A-level Chemistry/WJEC/Module 2/Alcohols and acids

HalogenoAlkane Production (Nucleophilic substitution) Reactants: An alcohol (e.g. ethanol), a hydrogen halide (e.g. HBr)Products: a HalogenoAlkane (e.g. bromoethane), waterConditions: no special C2H5OH + HBr → C2H5Br + H2O Oxidation Conditions: Acidified Potassium Dichromate(VI) or Sodium Dichromate(VI) is used as an oxidising agent. Reaction occurs in reflux. The products that form from oxidation depend on the structure of the alcohol. The oxidation of the primary alcohol, ethanol with Cr2O72- / H+ is as follows: CH3CH2OH + [O] → CH3CHO (the aldehyde; ethanal) Remember: Oxidation is defined as the gain of Oxygen AND/OR the loss of hydrogen. Primary alcohols: oxidise to aldehydes and then to carboxylic acids Secondary alcohols: Oxidise to ketones Tertiary alcohols: Cannot be oxidised Combustion (Complete) Combustion of any alcohol produces carbon dioxide and water. Burning completely in an excess of oxygen C2H5OH + 3 O2 → 2 CO2 + 3 H2O However, incomplete combustion can occur when oxygen is not in excess (lack of oxygen) which can cause carbon monoxide (CO) or even carbon residue (C) to form as the products. Esterification Remember the basic principle: ACID + ALCOHOL → ESTER + WATER An alcohol (e.g. ethanol) + a carboxylic acid (e.g. ethanoic acid) → an ester (e.g. ethyl ethanoate) and water Conditions: H2SO4 (sulfuric acid) Catalyst Dehydration Reactants: An alcohol Products: Alkene + water Conditions: hot and concentrated sulfuric acid An alcohol can be formed by the hydration of the alkene; ethene, shown below: CH2=CH2(g) + H2O(g) → CH3CH2OH(g) Conditions: 300 degrees Celsius 60 atm pressure H3PO4 (phosphoric acid) catalyst.