Cyanates structure

Both structures II and III have an arrangement of atoms that places a positive formal charge on atoms that are higher in electronegativity than carbon. Consequently, the most stable arrangement of atoms is as shown in structure I. Some compounds containing the ion having structure III (the fulminate ion) are known, but they are much less stable than the cyanates (structure I). In fact, mercury fulminate has been used as a detonator. 

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... 

The most stable Lewis structure for cyanate ion is F because the negative charge is on its oxygen... 

The improved method herein described is adapted from the procedure of Runti and Deghenghi. Hydroxyurea has been prepared from potassium cyanate and hydroxylamine hydrochloride. A lower melting isomeric substance, m.p. 71°, has been described." " The structure NH2CO2NH2 has been proposed for this low-melting substance. 

Because of this continued emphasis on adhesive bonding technology development over the years, the airframes of modem front-line aircraft such as the B-2 bomber and the F-117 and F-22 fighters are largely structurally bonded advanced composites. They tend to be comprised of materials that are more advanced (expensive) than commercial aircraft such as carbon and boron fiber reinforcements with cyanate esters, bismaleimides, polyimides or other high-temperature resin matrices and adhesives. 

Unsaturation, degree of. 174 Upfield, (NMR), 445 Uracil, structure of, 1101 Urea, from ammonium cyanate, 2 Urethane, 1214 Uric acid, pKa of, 778... 

The differences in structural parameters originating from different techniques and referring to different states have been mentioned in a similar review on cyanates and isocyanates3. A more detailed discussion can be found elsewhere4. 

The trinitride, cyanate, and isocyanate ions, the first two of which are known35 to be linear, no doubt have identical electronic structures. 

C09-0108. Carbon, nitrogen, and oxygen form two different polyatomic ions cyanate ion, NCO, and isocyanate ion, CNO". Write Lewis stmctures for each anion, including near-equivalent resonance structures and indicating formal charges. 

The complex [Co(NH3)5(OS02CF3)]2+ undergoes triflate substitution by cyanate and condensation with acetone to form the unusual bis-bidentate imine complex (213)917 in a reaction reminiscent of the classic Curtis condensation of acetone with ethylenediamine. Apart from the novelty of the synthesis, the reported crystal structure was only the second of a CoN6 complex bearing a cyanate ligand. 

Cyanogen bromide can be used to activate hydroxyl groups on particles to create reactive cyanate esters, which then can be coupled to amine-containing ligands to form an isourea bond (Figure 14.17). CNBr activation also can produce cyclic imidocarbonate groups, which are less reactive than the cyanate ester, but can form imidocarbonate bonds. The exact reactive species formed by the reaction is dependent on the structure of the hydroxylic support being activated (Kohn and Wilchek, 1982). 

Now that we have determined that structure I is correct for the cyanate ion, we still need to consider resonance structures. In keeping with the rules given earlier, the acceptable resonance structures that can be devised are... 

An additional example of the use of bond energies will be considered. Earlier in this chapter, we considered the structure of the cyanate ion, OCN-. Suppose the structures being considered are... 

The OCN ligand can attach to the XH3 group to form either the cyanate (—OCN) or isocyanate (—NCO) species. Experimental gas-phase geometric structures have been... 

Figure 2.1. Fluoromethylene cyanate ester structures and curing reaction.

The fluorine content for the fluoromethylene cyanate ester resin system is clearly significantly greater than that for AroCy F and also significantly less than that for PTFE (76.0%). Correspondingly, the density reflects the fluorine content. As a homologous series, the contribution of incremental CF2 units can be quantified. From the density data, the volume equivalent of 41. 0 A1 /CF, structural unit in an amorphous thermoset matrix has been determined.8... 

Now we will apply this formal-charge concept to the cyanate ion OCN We chose this example because many students incorrectly write the formula as CNO , and then try to use this as the atomic arrangement in the Lewis structure. Based on the number of electrons needed, the carbon should be the central atom. We will work this example using both the incorrect atom arrangement and the correct atom arrangement. Notice that in both structures all atoms have a complete octet. 

PECH did not react with potassium cyanate but reacted with equimolar potassium thiocyanate in DMF (90°Ci.16 h) to give the thiocyanated polymer (2g, IR, 2180 cm 1) in 53% of DS. Comparing the IR spectrum with those of model compounds, Me2CHCH2SCljl (2180 cm-1) and Me2CHCH2NCS (2200., 2125 cm-1), the isothiocyanate moieties are scarcely existed in the polymer 0. Since the -SCN is a protecting form of thiol likewise the -SCI, the polymer 20 are insolubilized with aqueous alkali presumably due to the S-S crosslinking (23.). Further, absorption at 2180 cm in 20 was completely disappeared treating it with two equivalents of triethyl phosphite at 90°C for 16 h in DMF probably due to the formation of phosphonate structure ( ,). ... 

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