ELSEVIER Talanta 43 (1996) 771-776 Talanta Thermometric titrations of amines with nitrosyl perchlorate in acetonitrile solvent Turgut Giindi.iz *, Esma Kilic, Orhan Cakirer Department q/ Chemistry, Faculty of Sciwrce. bniwrstty of Ankaru. Ankara. Turkq Received 8 May 1995; revised 3 October 1995: revised 1 I December 1995 accepted I I December 1995 Abstract Thirteen aliphatic and four aromatic amines, namely diethylamine, triethylamine. n-propylamine. di-n-propy- lamine, tri-n-butylamine, isopropylamine. di-isopropylamine. n-butylamine, di-n-butylamine, tri-n-butylamine, isobutylamine, set-butylamine, tert-butylamine, aniline, NJ-dimethylaniline, 2nitroaniline and 4-nitroaniline were titrated thermometrically with nitrosyl perchlorate in acetonitrile solvent. All the aliphatic amines gave very well-shaped thermometric titration curves. The calculated recovery values of the amines were very good. In comparison, the aromatic amines, aniline and NJ-dimethylaniline gave rather well-shaped titration curves, but the recovery values were fairly low. 2-Nitro- and 4-nitro anilines gave no thermometric response at all. The heats of reaction of the amines with nitrosyl perchlorate are rather high. However. the average heat of reaction of the aromatic amines is approximately two-thirds that of the average heat of the aliphatic amines. To support this method all the amines were also titrated potentiometrically and very similar results to those obtained with the thermometric method are seen. The nitrosyl ion is a Lewis acid, strong enough to titrate quantitatively aliphatic amines in acetonitrile solvent, but not strong enough to titrate aromatic amines at the required level in the same solvent. Key,vord.s: Aliphatic amines: Aromatic amines; Nitrosyl perchlorate; Thermometry 1. Introduction A number of methods such as potentiometry, conductimetry, spectrophotometry and ther- mometry can be used for the titration of diverse chemical compounds in non-aqueous media. Among these however, thermometry, in some re- spects, has definite advantages over the other methods [l-6]. These advantages briefly are as follows: (i) low electrical conductivity of non- * Corresponding author. Fax: + 90 312 2232395 aqueous media does not interfere; (ii) precipita- tion. which occurs during some titrations, does not affect this method: (iii) end points are gener- ally very sharp; (iv) there is no electrode poison- ing: and (v) the equipment can be set up in a medium equipped laboratory. Furthermore, in contrast to other methods, thermometry can be applied to (i) redox titration; (ii) acid-base titration; (iii) complexometry and; (iv) volumetric precipitation. As is well known, these are the basic and major analytical reactions on which titrimetry is based [7-201. 0039-9140/96/$15.00 G 1996 Elsevier Science B.V. All rights reserved PII SOO39-9140(96)01856-5