Alcohols

Difference in boiling temperatures of alcohols compared to their corresponding alkanes

Higher in alcohols

Why do alcohols have higher boiling temperatures than their corresponding alkanes?

Addition of hydrogen bonding adds to the VdW forces and increases overall intermolecular forces of attraction

Trend in solubility of alcohols with increasing carbon chain length

Solubility decreases because the large, insoluble hydrocarbon portion of the molecule outweighs the influence of the -OH group.

Are alcohols more reactive than alkanes?

Yes

Why are alcohols more reactive than alkanes?

The C-O and O-H bond in the molecules are polar and easier to break than C-C or C-H bonds.

How do alcohols burn in air?

Clean, colourless flame

Equation for alcohol reaction with sodium

Alcohol + sodium → sodium alkoxide salts + hydrogen

Properties of alkoxides

Ionic salts (CH₃CH₂O^-Na⁺)

What happens in a dehydration reaction?

The loss of a water molecule from an alcohol through an elimination reaction forming an alkene.

An -OH group leaves the molecule from one carbon and a hydrogen atom leaves from an adjacent carbon atom.

How does a dehydration reaction work?

Heating an alcohol with concentrated phosphoric acid (H₃PO₄) as a catalyst OR heating the alcohol to 600K with Al₂O₃ as a catalyst.

Uses for producing alkenes from alcohols

Provides a possible route to polymers without having to use monomers derived from crude oil.

Oxidising agent used in oxidation of alcohol

Dichromate ion. Sulphuric acid is used to provide H⁺ ions. Therefore it is called acidified potassium dischromate represented as [o].

Which alcohols cannot be oxidised?

Tertiary alcohols.

Equation for oxidation of primary alcohols

Primary alcohol --_^[o]>> aldehyde --_^[o]>> carboxylic acid

Partial oxidation

Secondary alcohol → Aldehyde