Theoretical Investigations for the Behavior of Hydrotropes in Aqueous Solution

Abstract

The presented paper introduces an attempt for finding a theoretical model capable for describing the critical aggregation concentration (cac) for some hydrotropes (a series of sodium-p-n-alkylbenzoates, n=0-8). Such a proposal was carried out through theoretical calculations based on density functional theory (DFT) for estimating some physical properties which might be helpful for supporting the recent published report as all of these hydrotropes are considered as surfactant like (see doi: 10.1021/la2025846). The estimated physical properties can be divided to three classes according to their effect: steric properties such as volume and surface area, electronic properties such as polarizability, and hydrophobic properties such as log P which represents the ratio of concentrations of a compound in two phases of octanol and water. The results show that both steric and hydrophobic properties play major roles in predicting the cac for the presented hydrotropes. The best model was found between cac and tail polarizability (PT) according to the following relation: cac = 1.52-1.09log PT ; with r² equal to  0.96, S.E equal to 0.026M and significant cross validation correlation coefficient (0.943). A unique feature of the presented model is containing only one descriptor with excellent statistical parameters. This actually supports the recent (above mentioned) published results of that all of these hydrotropes can be considered as surfactant-like. The suggested models were applied to some randomly selected surfactants with reasonable results. The results are generally suggesting for the possibility of estimating the cac or critical micelle concentration (cmc) for amphiphilic molecules using computational chemistry software.

Keywords

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Sulu çözeltide hidrotropların davranışı üzerine teorik araştırmalar

Abstract

Makale bazı hidrotroplar için (bir seri sodyum p-n-alkilbenzoatlar, n=0-8) kritik agregasyon konsantrasyonu (cac) bulunmasına yardımcı olacak bir teorik model önermektedir. Bu öneri , söz konusu bütün hidrotropların yüzey aktif benzeri olduğunu bildiren yakın zamanlardaki bir çalışmayı desteklemekte yardımcı olabilecek (bkz. doi: 10.1021/la2025846) bazı fiziksel özellikleri kestirmek için yoğunluk fonksiyonel teorisi (DFT) kaynaklı teorik hesaplamalar üzerinden yürütülmüştür. Kestirilen fiziksel özellikler etkilerine göre üç sınıfa ayrılabilir: hacim ve yüzey alanı gibi sterik özellikler, polarizlenebilirlik gibi elektronik özellikler ve log P (oktanol ve su fazlarında bir bileşiğin konsantrasyon oranını belirtir) gibi hidrofobik özellikler. Elde edilen sonuçlar, sterik ve hidrofobik özelliklerin söz konusu hidrotropların cac değerini tahmin etmekte büyük rol oynadığını göstermektedir. En iyi model, cac ve kuyruk polarizlenebilirliği (PT) üzerinden şu eşitlik ile bulunmuştur: cac = 1,52-1,09logPT; r2 -0,96’ya eşittir, S.E. 0,026 M’ye eşittir ve belirgin çapraz doğrulama korelasyon katsayısı 0,943’e eşittir. Önerilen modelin benzersiz bir özelliği, mükemmel istatistik parametreler içeren yalnızca bir belirleyici kullanmasıdır. Bu da yukarıda bahsedilen kaynak yayındaki sonuçları doğrulamaktadır (bütün bu hidrotroplar yüzey aktif madde gibidir). Önerilen modeller, makul sonuçlar vermek üzere rasgele seçilmiş bazı yüzey aktif maddelere uygulanmıştır. Sonuçlar genel olarak, hesapsal kimya yazılımları kullanılarak amfifilik moleküller için cac veya kritik misel konsantrasyonu (cmc) değerlerini kestirme olasılığını ortaya koymaktadır.

Keywords

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