Hydrogen cyanide dimer

Legon A 0, Millen D J and Mjdberg P J 1977 The hydrogen cyanide dimer identification and structure from microwave spectroscopy Chem. Phys. Lett. 47 589... 

Fillery-Travis, A. J., Legon, A. C., Willoughby, L. C., and Buckingham, A. D., Rotational spectroscopy of N-hydrogen cyanide dimer Detection, relative stability and D-nuclear quadrupole coupling of deuterated species, Chem. Phys. Lett. 102, 126-131 (1983). 

Jucks, K. W., and Miller, R. E., The intermolecular bending vibrations of the hydrogen cyanide dimer, Chem. Phys. Lett. 147, 137-141 (1988). 

K. W, JucksandR, E. Miller,/. Chem. Phys., 88,6059(1988). Infrared Spectroscopy of the Hydrogen Cyanide Dimer. 

This section provides information regarding known health effects of cyanide exposure. Exposure to hydrogen cyanide (HCN) gas is most common by inhalation. In the discussion below, inhalation exposures are expressed as ppm hydrogen cyanide. Exposure to cyanide can also occur by inhalation of cyanogen gas, a dimer of cyanide. However, cyanogen breaks down in aqueous solution into cyanide ion (CN1) and OCN" ions (Cotton and Wilkinson 1980). The rate of the breakdown depends on pH and is... 

In 1821 Wohler discovered that a solid deposited from concentrated aqueous solutions of thiocyanic acid. The solid, which was called isoperthiocyanic acid (3-imino-5-mercapto-1,2,4-dithiazole) (361), formed a new product perthiocyanic acid (3,5-dimercapto-l,2,4-thiadiazole) (18) when treated with alkali and then acid. On storage perthiocyanic acid (18) readily reverted to isoperthiocyanic acid (361) (65AHC(5)119). The mechanisms of these interconversions are still not known with certainty but the transformations outlined in Scheme 130 are suggested. Wohler proposed the initial formation of a dimer of thiocyanic acid for which structure (359) appears resonable. Addition of the imine function of (359) to the nitrile function of HSCN would produce the trimer (360) which could readily eliminate hydrogen cyanide to produce isoperthiocyanic acid (361). 

The first attempt to resolve rotational fine structure on the IR bands of H-bonded systems has been due to Jones, Seel and Sheppard74). They studied the complexes H3N. .. HCN, D3N. .. DCN and the dimer of hydrogen cyanide (HCN)2. Three parallel bands were observed for these complexes the C-H (or C-D) stretching band, the CsN stretching band and the NH3 (or ND3) symmetric deformation band. For the ammonia-hydrogen cyanide complex these bands are at at 3150, 2085 and 1040 cm"1 respectively. 

The initial drive for acrylonitrile (AN) production (6.2 Mt/a in 2004 worldwide) was the discovery, in the late 1930s, of the synthetic rubber Buna N. Today nitrile rubbers represent only a minor outlet for AN which is utilized primarily for polymerization to give textile fibres (50%) and ABS resins (24%), and for dimerization to adiponitrile (10%). Early industrial processes depended on the addition of hydrogen cyanide to acetylene or to ethylene oxide, followed by the dehydration of intermediate ethylene cyanohydrin. Both processes are obsolete and are now supplanted by the ammoxidation of propylene (Equation 34) introduced in 1960 by Standard Oil of Indiana (Sohio). The reason for the success stems from the effectiveness of the catalyst and because propylene,... 

Another procedure consists in slowly adding pyridine to an ethereal solution of an acyl chloride and anhydrous hydrogen cyanide. This order of addition of the reactants is important in order to retard the formation of acyl cyanide dimers. In this manner, certain benzoyl cyanides as well as furoyl cyanide have been prepared (40-80%). 

Chattopadhyay, S., and Plummer, P. L. M., Ab initio studies on the dimer of sulfur dioxide and hydrogen cyanide, J, Chem. Phys. 93,4187-4191 (1990). 

In a more detailed study, the structure of the catalyst precursor was determined and found to be Pd(Diop),32. Other L2Pd and L2Ni complexes [L = Diop, BPPM, BINAP, etc.] were prepared [e.g., by in situ reduction of Pd(Il)Cl,L with sodium borohydride or as isolated palladium(O) complexes] and used as catalysts for the asymmetric addition of hydrogen cyanide to norbornene. norbornadiene, benzonorbornadiene, and cyclopentadiene dimer. In the presence of excess ( + )-Diop and L,Pd, norbornene gives 91 -95% of exo-2-cyanonorbornane with 24% cc of the ( + )-(15.25,4/ )-isomer. Similarly, use of the ( —)-Diop complex leads to the (-)-(l/ ,2f ,4S)-isomer with 24% ee (95% yield). Lower reaction temperatures, instead of the 120 "C used above, give better ee values (80 =C 32% ee with 94% yield 35 °C 35 % ee with 6% yield)32. 

Triazines are one of the oldest known compound classes in organic chemistry. First reports date back to 1776 when cyanuric acid (l,3,5-triazine-2,4,6-triol 1,3,5-triazine-2,4,6(l//,3//,5f/)-trione) was obtained by the pyrolysis of uric acid.1 The same method was also utilized in 1820 2 however, triazine compounds were probably first prepared in 1704 upon trimerization of cyanide derivatives when the Berlinerblau -complex salt, the first known cyano compound, was discovered.468 Cyanuric chloride was synthesized in 1828 from hydrogen cyanide and chlorine.3 Another method, discovered in 1834, involves treatment of potassium thiocyanate with chlorine. When heated, cyanuric chloride is obtained.4 Melamine (1,3,5-triazine-2,4,6-triamine) was also prepared in 1834 by heating potassium thiocyanate with ammonium chloride.5 Although 2,4,6-substituted 1,3,5-triazine derivatives were identified very early, the unsubstituted parent compound was not synthesized before 1895.6 At that time, however, the isolated compound was assigned to a dimeric species and not to the trimeric hydrogen cyanide. This was finally proven much later."... 

Finally this is the place to mention the hydrogen cyanide derivatives that react with themselves to give dimers, trimers, or polymers. In the presence of acidic catalysts53 cyanogen chloride trimerizes very easily to cyanuric chloride cyanamide is dimerized smoothly by alkali to dicyanodiamide 54 and trimerization to melamine is suitable as a preparative method starting from dicyanodiamide and ammonia under pressure.55... 

By-products formed during their preparation (e.g., ethylbenzene and divin-ylbenzenes in styrene acetaldehyde in vinyl acetate) added stabilizers (inhibitors) autoxidation and decomposition products of the monomers (e.g., peroxides in dienes, benzaldehyde in styrene, hydrogen cyanide in acrylonitrile) impurities that derive from the method of storage of the monomer (e.g., traces of metal or alkali from the vessels, tap grease etc.) dimers, trimers, and polymers that are generally soluble in the monomer, but sometimes precipitate, for example, polyac-rylOTiitrile from acrylonitrile. Likewise, in polycondensation reactions it is important to remove reactive impurities because they can cause considerable interference during the polyreaction. 

It has been widely reported that electrooxidation of the thiocyanate ion at pH 4 yields hydrogen cyanide and (or) cyanide and sulfate ions as main products [134]. However, there is a huge gap in terms of the mechanism that takes place between the binding of thiocyanate to the catalyst and the products experimentally found. In order to get insight about the elemental reactions between these processes, it is proposed based on experimental evidence that the oxidation of thiocyanate particularly catalyzed by MPc and MPc like systems, leads to the production of thiocyanate radicals that dimerize to form the pseudohalogen molecule thio-cyanogen (SCN)2 [132, 135-139]. 

A proposed step in the prebiotic polymerization of hydrogen cyanide, the dimerization of iminoacetonitrile (22) to the HCN tetramer, diaminomaleo-nitrile (23), has been achieved with the A-t-butyl derivative of (22). Di-iminosuccinonitrile (24), an oxidized form of the tetramer, has been pre-... 

In the probable prebiotic chemical evolution of adenine by pentameriza-tion of hydrogen cyanide, the intermediacy of a dimer of the latter has been assumed although it remains undetected, iminoacetonitrile (119) has been suggested as a plausible structure for the dimer, and the synthesis of iV-t-butyliminoacetonitrile, the first known member of this family, has been reported by a Chicago school (Scheme 44). ... 

Nickel.— Phosphine and phosphite complexes of nickel(0) react with strong acids to produce complexes [NiHL4]+. Reaction with weak acids may proceed further, with attack of the anion at the nickel. Thus the complex Ni(LL)a, where LL = l,4-bis(diphenylphosphino)butane, reacts with hydrogen cyanide to form firstly a hydride, which reacts quickly with cyanide to give the bimolecular intermediate Ni2(CN)2(LL)a. The ultimate products are the nickel(n) monomer Ni(CN)2(LL)2 and dimer [Ni(CN)2-(LL)]2. Ni(PPh3)4 undergoes normal oxidative elimination reactions with aryl halides to produce the new nickel(n) complexes Ni(aryl)(X)-(PPh3)2. ... 

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