Nitrites groups

The nitrate group, like the nitrite group, is a versatile ligand and numerous modes of coordination have been found in nitrato complexes. ° The uncoordinated N03 ion (isoelectronic with BF3, B03 , C03 , etc.) is planar with N-O near 122 pm this value... 

Another related reaction is the Barton reaction, by which a methyl group in the 0 position to an OH group can be oxidized to a CHO group. The alcohol is first converted to the nitrite ester. Photolysis of the nitrite results in conversion of the nitrite group to the OH group and nitrosation of the methyl group. Hydrolysis of the oxime tautomer gives the aldehyde, for example,... 

This salt is used as an inhibitor for the polymerisation of butadiene. It seems to play its role very well when its concentration is lower than 0.5%. If the concentration is greater than 5%, a black precipitate forms which contains 80% of organic polymer containing nitrate and nitrite groups in the proportions of 2 1. This solid combusts spontaneously at 150 C even when there is no air. 

The Barton reaction [102], A photochemical exchange process between a nitrite group and a proximate nonactivated hydrogen has been called the Barton reaction. The process appears to be limited to aliphatic compounds (Eq. 52). 

The existence of an N—N bond in jjrimary nitramines is also proved by the fact that these substances are obtained by the oxidation of diazo compounds. Additional evidence that nitramines contain a nitro and not a nitrite group and hence have a structure different from R—N—ONO is provided by the fact that nitramines are relatively resistant to alkali, whereas nitrous esters are highly unstable. 

Photolysis of primary, secondary, and tertiary alkyl nitrites in benzene indicated that a minimum chain length of five carbon atoms attached to the nitrite grouping is required for appreciable yields of secondary nitroso dimers via the Barton reaction. In the case of primary and secondary nitrites, a chain of length of four carbon atoms or more attached to the nitrite grouping is required for formation of the six-membered intermediate (e.g., A) involved in the Barton reaction.139140... 

Bipositive cobalt forms hypoligating bonds with water and hyper-ligating bonds with nitrite groups.47... 

The syntheses presented here are examples of two types of "ligand isomers (1) Nitrito complexes, [Ni 2-[(methylamino)-methyl]pyridine 2(ONO)2], and [Ni 2-[(methylamino)methyl]-piperidine)2(ONO)2] (2) Chelating nitrite groups, [Co(2,4,6-trimethylpyridine iV-oxide NCh ], [Co(2,6-dimethylpyridine iV-oxide) 2 (NO 2)2], and [Co(4-methylquinoline iV-oxide)2(N02)2]. 

The nitrite group has three fundamental vibrational modes which are all active in the infrared region, and upon coordination the band positions are shifted as compared to the free nitrite frequencies. In Table I the infrared frequencies of the N02 ... 

The gas phase reaction proceeds very much as described for nickel carbonyl, but the product does not contain the nitrite group (10). A smoke is formed immediately the gases come into contact, but the analysis and infrared spectrum of the solid formed show it to be the oxide-nitrate Fe0(N03). It seems likely that initial reaction involves the NO2 radical, and an iron nitrite such as Fe(N02)3 may be produced initially. The oxidation-reduction properties of the ferric and nitrite ions may render them incompatible Fe0(N03) would then be left as a decomposition product. So little is known about transition metal nitrites that this must remain conjecture at present, but it may be relevant to recall that it has not yet been possible to isolate pure samples of Fe(N03)3, A1(N03)3, or Cr(N03)3. 

The nitrite group is one of the most strongly deshielding substituents in its effect on the alpha aliphatic groups. Methylene groups are deshielded to about 4.5 ppm and methines to about 5.5 ppm. Such extremes of chemical shift are characteristic of only a few substituents making the identification of a Nitrite compound a relatively easy matter. 

The oxidation clearly removes an electron from a Pt-Pt antibonding orbital since the Pt-Pt distance is shortened by about O.4S. In addition, two N-bonded nitrite groups are added in the terminal positions. 

Polymers can be divided into two main classes on the basis of their reactivity to NO [1]. Saturated polymers such as polyethylene (PE) and polypropylene (PP) belong to the first group, but Nylon 66 does not. The second group covers elastomers. Butyl rubber (BR) undergoes scissions of the main chain, and polybutadiene is extensively cross-linked under the action of NO. These elastomers have approximately the same reactivity to NO as to ozone. All films exposed to NO become yellow, and their infrared (IR) spectra show that nitro groups enter into macromolecules. In polyvinylchloride in the presence of NO, a decrease in the amount of chlorine, along with the appearance of nitro and nitrite groups, are observed from IR spectra. 

---