Cyanation compounds

Table XIX gives some shift data for cyanate compounds, where a high-field shift is seen for JV"-cyanato complexes and a downfield shift observed for EtOCN (192). Similar arguments to those used for thiocyanate complexes presumably may be also applied here.

Although the only cyanate compound reported for these metals is cp2V(NCO)2 (the analogous NCS and NCSe compounds are also known) which is in contrast to the 0-cyanatotitanium analog (145, 261), there are numerous examples of thiocyanate complexes. 

Procedures for the corresponding cyanate compounds are described in synthesis 6. 

Alkyl derivatives of these cyanate compounds in which the alkyl radical is derived from a saturated hydrocarbon of the methane series are not of any special importance. When, however, we study another series of hydrocarbons known -as the unsaturated hydrocarbons we shall find important derivatives which occur in nature. We shall then refer to this study of the general relationships which we have here discussed. 

These substances, having the formula CjHjNHCONH, and OC(NHCjH6)j respectively, are both formed when an aqueous solution of urea and aniline hydrochloride is heated. Their subsequent separation is based on the fact that diphenylurca is insoluble in boiling water, whereas monophenylurea is readily soluble. The formation of these compounds can be explained as follows. When urea is dissolved in water, a small proportion of it undergoes molecular rearrangement back to ammonium cyanate, an equilibrium thus being formed. 

Some organosilicon compounds undergo transmetallation. The allylic cyanide 461 was prepared by the reaction of an allylic carbonate with trimethylsi-lyl cyanide[298]. The oriho esters and acetals of the o. d-unsaturated carbonyl compounds 462 undergo cyanation with trimefhylsilyl cyanide[95]. 

What particularly seemed to excite Wohler and his mentor Berzelius about this experiment had very little to do with vitalism Berzelius was interested m cases m which two clearly different materials had the same elemental composition and he invented the term isomerism to define it The fact that an inorganic compound (ammonium cyanate) of molecular formula CH4N2O could be transformed into an organic compound (urea) of the same molecular formula had an important bearing on the concept of isomerism... 

From the concept of isomerism we can trace the origins of the structural theory—the idea that a precise arrangement of atoms uniquely defines a substance Ammonium cyanate and urea are different compounds because they have different structures To some degree the structural theory was an idea whose time had come Three scientists stand out however for independently proposing the elements of the structural theory August Kekule Archibald S Couper and Alexander M Butlerov... 

In the introduction we noted that both Berzelius and Wohler were fascinated by the fact that two different compounds with different properties ammonium cyanate and urea pos sessed exactly the same molecular formula CH4N2O Berzelius had studied examples of similar phenomena earlier and invented the word isomer to describe different compounds that have the same molecular formula... 

Thousands of compounds of the actinide elements have been prepared, and the properties of some of the important binary compounds are summarized in Table 8 (13,17,18,22). The binary compounds with carbon, boron, nitrogen, siUcon, and sulfur are not included these are of interest, however, because of their stabiUty at high temperatures. A large number of ternary compounds, including numerous oxyhaUdes, and more compHcated compounds have been synthesized and characterized. These include many intermediate (nonstoichiometric) oxides, and besides the nitrates, sulfates, peroxides, and carbonates, compounds such as phosphates, arsenates, cyanides, cyanates, thiocyanates, selenocyanates, sulfites, selenates, selenites, teUurates, tellurites, selenides, and teUurides. 

Synthesis from OC-Amino Acids and Related Compounds. Addition of cyanates, isocyanates, and uiea derivatives to a-amino acids yields hydantoin piecuisois. This method is called the Read synthesis (2), and can be considered as the reverse of hydantoin hydrolysis. Thus the reaction of a-amino acids with alkaline cyanates affords hydantoic acids, which cyclize to hydantoins in an acidic medium. 

Organosulfur Compounds. These compounds, Hsted in Table 8, are used in a variety of appHcations, including cooling water, paint, and metalworking. Methylenebisthiocyanate hydroly2es rapidly at a pH above 8 to cyanate ion which complexes with ferric iron to poison the cytochrome systems (36). 

The name cyanates indicates that the compounds contain an oxygen atom, in contrast to cyanides. 

Ozone can be used to completely oxidize low concentrations of organics in aqueous streams or partially degrade compounds that are refractory or difficult to treat by other methods. Compounds that can be treated with ozone include alkanes, alcohols, ketones, aldehydes, phenols, benzene and its derivatives, and cyanide. Ozone readHy oxidizes cyanide to cyanate, however, further oxidation of the cyanate by ozone proceeds rather slowly and may require other oxidation treatment like alkaline chlorination to complete the degradation process. 

Ethyl carbamate, C2HyN02, is developed naturally during the fermentation of alcohoHc beverages. It also appears in foods such as bread and yogurt. Since ethyl carbamate is not easily distilled, its formation most likely involves a distillable precursor. The mechanism of ethyl carbamate formation probably involves cyanate produced from the oxidation of cyanide or from urea-based compounds in the beer. Cyanate reacts with alcohol to form ethyl carbamate as follows ... 

It is also prepared by direct cyanation of l,4-diamino-2,3-dichloroanthraquinone (35) or 1,4-diaminoanthraquinone (33) in an aprotic organic solvent. In the latter case, the presence of an ammonium compound and a dehydrogenating agent is necessary (55). 

Azoles can form stable compounds in which metallic and metalloid atoms are linked to nitrogen. For example, pyrazoles and imidazoles Af-substituted by B, Si, P and Hg groups are made in this way. Imidazoles with a free NH group can be Af-trimethylsilylated and Af-cyanated (with cyanogen bromide). Imidazoles of low basicity can be Af-nitrated. 

Cyanides are dangerously toxic materials that can cause instantaneous death. They occur in a number of industrial situations but are commonly associated with plating operations, and sludges and baths from such sources. Cyanide is extremely soluble and many cyanide compounds, when mixed with acid, release deadly hydrogen cyanide gas. Cyanide is sometimes formed during the combustion of various nitrile, cyanohydrin, and methacrylate compounds. Cyanides (CN ) are commonly treated by chlorine oxidation to the less toxic cyanate (CNO ) form, then acid hydrolyzed to COj and N. Obviously, care should be taken that the cyanide oxidation is complete prior to acid hydrolysis of the cyanate. 

Undoubtedly these reactions proceed via an intermediate ureido or thioureido derivative. These compounds have been obtained by Dornow and Hahmann by the action of potassium cyanate or ammonium isothiocyanate on 2-amino-4,6-dimethylnicotinic acid (11), but whereas the urea (12, X = 0) was converted into the pyrido[2,3-li]-pyrimidine-2,4(lI/,3/7)-dione (13, X = 0) by the action of heat, the thiourea (12, X = S) was unchanged after similar treatment. 

The 6-methyl derivative (98, R = Me) was an important intermediate in the synthesis of analogs (e.g., 183) of folic acid. Korte has shown that 2-aminopyrido[3,2-guanidine carbonate with 3-aminopicolinic acid and that treatment of the same acid with ammonium thiocyanate or potassium cyanate yields the thioureido and ureido derivatives (100, X = S and X = 0). In contrast to the pyrido[2,3-d]pyrimidine system bsoth of these compounds could be cyclized by heat and the latter (100, X = O) is a likely intermediate in the synthesis of the dione (98) by the fusion with urea. 

Selen-verbindung, /. selenium compound, -wasserstoff, m, hydrogen selenide. -was-serstoffsaure, /. hydroselenic acid, -wismut-glanz, m. guanajuatite. -zelle, /. selenium cell, -zyanid, n. selenium cyanide seleno cyanate. -zyankalium, n. potassium selenocyanate. 

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