7134-09-0Relevant articles and documents
Cornforth and Corey-Suggs reagents as efficient catalysts for sulfonation of aromatic and heteroaromatic compounds using NaHSO3 under solvent free and microwave conditions
Fatima, Touheeth,Duguta, Govardhan,Purugula, Venkanna,Yelike, Hemanth Sriram,Kamatala, Chinna Rajanna
, p. 1001 - 1006 (2020/07/27)
Cornforth and Corey-Suggs reagents Pyridinium Dichromate (PDC) and Pyridinium Chlorochromate (PCC) were explored as efficient catalysts for sulfonation of aromatic and heteroaromatic compounds using NaHSO3 in aqueous acetonitrile medium at room temperature within 1–4 h, while microwave assisted reactions took place within 1–4 min under solvent-free conditions. These observations indicate significant rate accelerations in microwave assisted reactions. which were explained due to the bulk activation of molecules induced by insitu generated high temperatures and pressures when microwaves are transmitted through reaction medium.
DPPH (=2,2-diphenyl-1-picrylhydrazyl) radical-scavenging reaction of protocatechuic acid (=3,4-dihydroxybenzoic acid): Difference in reactivity between acids and their esters
Saito, Shizuka,Kawabata, Jun
, p. 1395 - 1407 (2007/10/03)
Prolocatechuic acid (=3,4-dihydroxybenzoic acid; 1) exhibits a significantly slow DPPH (=2,2-diphenyl-1-picrylhydrazyl) radical-scavenging reaction compared to its esters in alcoholic solvents. The present study is aimed at the elucidation of the difference between the radical-scavenging mechanisms of protocatechuic acid and its esters in alcohol. Both protocatechuic acid (1) and its methyl ester 2 rapidly scavenged 2 equiv. of radical and were converted to the corresponding o-quinone structures 1a and 2a, respectively (Scheme). Then, a regeneration of catechol (=benzene-1,2-diol) structures occurred via a nucleophilic addition of a MeOH molecule to the o-quinones to yield alcohol adducts 1f and 2c, respectively, which can scavenge additional 2 equiv. of radical. However, the reaction of protocatechuic acid (1) beyond the formation of the o-quinone was much slower than that of its methyl ester 2. The results suggest that the slower radical-scavenging reaction of 1 compared to its esters is due to a dissociation of the electron-withdrawing carboxylic acid function to the electron-donating carboxylate ion, which decreases the electrophilicity of the o-quinone, leading to a lower susceptibility towards a nucleophilic attack by an alcohol molecule.
Sulfonation and sulfation on reaction of 1,2-dihydroxybenzene and its methyl ethers in concentrated aqueous sulfuric acid
Cerfontain, Hans,Coenjaarts, Norbert J.,Koeberg-Telder, Ankie
, p. 325 - 330 (2007/10/02)
The homogeneous sulfonation of 1,2-dihydroxybenzene (1), its monomethyl (2) and dimethyl ether (3) in concentrated aqueous sulfuric acid at 25 deg C has been studied and isomer distributions, as well as rate coefficients for the sulfonation of 1-3 and their monosulfonic acids, have been determined.In 73.5-87.5percent H2SO4, 1 yields the 3- and 4-sulfonic acids in a ratio of 25:75, 2 yields the 4-, 5- and 6-sulfonic acids in a ratio of 46:36:18 in 73.5percent H2SO4 and 50:39:11 in 87.5percent H2SO4, whereas 3 yields only the 4-sulfonic acid.The remarkable absence of the 3-sulfonic acid (87.5percent H2SO4, the 4-sulfonic acid of 1 and the 5-sulfonic acid of 2 are present in part in the form of their hydrogen sulfate.In that acid region, the 3- and 4-sulfonic acids of 1 both yield the 3,5-disulfonic acid, the 4- and 6-sulfonic acids of 2 both yield the 4,6-disulfonic acid and the 4-sulfonic acid of 3 mainly yields the 4,6- together with some 4,5-disulfonic acid.
