Tautomer

Tautomeri er et specialtilfælde af strukturel isomeri. En tautomer er sin egen isomer af en organisk forbindelse, som har den egenskab at den hurtigt kan ændre sin isomeriske form ved en kemisk reaktion som kaldes tautomerisering.

Sædvanligvis forekommer dette som migrering af hydrogenatomer (protoner) med en ombytning af en enkeltbinding med en dobbeltbinding. I opløsninger hvor tautomeri er mulig, vil en kemisk ligevægt mellem de to tautomerene opnås. Forholdet mellem tautomerene kommer an på mange faktorer, inklusiv temperatur, opløsningsmiddel og pH. Tautomeri kan katalyseres med syrer og baser.^[1]

^ J Comput Aided Mol Des. 2009 Oct; 23(10): 693–704, ncbi.nlm.nih.gov: Let’s not forget tautomers Citat: "...A compound exhibits tautomerism if it can be represented by two structures that are related by an intramolecular movement of hydrogen from one atom to another...Frequency of molecules that can tautomerize. A summary of one program’s enumeration of tautomers [31] of marketed drugs [32] is shown in Fig. 13. Of the 1,791 compounds, 1,334 or 74% exist as only one tautomer—put another way, 26% exist as an average of three tautomers...Although many workers have investigated the relative stabilities of tautomers in different liquid phases, because of the difficulty of measuring the equilibrium constants there is no publically available comprehensive database of this data. This lack hinders the development of empirical methods to predict the ratios of tautomers of a molecule..."

[1] J Comput Aided Mol Des. 2009 Oct; 23(10): 693–704, ncbi.nlm.nih.gov: Let’s not forget tautomers Citat: "...A compound exhibits tautomerism if it can be represented by two structures that are related by an intramolecular movement of hydrogen from one atom to another...Frequency of molecules that can tautomerize. A summary of one program’s enumeration of tautomers [31] of marketed drugs [32] is shown in Fig. 13. Of the 1,791 compounds, 1,334 or 74% exist as only one tautomer—put another way, 26% exist as an average of three tautomers...Although many workers have investigated the relative stabilities of tautomers in different liquid phases, because of the difficulty of measuring the equilibrium constants there is no publically available comprehensive database of this data. This lack hinders the development of empirical methods to predict the ratios of tautomers of a molecule..."

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