O/P-toluene sulfonamide (OPTSA)

O/P-toluene sulfonamide (OPTSA) consists of the two compounds ortho-toluenesulfonamide and para-toluenesulfonamide. In the centre of the molecules of both substances is an unsaturated phenyl ring of six carbon atoms, which gives the compounds an aromatic character and enables them to undergo addition reactions with the addition of hydrogen atoms. The typical methyl group of toluene and a sulfonamide group composed of sulphur, oxygen and a nitrogen-containing amide residue are linked to this ring-shaped centre. In the case of ortho-toluenesulfonamide, these groups are joined to directly adjacent carbon atoms in the phenyl ring, while in the para-toluenesulfonamide molecule they are joined to opposite carbon atoms.

Under normal conditions, o/p-toluene sulfonamide (OPTSA) is a solid in the form of a colourless-to-white crystalline powder. The precise properties of the odourless mixture of substances vary depending on the concentration of the compounds o-toluenesulfonamide and p-toluenesulfonamide. P-toluenesulfonamide melts when heated to 136 °C; at temperatures above 220 °C it changes to a gaseous state. However, o-toluenesulfonamide, only becomes liquid at 156 °C due to differences in the crystal structure and decomposes directly on further heating to 188 °C without entering the gaseous phase. O/P-toluene sulfonamide is only slightly soluble in water. Certain organic solvents such as ethanol can be used to dissolve the mixture of substances.

When stored as directed under dry and airtight conditions, o/p-toluene sulfonamide (OPTSA) is chemically stable. However, in contact with potassium iodide, amines and many other organic substances, o/p-toluene sulfonamide can react violently and explosively.

O/P-toluene sulfonamide is combustible but difficult to ignite. However, the dust of the crystalline powder poses a particular risk. If fine particles are suspended, highly flammable and combustible dust/air mixtures can form with the ambient air. When processing open packaging containing the mixture of substances, it is therefore important to ensure a sufficiently safe distance from potential sources of ignition such as open flames, mechanical sparks, electrostatic devices and strongly heated surfaces. The incineration and thermal decomposition of o/p-toluene sulfonamide produce harmful and dangerous gases. This includes the release of significant quantities of carbon monoxide, carbon dioxide, sulphur oxides and nitrogen oxides.

O/P-toluene sulfonamide (OPTSA) poses acute and chronic health risks. Repeated contact with the skin can cause redness, itching, inflammation, allergic reactions and persistent sensitization. Affected parts of the body should be cleaned with soap and water and with polyethylene glycol 400. If symptoms persist, it is essential to seek medical advice. O/P-toluene sulfonamide can also cause reddening of the eyes and painful irritation of the mucous membranes. In order to rule out damage to the cornea, the eye must be rinsed under running water to remove any residue of the crystalline solid and then examined by an ophthalmologist.

Inhaling dust from the compound may cause irritation to the respiratory tract. Persistent respiratory sensitization is possible. Mild irritation of the mucous membranes may also occur after swallowing o/p-toluene sulfonamide. The absorption of the compounds into the metabolism can lead to disorders of the central nervous system and damage to the liver and kidneys.

With regard to potential risks to aquatic life, p-toluenesulfonamide has been assessed as slightly hazardous to water and o-toluenesulfonamide as obviously hazardous to water. The substances may therefore not be released into the environment. The local authorities must be informed of any leakage of o/p-toluene sulfonamide into soil, waterways or sewage. The compounds are not subject to any special transport regulations.