Hydrogen pseudohalides

Nucleophiles like alcohols [2, S], hydrogen sulfide [2], thiols [2,10], ammonia, amines, hydrazines, hydroxylamines [2 11, 12, 13, 14, 75], azides [2], other pseudohalides [2], phosphonates [2,16,17,18,19, 20], and phosphanes [2,19] add rapidly across the CO or CN double bond to yield stable adducts The phosphonate adduets undergo a subsequent aleohol—lester rearrangement [19, 20] (equation 2)... 

Hydrogen cyanide (Table 15.1) is a colorless, flammable liquid or gas that boils at 25.7°C and freezes at minus 13.2°C. The gas rarely occurs in nature, is lighter than air, and diffuses rapidly. It is usually prepared commercially from ammonia and methane at elevated temperatures with a platinum catalyst. It is miscible with water and alcohol, but is only slightly soluble in ether. In water, HCN is a weak acid with the ratio of HCN to CN about 100 at pH 7.2, 10 at pH 8.2, and 1 at pH 9.2. HCN can dissociate into H+ and CN. Cyanide ion, or free cyanide ion, refers to the anion CN derived from hydrocyanic acid in solution, in equilibrium with simple or complexed cyanide molecules. Cyanide ions resemble halide ions in several ways and are sometimes referred to as pseudohalide ions. For example, silver cyanide is almost insoluble in water, as are silver halides. Cyanide ions also form stable complexes with many metals. 

Amendola, V., Boiocchi, M., Colasson, B., Fabbrizzi, L., Douton, M.-J. R., Ugozzoli, F., A Metal based tris-imidazolium cage that provides six C-H hydrogen bond donor fragments and includes halides and pseudohalides. Angew. Chem. Int. Ed. 2006, 45, 6920-6924. 

Organotin hydrides are advantageous as reductants in terms of their facile availability, stability, and reactivity. - Almost all tin hydrides are liquids, and stoichiometric tin-hydrogen bonds can be used. In general, the tin hydride reductions have been performed under radical conditions using initiators such as azobisisobutyroni-trile (AIBN), triethylborane, and UV irradiation. The reduction of organic halides and pseudohalides by tri- -... 

Between 1953 and 1955, Ziegler and his coworkers developed a simple and direct synthetic route to aluminum trialkyls from aluminum, hydrogen, and the corresponding alkene [213,231]. Aluminum trialkyls, which are Lewis acids, show a strong tendency to react with alkali metal and tetraorganoammonium halides and pseudohalides to... 

Hydrogen peroxide is a substrate for myeloperoxidase, a multisubunit heme protein of M.W. 150,C, present in primary neutrophilic granules. The active prosthetic groups are two hemes covalently attached to the apoen-zyme. This enzyme catalyzes many kinds of oxidation reactions, but oxidation of halide ions to hypohalite ions appears to be the most important. Hypochlorite ion is the principal compound formed, although Br , I, and SCN (a pseudohalide) can also serve as substrates. The reaction catalyzed is... 

There are therefore two main reasons for the laige deviations observed for water (a) entropic effects and enthalpic effects by hydrogen bonding interactions between water molecules of neighbouring hydration shells, as discussed in the preceding section, and (b) the strong solvating power of water towards halide and pseudohalide ions. 

---