Changed reactivity of the 1-bromo-4-nitrobenzene radical anion in a room temperature ionic liquid

Abstract

Radical anions of 1-bromo-4-nitrobenzene (p-BrC6H4NO2) are shown to be reactive in the room temperature ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, ([C4mPyrr][NTf2]), by means of voltammetric measurements. In particular, they are shown to react via a DISP type mechanism such that the electrolysis of p-BrC6H4NO2 occurs consuming between one and two electrons per reactant molecule, leading to the formation of the nitrobenzene radical anion and bromide ions. This behaviour is a stark contrast to that in conventional non-aqueous solvents such as acetonitrile, dimethyl sulfoxide or N,N-dimethylformamide, which suggests that the ionic solvent promotes the reactivity of the radical anion, probably via stabilisation of the charged products.

The role of cations in the reduction of 9-fluorenone in bis(trifluoromethylsulfonyl)imide room temperature ionic liquids

“…It has been previously reported by some of us, and other research groups, that the E1 values obtained for the reduction process of several redox probes on RTILs are strongly associated with the solvation process of the electrogenerated radical anions. 15,16,[22][23][24][25][26] For simplicity we will analyze the data by considering a concerted solvation process when the radical anion is electrogenerated, 34 which implies that the difference between the E1 values (E1 (DMF) À E1 (RTIL)) can be related to the D ion-pair solvation G1. 35 The E1 values for the formation of the 9-fluorenone anion radical (1 À ) in RTILs are negatively shifted with respect to the reference value obtained in DMF (Table 1, Fig.…”

“…[5][6][7] Hence, the most active field in electrochemistry, together with RTILs, is currently focused on electrodeposition, [8][9][10] supercapacitors, 11 batteries, [12][13][14] and the study of the heterogeneous electron transfer of electroactive organic compounds in RTILs. [15][16][17][18][19][20][21] It is important to note that the ''stabilization'' of radicals and radical anions has been observed in few cases (such as nitroderivatives, 15,16 halogenated compounds, 22,23 acetophenone, 24 stilbene, 25 and superoxide ions 26 ). Following this approach, it is possible to determine the electrocatalytic properties of some RTILs, understanding as electrocatalytic properties the fact that the same reduction or oxidation process can take place at a lower potential value depending on the composition of the RTILs.…”

Electrochemical Reaction of Organic Compounds in Ionic Liquids

“…It is important to mention that even when the one-electron mechanism to form the stable radical anion (Eq. 15.54) is also observed in a range of organic solvents (e.g., acetonitrile, dimethyl sulfoxide, and N,N-dimethylformamide), the debromination step only occurs in organic solvents after the absorption of light by the 1-bromo-4-nitrobenzene radical anion (photochemical reaction) [50,[52][53][54].…”

“…15.54) [50]. This step is followed by a debromination step, which also involves the fast scavenge of a proton from the solvent system to yield nitrobenzene (Eq.…”

Electrochemical Properties of a Verdazyl Radical in Room Temperature Ionic Liquids

“…This was attributed to the formation of a more ordered bilayer structure consisting of alternating ionic and lipophilic regions. The mechanisms and reactions of some charged radical speciesincluding the N,N,N′,N′-tetramethylpara-phenylenediamine (TMPD) radical cation, [13] and the 1-bromo-4-nitrobenzene radical anion [14] have been studied in RTILs. We note that many electrogenerated species in RTILs are radicals (e.g.…”