Carboxylic acids are most acidic and alcohols are least acidic. Phenols are more acidic than alcohols but less acidic than carboxylic acids or carbonic acid. Thus, acidic strength order is R−O∣∣C−OH>H−O−H>R−O−H>H−C≡C−H Related Theory Acid strength increases with : 1. increasing electronegativity of the central atom: The more electronegative the central atom, the more electron drift occurs, polarizing the O−H bond which makes it easier for the molecule to dissociate. 2. increasing oxidation number of the central atom: The higher the oxidation state of the central atom, the greater the number of oxygens attached to the central atom. Oxygen is a highly electronegative element, contributing to greater electron drift away from the O−H bond.