Anodic and cathodic reactions in acetonitrile/tetra-n-butylammonium tetrafluoroborate: an electrochemical and infrared spectroelectrochemical study

Abstract

In situ infrared spectroelectrochemistry has been used to observe electrolyte/solvent breakdown processes in TBAF/acetonitrile at a platinum electrode. Anodic breakdown gives the adduct CH3CNBF3 as the major product. Cathodic breakdown gives the anion of 3-aminocrotonitrile as the major product in the absence of water, and the formation of this product is a consequence of reduction of hydrogen dissolved in the metal. In the presence of water the anion of acetamide is also formed, and breakdown commences at much less negative potentials.

SNIFTIRS studies of the electrochemical oxidation of 1,3-dimethoxybenzene on platinum in acetonitrile/tetrabutilammonium electrolytes

“…However, the bands observed for these species changed from negative to positive values, indicating that BF À 4 is being either consumed or transformed during the process. The same behaviour was reported also by Foley et al [22], who established that this system could generate, under defined conditions, an adduct (CH 3 CNBF 3 ) with characteristic IR signals at 2360 and 855 cm À1 . Swanson and Shriver [30] also reported these characteristic vibrations for the chemically synthesised adduct.…”

“…The other band, at 2150 cm À1 corresponding to C@N [33]. Besides this, aminocrotonitrile has been reported to be formed [22] at potentials as high as )3.30 V, which most prominent signals appear at 2116 and 1516 cm À1 . In spite of such studies, the role of traces of water in acetonitrile in anodic reactions has not yet been completely understood.…”

“…Furthermore, it has been demonstrated that, in such systems, CO 2 is obtained as a major oxidation product at positive potentials [11]. On the other hand, according to Foley et al [22], a characteristic band (2356 cm À1 ) attributed to a proposed adduct is found when hydrogen (adsorbed on platinum at negative potentials; i.e. )2.00 V vs. Ag/Ag þ ) is oxidized.…”

“…This band attributed to the asymmetric stretching of the anion shows up as a complex band due to the effect of the two isotopes of boron [30] ( 10 B 11 B; natural abundance: 19.9% and 80.1%, respectively). Foley et al [22] assigned two bands to BF À 4 , one at 1060 cm À1 and another one at 1030 cm À1 . On the other hand, acetonitrile shows strong adsorption bands at about 1040 cm À1 , due to the methyl rotational mode (-CH 3 ), and at 918 cm À1 due to the C-C symmetric stretching.…”

A study of the adsorption of acetonitrile on a gold electrode from aqueous solutions using in situ vibrational spectroscopy

“…The electrolyte used in the expeiments was KC1O 4 , it having been shown elsewhere that the K + cation has a very small effect on the spectrum of acetonitrile [7]. The spectroscopic technique used was subractively nmmlized interfacial FTIR spectroscopy (SNIFTIRS) as developed by Pons and colleagues [1,2].…”