Safer for human health: examples of safer reactions

Biocatalysis	Cyanide
Safer temperatures and pressures are generally used in bio-catalytic reactions.	Compounds of cyanide have been used as reagents for many reactions. Alternatives are being developed.
Phosgene	Solvents
Phosgene gas is being replaced as a reagent for some processes	New, safer solvents are being developed for many applications

Biocatalysis

Many industrial processes are carried out at high temperatures and pressures, which brings higher risks to employees in particular. Reactions using biocatalysts generally take place at atmospheric pressure, and only a little above room temperature, making the process safer in this respect.

Cyanide

Compounds like hydrogen cyanide and potassium cyanide are extremely toxic, but they also happen to be very useful reagents and have been used in manufacturing for many years.

Hydrogen cyanide has commonly been used in the manufacture of weed-killers, including domestic products like "Roundup". In the event of an accident at the chemical plant, the consequences could be very serious if cyanide compounds are involved.

The important intermediate "catechol" can be made by a biosynthetic route
For other examples of Biocatalysis see the catalysis site

Monsanto, the company that makes "Roundup" has developed an alternative manufacturing route that uses a different starting material, a copper catalyst and cyanide is no longer needed. The old process also involved exothermic generation of potentially unstable intermediates, with the danger of a "runaway" reaction. The new process is endothermic, making it even safer.

photo: weed-killer made using safer method

Alternative, safer routes are now available for polyurethane and polycarbonate plastics.

equations: alternative routes to diisocyanates

chemical equations: safer route to polycarbonates

In the case of polycarbonate is it possible to use dimethyl carbonate instead of phosgene. This used to be made from phosgene, but is now manufactured using methanol and carbon monoxide, both obtained from methane.

Phosgene

The gas phosgene has many uses, primarily as an intermediate or reagent in the synthesis of many compounds. It is, for example, commonly used in the manufacture of intermediates for polyurethane and polycarbonate plastics. Unfortunately it is also highly toxic. In the First World War it was used as a chemical weapon, where its high vapour density (more than 3 times that of air) meant it did not easily disperse, and phosgene was responsible for about 80% of chemical fatalities.

Organic Solvents

Water is, of course, a common solvent, but many of the compounds manufactured in the chemical industry are water insoluble. This means that reactions and product purification are often carried out in organic solvents. Paints, varnishes and other coatings also contain solvents that evaporate as the coating dries. Several of the volatile organic compounds (VOCs) used as solvents are toxic, irritants or even suspected carcinogens.

Manufacturers are now seeking to replace these with safer alternatives. There are now, for example, several water-based, low-odour paints available to the consumer, reducing emissions of VOCs when painting.

Researchers are also finding alternative solvents for manufacturing and developing processes that use no solvent at all. Supercritical carbon dioxide is already used in several processes. Ionic liquids are also receiving much attention from researchers. These have very low vapour pressure, which means they produce very little vapour, and can act as solvent and catalyst at the same time.