The OH group in alcohols, phenols and acids

  • Created by: J.E.C.
  • Created on: 11-04-14 12:39

Acidic Properties

R-OH + H2O <-> R-O- + H3O+

H-OH + H2O <-> H-O- + H3O+

At one time, a small number of water molecules donate H+ ions to other water molecules = behaves as a weak acid.

With phenols, the equilibrium lies further to the right so it is more acidic than water.

Ethanol < water < phenol < carboxylic acids

The stability of the R-O- formed determines how strong the acid is and where the equilibrium lies.

If the negative charge on the O atom can be shared with other atoms it will be more stable.

If the R-O- is derived from a phenol or carboxylic acid the charge gets spread out - delocalisation.

Phenols and carboxylic acids can react with strong bases to form salts. (React with NaOH to form their sodium salts)

1 of 2

The Iron (III) Chloride test & Ester formation

Iron (III) Chloride is test for phenol and its derivatives

The enol group (-C=C-OH) reacts with the Fe3+ ion to form a complex

Alcohol + Carboxylic Acid <-> Ester

Concentrated Sulphuric of Hydrochloric acid must be added to speed up reaction & heated

Can be made using phenols instead of alcohols (& use acyl chloride or acid anhydride instead of carboxylic acid)

Salicylic Acid > esterify the -OH group --> Aspirin (soluble in water/absorbed into bloodstream)

Salicylic Acid > esterify the -COOH group --> Oil of wintergreen (soluble in fat/absorbed through skin)

2 of 2


No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all What's in a medicine? resources »