Guaiacol is a naturally occurring organic compound with the formula C6H4(OH)(OCH3). This colourless aromatic oil is derived from guaiacum or wood creosote. Samples darken upon exposure to air and light. Guaiacol is present in wood smoke, resulting from the pyrolysis of lignin Guaiacol is a naturally occurring organic compound with the formula C6H4(OH)(OCH3). This colourless aromatic oil is derived from guaiacum or wood creosote. Samples darken upon exposure to air and light. Guaiacol is present in wood smoke, resulting from the pyrolysis of lignin