The Pharmaceutical Journal
Vol 278 No 7454 p650
2 June 2007

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Why are chemists so fond of explosions? more
Polysiloxanes and the unfortunate motorist more
The hazards of pollution in the indoor world more
Abuse of prescription drugs is increasing more

Why are chemists so fond of explosions?

A commentary in the 10 May issue of Nature considers why chemists persist in making compounds that blow up in their faces and discovers an area of inconclusive suppositions. It points out that explosives arise in many varieties from regular military munitions to compounds designed to inflate airbags rapidly in times of emergency. One material that serves as a standard for comparisons is the now familiar trinitrotoluene which, in contrast to many related compounds, remains safe and solid until deliberately detonated by means of a more hazardous one.

But why should anyone wish to synthesise a highly unstable material prepared to release a great deal of energy on the slightest provocation? The short answer is that, for some obscure reason, chemists enjoy explosions. After years of playing with traditional chemistry sets, the desire to make more sparks and bangs continues in most amateur chemists.

Explosives release energy stored in chemical bonds in a process that often turns solids into gases, causing massive expansion and creating heat and pressure waves that promote further reactions. However, many explosive compounds are so unstable that their use in any deliberate process is virtually ruled out except by suicide bombers.

The polyazides are particularly sensitive when it comes to synthesising touchy substances. Tetraazidomethane has recently come in for criticism. It can explode at any time without a recognisable stimulus, and anyone handling it requires the full protection of safety shields. So why make it in the first place? A professor at Chemnitz University, Germany, maintains that since receiving his first chemistry set at the age of 11 he had done experiments but had found that explosions were of secondary interest. It appears to be the synthesis that grips the imagination, not the disintegration. Meanwhile, crazy pyromaniacs will enjoy blowing themselves up.

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Polysiloxanes and the unfortunate motorist

Before interest in the recent spate of car breakdowns in the south-east of England fades away completely, it is perhaps worth taking a look at the background to the motorists' problem.

A discussion on the cause of the epidemic appeared in the April issue of Chemistry World. Silicon was quickly detected in the fuel and the problem was eventually attributed to contamination with polysiloxanes, which are composed of silicon and oxygen in different ratios.

Also known as silicones, polysiloxanes have a wide commercial value, comprising compositions that range from gel-like through rubbery to stiff. They are soluble in petrol, but on ignition they produce a fine white deposit of silicon dioxide, which can clog the oxygen sensors found in modern cars.

How the silicones came to be in the petrol is unclear, but they may have come from toluene solvents that should never have been allowed to enter the fuel mixture.

Unleaded fuel in Europe and Britain has hitherto not been tested for silicon content, but that precaution is to be applied in future.

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The hazards of pollution in the indoor world

In Nature for 17 May there is a note to the effect that a United Nations meeting has just failed to agree an action plan dealing with indoor pollution. A range of serious hazards related to cooking indoors is held to kill more people every year in poor countries than malaria. After a meeting, representatives from Switzerland and the European Union rejected a draft communication.

The problem has been ignored, it is thought, because it is a situation affecting mainly women, who spend more time in the kitchen than do men. About half of the world’s population cooks on stoves that use wood, crop residues and dung as fuel. The World Health Organization has estimated that smoke from traditional cookers kills 1.6 million people every year, most of them women and children. In Africa alone, if these trends continue, cooking pollution will kill 10 million people by 2030. Switching to petroleum-based fuels such as kerosene could prevent nearly half of those deaths. Constant exposure to carbon monoxide, particulates, hydrocarbons and carcinogens such as formaldehyde and benzene in cooking smoke accounts for much lung cancer, pneumonia and lower respiratory tract infections.

The growing threat of indoor pollution can no longer be regarded without deep anxiety. Agreement over dealing with it, however, seems difficult to achieve.

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Abuse of prescription drugs is increasing

According to statistical reports from the US the abuse of prescription drugs there is on the increase, as visits to emergency departments reveal. A note in The Lancet for 5 May claims that hospital visits related to non-medical use of pharmaceuticals, including prescription drugs and over-the-counter products, increased 21 per cent between 2004 and 2005. Of drug-related visits, 31 per cent involved illicit drugs, 27 per cent regular pharmaceuticals and 36 per cent a combination of illicit drugs, alcohol and pharmaceuticals.

In particular, the classes of pharmaceuticals implicated in non-medical uses included benzodiazepines (up 19 per cent), opiates and opioids (up 24 per cent), methadone (up 29 per cent) and central nervous stimulants (up 33 per cent). Compared with the previous year, the non-medical use of prescription pain relievers came second only to that of marijuana. It is reported that 11.3 million people aged 12 years or older reported the non-medical use of prescription pain relievers.

The rise in abuse of prescription drugs was attributed to increased availability and growing social acceptance of pain relievers and antianxiety products, with a belief that pharmaceutical drugs are safe for young people. On the other hand, 19 per cent of those surveyed said they had taken a drug to get high, 10 per cent abusing a cough medicine for the purpose; 29 per cent believed that pain medicines were not addictive and 55 per cent thought that taking cough medicines to achieve a “high” was not unduly risky.

A fall in consumption of illicit drugs was attributed to a growing idea that they might be hazardous. Other pharmaceutical drugs on the contrary have come to be regarded as safe. As regards availability, modern electronic methods of obtaining supplies present a challenge. Doctors and pharmacists should pay more attention to storing drugs and destroying them when no longer needed.