With cyanate and thiocyanate

A striking difference to the reactions with cyanate and thiocyanate [Eq. (95)] has been found with potassium selenocyanate. Elemental selenium is precipitated and cyanide ion is the reactive species in accordance with Eq. (86) (237). 

G., Photoreactivity of some a-arylvinyl bromides in acetic acid. Selectivity toward bromide versus acetate ions as a mechanistic probe, J. Am. Chem. Soc., 113,4261,1991. See also (b) Kitamura, X, Kabashima, X, Kobayashi, S., and Taniguchi, H., Isolation and alcoholysis of an ipso adduct, vinylidenecyclohexadiene, from photolysis of l-(p-ethoxyphenyl)vinyl bromide. Tetrahedron Lett., 29, 6141, 1988 (c) Kitamura, X, Nakamura, I., Kabashima, X, Kobayashi, S., and Taniguchi, H., A novel spiro adduct from intramolecular ipso substitution in the photolysis of an a-[p-(2-hydroxyalkoxyjphenyl]vinyl bromide,/. Chem. Soc., Chem. Commun., 1154, 1989 (d) Kitamura, X, Kobayashi, S., and Xaniguchi, H., Photolysis of vinyl halides. Reaction of photogenerated vinyl cations with cyanate and thiocyanate ions,/. Org. Chem., 55, 1801, 1990 (e) Hori, K., Kamada,... 

Low detection limits (low ng/mL) have been achieved using a headspace/gas chromatographic (GC) technique (Seto et al. 1993). The sample is acidified and incubated, and the headspace analyzed by GC with a nitrogen-specific detector (NPD) (Carseal et al. 1993 Levin et al. 1990 Seto et al. 1993). Reported recovery is good (>90%) (Carseal et al. 1993), and precision is good as well (<15% RSD) (Carseal et al. 1993 Levin et al. 1990 Seto et al. 1993). Blood samples may be treated with chloramine T priorto incubation to produce a derivative which can be determined by GC with electron capture detection (ECD). Cyanate and thiocyanate do not interfere in this method (Odoul et al. 1994). The detection limit is 5 pg/L (ppb) precision is good (<15% RSD) (Odoul et al. 1994). 

Diaryl tellurium iodide cyanates and thiocyanates have been prepared. They arc colored, crystalline solids with sharp melting points, soluble in organic solvents and stable at 20 ... 

It becomes apparent when one is faced with a synthetic problem in imidazole chemistry that there is no single, widely applicable synthetic procedure. Even the methods devised by Bredereck (Section II, A) and the reaction of a-aminoketones with cyanates or thiocyanates (Section II, F) have limitations. 

With evolution of COj or COS, respectively, cyanate and thiocyanate anions react with HFA to form an ionic hexafluoropropaneimine 113, whose crystal structure shows the anion to be dimeric in the solid state (237). 

An important area of inorganic carbon chemistry is that of compounds with C—N bonds. The most important species are the cyanide, cyanate, and thiocyanate ions and their derivatives. We can regard many of these compounds as being pseudohalogens or pseudohalides, but the analogies, although reasonably apt for cyanogen, (CN)2, are not especially valid in other cases. 

Infrared spectra of a number of single crystals of cyanates and thiocyanates have been recorded and correlations made with the crystal structure. However, these results are not listed here since they have been reviewed recently by Iqbal 398). 

The NMRs of aqueous solutions of potassium cyanate and thiocyanate are — 1.1 and —5.7 ppm (relative to benzene) 504) and comparison of these data with those from related compounds suggests that the ions have a small or zero formal charge on the carbon, in general agreement with the results. 

The earliest method of this type, developed by Marckwald, employed the reaction of a-aminocarbonyl compounds (or their acetals) with cyanates, thiocyanates or isothiocyanates to give 3//-imidazoline-2-thiones. These compounds can be converted readily into imidazoles by oxidation or dehydrogenation. The major limitations of this synthetic procedure are the difficulty of synthesis of a wide variety of the a-aminocarbonyl compounds, and the limited range of 2-substituents which are introduced. The reduction of a-amino acids with aluminum amalgam provides one source of starting materials. The method has been applied to the preparation of 4,5-trimethyleneimidazole (83) from 2-bromocyclopentanone (70AHC(12)103), and to the synthesis of pilocarpine (84 Scheme 47) (80AHC(27)24l). If esters of a-amino acids react with cyanates or thiocyanates, the products are hydantoins and 2-thiohydantoins, respectively. 

Decomposition of sulphur dicyanide in aqueous solution is a general-base catalysed reaction , leading to formation of cyanate and thiocyanate. Catalytic coefficients have been estimated for acetate and hydroxide ions. With thiocyanate ion, side reactions also occur these are responsible for some apparent dependence of rate coefficients on sulphur dicyanide concentrations previously found. At 20 °C, /c(OH ) = 5.8 x 10 l.mole- sec" and it(CH3COO") = 7.7 X 10 1.mole sec ... 

Imidazole-4-carboxylates have been made from amidines derived from or-ainino acids (see Section 2.2.1 and Table 2.2.1), by Claisen rearrangement of the adduct formed when an arylamidoxime reacts with a propiolate ester (see Section 2.2.1 and Scheme 2.2.6), from a-aminocarbonyls with cyanates or thiocyanates (see Section 4.1 and Table 4.1.1), from a-oximino- 6-dicarbonyl compounds heated with an aUcylamine (see Section 4.1 and Scheme 4.1.7), and by anionic cycloaddition of an alkyl isocyanoacetate to diethoxyacetonitrile (see Section 4.2 and Scheme 4.2.11 see also Scheme 4.2.12). A further useful approach is to use an appropriate tricarbonyl compound with an aldehyde and a source of ammonia (see Chapter and Scheme 5.1.1). Irradiation of 1-alkenyltetrazoles bearing an ester substituent may have applications (see Section 6.1.2.3). 

No simple reactions between CO2 or CS2 and group IVB hydrides have been reported. On the other hand, a vast literature exists on insertion of CO2 and CS2 into N-H bonds. The reactions of NH3 with CO2 and CS2, to form ammonium carbamate and dithiocarbamate, respectively, are of commercial importance in the synthesis of urea, cyanates, and thiocyanates but are properly considered in the realm of organic chemistry. Secondary phosphines react with CS2 in the presence of a base ... 

In this chapter we deal first with compounds formed by metals containing the isoelectronic groups CN , Cl, and CO. (HCN and non-metal cyanides, and also cyanates and thiocyanates are included in Chapter 21.) We then describe briefly compounds of metals with hydrocarbon radicals or molecules other than olefine compounds of Pd and Pt (Chapter 27) and certain compounds of Cu and Ag (Chapter 25). 

All the crystalline metal fulminates and the heavy metal azides explode and detonate on the application of thermal shock and in some cases in the presence of an electric field, while the heavy metal cyanates and thiocyanates only deflagrate at high temperatures. According to Bowden and Williams (83) the stability to thermal shock increases in the order fulminate heavy metal salts are more thermally unstable. During the last decade Yoffe and co-workers have tried to explain the thermal and photochemical behaviour of these meterials in terms of their electronic structure. This work has been extensively reviewed by Yoffe (2) and will not be considered here. We will however explore briefly a few ideas which qualitatively correlate the geometry of the electronic and atomic configurations with the kinetic stability of these materials. 

When primary amines (43 R6 = H) are used as the amine component, hydantoinimides (42e) and thiohy-dantoinimides (42f) result from hydrogen cyanate and thiocyanate as the acid component HX.53,54 The most important acid components are the carboxylic acids. With primary amines (43 R6 = H) they yield a-acylaminocarboxamides (42g),39,55-57 whereas with secondary amines (42 R1, R2 = organyl), the di-acylimines (42h) are the products, provided that acylatable nucleophiles are absent.55,58,59 The diacyl-imides (42h) are acylating reagents that transfer an R CO group, and so are their precursors, the a-adducts (41 X = R CCh).55... 

Firstly, a group consisting of carbon monoxide, the cyanide ion and alkyl isocyanides, which exhibit chemical shifts in the range 12-37 p.p.m., and secondly a group made up of carbon dioxide, alkyl cyanides, isothiocyanates and the cyanate and thiocyanate ions with chemical shifts in the range 55-76 p.p.m. (from CS2). The groupings reflect similarities between the valence bond description of each set of compounds with their parent molecules, carbon monoxide and carbon dioxide. 

The triple bonded organic functional groups considered in the present chapter are —CC—, —CN, —CNO (nitrile oxide), —OCN, —SCN and —N2. Some isomeric functions such as —NC, —NCO and —NCS, will also be included, as they sometimes occur together with their isomers. The general aspects and specific methods for the analysis of alkynes, nitriles, diazonium compounds, cyanates and thiocyanates, and other related functional groups were adequately described in previous books of the series The Chemistry of Functional Groups, Consideration was made there of detection and determination by means of chemical reactions and application of characteristic spectroscopic properties of the groups. 

The compounds with C-N bonds form a significant branch of inorganic chemistry of carbon, these are hydrogen cyanide (HCN) and the cyanides, cyanic acid (HNCO) and the cyanates, and thiocyanic acid (HNCS) and the thiocyanates. 

Iron(II) has been used as a supramolecular template for the formation of a tris-imidazoUum receptor from Ugand 117 [79]. NMR studies and X-ray crystal structure determination were used to demonstrate the encapsulation of bromide in the cavity of the receptor, with the anion coordinated by six C-H fragments (Fig. 2). Spectrophotometric titrations in acetonitrile solution revealed that this receptor binds halides with selectivity for chloride > bromide > iodide, but has no affinity for dihydrogenphosphate or hydrogensulfate. Presumably the restricted size of the receptor cavity excludes the binding of these larger tetrahedral anions. The Hnear anions azide, cyanate and thiocyanate also produced a response in the UV/vis spectrum, and azide was found to bind preferentially to 117 in comparison to the non-symmetrical linear anions. 

During our research on conducting and superconducting salts of ET>we have made also several attempts to synthesize salts with metal-thiocyanato (and metal-selenocyanato) counterions, as well as with the cyanate and thiocyanate anions themselves (3,4). 

Direct azidation, cyanation, and thiocyanation of diesters of H-phosphonic acid were accomplished readily with sodium pseudohalides in acetonitrile under mild modified Atherton-Todd conditions [124]. 

The treatment of cyanates and thiocyanates can generally use technology identical with that for cyanides. In the treatment of thiocyanate at... 

With cyanide, cyanate and thiocyanate K Fe(CN), room -0.3739 -158 Gouy 67K3... 

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