Determination of the relative pKa's of mixtures of organic acids using NMR titration experiments based on aliased 1H–13C HSQC spectra
[摘要] NMRtitrationscanbeusedtosimultaneouslydeterminethepKa'sofmixturesoforganicacidsandbasesprovidedchemicalshiftsaresensitivetotheirchangeofprotonationstates.Carbonsareinprinciplebetterprobesthanprotonsbecausetheirchemicalshiftsaretypicallymoresensitivetothechangesintheelectronicdensitiesofthefunctionalgroupstheyareboundto.Theyarealsolesspronetooverlap,donotsufferfromsecond-ordereffectsandarelesssensitivetochangesinsolventconditions.RecordingHSQCspectrasatisfactorilyreducesthelackofsensitivityofcarbon-detectedexperimentsandthesignaldispersionintwodimensionsallowstoautomaticallyandfinelytrackthedriftsofalargenumberofsignalssimultaneously.Theapplicationofspectralaliasingtothecarbondimensionsallowstoquicklyreachthehighresolutionrequiredtopreciselymeasurevariationsincarbonchemicalshifts.Thepaperextendsthemethodologytothetreatmentofthedatastemmingfromthesimultaneousanalysisofmixturesofcompounds.Italsointroducesmethodstoimprovethenormalizationprocessanddealwithmissingpoints.TheapplicationisnotlimitedtothedeterminationofpKaandcanbereadilyextendedtothedeterminationofotherchemicalconstantsinexperimentswherethecomponentsofthemixturedynamicallycompeteforsubstratesotherthanprotons...
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[效力级别] [学科分类] 分析化学
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