<title>Abstract</title>A non-phenolic C₆-C₂-type lignin model compound with the <italic>β</italic>-<italic>O</italic>-4 bond, 2-(2-methoxyphenoxy)-1-(3,4-dimethoxyphenyl)ethanol (<bold>I</bold>), was acidolyzed in aqueous 82% 1,4-dioxane containing HBr, HCl, or H₂SO₄ with a concentration of 0.2 mol/L at 85 ℃ to examine the differences between these acidolyses. Compound <bold>I</bold> primarily converted to an enol ether compound, 1-(2-methoxyphenoxy)-2-(3,4-dimethoxyphenyl)ethene (<bold>II</bold>), via the benzyl cation followed by acidolytic <italic>β</italic>-<italic>O</italic>-4 bond cleavage regardless of the acid-type, although the disappearance rates of compound <bold>I</bold> were remarkably different (HBr &gt; HCl &gt;&gt; H₂SO₄). Acidolyses of compound <bold>II</bold> using these acids under the same conditions showed a similar tendency, but the rate differences were much smaller than in the acidolyses of compound <bold>I</bold>. Acidolyses of the <italic>α</italic>-methyl-etherified derivative of compound <bold>I</bold> (<bold>I</bold>-<italic>α</italic>-OMe) using these acids under the same conditions suggested that the formation rates of the benzyl cation from compound <bold>I</bold>-<italic>α</italic>-OMe (also from compound <bold>I</bold>) are not largely different between the acidolyses using these acids, but those of compound <bold>II</bold> from the benzyl cation are remarkably different. Acidolysis of the <italic>α</italic>-bromo-substituting derivative of compound <bold>I</bold> (<bold>I</bold>-<italic>α</italic>-Br) using HBr under the same conditions showed a characteristic action of Br¯ in the acidolysis. Br¯ adds to the benzyl cation generated from compound <bold>I</bold> or <bold>I</bold>-<italic>α</italic>-OMe to afford unstable compound <bold>I</bold>-<italic>α</italic>-Br, resulting in acceleration of the formation of compound <bold>II</bold> and of the whole acidolysis reaction.