Farhoush Kiani¹, S. Bita Hosseini², S. Ahmad Shahidi², Fardad Koohyar*¹
*Corresponding author
1. Department of Chemistry, Faculty of Science, Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran
2. Department of Agriculture of Food Science Engineering, Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran

Abstract

The acidic dissociation constant is a particular example of equilibrium constant. The quantitative behavior of acids and bases in solution can be understood only if their pKa values are known. In this research work, we calculated the pKa values of saccharin in aqueous solution by an ab initio method. We used the density functional theory (DFT) to describe the acid dissociation constant. To explain the analyze the formation of intermolecular hydrogen bonds (IHBs) between the existent species and water molecules, Tomasi,s method (B3LYP/6-31+G(d)) was used. It was shown that anion, and neutral species of saccharin are solvated with one, two, three, and four molecules of water in alkaline aqueous solutions. We obtained a reasonable comparison between the experimentally determined pKa values for the acid-base reactions selected by potentiometric and those reported in the literature demonstrating the theoretically calculated pKa values.

INTRODUCTION

In the modern food industry, food additives are important to improve shelf life and quality of food products. Among them, artificial sweetener is widely used throughout the world. They are used as sugar substitutes. They don’t have the energy and calories. They are beneficial option for those people who going to diet and uses products in order to reduce energy or sugar intakes for health reasons. The type of sweeteners that approved as food additives in food stuffs by the European Union (EU) include: acesulfame (ACE, code of food contents E950), aspartame (ASP, code E951), cyclamate (CYC, code E952), saccharin (SAC, code E954), sucralose (SUC, code E955) and neohesperidindi hydrochalcone (NHDC, E959) (1). Saccharin (O-sulphobenzimide first prepared in 1879 (2). It is non-nutritive sweetener. The saccharin can exist in ionic or neutral forms. It is about 550 times sweeter than cane sugar. Saccharin is not metabolized in the human organism to produce energy, and it is excreted unchanged by the urine. It is valuable for the diabetic persons and people who need to control intake of calories (3). High dosage of sodium saccharin causes bladder t ...