Revisiting the photochemistry 2,5‐dihydroxy benzoic acid (gentisic acid): Solvent and pH effect

Abstract

In the present study, we have reinvestigated photochemistry of 2,5‐dihydroxy benzoic acid (DHBA) in a series of organic solvents of different polarities and the aqueous solution of varying pH from 1 to 14. The investigation was carried out using steady‐state and nanosecond (ns) time‐domain fluorescence measurement techniques at room temperature. Some hitherto not explored spectral features with new insight on different forms of DHBA are reported. It is found that DHBA exists as monoanionic and neutral forms in various polar protic, aprotic, and nonpolar solvents. In aqueous solution (pH 1 to 14), neutral, monoanionic, and dianion forms are found to be responsible for the observed optical spectral profiles. The observed significant Stokes shift in emission is attributed to species undergoing excited‐state intramolecular proton transfer (ESIPT) in different solvents. The analysis presented in this work elucidates and validate the presence of various species and conformers of DHBA.

Excited-State Intramolecular Proton Transfer: A Short Introductory Review

“…The families of hydroxy carboxylic acids that have been exploited as proton transfer systems are hydroxyl-benzoic acids and esters [ 34 , 35 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 ], hydroxynaphthoic acids [ 71 , 72 , 73 , 74 , 75 ] and anthranilic acid and its esters [ 76 , 77 , 78 , 79 , 80 , 81 ]. Besides carboxylic acids, other compounds belonging to hydroxyflavones [ 82 , 83 , 84 ], quinoline family and anthraquiniones [ 85 , 86 , 87 ,…”

Application of environmental-safe fermentation with Saccharomyces cerevisiae for increasing the cinnamon biological activities

“…According to HPLC analysis (Table 6 ), p -hydroxybenzoic acid, gentisic acid, catechin, chlorogenic acid, caffeic acid, and syringic acid increases by 116, 33.2, 59.6, 50.6, 1.6, and 16.9%, respectively. The content of antioxidant p -hydroxybenzoic acid and gentisic acid may be enhanced because of hydrolysis of benzoic acid during fermentation (Dvorackova et al 2015 ; Adhikari et al 2021 ). p -Hydroxybenzoic acid has antioxidant, and anti-inflammatory characteristics by increasing the expression of antioxidants leading to better plasma lipid profiles (Juurlink et al 2014 ).…”