Cyanides work practices

OSHA requires employers of workers who are occupationally exposed to cyanide to institute engineering controls and work practices to reduce and maintain employee exposure at or below permissible exposure limits (PEL). The employer must use engineering and work practice controls, if feasible, to reduce exposure to or below an 8-hour time-weighted average (TWA) of 5 mg/m3 as cyanide. Respirators must be provided and used during the time period necessary to install or implement feasible engineering and work practice controls (OSHA 1974). 

Occupational exposures to cyanide resulting from unsafe work practices and inadequate worker protection procedures typically involve longer term exposure to lower concentrations than those that are identified in association with industrial accidents. El Ghawabi et al. (1975) reported on the effects of hydrogen... 

A solution of sodium ethylate is prepared from 60 g. (2.6 gram atoms) of clean sodium and 700 cc. of absolute alcohol (Note 1) in a 2-1. round-bottomed flask, equipped with a reflux condenser. To the hot solution is added a mixture of 234 g. (2 moles) of pure benzyl cyanide (Note 2) and 264 g. (3 moles) of dry ethyl acetate (Note 3). The mixture is thoroughly shaken, the condenser closed with a calcium chloride tube, and the solution heated on the steam bath for two hours before standing overnight (Note 4). The next morning the mixture is stirred with a wooden rod to break lumps, cooled in a freezing mixture to — io°, and kept at this temperature for two hours. The sodium salt is collected on a 6-in. Buchner funnel and washed four times on the funnel with 250-cc. portions of ether. The filter cake is practically colorless and corresponds to 250-275 g. of dry sodium salt, or 69-76 per cent of the calculated amount. The combined filtrates are placed in the freezing mixture until they can be worked up as indicated below. 

Countless publications elaborated the topic further. Practical experiments were also conducted to increase man s understanding of means for the successful control of the cause. For example, Dr. G. Peters reports in his work Blausdure zur Schadlingsbekampfung 11 about the fumigation of ships with hydrogen cyanide, done in the United States as early as 1910, and about tunnel facilities which entire railway trains could drive into to be disinfested. Thus it is no surprise that Peters also mentions the quantity of hydrogen cyanide that is lethal when absorbed by humans, and therefore, Pres-sac s claim12 that the lethal dose was not known is completely false. It was also already a known fact in those days that HCN could be absorbed via the skin. 

By means of this reaction, Wood, Smith, Gidden, Salamon, and Albri (English Patent, 13,658, 1901) introduced a successful process of recover practically all the cyanogen (98 per cent.) of coal gas, which is now worked by British Cyanides Co. Ltd., and by several gas works. It yields practically the wfc of the sulphocyanides now made. 

These two sources of labelled cyanide, one with a positive cyano group ( CNBr) and one with a negative cyano group (H CN), have opened up synthetic routes to a wide variety of labelled compounds. However, an essential requirement with using short-lived isotopes such as carbon-11 is that the synthesis must be completed rapidly. In practice, this means that the total synthesis and purification must be complete within three half-lives, i.e. in the case of carbon-11, within 60 minutes. In spite of this limitation, much work has been done with these synthons. 

Storage and Handling Sodium cyanide and potassium cyanide should be handled in the laboratory using the "basic prudent practices" described in Chapter 5.C, supplemented by the additional practices for work with compounds of high toxicity (Chapter 5.D). In particular, work with cyanides should be conducted in a fume hood to prevent exposure by inhalation, and splash goggles and impermeable gloves should be worn at all times to prevent eye and skin contact. Cyanide salts should be stored in a cool, dry location, separated from acids. 

The addition of cyanide to imine (Strecker-type reaction) can also be catalyzed by chiral Ti complexes. In a pioneering work reported by Snapper and Hoveyda, a series of titanium complexes of tripeptide-based Schiffbase ligands have been discovered by combinatorial chemistry approach for the addition of TMSCN to imine derivatives with >93% conversion of substrates and excellent enantioselectivities (85-97% ee) [227]. This methodology has provided a practical procedure for the... 

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