Replacement of other elements by nitrogen

Replacement of other elements by nitrogen 1. Replacement of nitrogen by nitrogen 

The greatest interest in such replacements attaches to transamination and transamidation and to the various methods of forming C—N bonds by means of diazonium salts and diazo compounds. Substitution of amino for nitro groups is almost wholly restricted to o- and / -dinitro compounds and is of little importance. Preparation of a-nitroso and x-hydroxyimino esters from oc-nitro esters and sodium nitrite has been discussed above (pages 431, 478 and 479). 

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We fool ourselves, however, if we dwell on energy alone. The uses of all natural resources are intertwined. Oil is of little use without engines built of iron, copper, zinc, and other metals. Farmlands will yield maximum crops only if they are tilled by tractors emd plows and fertilized with compounds of phosphorus, nitrogen, and potassium. A failure in the supply of one resource will inevitably influence the use of others. Viewing the panoply of natural resources, we see that one group, metals, occupies a unique position. Without metals we could not build machines to replace human muscle. Without metals we could use little of the available energy. Metals are, in effect, the enzymes of industry. If supplies of metals are limited, then society must ultimately be limited too. It is my contention that the distribution of the chemical elements in nature means, inevitably, that there are natural limits to supplies of metals, and that these limits are much more important to the future of society than limits on energy. I also contend that, with sufficient work, the limits can be predicted. It is the piu-pose of this paper, therefore, to explore briefly the way metals occur and to attempt to place in perspective the limitations they may ultimately impose on us. 

A further kind of modification that may be considered is the replacement of the glycosidic oxygen atom by other elements, notably sulfur and nitrogen. A variety of synthetic 1-deoxy-l-thioglycosides have been prepared and have been shown to be extremely stable toward acid hydroly-... 

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