Cyanogen radicals

Apart from the interferences which may arise from other elements present in the substance to be analysed, some interference may arise from the emission band spectra produced by molecules or molecular fragments present in the flame gases in particular, band spectra due to hydroxyl and cyanogen radicals arise in many flames. Although in AAS these flame signals are modulated (Section 21.9), in practice care should be taken to select an absorption line which does not correspond with the wavelengths due to any molecular bands because of the excessive noise produced by the latter this leads to decreased sensitivity and to poor precision of analysis. 

The nitrous oxide-acetylene flame is both hot and reducing. A characteristic red, interconal zone is obtained under slightly fuel-rich conditions. This red feather is due to emission by the cyanogen radical. This radical is a very efficient scavenger for oxygen, thus pulling equilibria such as... 

Silver cyanide acts on a benzene solution of the tetrabromide, replacing bromine by the cyanogen radical, with simultaneous reduction, the product being a solid tellurium dicyanide ... 

The theoretical yields of cyanogen obtained by the reaction of carbon and nitrogen can also be derived from thermodynamic data. At high temperatures cyanogen is partly dissociated into cyanogen radicals, and the following simultaneous equilibria must be considered ... 

The mass-action equations have been written in the same form as those given by Marynowski et al. (6) so that the equilibrium constants can be used directly. (Should more accurate data become available, the equilibrium yields calculated here will require revision.) The fourth equation, which applies to the heterogeneous equilibrium between carbon and nitrogen, is included for completeness but is unnecessary for the general solution. It can be shown that when the total pressure of the system is F, the partial pressure of cyanogen radicals is given by the equation ... 

When the system is heterogeneous—i.e., the temperature and pressure are such that solid carbon exists in equilibrium with its vapor, the value of Pci is uniquely determined by the temperature and can be calculated directly from the equilibrium constant Ki. Hence in a heterogeneous system, the partial pressure of cyanogen radicals and of cyanogen depend only on the temperature... 

Bachmeier et al. also measured the HCN concentrations through propane-air flames. These results, which are shown in Fig. 5, show that HCN concentrations rise sharply somewhere in the flame, reach a maximum, and then decrease sharply. However, for an equivalence ratio of 1.5, a fuel-rich condition for which little prompt NO is found, the HCN continues to rise and is not depleted. The explanation offered for this trend is that HCN forms in all the rich hydrocarbon flames however, below an equivalence ratio of 1.4,0 radicals are present in sufficient abundance to deplete HCN and form the NO. Since the sampling and analysis techniques used by Bachmeier et al. [13] did not permit the identification of the cyanogen radical CN, the HCN concentrations found most likely represent the sum of CN and HCN as they exist in the flame. The CN and HCN in the flame are related through the... 

When methyl iodide is treated with potassium cyanide a compound with the composition C2H3N is formed by a simple reaction of metathesis. As this and many other reactions prove that both the methyl and the cyanogen radicals are present in the compound we express the reaction. 

Methods of Preparation.—The general methods of preparing the acids are the following (i) From the acid nitriles by boiling with water. In this reaction the carbon of the cyanogen radical of the nitrile re-... 

Cyanamide.—An important compound formed from cyanogen chloride is known as cyan-amide and as its name indicates is composed of the cyanogen radical linked to the amine radical. It may be formed by the action of ammonia, in ethereal solution, on cyanogen chloride. 

Cyanides Yield Nitriles.—Sandmeyer also applied the principle of his reaction to the preparation of cyanide substitution products, i.e. replacement of the diazo group with cyanogen radical. The reaction is brought about by warming a diazonium salt solution with a solution of cuprous cyanide in potassium cyanide. 

It was shown that the composition and properties of many compounds containing the cyanogen radical were similar to those of the corresponding compounds which contained a halogen atom. The analogy between the two series of compounds is shown by the following formulas —... 

The cyanogen radical which may be introduced into many compounds is present in potassium cyanide, from which such compounds are prepared. Only the more important substances which contain this radical will be described here. 

Capillary detection of ions that contain the cyanogen radical ... 

Fig. 2.6. Rate coefficients for the reaction of (a) aluminium Al( Pj) atoms with O2, (b) boron atoms B( Pj) with acetylene, (c) the cyanogen radical CN with C2H6 and (d) with allene CH2=C=CH2 as a function of temperature, displayed on a log-log scale. The filled circles represent the results obtained in the CRESU experiment. Results from Garland et ol. at higher temperatures are also shown in Fig. 2.6(a) ( ) as well as those from Herbert et al. (A) and data from cooled cell experiments (o) in Fig 2.6(c). CRESU results are fitted using the following formula k(T) = 1.72 x 10 ...

Bullock GE, Cooper RE. (1972) Reactions of cyanogen radicals. Part 3. Arrhenius parameters for reactions with alkanes. J. Chem. Soc. Faraday Trans. I 68 2185-2190. 

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