NMR active nuclei and isotopes as tracers

Despite its low abundance (Table 15.1), O has been used in studies of, for example, hydrated ions in aqueous solution and polyoxometallates (see Section 22.7). 

The isotope O is present to an extent of 0.2% in naturally occurring oxygen and is commonly used as a (non-radioactive) tracer for the element. The usual tracer for sulfur is which is made by an (n,p) reaction on Cl is a P-emitter with h = 87 days. 

The solution Te NMR spectrum of Tt cyclo-C i )2 at 298 K shows one broad signal. On increasing the temperature to 353 K, the signal sharpens. On cooling to 183 K, the signal splits into three signals at 601, 503 and 381 with relative integrals of 25 14 1. Rationalize these data. 

Te(cyc/o-C6Hii)2 contains only one Te environment, but the Te atom can be in either an equatorial or axial position of the cyclohexyl ring. This leads to three possible conformers  

The reaction of SeCl2 with BuNH2 in differing molar ratios leads to the formation of a series of compounds, among which are the following  

How many signals would you expect to see for each compound in the Se NMR spectrum  

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