VOL. 2, No. 2
ORIENTATION o*. BONDSOF
TERVALENT NITROGEN
105
THE ORIENTATION OF THE BONDS OF TERVALENT NITROGEN 1. A. NIEUWLAWD, PROPESSOROF ORGANIC CEEMISTRY, NOTREDAMEUN~VERSITY The reference works and textbooks of organic chemistry do not seem to give a uniform or satisfactory way of illustrating the spacial relationship of the honds of the tervalent nitrogen atom sufficiently explanatory to cover all the possible conditions, especially that of the isomerism of the aldoximes. If the nitrogen atom lies in the same plane with the other two honds in henzaldoxime, there should not he possible a condition admitting cis-transisomerism. Therefore, these compounds cannot have nitrogen bonds in the same plane. On the other hand if the nitrogen atom he shown a t the apex of a tetrahedron (open or closed), with groups a, b, c, attached a t the other corners, then there ought to be optical isomers as
in the configuration of the asymmetric carbon atom. Although many attempts have been made, no such isomers have been isolated. Teachers are, therefore, put in the somewhat anomalous position of explaining the orientation of amines and of oximes by two different schemes, or configurations. If, however, we assume that ordinarily nitrogen has its valences distributed in three directions in one plane for the amines, the f a d s of experiment are in perfect agreement so far. Whenever nitrogen has two valences for one other element, as for example, for carbon in the aldoximes, ethylidene, etc., there is no reason why the application of Baeyer's Strain Theory would not play a part as it does in the case of double bonds hetween carbon and carbon as in ethylene, or in a ring system. One can suppose, then, that the two nitrogen valencies of the double bond, being drawn out of their angle of 120' by attachment to carbon or any other element, they will tend to draw in the remaining valence and its element or group to take the open tetrahedral configuration. It must be remembered that the nitrogen tetrahedron is open, unlike the carbon one with this element in the center. The remaining substituted element or radical will then he drawn to one side and out of plane with the other nitrogen valences. This will insure "molecular comfort." All the valences will tend to be so distributed that the third bond be directed in such a direction that its angle he equal as much as possible to the angle between douhle bonds themselves. Hyponitrous and isohyponitrous add, inorganic compounds with cistrans arrangement, may be thus explained; the strain of a douhle bond in this case being between two nitrogen atoms. The preparation of the latter compound, however, points, according to some authors, to the formula of nitramide. It is, of course, obvious that the tervalent nitrogen atom in hydrocyanic acid cannot show as-trans isomerism, because all of the nitrogen bonds are under equal strain, and are all used up in the union. This status of the question postulates the opened tetrahedral formula for oximes and similar conditions, but appealing to Baeyer's Strain Theory explains why the ordinary distribution of nitrogen's valences in one plane are forced into the other configuration. There is no reason why the strain theory should not be applied to other elements beside carbon, and i t seems to me to be a very simple way out of a difficulty which I cannot find clearly explained anywhere.
