Nitrogen Trivalent

The bivalent radical —NH— linked to two identical radicals can be denoted by the prefix imino-, as well as when it forms a bridge between two carbon ring atoms. A trivalent nitrogen atom linked to three identical radicals is denoted by the prefix nitrilo-. Thus ethylenediaminetetraacetic acid (an allowed exception) should be named ethylenedinitrilotetraacetic acid. 

Uric acid is odourless in spite of three carbonyl groups, four trivalent nitrogen atoms and a double bond, and that it is similarly colourless in spite of four chromophores. Measurements of its refractive and dispersive properties indicate that it is a saturated body which suggests that molecular attraction exists between the various groups. 

The most common cause of chirality is the presence of four different substituents bonded to a tetrahedral atom, but that atom doesn t necessarily have to be carbon. Nitrogen, phosphorus, and sulfur are all commonly encountered in organic molecules, and all can be chirality centers. We know, for instance, that trivalent nitrogen is tetrahedral, with its lone pair of electrons acting as the fourth "substituent" (Section 1.10). Is trivalent nitrogen chiral Does a compound such as ethylmethylamine exist as a pair of enantiomers ... 

The answer is both yes and no. Yes in principle, but no in practice. Trivalent nitrogen compounds undergo a rapid umbrella-like inversion that inter-converts enantiomers. We therefore can t isolate individual enantiomers except in special cases. 

Pyramidal inversion (Section 24.2) The rapid stereochemical inversion of a trivalent nitrogen compound. 

We have recently characterized the heptacyclic alkaloid chilocorine from the ladybird (coccinellid) beetle Chilocorus cacti (23). In spite of its superficial complexity, this structure is easily dissected into two tricyclic moieties, A and B, each of which can be regarded as an acetogenin which has been elaborated from a straight chain of 13 carbon atoms stitched together at three points by a trivalent nitrogen atom. 

Elements which form pyramidal bonding also form optically active compounds provided the groups are different. To this class belong derivatives of trivalent nitrogen, phosphines, arsines or stibines. 

An exchange quantity, S(,(tert/sec, sec, sec), not previously calculated, is found to be ca —59 kJmol-1 from this example. By comparison with other exchange quantities in Table 2 this value seems inaccurate26. However, we note that the cis/trans enthalpy difference of pyrrolizidine (ca 14 kJ mol-1 from Reference 25) is significantly less than the ca 26 kJmol-1 we deduce for bicyclooctane. This should not surprise us because trivalent nitrogen has been known to accommodate strain by partial or total planarization27. 

Imides are usually included for main group elements because bi- and oligonuclear metal imides are ubiquitous and were often developed in parallel with the amides. They generally feature trivalent nitrogen, as in [ As(Cl)(p-NBu )]2. Imido derivatives of the transition... 

The majority of amides (or imides) of arsenic, antimony and bismuth (collectively designated as of M ), have M in the - -3 oxidation state, although several examples of As and Sb amides or imides have been reported but only three papers have dealt with Bi compounds. The imides considered to be within the scope of this chapter are those having trivalent nitrogen as, for instance, in [As(p-NR)X]2. There are very few examples of As —N compounds, such as the bis(imido)arsenic(I) cation 1," and only one of a thermally stable... 

It is well known that iraras-bicyclo[3,3,0]octane is a rigid and strained system, whereas the cis-isomer is almost strain-free. Pyrrolizidine differs in that one of the carbon atoms is substituted by a trivalent nitrogen atom which does not rigidly fix the bicyclic system. For this reason, pyrrolizidine, although it probably occurs in the preferred cia-conformation,74 has no stereoisomers. The two rings of the pyrrolizidine system form a dihedral angle with the axis along the C(8)—N bond. 

The transformation of amines over acidic catalysts is more complicated than that of other compounds which can undergo elimination. Like alcohols, amines form either an olefin or a higher substituted amine (the formal counterpart of an ether). With trivalent nitrogen, the reaction scheme includes more compounds than divalent oxygen allows, viz. 

The nitroamines are substituted ammonias, substances in which a nitro group is attached directly to a trivalent nitrogen atom. They are prepared in general either by the nitration of a nitrogen base or of one of its salts, or they are prepared by the splitting off of water from the nitrate of the base by the action of concentrated sulfuric acid upon it. At present two nitroamines are of particular interest to the explosives worker, namely, nitro-guanidine and cyclotrimethylenetrinitramine (cyclonite). Both are produced from synthetic materials which have become available in large commercial quantities only since the first World War, the first from cyanamide, the second from formaldehyde from the oxidation of synthetic methyl alcohol. 

In nomenclature, the prefixes a and are used to distinguish between the two structures a indicates that the substituent is attached to the benzene ring which is linked to trivalent nitrogen... 

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