Electrophilic reactivities of 7‐L‐4‐nitrobenzofurazans in σ‐complexation processes: Kinetic studies and structure–reactivity relationships

Abstract

The second‐order rate constants (k) for reaction of 7‐chloro‐4‐nitrobenzofurazan 1 and 7‐methoxy‐4‐nitrobenzofurazan 2 with a series of nitroalkyl anions and several of para‐substituted phenoxide anions in aqueous solution at 20 °C have been reported. On the basis of the linear novel approach recently designed by Mayr and coworkers, the electrophilicity parameters E at the C‐5 position of the two nitrobenzofurazans 1 and 2 have been quantified and ranked on the comprehensive electrophilicity scale. Mayr's approach was found to correctly predict the rate constants for the addition of phenoxide anions at the C‐5 position of 1 and 2 witting a factor of <2. Analysis of the kinetic measurements using Brønsted's model shows that βnuc values remain remarkably constant for changes in the nature of the substituent and that the σ‐complexation process is associated with high Marcus intrinsic barriers. In addition, satisfactory correlations between the log kexp (kexp values measured in this work for reactions of benzofurazans 1 and 2 with a series of phenoxide anions in aqueous solution at 20 °C) and log kcalcd (kcalcd values calculated from equation 1 using the electrophilicity parameters E of benzofurazans 1 and 2 and the previously published nucleophilicity parameters N and sN of the phenoxide anions) with a slope very close to unity have been obtained and discussed.

Structure-Property Relationships in Benzofurazan Derivatives: A Combined Experimental and DFT/TD-DFT Investigation

“…Samples of 7-methoxy-4-nitrobenzofurazan (NBD-OCH 3 ) and 7phenoxy-4-nitrobenzofurazan (NBD-OC 6 H 5 ) were prepared according to the standard methods described in the literature. [27][28][29] The secondary cyclic amines (morpholine, piperidine and pyrrolidine) were commercial products (Aldrich, Darmstadt-Germany) and were redistilled before use whenever necessary.…”

“…[24][25][26] Recently, we reported a kinetic study for S N Ar reactions of NBD with secondary amines. [27][28][29][30] The present chapter is focused on the elucidation of the combined experimental-theoretical investigation relationships between the optical (UV-Vis, PL and time resolved photoluminescence (TR-PL), electrochemical (CV) properties and the chemical structures of 4.7-di-substituted benzofurazans (NBDs), based on the kinetic reactivity process of compounds. Parr's approach was employed to develop a relationship which rationalizes the kinetic data previously reported for the reactions of 4-X-7-nitrobenzofurazans with various nucleophiles.…”

“…Parr's approach was employed to develop a relationship which rationalizes the kinetic data previously reported for the reactions of 4-X-7-nitrobenzofurazans with various nucleophiles. [27][28][29].…”

Quantification of the Electrophilic Reactivities of Benzotriazoles and Structure‐Reactivity Relationships

“…We have previously reported that the 4-nitrobenzochalcogenadiazoles 4, [1][2][3] the 7-L-4-nitrobenzofurazans 5, [4][5][6] and the 2methoxy-3-X-5-nitrothiophene 6 [7][8][9] (Scheme 1) represent a class of neutral electron-deficient substrates which can be described by the experimental model based on the following three-parameter equation (1):…”

Nucleophilicities of para‐substituted aniline radical cations in acetonitrile: Kinetic investigation and structure–reactivity relationships

“…The behavior of anilines in S N Ar and sigma complexation reactions has been examined extensively by several research groups with the aim of understanding the electronic, basicity, and nucleophilic effects of the aniline group 16–19 . More recently, Ben Salah and coworkers 16 have shown that the reactions of N1‐methyl‐4‐nitro‐2,1,3‐benzothiadiazolium tetrafluoroborate 4 with a series of para‐X‐anilines possessing an electron‐withdrawing group (X = H, Cl, and CN) in acetonitrile at 20°C can be described by the linear free‐energy relationship equation (1), where E is the electrophilicity parameter, N is the nucleophilicity parameter, and s N is the nucleophile‐specific slope parameter 20–28 . While the Ben Salah work revealed that a Mayr‐type plot 16 with aniline donors (X = OH, OMe, Me, and H) exhibited an abnormally high slope value, ca.…”