Trioxo

Nitrous acid, HNO2. See separate entry. Hyponitric acid, H2N2O3, trioxo di-nitrate(Il). Sodium salt from HjNOH in MeOH with CiHiNOi many complexes are known the free acid is unstable. 

Boron trioxide is not particularly soluble in water but it slowly dissolves to form both dioxo(HB02)(meta) and trioxo(H3B03) (ortho) boric acids. It is a dimorphous oxide and exists as either a glassy or a crystalline solid. Boron trioxide is an acidic oxide and combines with metal oxides and hydroxides to form borates, some of which have characteristic colours—a fact utilised in analysis as the "borax bead test , cf alumina p. 150. Boric acid. H3BO3. properly called trioxoboric acid, may be prepared by adding excess hydrochloric or sulphuric acid to a hot saturated solution of borax, sodium heptaoxotetraborate, Na2B407, when the only moderately soluble boric acid separates as white flaky crystals on cooling. Boric acid is a very weak monobasic acid it is, in fact, a Lewis acid since its acidity is due to an initial acceptance of a lone pair of electrons from water rather than direct proton donation as in the case of Lowry-Bronsted acids, i.e. 

The most important property of phosphorus(V) oxide is its great tendency to react with water, either free or combined. It reacts with ordinary water with great vigour, and much heat is evolved trioxo-phosphoric(V) acid is formed, but the local heating may convert some of this to tetraoxophosphoric(V) acid ... 

Nomenclature is based on the keto-enol tautomers. The trihydroxy form is variously designated cyanuric acid, j -triaziae-2,4,6-triol or 2,4,6-trihydroxy-j -triaziQe. The trioxo stmcture, or j -triaziae-2,4,6(lJT,3JT,5JT)-trione is the basis for the isocyanuric acid nomenclature. 

The structure of barbituric acid was the subject of disagreement for many years, but since 195 2 (52BSB44) the trioxo formulation (57 R = H) has been accepted generally, along with the fact that barbituric acid loses a proton, first from carbon (anion) and subsequently from nitrogen (dianion). Barbital (5,5-diethylbarbituric acid) adopts a similar trioxo form (57 R = Et) (69AX(B)1978). 

Trioxo-l,3,5-triazinanetriide ( isocyan-urate, a canonical form of cyanurate)... 

Chemical Designations - Synonyms Trichloroiminoisocyanuris acid Trichloroisocyanuric acid Trichloro-s-Triazine-2,4,6-(lH,3H,5H)-trion Trichlorotriazinetrion 1,3,5- Trichloro- 2,4,6-trioxo-1,3,5-triazine Chemical Formula Cl3(NCO)3. 

The ultraviolet and infrared spectra and the crystal structure (as determined by X-rays) of cyanuric acid have been interpreted on the basis of the trioxo structure 157 however, other ultraviolet data have been reported from which it was concluded that approximately 5% of this compound exists in a hydroxy form in solu-tion. The monoanion of cyanuric acid exists as 158. Ultraviolet spectral data suggest that ammelide (159) and ammeline (160) exist as shown (available infrared spectra offer less conclusive evi-... 

The trioxo formulation (190, R — H) of 2,4,6-trihydroxypteridine is supported by the fact that its ultraviolet spectrum resembles that of the A-methyl derivative (190, R = Me), the pyrimidine ring in the parent compound having been assigned the dioxo configuration by analogy. On the basis of ultraviolet spectral data, the trioxo con-... 

Trihydroxypteridine exists predominantly in the dioxo-mono-hydroxy form 191(R = H), its ultraviolet spectrum closely resembling those of both the 1- and the 3-methyl derivatives and that of l,3-dimethyl-7-methoxypteridine-2,4-dione (191, R = Me). These spectra are quite different from those of 8-methyl- (192, R = H) and l,3,8-trimethyl-pteridine-2,4,7-trione (192, R = Me), which are similar to each other and to those of other 8-substituted pteridine-2,4,7-triones. However, the ultraviolet spectrum of 2,4,7-trihydroxypteri-dine does, indeed, show that a small proportion of the trioxo form is present at equilibrium. A somewhat larger proportion of the 6-methyl derivative exists in the trioxo form, although structure 193 predominates. The trioxo form (194) of 2,4,7 trihydroxy-l,3,6-trimethyl-pteridine is the most important tautomer, but the corresponding 6-carboxylic acid exists entirely in the monohydroxy-dioxo form 195. 

Both the infrared and ultraviolet spectra of pyrrolidine-2,3,5-triones (75) have been interpreted to support their existence as hydroxy-maleimides (76), and the occurrence of a strong OH stretching band in the infrared spectrum of 4-phenylpyrrolidine-2,3,5-trione has been taken as evidence that it too exists in a hydroxy form, probably 76 (R CeHg). However, the trioxo formulation is suggested by t/j the infrared spectra of jV-substituted pyrrolidine-2,3,5-triones, although an equilibrium apparently occurs depending upon the substituents and conditions. The zwitterion formulation 77 has been advanced for 4-aminopyrrolidine-2,3,5-trione. For chemical evidence... 

Thermolysis of tricyclic 425 in Dowtherm A afforded 6,8,10-trioxo-9,10-dihydro-6//-pyrido[l,2-a]quinoxaline-7,9-dicarboxylate 426 (00CHE615). 

Lactame mit cyclischer Acyl-harnstoff-Struktur (z. B. 2,4-Dioxo-imidazolidin, S. 138f., 252f., 2,4-Dioxo- bzw. 2,4,6-Trioxo-hexahydropyrimidine) werden in der Regel an der Lactam-Struktur angegriffen, wahrend die Carbonyl-Funktion der Harnstoff-Gruppe nur z. Tl. reduziert wird (s. S. 135ff.). 

Beim 2,4,6-Trioxo-l,l,3,3,5,5-hexamethyl-cyclohexan in Gegenwart von Acetanhy-drid/Acetonitril reagieren zwei Oxo-Gruppen zum 1,5-Diacetoxy-3-oxo-2,2,4,4,6,6-he-xamethyl-bicycla[3.1.0]hexan (71% d.Th.)1 ... 

Im folgenden werden einige Beispiele der Reduktion von Dioxo- und Trioxo-steroiden aufgefiihrt ... 

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