Hydrogen cyanide toxicity

Chemical Hazards. Chemical manufacturers and employees contend with various ha2ards inherent ia productioa of evea commonplace materials. For example, some catalysts used ia the manufacture of polyethylene (see Olefin polymers) ignite when exposed to air or explode if allowed to become too warm the basic ingredient ia fluorocarboa polymers, eg, Tefloa (see Fluorine compounds, organic), can become violently self-reactive if overheated or contaminated with caustic substances (45,46) one of the raw materials for the manufacture of acryflc fibers (see Fibers, acrylic) is the highly toxic hydrogen cyanide (see Cyanides). 

Health nd SMety Factors. The lowest pubhshed human oral toxic dose is 430 mg/kg, causing nervous system disturbances and gastrointestinal symptoms. The LD q (rat, oral) is 750 mg/kg (183). Thiocyanates are destroyed readily by soil bacteria and by biological treatment systems in which the organisms become acclimatized to thiocyanate. Pyrolysis products and combustion products can include toxic hydrogen cyanide, hydrogen sulfide, sulfur oxides, and nitrogen oxides. 

Cyanide compounds are classified as either simple or complex. It is usually necessary to decompose complex cyanides by an acid reflux. The cyanide is then distilled into sodium hydroxide to remove compounds that would interfere in analysis. Extreme care should be taken during the distillation as toxic hydrogen cyanide is generated. The cyanide in the alkaline distillate can then be measured potentiometricaHy with an ion-selective electrode. Alternatively, the cyanide can be determined colorimetricaHy. It is converted to cyanogen chloride by reaction with chloramine-T at pH <8. The CNCl then reacts with a pyridine barbituric acid reagent to form a red-blue dye. 

Hazards of Combustion Products Toxic hydrogen cyanide gas may form in fires Behavior in Fire Not pertinent Ignition Tenqterature Not pertinent Electrical Hazard Not pertinent Burning Rate Not pertinent. 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials No reaction Stability During Transport Stable, in presence of moisture, toxic hydrogen cyanide gas may collect in enclosed spaces Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Not pertinent Inhibitor cf Polymerization Not pertinent. 

The electrophile 4 adds to the aromatic ring to give a cationic intermediate 5. Loss of a proton from 5 and concomitant rearomatization completes the substitution step. Subsequent hydrolysis of the iminium species 2 yields the formylated aromatic product 3. Instead of the highly toxic hydrogen cyanide, zinc cyanide can be used. The hydrogen cyanide is then generated in situ upon reaction with the hydrogen chloride. The zinc chloride, which is thereby formed, then acts as Lewis acid catalyst. 

Caution Potassium cyanide is a potent poison, which should always be handled with gloves in a well-ventilated hood. Contact with acid releases toxic hydrogen cyanide gas. 

This process is carried out at a temp, from about 200C up to the critical temperature of water at autogenous pressure. PAN is degraded without the production of toxic hydrogen cyanide as a by-product. 

Cyanide-based metal finishing solutions usually operate at basic pH levels to avoid decomposition of the complexed cyanide and the formation of highly toxic hydrogen cyanide gas. 

The solid or its solution is highly toxic. Ingestion can cause death. Exposure to the solid can be harmful as it decomposes to highly toxic hydrogen cyanide and ammonia. 

By contrast, formamidine acetate is not hygroscopic and no particular care need be taken to protect it from atmospheric moisture. Furthermore, formamidine acetate can be used directly without prior treatment with base in syntheses requiring free formamidine.8,7-10 Finally, this preparation of formamidine is by far the simplest and most convenient yet reported it obviates the necessity of using either toxic (hydrogen cyanide) or cumbersome (Raney nickel) reagents, and the method can be adapted to the preparation of N,N -disubstituted formamidines by substitution of primary amines for ammonia.11... 

Methacrylic acid has been used for the synthesis of polyfmethyl methacrylate). It has been synthesized industrially via a reaction of acetone with hydrogen cyanide (12, 17, 330, 331). However, the process produces ammonium bisulfate and uses the toxic hydrogen cyanide. Recently, an alternative, a two-step oxidation of isobutylene, has been developed. The first step is the oxidation of isobutylene to methacrolein, and the second is the oxidation of methacrolein to methacrylic acid ... 

Cyanide species are reactive and unstable, and the addition of sodium hydroxide (in pellets or as a strong solution) stabilizes them as simple and complex alkali cyanides. Sodium hydroxide also prevents the release of the toxic hydrogen cyanide gas. 

Strong acids and strong bases are corrosive substances that exhibit extremes of pH. They are destructive to materials and flesh. Strong acids can react with cyanide and sulfide compounds to release highly toxic hydrogen cyanide (HCN) or hydrogen sulfide (H2S) gases, respectively. Bases liberate noxious ammonia gas (NH3) from solid ammonium compounds. 

Nitriles are organic analogs of highly toxic hydrogen cyanide, HCN (see Section 11.2), where the H is replaced by a hydrocarbon moiety. The two most common nitriles are acetonitrile and acrylonitrile ... 

Bond et al. [68] have described a method for the simultaneous determination of down to lmg L 1 free sulphide and cyanide by ion chromatography, with electrochemical detection. These workers carried out considerable exploratory work on the development of ion chromatographic conditions for separating sulphide and cyanide in a basic medium (to avoid losses of toxic hydrogen cyanide and hydrogen sulphide) and on the development of a suitable amperometric detector. 

Cyanogenic glycosides, which are widely distributed in higher plants, are a bound form of toxic hydrogen cyanide, which is released from the glucoside following enzyme hydrolysis.214... 

In the case of a mixed cyanide/nitrite waste stream, it is advisable to treat the effluent first at alkaline pH to remove cyanide before reducing the pH to the acid range for nitrite treatment. This reduces the risk of toxic hydrogen cyanide laden waste streams. 

Toxic chemicals tliat could potentially cause a major problem if accidentally released into tlie atmosphere include clilorine, hydrogen fluoride, hydrogen chloride, ammonia, chloropicrin, gasoline lead additives, vinyl cliloridc. and benzene. Hiis chapter addresses the process application of some chemicals from the foregoing list, as well as some others that are considered to be highly toxic hydrogen cyanide, sulfuric acid, and etliylene. Process considerations, physical and chemical properties, healtli effects, and metliods of manufacture of tliese chemicals are discussed in conjunction with potential causes of release. 

Atiliydrous hydrogen fluoride reacts with cyanides and sulfides to produce toxic hydrogen cyanide and hydrogen sulfide, respectively. Since both tlicse compounds are flammable, tlieir formation in confined areas can result in potentially explosive mixtures. 

Currently, most amino acids are obtained from natural resources and/or by fermentation. Amidocarbonylation is a viable alternative to the conventional Strecker reaction, which utilizes toxic hydrogen cyanide and anunonia to make aliphatic amino acids from aldehydes. 

Adiponitrile is an odorless, oily colorless liquid, which decomposes on heating and reacts violently with strong oxidants. Upon burning, adiponitrile produces highly toxic hydrogen cyanide. 

Hazard Evolves a highly toxic hydrogen cyanide when heated. 

Chlorine and calcium hydroxide (slaked lime), used to ensure high pH conditions to avoid generation of extremely toxic hydrogen cyanide gas, are used in combination to chemically neutralize waste aqueous solutions of sodium cyanide. In this way the much less toxic cyanate ion (CNO ) is produced for discharge by oxidation of the cyanide ion. 

An earlier process that did not use the toxic hydrogen cyanide was discarded because it produced more waste... 

Butane has been isomerized to isobutane in 95% yield (at 24.5% conversion) with platinum/Cs2 5H0.5PW12O40 at 200-300X. under hydrogen at 0.05 atm.294 The hydrogen reduced deactivation of the catalyst. The oxidation of isobutane to isobutylene is needed for the synthesis of tert-butyl methyl ether to put into gasoline. Isobutylene, in turn, can be oxidized to methacrylic acid for conversion to methyl methacrylate, an important monomer (6.56). Making methyl methacrylate this way avoids the use of toxic hydrogen cyanide in the present commercial process. 

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