Determination of pKa for some Schiff bases derived from benzaldehyde and amino phenols by conductivity measurement

Abstract

‫ي‬ ‫عنى‬ ‫ه‬ ‫ل‬ ‫ي‬ ‫دير‬ ‫ت‬ ‫لبح‬ pKa ‫ت‬ ‫ليد‬ ‫ت‬ ‫ةر‬ ‫لل‬ ‫لت‬ ‫ق‬ ‫دد‬ ‫ا‬ ‫ا‬ ‫ش‬ ‫عد‬ ‫بعو‬ ‫ل‬ ‫ع‬ ‫نات‬ ‫اليم‬ ‫ت‬ ‫حض‬ ‫مع‬ ‫يهاي‬ ‫ل‬ ‫لبنز‬ ‫تفاشالت‬ ‫ةق‬ ‫ط‬ ‫شن‬ ‫قت‬ ‫ر‬ ‫ل‬ p,m,o ‫م‬ ‫باقيخ‬ ‫ندل‬ ‫ف‬ ‫ند‬ ‫م‬ ‫ت‬ ‫اق‬ ‫لس‬ ‫ت‬ ‫ةر‬ ‫لل‬ . ‫د‬ ‫ف‬ ‫عت‬ ‫الا‬ ‫ات‬ ‫اق‬ ‫ى‬ ‫ش‬ ‫اق‬ ‫باالشيم‬ ‫ت‬ ‫ب‬ ‫ع‬ ‫لي‬ ‫ا‬ ‫باته‬ ‫ه‬ ‫ن‬ ‫م‬ ‫لياه‬ ‫ك‬ ‫ت‬ ‫وع‬ ‫ل‬ ‫النصهار.‬ ‫قرجات‬ ‫لى‬ ‫باالضافت‬ ‫ء‬ ‫لحم‬ ‫وتحت‬ ‫ت‬ ‫بنفسج‬ ‫ا‬ ‫شم‬ ‫دحع‬ ‫ل‬ " ‫ل‬ ‫ت‬ ‫م‬ ‫اة‬ ‫نرص‬ ‫ه‬ ‫ف‬ ‫اهك‬ ‫تس‬ ‫ع‬ ‫ت‬ ‫ن‬ ‫روج‬ ‫له‬ ‫و‬ ‫ال‬ ‫ة‬ ‫ت‬ ‫ق‬ ‫ر‬ ‫ل‬ ‫د‬ ‫ه‬ ‫ه‬ ‫ف‬ pKa ‫ل‬ benzylidene -o-hydroxy aniline. ‫ه‬ ‫ف‬ ‫دل‬ ‫ن‬ ‫لف‬ ‫ت‬ ‫مجمدش‬ ‫دق‬ ‫لدج‬ ‫ة‬ ‫دحع‬ ‫ل‬ ‫ا‬ ‫عم‬ ‫عع‬ ‫مد‬ p,m ‫لد‬ ‫ليأث‬ ‫ا‬ ‫ا‬ ‫ش‬ ‫لرد‬ ‫الوله‬ ‫ن‬ ‫الم‬ ‫جهت‬ ‫من‬ ‫ل‬ ‫ك‬ ‫ى‬ ‫ش‬ ‫ضح‬ pKa ‫ت.‬ ‫لمسيحص‬ ‫خ‬ ‫ه‬ ‫لي‬ ‫ا‬ ‫ا‬ ‫ش‬ ‫عد‬ ‫أين‬ ‫ت‬ ‫اشالت‬ ‫ليف‬ ‫ت‬ ‫ال‬ ‫ينم‬ ‫مدق‬ ‫لي‬ ‫ت‬ ‫لميا‬ ‫اغ‬ ‫حس‬ ‫ك‬ ‫ت‬ ' ‫تظه‬ ‫ك‬ ‫لس‬ ‫ت‬ ‫لمدجب‬ ‫و‬ ‫ار‬ ‫الا‬ ΔG˚ ‫و‬ ΔH˚ ‫ك‬ ‫م‬ ‫تمي‬ ‫ا‬ ‫نم‬ ‫د‬ ΔS˚ ‫يها‬ ‫مناع‬ ‫ك‬ ‫ت‬ ‫ه‬ ‫لي‬ ‫و‬ ‫البت‬ ‫لس‬ ‫و‬ ‫ار‬ ‫الا‬ ‫ل‬ ‫باليفص‬ . Abstract:The aim of this work is concerned with the determination of pka for some Schiff bases by conductivity method.These imines are prepared by reactions of benzaldehyde with o,m,p-amino phenols by standard method.The structures of these imines are confirmed by using some physical methods, namely, U.V,I.R and melting points.Experimentally it is observed,that intramolecular hydrogen bonding may contribute in decreasing pka value of benzylidene-ohydroxyaniline. The presence of phenolic groups at m and p-positions of Determination of pKa for some Schiff bases derived from benzaldehyde and … 2 primary amine side of the Schiff bases, have a noticeable influence on the collected pka values.The thermodynamic of ionization reactions of these Schiff bases are determined. These showed a positive sign values of ΔG˚ and ΔH˚ thermodynamic parameters. Also ΔS˚ value has a negative sign. These positive and negative signs values are discussed in detail.