Cyanogen limitations

The photolytic and thermolytic decomposition of azides in the presence of olefins has been applied to aziridine synthesis. However, only a limited number of steroid aziridines have been prepared in this manner. The patent literature reports the use of cyanogen azide at ca. 50° for 24 hours in ethyl acetate for the preparation of an A-nor- and a B-norsteroidal aziridine. The addition is believed to proceed via a triazoline. The reaction of cholest-2-ene with ethyl azidoformate takes place in a nonselective manner to produce a mixture of substances, including C—H insertion products. 

Cyanide and thiocyanate anions in aqueous solution can be determined as cyanogen bromide after reaction with bromine [686]. The thiocyanate anion can be quantitatively determined in the presence of cyanide by adding an excess of formaldehyde solution to the sample, which converts the cyanide ion to the unreactive cyanohydrin. The detection limits for the cyanide and thiocyanate anions were less than 0.01 ppm with an electron-capture detector. Iodine in acid solution reacts with acetone to form monoiodoacetone, which can be detected at high sensitivity with an electron-capture detector [687]. The reaction is specific for iodine, iodide being determined after oxidation with iodate. The nitrate anion can be determined in aqueous solution after conversion to nitrobenzene by reaction with benzene in the presence of sulfuric acid [688,689]. The detection limit for the nitrate anion was less than 0.1 ppm. The nitrite anion can be determined after oxidation to nitrate with potassium permanganate. Nitrite can be determined directly by alkylation with an alkaline solution of pentafluorobenzyl bromide [690]. The yield of derivative was about 80t.with a detection limit of 0.46 ng in 0.1 ml of aqueous sample. Pentafluorobenzyl p-toluenesulfonate has been used to derivatize carboxylate and phenolate anions and to simultaneously derivatize bromide, iodide, cyanide, thiocyanate, nitrite, nitrate and sulfide in a two-phase system using tetrapentylammonium cWoride as a phase transfer catalyst [691]. Detection limits wer Hi the ppm range. 

Information regarding ocular effects in animals after inhalation exposure to cyanide is limited to a report of eye irritation in rats acutely exposed (7.5-120 minutes) to 250 ppm cyanogen (500 ppm cyanide) (McNemey and Schrenk 1960). 

Health-Based Limits for Exclusion of Waste - Derived Residues Calcium cyanide Copper cyanide Cyanogen sodium cyanide Hydrogen cyanide Potassium cyanide Potassium silver cyanide 1x1 O 6 mg/kg 2x1 O 1 mg/kg 1 mg/kg 7x1 O 5 mg/kg 2 mg/kg 7 mg/kg 40 CFR 266, App VII EPA 1991c... 

Guidelines a. Air ACGIH Threshold Limit Values for Occupational Exposure (TLV-TWA) Cyanogen TLV - Ceiling Hydrogen cyanide, sodium cyanide, calcium cyanide, potassium cyanide, acetone cyanohydrin Cyanogen chloride 21 mg/m3 5 mg/m3 0.75 mg/m3 ACGIH 1996... 

NIOSH Recommended Exposure Limit for Occupational Exposure (TWA) Cyanogen 20 mg/m3 NIOSH 1992... 

Particularly important compounds have been studied by flame combustion calorimetry. Methane [92-94], ethanol [95], diethyl ether [96], carbon monoxide [92,93,97], hydrochloric acid [98], and water [93,97,99] are representative examples. With a few exceptions (HC1, H2O, D2O [100], SO2 [101], cyanogen [102,103], and some lower chloroalkanes [104,105]), measurements by flame combustion calorimetry have been limited to substances of general formula CaHbOc. 

Cyanogen has limited appHcations, the most important of which are in organic synthesis. Also, it is used in welding metals as a fumigant and in... 

Vanpee (62) has studied the explosion of formaldehyde-oxygen mixtures. The dependence of explosion pressure upon temperature, vessel diameter, and the addition of inert diluent is in agreement with the thermal theory and consistent with studies of the slow reactions (54, 61). Typical of other reactions which have been reported to exhibit thermal explosion limits are the decomposition of nitrous oxide (75), the reaction between nitrous oxide and hydrogen (38), and cyanogen-air (32). 

In an alternative approach, cyanide and thiocyanate can be converted to cyanogen chloride using the chlorinating agent chloramine T. Conversion can be performed in solution or in the headspace. Conversion in solution followed by headspace analysis gave a detection limit of 5 ng/ml by gas chromatography/electron capture detection (GC/ECD) (72). Conversion in the headspace above acidified blood, in a precolumn packed with chloramine T powder and attached to the injection port of the GC, gave a detection limit of 50 ng/ml (73). 

A similar limit is obtained with dinitriles. However for the shortest of them, the presence of a second, electronegative cyano group leads to an increase of the coupling, which is maximal for cyanogen and still observable for malono- and succinonitrile. 

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