Catechol has part(s) hydrogen
Isolation and synthesis
Catechol was first isolated in 1839 by Edgar Hugo Emil Reinsch (1809–1884) by distilling it from the solid tannic preparation catechin, which is the residuum of catechu, the boiled or concentrated juice of Mimosa catechu (Acacia catechu). Upon heating catechin above its decomposition point, a substance that Reinsch first named Brenz-Katechusäure (burned catechu acid) sublimated as a white efflorescence. This was a thermal decomposition product of the flavanols in catechin.  In 1841, both Wackenroder and Zwenger independently rediscovered catechol; in reporting on their findings, Philosophical Magazine coined the name pyrocatechin. By 1852, Erdmann realized that catechol was benzene with two oxygen atoms added to it; in 1867, August Kekulé realized that catechol was a diol of benzene, so by 1868, catechol was listed as pyrocatechol. In 1879, the Journal of the Chemical Society recommended that catechol be called "catechol", and in the following year, it was listed as such.Catechol has since been shown to occur in free form naturally in kino and in beechwood tar. Its sulfonic acid has been detected in the urine of horses and humans.Catechol is produced industrially by the hydroxylation of phenol using hydrogen peroxide.C
            
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    {\displaystyle {\ce {C6H5OH + H2O2 -> C6H4(OH)2 + H2O}}}
  It can be produced by reaction of salicylaldehyde with base and hydrogen peroxide (Dakin oxidation), as well as the hydrolysis of 2-substituted phenols, especially 2-chlorophenol, with hot aqueous solutions containing alkali metal hydroxides. Its methyl ether derivative, guaiacol, converts to catechol via hydrolysis of the CH3−O bond as promoted by hydroiodic acid (HI).
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