Acidity of phenols:

      Today we will discuss the some theories that are helpful in studying "acidity of phenols". Let’s get started.

       By the K_a values we can say that phenols are less acidic than carboxylic acid and more acidic than alcohols.

       As we know that acid loses proton in reaction. Phenol does it too. Phenol losses its hydrogen as a proton and forms more stable phenoxide ion.

      As it is more stable the phenol will always try to lose one proton. Phenoxide ion is stable because it has many resonating structures stabilising it. Means phenol losses its proton in a reaction. That confirms that phenol is acidic.

     

        As we know that phenol losses its proton and forms more stable phenoxide ion. The formed phenoxide ion is strongly basic (because it has 3 lone pair of electrons with it and readily donate those electrons).

      If u remember conjugate acid base theory that states that when weak acid loses proton it forms strong conjugate base. Here phenol losses proton and forms strongly basic conjugate base i.e. phenoxide ion. That means phenol must be weak acid.

      When  phenol reacted with the sodium hydroxide then it forms sodium phenoxide. Which is a basic salt (turns red litmus blue). when weak acid reacted with stronger base then the salt formed is basic. Here phenol react with strong base i.e. sodium hydroxide  and forms basic salt i.e sodium phenoxide . Then we can say that phenol is weakly acidic. 

Stay tuned for further updates . next blog will come with topic effect of substituents on acidity of phenols .if u like it share & comment .