OH SO3H H2SO4(l) (aerosol)OH

SO2 + H2O H2SO3

Page 25: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Sulfur Compounds and Air Pollution

How to minimize SO2 emissions :1) Desulfurization of fuels: difficult and expensive

e.g. Battelle hydrothermal coal process

2) Scrubbing of stack gases with wet limestone: Fuels are burnt as received and resulting SO2 is removed in the stack.

3) Recovery of SO2 as H2SO4: The stack is scrubbed with a cool spray of an organic amine solution which absorbs the SO2. The resulting complex is then heated in a separate column to release SO2 which is then converted to H2SO4. (Union Carbide CanSolv process)

All forms of S in coal + NaOH(aq) S2-

(aq) H2S(g) + Na2CO3(aq)

220-350C CO2(g)

CaCO3(s) + SO2(g) CaSO3(s) + CO2(g)

H2O

Page 26: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Sulfur Compounds and Air Pollution

How to minimize SO2 emissions :

4) Fluidized bed combustion: @ T = 820 - 870°C, limestone reacts with SO2 and air to give CaSO4

• CaSO4 (gypsum) is non-toxic and useful (roadbed cement)

• unlike CaSO3 which is toxic to plants (hard to dispose of)

5) Use of low-sulfur fuels: e.g. Coal from western Canada: • transportation costs and politics are the major concerns

Page 27: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

ChlorineOccurrence • as chloride ion Cl¯, the most abundant anion in seawater• as rocksalt NaCl

Recovery• Chloralkali process: electrolysis of brine NaCl(aq)

by-product ofNaOH synthesis

Industrial Uses• 67% to organic chemicals industry (25% for EDC alone!)• 30% to pulp & paper mills, and 5% to water treatment

Page 28: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Chlorine

Hypochlorite ion OCl¯ and Hypochlorous acid HOCl :

1) Cl2 disproportionates when dissolved in water

2) HOCl decomposes slowly releasing oxygen

Since HOCl is a powerful disinfectant, Cl2 is used to treat water.

3) Cl2 dissolved in cold, dilute aqueous NaOH generates kinetically

stable solutions of OCl¯…. HOUSEHOLD BLEACH!

Cl2(aq) + H2O(l)

Cl(0)

HOCl(aq) + H+ + Cl Cl(+1) Cl(-1)

HOCl 1/2O2 + H+ + Cl

Cl2 + 2OH OCl + Cl +H2O

Page 29: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Chlorine

Chlorate ion ClO3¯ :

1) Cl2 dissolved in hot, concentrated aqueous NaOH forms ClO3¯

2) Chlorate salts are strong oxidizing agents….KClO3 can be used

in place of KNO3 as an oxidant for C and S in black powder.

3) Chlorate salts can be used as an unselective herbicide.

4) Chlorate salts are mainly used as a source of ClO2 for bleaching

paper pulp and for sterilizing water.Recall: Mathieson process and Solvay process

3Cl2 + 6OH 5Cl + ClO3 + 3H2O

Cl(0) Cl(-1) Cl(+5)

Page 30: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Chlorine

Chlorine dioxide ClO2 and the Chlorite ion ClO2¯ :

1) ClO2 is an orange-yellow gas, explosive in high concentrations.

2) ClO2 is often converted to sodium chlorite NaClO2 for safer shipping and handling….there is still a friction explosion hazard!

Perchloric acid HClO4 and the Perchlorate ion ClO4¯ :

1) Electrolysis of chlorate ClO3¯ solutions gives perchlorate ClO4¯.

2) ClO4¯(aq) is often used to adjust acidity / ionic strength.

3) Perchlorates are explosive! e.g., Solid Rocket Fuel: NH4ClO4 is used to oxidize Al powder. e.g., A single drop of conc. HClO4 in DMSO BOOM!

Page 31: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Chlorine and Industrial ChemistryVCM, vinyl chloride monomer : H2C=CHCl

1) VCM is made almost exclusively by thermal cleavage of EDC, ethylene dichloride (or 1,2-dichloroethane) ClCH2CH2Cl.

2) EDC is formed by chlorinating ethylene….Cl2 + H2C=CH2

3) 95% of the VCM produced is used to make polymers e.g. PVC, poly(vinyl chloride) [-CH2-CHCl-]n

Hydrochloride HCl salts as pharmaceuticals :

A common technique used to stabilize amine-containing drugs is to synthesize the HCl salt. e.g., US 2003125336 patented the HCl and HBr salts of this HIV protease inhibitor: N

H3CO

O

NN

H3C CH3

N

NH

O CF3

OHHN

O O

OH

Page 32: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Chlorine and Environmental ConcernsChlorofluorocarbons CFCs : e.g., CF2Cl2 and CFCl3

1) Were widely used as refrigeration fluids, cleaning fluids for electronics manufacture, aerosol propellants, and plastic foam blowing agents.

2) Were thought to be inert, but now are known to be the major factor in the destruction of the stratospheric ozone layer!

3) Montréal Protocol (1988): phase-out of CFC production by 1995.

CF2Cl2 or CFCl3 Clphotolysis instratosphere

Cl + O3 ClO + O2

O3 O(1D) + O2(1)UV

O + ClO Cl + O2

O(1D) + CF2Cl2 or CFCl3 ClO, etc.

Page 33: Lecture Topic 5: Inorganic Chemistry and Industry Ref: “Inorganic Chemistry: An Industrial and Environmental Perspective” by T. W. Swaddle Premise:Inorganic

Chlorine and Environmental ConcernsChlorinated organic compounds :

1) DDT, dichlorodiphenylchloroethane: An insecticide still used in the tropics to combat the anopheles mosquito (carriers of malaria).

2) TCDD, tetrachlorodibenzo-p-dioxin: A potent toxin and carcinogen, this dioxin is a byproduct of Cl2 bleaching of pulp and paper.

3) PCBs, polychlorobiphenyls: Once used as electrical transformer oils. Mimic natural hormones & disrupt endocrine systems of animals.

4) Chlorinated solvents such as chloroform CHCl3, carbon tetra- chloride CCl4, etc. : carcinogenic and threaten ozone pool.

ClCl

Cl

Cl Cl

O

O ClCl

ClCl

ClnCln