Publication: Sulu çözeltilerde bazı nötr aminoasitlerin makro ve mikro ayrışma sabitlerinin sıcaklıkla değişiminin incelenmesi ve ayrışmanın termodinamik niceliklerinin belirlenmesi
Abstract
1.ÖZET Bu çalışmada; Glisin, L-Alanin ve L-Lösin ile Glisin Metil Esteri, L-Alanin Metil Esteri ve L-Lösin Metil Esterin, 5,0, 20,0 ve 35,0C sıcaklıklarda iyonik kuvveti sabit tutmak amacıyla, 0,1 mol L1 NaClO4 içeren ortamda potansiyometrik pH titrasyonu yöntemi kullanılarak protonlanma sabitleri bulundu. Bu sabitler makroskopik protonlanma sabitleri olup esterlerin protonlanma sabitleri yardımıyla Glisin, L-Alanin ve L-Lösinin mikropkopik protonlanma sabitleri de hesaplandı. Tüm ligandların pKNH2 değerleri sıcaklık arttıkça azalmakta, pKCOOH değerleri ise artmaktadır. Bu protonlanma sabitlerinden protonlanma tepkimesinin termodinamik nicelikleri , ve hesaplandı. Aminoasitlerin –NH2 grubunun protonlanması için serbest enerji azalmasına entropi teriminin katkısı ortalama %44 olup, –COOH için %100 dür. Aminoasit Metil Esterlerinin –NH2 grubunun protonlanması için serbest enerji azalmasına entropi teriminin katkısı ise ortalama %23 tür. Ayrıca sonuçlar yumuşak veya sert asit ve bazlar kuralına göre yorumlandı. 1.
''THE STUDY OF THE CHANGE OF NEUTRAL AMİNOACİD’S MACRO AND MİCRO PROTON STABİLİTY WİTH TEMPERATURE İN WATERY SOLUTİON.’’ In this study, the protonation constants of glycine, glycine methyl ester, L-alanine, L-alanine methyl ester L-leucine and L-leucine methyl ester have been determined by potantiometric pH titrations at 5.0, 20.0 and 35.0oC and 0.1 mol L-1 NaCIO4 ionic strength. The calculated constants are the macroscopic protonation constans. In terms of macroscopic protonation constants of esters the microscopic protonations constans of glycine, L-alanine and L-leucine were determined. pKNH2 of whole ligands decrease, pKCOOH increase with increasing temperature. The thermodynamic parameters, , and were calculated for protonation reactions. Contribution of the entropic term to the free energy decrease is average 44% for protonation of –NH2 and average 100% for –COOH groups of amino acids. Contribution of the entropic term to the free energy decrease is average 23% for protonation of –NH2 group of amino acid methyl esters The results were concluded according to Hard and Soft Acids and Bases Rule.
''THE STUDY OF THE CHANGE OF NEUTRAL AMİNOACİD’S MACRO AND MİCRO PROTON STABİLİTY WİTH TEMPERATURE İN WATERY SOLUTİON.’’ In this study, the protonation constants of glycine, glycine methyl ester, L-alanine, L-alanine methyl ester L-leucine and L-leucine methyl ester have been determined by potantiometric pH titrations at 5.0, 20.0 and 35.0oC and 0.1 mol L-1 NaCIO4 ionic strength. The calculated constants are the macroscopic protonation constans. In terms of macroscopic protonation constants of esters the microscopic protonations constans of glycine, L-alanine and L-leucine were determined. pKNH2 of whole ligands decrease, pKCOOH increase with increasing temperature. The thermodynamic parameters, , and were calculated for protonation reactions. Contribution of the entropic term to the free energy decrease is average 44% for protonation of –NH2 and average 100% for –COOH groups of amino acids. Contribution of the entropic term to the free energy decrease is average 23% for protonation of –NH2 group of amino acid methyl esters The results were concluded according to Hard and Soft Acids and Bases Rule.