PubMed · 5651095
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E C Griesemer. 1968-01-23. Contour thin-layer chromatography.. https://doi.org/10.1016/s0021-9673(01)80493-3
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In this paper a high-performance thin-layer chromatography (HPTLC) scanner is presented in which a special fibre arrangement is used as HPTLC plate scanning interface. Measurements are taken with a set of 50 fibres at a distance of 400 to 500 microm above the HPTLC plate. Spatial resolutions on the HPTLC plate of better than 160 microm are possible. It takes less than 2 min to scan 450 spectra simultaneously in a range of 198 to 610 nm. The basic improvement of the item is the use of highly transparent glass fibres which provide excellent transmission at 200 nm and the use of a special fibre arrangement for plate illumination and detection.
Two N-methyl-5-lithio-2-pyrrolidinones have been prepared by tin-lithium exchange. These two alpha-aminoorganolithium compounds that are stabilized by an amide dipole, but not by chelation to the amide carbonyl. Both constitute test cases for comparing the stability and reactivity of "dipole-stabilized" and "unstabilized" alpha-aminoorganolithiums. We find that active methylene protons interfere with the reaction, so geminal disubstitution alpha to the amide carbonyl was necessary to suppress side reactions. These species do not react as efficiently as unstabilized alpha-aminoorganolithiums, or even as well as chelated dipole-stabilized alpha-aminoorganolithiums, toward typical electrophiles. The tin-lithium exchange to form these species was also not as facile as with other alpha-aminoorganostannanes.
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