Cyanides kinetics

Kirk M, Kulig K, Rumack BH. 1989. Methemoglobin and cyanide kinetics in smoke inhalation [Abstract]. Vet Hum Toxicol 31 353. 

The case of 2-nitrofuran is especially interesting. The quantum yield of disappearance of starting material in the photocyanation reaction is 0.51 at 313 nm and not dependent on the cyanide ion concentration. The quantum yield of product formation, however, is dependent on the concentration of cyanide, a limiting value of 0.51 is reached at approximately 1 mole l i cyanide. Kinetics are in agreement with the formation of an intermediate X (the nature of which needs to be clarified) which is subsequently intercepted by a nucleophile. Water competes with cyanide in this product-forming step. This cyanation has been both sensitized and quenched, thus very likely it proceeds via a triplet state. 

Dissolution of gold and silver from Au/Ag alloys in aerated cyanide solutions has been investigated using rotating disc electrodes [551]. Dissolution was partially controlled by transport of either oxygen or cyanide. Kinetics of anodic dissolution of gold in cyanide solutions containing different metal ions has been extensively... 

The rate of dissolution is limited by oxygen availabiUty rather than by cyanide concentration. When oxygen solubiUty is reduced by water salinity or by consumption by ore constituents such as sulfide minerals, enrichment of the air with oxygen or addition of hydrogen or calcium peroxide improves leaching kinetics and decreases cyanide consumption (10). 

Nucleophilic Substitution. The kinetics of the bimolecular nucleophilic substitution of the chlorine atoms in 1,2-dichloroethane with NaOH, NaOCgH, (CH2)3N, pyridine, and CH COONa in aqueous solutions at 100—120°C has been studied (24). The reaction of sodium cyanide with... 

This contrary stereochemistry in the Bucherer - Bergs reaction of camphor has been attributed to steric hindrance of e.w-attack of the cyanide ion on the intermediate imine. Normally, equatorial approach of the cyanide ion is preferred, giving the axial (t>Mr/o)-amino nitrile by kinetic control. This isomer is trapped under Bucherer-Bergs conditions via urea and hydan-toin formation. In the Strecker reaction, thermodynamic control of the amino nitrile formation leads to an excess of the more stable compound with an equatorial (e.w)-amino and an axial (endo)-cyano (or carboxylic) function13-17. 

The synthesis of a-amino acids by reaction of aldehydes or ketones with ammonia and hydrogen cyanide followed by hydrolysis of the resulting a-aminonitrile is called the Strecker synthesis. Enzymatic hydrolysis has been applied to the kinetic resolution of intermediate a-aminonitriles [90,91]. The hydrolysis of (rac)-phenylglycine nitrile... 

It was suggested that this change in product distribution was due to the existence of an equilibrium between two types of complex, viz., a cr-butenyl-pentacyanocobaltate(III) and a 7r-butenyltetracyanocobaltate(III) 107, 109). However, further study of the kinetics and product distribution suggested the presence of two o-bonded complexes, viz., cr-but-l-en-3-yl and a-but-2-en-l-yl 24a). Direct evidence for the existence of a cyanide-dependent equilibrium between the a- and rr-bonded organocyanide complexes has been obtained from NMR studies of the complex prepared by the reaction of allyl halides with Co—H 109) (see also Section V,C). Both butadiene and crotyl chloride react with Co—H to give the same... 

Similar kinetics are reported for the reduction of several quinones by ferro-cyanide, but the rate coefficients, k are affected by added ferricyanide , viz. 

Ogura, Y. and Yamazaki, I. (1983). Steady-state kinetics of the catalase reaction in the presence of cyanide. J. Biochem. (Tokyo) 94, 403-408. 

Three cyanide-degrading nitrilases were recently cloned and purified and their kinetic profiles were evaluated in order to better understand their applicability to cyanide bioremediation. CynD from Bacilluspumilus Cl and DyngD from Pseudomonas stutzeri exhibit fairly broad pH profiles with >50% activity retained across pH 5.2 to pH 8.0 while the CHT (NHase) from Gloeocercospora sorghi exhibited a more alkaline pH activity profile with almost all of its activity retained at pH 8.5, slightly lower thermal tolerance, and quite different metal tolerance compared with the two bacterial enzymes [46]. 

Cyanide is not the only nucleophile to effect reactions as in Scheme 35, C, but of those studied so far only benzenesulfinate and phenoxide are similar (and also show second order kinetics) while others give simple substitution with no rearrangement (and show first order kinetics). No doubt ionization to a furylium ion plays an important part in some of these transformations, but it is harder to account for the behavior of 70 which yields a lactone (71) and almost no cyano products.198... 

Yu, XZ, Gu J-D (2006) Uptake, metabolism, and toxicity of methyl ter/-butyl ether (MTBE) in weeping willows. J Hardz Mat B137 1417-1423 Yu, XZ, Gu J-D (2007a) Differences in Michaelis-Menten kinetics for different cultivars of maize during cyanide removal. Ecotoxicol Environ Saf 67 254-259... 

Kinetic studies indicate that the dissociation of the Cu(i) complex of (114) in the presence of cyanide is several orders of magnitude slower than occurs for the corresponding complex of (115) because of the necessary unravelling of the two cycles before demetallation can occur (Albrecht-Gary, Saad, Dietrich-Buchecker Sauvage, 1985). 

---