Ion definition

Piperidines have not been reported as products in the numerous other reductions however, the products of 4-imsubstituted pyr-idinium ions definitely contain piperidines as shown by gas chromatographic analysis. The amount of the substituted piperidine can be related directly to the degree of steric interference to attack of the borohydride ion at the 2- or 6-positions, and thus by inference the completely saturated rings must be formed from 1,4-dihydropyridine intermediates16 (Eq. 5 and Table I). 

In a study of the displacement of anions from soil by soluble silicate, Toth (131) showed that phosphate ion was released from the absorbed state only in slightly alkaline media, so thai t displacement s by hydroxyl or silicate ions rather than silicic acid. At about pH 7 soluble silica is essentially nonionized and has little tendency to displace phosphate ion. Definite increases in yield of barley and Sudan grass were noted when calcium or magnesium silicate was added to soil, these materials being apparently sufficiently alkaline to furnish some silicate ions. There was marked absorption of silica by rape, barley, and Sudan grass when grown in silicated soils. 

Synthetic compounds if available are always preferable for structural characterization and fragmentation elucidation since individual lipid ions selected from the analysis of biological samples may contain isomeric species. The presence of isomers at a selected ion definitely leads to a comphcated mass spectrum and an inaccurate fragmentation pattern. 

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