Isomers oxidation numbers

What usefulness has the concept of oxidation number in deciding whether two classes of compounds can be isomers of each other ... 

Ans. In order to be isomeric, two classes of compounds with only one functional group each can be isomeric only if the carbon atoms of the functional group (or attached to the functional group) have the same oxidation number. For example, aldehydes and ketones can be isomers because the carbon atoms of their functional groups have the same oxidation number (0). 

Established Practice in the English Language. The nearly literal translation of the French terms in English, Russian and other languages resulted in the system whose use has become standard practice in English-speaking as well as other countries. The system has been molded by the fact that elemental composition and valence (or oxidation number) are the principal variables for most inorganic compounds other than the most complex, whereas connectivity and the possibility foi isomers have been of little concern. 

Tin, like iron, is an element for which Mossbauer spectroscopy can be broadly useful.5 Using the Sn119m nucleus, isomer shift (IS) measurements allow one to determine oxidation number and to some extent to estimate structural and bonding features. The IS values are usually in the order Sn11 > Sn° > SnIV, though this cannot be trusted absolutely. 

Oxidation of the p-nitrophenylhydrazine (38) derived from 1,2 5,6-di-O-isopropylidene-0i-D-n/)0-hex-3-ulose with lead tetra-acetate gave the 3-C-(p-nitrophenyldiazo)glucofuranose (39) exclusively, with none of the a//o-isomer. A number of other hydrazones were similarly oxidized, the reactions in most cases showing a high degree of stereoselectivity. ... 

These structural units are assigned formal oxidation numbers as given in Chapter 3.1. Thus, orthophosphoric, phosphorous and hypophosphorous acids may be termed 5/P, 3/P and 1/P acids, respectively. Pyrophosphoric acid is 5/P-0-5/P and hypophosphoric acid is 4/P-4/P. Isomers can be clearly distinguished on this system. The two acids with the formula H4P2O5, for example, are written as 3/P-0-3/P and 2/P-4/P. 

Reaction (3.1.9) is a typical trans addition. The oxidation number increases by two units, since two ligands are added in the rrans-positions. The intermediate has a square pyramid structure the equatorial geometry is preserved. On the other hand, if the reaction is carried out in a more polar solvent, e.g., methanol, the intermediate becomes trigonal bipyramidal, and the products are cis- and tran -isomers. It is not clear why polar solvents favor the trigonal bipyramidal intermediate. The condition for these reactions is that the complex in its reduced form has the possibility of additional coordination and that it can accept two new ligands. 

Explain the important distinction between each of the following pairs (a) coordination number and oxidation number (b) monodentate and polydentate ligands (c) cis and trans isomers (d) dextrorotatory and levorotatory compounds (e) low-spin and high-spin complexes. 

Albright Wilson s Vircol 82 is a diol mixture obtained by the reaction of propylene oxide and dibutyl acid pyrophosphate (112). The neutral Hquid has an OH number of 205 mg KOH/g and contains 11.3% phosphoms corresponding to the formula shown where x y = 3.4. The product is a mixture of isomers. 

In the case of substituted phenazine fV-oxides some activation of substituents towards nucleophilic substitution is observed. 1-Chlorophenazine is usually very resistant to nucleophilic displacements, but the 2-isomer is more reactive and the halogen may be displaced with a number of nucleophiles. 1-Chlorophenazine 5-oxide (56), however, is comparable in its reactivity with 2-chlorophenazine and the chlorine atom is readily displaced in nucleophilic substitution reactions. 2-Chlorophenazine 5,10-dioxide (57) and 2-chlorophenazine 5-oxide both show enhanced reactivity relative to 2-chlorophenazine itself. On the basis of these observations, similar activation of 5- or 6-haloquinoxaline fV-oxides should be observed but little information is available at the present time. 

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