Quaternary salts, ultraviolet absorption

Quaternary salts, ultraviolet absorption, 50 Quaternization, of alkylthiazoles, by alkyl halide or methyl tosylate, 386 of 5-alkylthiazoles, kinetic data, 391 of dialkyl thiazoles, kinetic data, 389 kinetic data, 388... 

The ultraviolet absorption spectra of 3,4-dihydro-jS-carboline derivatives exhibit a dependence on pH similar to that shown by the speetra of the fully aromatie compounds. 3,4-Dihydro-/S-carboline and 1-methyl- and 7-methoxy-l-methyl-3,4-dihydro-jS-carbo-line serve as examples. The quaternary 3,4-dihydro-jS-earbolin-ium salts obtained on p /r-A-alkylation of these dihydro-j3-earbo-lines show a bathoehromic shift of 5 mp, eompared to the... 

The pyridinium salts have been shown to have electrophilic positions at the 2-, 4-, and 6-carbon atoms. Of these, the 2- and 6-positions should be the more positive because of the proximity to the quaternary nitrogen. From the ultraviolet absorption spectra of the reaction mixtures during the reduction and of the isolated products, it can be demonstrated that the predominant attack of the hydride ion from sodium borohydride occurs at these two positions.5,6 The 1,6-dihydro-pyridine (such as 5) formed from the reduction of a 1,3-disubstituted pyridinium ion appears to be stable toward further reduction, for a number of such compounds have been isolated from sodium borohydride reductions containing sufficient borohydride to complete the reduction to the tetrahydro-state.7"10 Since 1,4-dihydropyridines having a 3-substituent which is electron-withdrawing have also been... 

The absorption spectra of these complexes can be obtained in the visible and near infrared region using solutions of the triphenylphos-phonium salts, but if the ultraviolet spectrum is desired, the complex must be formed in solution using an aliphatic quaternary ammonium halide and the actinide trihalide or oxyhalide. 

---