A-level Chemistry/OCR/Chains, Energy and Resources/Alcohols, Halogenoalkanes and Analysis/Alcohols

There are six reactions of alcohols that you must be aware of for this module. For each you must be able to remember the reactants, products and conditions. For some of them you must be able to draw the mechanisms from memory.

Remembering all of these reactions can be made easier with the SHOCED (or SHOCKED with K missing) Mnemonic:

Sodium Substitution Halogen alkane formation Oxidation Combustion Esterification Dehydration

Reactants: An alcohol (e.g. propanol C3H7OH), Sodium Metal (Na) Products: A “sodium salt” (e.g. sodium methoxide) [alkoxide] Conditions: n/a C3H7OH + Na → C3H7O-Na+ + 0.5 H2 nd the alphenic acid change in phenol by this reaction

Reactants: An alcohol (e.g. ethanol), a hydrogen halide (e.g. HBr)Products: a Halogen alkane (e.g. bromoethane), waterConditions: no special C2H5OH + HBr → C2H5Br + H2O

Conditions: Acidified Potassium Dichromate (VI) or Sodium Dichromate 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 K2Cr2O72- / 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

(Complete) Combustion of any alcohol produces carbon-dioxide and water. Burning completely in an excess of oxygen C2H5OH + 3O2 → 2CO2 + 3H2O

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.

Remember the basic principle:

ACID + ALCOHOL → ESTER + WATER (as quoted from Dr. Carmel Stanley of Barnsley College)

An alcohol (e.g. ethanol) + a carboxylic acid (e.g. ethanoic acid) → an ester (e.g. ethyl ethanoate) and water Conditions: H2SO4 (sulphuric acid) Catalyst

Reactants: An alcohol Products: Alkene + water Conditions: hot and concentrated sulphuric 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 of pressure H3PO4 (phosphoric acid) catalyst.