Демефион

Identification

Demephion (English: Demephion, CAS 8065-62-1) is an organophosphorus systemic insecticide and acaricide. The commercial product is a mixture of two structural isomers - demefion-O and demefion-S: O,O-dimethyl O-[2-(methylthio)ethyl]phosphorothioic acid ester mixed with O,O-dimethyl S-[2-(methylthio)ethyl]phosphorothioate. Also known under the trade names Tinox, Atlasetox, Tinox 50, Tonics, and under the technical name methyldemeton-methyl.

Physico-chemical characteristics

• Molecular weight: 432.52 (for a mixture of two isomers of the formula C5H13O3PS2)
• Exact weight: 432.00900
• EU number: 219-971-9
• DSSTox ID: DTXSID50274158
• HS code: 29309090
• PSA characteristic: 171 Ų
• XLogP3: 5.01740
• Density: 1.2000 (approximate estimate)

Mechanism of action

Demefion is an acetylcholinesterase (AChE) inhibitor, with a typical mechanism of action for organophosphorus insecticides: the phosphoryl group irreversibly binds to the active center of the enzyme, blocking the breakdown of acetylcholine in synapses, which leads to overexcitation of the pest's nervous system. It has systemic activity - it moves through plant tissues, protecting the vegetative mass from sucking pests, regardless of the point of contact with the treated surface.

Application

It is classified as an insecticide and acaricide of systemic action and belongs to the group of organothiophosphate pesticides. Considered to be an obsolete compound by modern knowledge, Demefion-S is noted as being excluded from agricultural use in most jurisdictions that have studied this class of compounds.

Toxicity and precautions

As an acetylcholinesterase inhibitor, demefion poses a risk of acute poisoning through skin contact, inhalation, and ingestion—a common property of organophosphorus insecticides in this group. Detailed data on acute toxicity parameters (LD50), UN transport codes and GHS labeling specifically for Demefion are not provided in the dump and have not been found in open sources.

Related compounds

Demefion is structurally and pharmacologically related to demeton, a more well-known representative of the same group of insecticide systems based on O,O-dimethylphosphorothioates with a methylthioethyl substituent; both compounds share the mechanism of irreversible inhibition of cholinesterase and the ability to systemically move through plant tissues. This structural relationship is typical of a whole generation of organophosphate insecticides in the mid-20th century, developed almost simultaneously and differing in the details of substituents on the phosphorus atom and the degree of systemic mobility in plant tissues and soil.

Storage

Organophosphorus insecticides are stored in a cool, dry, ventilated area, in original tightly closed containers, separately from food and feed. Work in personal protective equipment, avoiding contact with skin and inhalation of vapors.