Conductometric Titration of Halides with EDTA in N, N-Dimethylformamide and Determination of Acid Halides

Abstract

Conductometric titration of acid halides were examined by ethylenediaminetetraacetic acid (EDTA) in N, N-dimethylformamide (DMF). DMF was used as the solvent because the acid halide did not dissolve in water, but dissolved in the organic solvents such as DMF, dimethyl sulfoxide (DMSO), pyridine, etc., while EDTA could dissolve in DMF only. The acid halides used therein were butyryl chloride, octanoyl chloride, palmitoyl chloride and acetyl halide. Standerdization of the solutions was made by gravimetry.
After the sample solution was taken in the titration cell, DMF was added and they were stirred and titrated. Titration was carried out at the speed from 0.5 cm³·min^-1 to 1.0 cm³·min^-1 at room temperature. The observed molar ratio between the chlorides and EDTA w as found to be 1: 1. The significant inflection point was not obtained by the use of other solvents (DMSO, pyridine, etc. ).
Less than 1 v/v% of water gave no influence on this method, but the equivalent molar of various metal ions such as Ni²⁺, Cu²⁺, Co²⁺, etc., gave a posxitive error respectively.
The total of 1 × 10^-2 mol·dm^-3 of chloride and acid halides was obtained. The applicable concentration range of the method was from about 1 × 10^-3 mol·dm^-3 to 5 × 10^-2 mol·dm^-3.
It seemed that these reactions were addition reactions for nitrogen atom of EDTA. These reactions seemed to depend on length of the ionic radius and electronegativity, but did not relate to dissociation energy between carbon and the halogen atom.