Poisoning by cyanide

Meredith, T.J., Jacobsen, D., Haines, J.A., Berger, J-C. (1993). Antidotes for poisoning by cyanide. In IPCS/CEC Evaluation of Antidote Series, Vol. 2. Cambridge University Press. 

Tamper-Resistant Packaging Regulations Issued for OTC Products. Tragedy Acetaminophen-capsule poisoning by cyanide causes seven deaths. Result Revision of GMPs to require tamper-resistant packaging. 

Rats pretreated by inhalation with sub-lethal concentrations of acrylonitrile became immune to subseqnent lethal exposnre (Cote et al. 1983). Such inhalation-induced tolerance to acrylonitrile did not protect against snbseqnent poisoning by cyanide. 

Meredith TJ, Jacobsen D, Haines JA, Berger J-C, van Heijst ANP, eds. Antidotes for Poisoning by Cyanide. Vol 2. In International Program on Chemical Safety/Commission of the European Communities Evaluation of Antidotes Series. Geneva, Switzerland World Health Organization and Commission of the European Communities 1993. Publication EUR 14280 EN. 

Fig. 13. Effective and true poisoning graphs for a platinum hydrogenation catalyst (0.05 g. Pt) poisoned by cyanide ions.

The use of fire retardants in polymers has become more complicated with the realisation that more deaths are probably caused by smoke and toxic combustion products than by fire itself. The suppression of a fire by the use of fire retardants may well result in smouldering and the production of smoke, rather than complete combustion with little smoke evolution. Furthermore, whilst complete combustion of organic materials leads to the formation of simple molecules such as CO2, H2O, N2, SO2 and hydrogen halides, incomplete combustion leads to the production of more complex and noxious materials as well as the simple structured but highly poisonous hydrogen cyanide and carbon monoxide. 

Acrylonitrile (Vinyl cyanide) CH,CHCN Closely resembles HCN in toxic action Poisonous by inhalation, ingestion or skin absorption Emits cyanides when heated or contacted by acids or acid fumes Symptoms flushed face, irritation of eyes and nose, nausea etc. Colourless flammable liquid with mild, faintly pungent odour Elash point 0°C. Dilute water solutions also have low flash points... 

Potassium cyanide KCN On exposure to air, gradually decomposes to release HCN Poisonous by ingestion, inhalation or skin absorption Do not handle with bare hands. Strong solutions may be corrosive to the skin Nonflammable white lumps or crystals Eaint odour of bitter almonds Completely water soluble... 

Sodium cyanide NaCN Poisonous by inhalation, ingestion or skin absorption Do not handle with bare hands Releases HCN slowly with water, more rapidly with acids Nonflammable white granules, fused pieces or eggs Odourless when dry slight almond odour in damp air Completely water soluble... 

Most low-valence metal complexes are generally deactivated by air and sometimes also by water. Carbon monoxide, hydrogen cyanide, and PH3 frequently act as poisons for these catalysts. Poisoning by strongly co-ordinating molecules occurs by formation of catalytically inert complexes. An example is the poisoning of Wilkinson s catalyst for alkene hydrogenation ... 

We have studied the hydrogenolysis of 2-(perfluorohexyl)ethane thiocyanate to 2-(perfluorohexyl)ethane thiol. It was discovered that perfluoroalkyl thiocyanates can be reduced to thiols and co-product hydrogen cyanide with molecular hydrogen in the presence of a carbon-supported palladium-tin catalyst. This result is surprising since it is known that palladium and other gronps 8 to 10 metal catalysts are poisoned by the product thiol, traces of hydrogen snlfide byprodnct, and the hydrogen cyanide co-product. For that reason, we characterized the catalyst to understand why it was so robust under conditions that would normally poison snch a catalyst. 

It is apparent that a new synthetic methodology, preferably catalytic, is needed for the synthesis of this important class of 2-(perfinoroalkyl)ethane thiols. In this context, a variety of catalysts was examined to determine if they wonld catalyze the hydrogenolysis of 2-(perfinorohexyl)ethane thiocyanate. In the conrse of this study, much to our surprise, it was discovered that a carbon supported Pd-Sn would catalyze the reaction. It is known that palladium and other group Vtll metal catalysts are poisoned by the product thiol, traces of hydrogen sulfide byproduct, and the hydrogen cyanide co-prodnct (6), but our observations are that this catalyst is surprisingly robust in the reaction medium. 

The thiol was obtained in >98% yield with trace amounts of the disulfide at 175°C and 700 psig H2 reactor pressnre in 1.5 honrs at a 900 1 substrate catalyst molar ratio. As discussed above, it is known that palladinm and other groups 8 to 10 metal catalysts are poisoned by the prodnct thiol, traces of hydrogen sulfide byproduct, and hydrogen cyanide coprodnct (6), bnt it is surprising that this catalyst is so robnst The effects of solvents, temperature, pressure, catalyst, and recycle will be discnssed. The characterization of the catalyst by various techniques will help to explain some of these observations. 

It is well known that palladium on carbon catalysts are poisoned by hydrogen cyanide and thiol products or hydrogen sulfide (6). Therefore, it was of interest to investigate the reduction of perfluoroalkyl thiocyanates as a function of tin concentration, keeping the concentration of palladium and reaction conditions constant. Figure 15.1 delineates the % conversion vs. Sn/Pd ratio, under the same reaction conditions of 175°C, 700 psig H2 for 2 hours with 5% Pd on carbon catalysts in ethyl acetate solvent at a 1000 1 substrate catalyst molar ratio. The increase in... 

Combined intoxications of carbon monoxide and cyanide should not be treated with the nitrites found in cyanide antidote kits. These nitrites are used to create methemoglobinemia, which will exacerbate carbon monoxide poisoning by further reducing the ability of the blood to deliver oxygen to body tissue. 

Smit and Hertogen [5] also concluded a large meteorite may have struck the earth and caused the extinctions. K. J. Hsii [14] suggested the extinctions were caused by cyanide poisoning... 

Metabolic Effects. Yen et al. (1995) reported metabolic acidosis in 67% of patients acutely poisoned by unknown concentrations of cyanide. 

Respiratory Effects. Respiratory effects commonly occur after inorganic cyanide poisoning by any route of exposure. Following inhalation, the first breath of a lethal concentration of hydrogen cyanide causes hyperpnea (Rieders 1971). The victims experience shortness of breath that may be rapidly (>1 minute) followed by apnea. Dyspnea was reported in patients who survived acute inhalation exposure to cyanide... 

Lasch EE, El Shawa R. 1981. Multiple cases of cyanide poisoning by apricot kernels in children from Gaza. Pediatrics 68 5-7. 

Palmer IS, Olson OE. 1979. Partitial prevention by cyanide of selenium poisoning in rats. Biochem Biophys Res Comm 90 1379-1386. 

Finally, it should be mentioned that HA is effective as an antidote against cyanide poisoning by virtue of converting ca 20% of the hemoglobin to methemoglobin. This will be discussed at length in Section ILF. 

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