CHAPTER 1. ORGANICMOLECULES 1.8
Physical and chemical properties of
the alcohols
ESCW
The hydroxyl group affects the solubility of the alcohols. The hydroxyl group generally
makes the alcohol molecule polar and therefore more likely to be soluble in water.
However, the carbon chain resists solubility, so there are two opposing trends in the al-
cohols. Alcohols with shorter carbon chains areusually more soluble than those with
longer carbon chains.
Alcohols tend to have higher boiling points than the hydrocarbons because of the strong
hydrogen bond betweenhydrogen atoms of onemolecule and the oxygen atom of an-
other molecule.
Alcohols can show either acidic or basic properties because ofthe hydroxyl group.
They also undergo oxidation reactions to form aldehydes, ketones and carboxylic acids.
Activity: The uses of the alcohols
Read the extract below and then answer the questions that follow:The alcohols are a veryimportant group of organic compounds, and they
have a variety of uses. Our most common use ofthe word ’alcohol’ is with ref-
erence to alcoholic drinks. The alcohol in drinks is in fact ethanol. But ethanol
has many more uses apart from alcoholic drinks! When ethanol burnsin air,
it produces carbon dioxide, water and energy and can therefore be used as a
fuel on its own, or in mixtures with petrol. Because ethanol can be produced
through fermentation, this is a useful way for countries without an oil industry
to reduce imports of petrol. Ethanol is also usedas a solvent in many perfumes
and cosmetics.Methanol can also be used as a fuel, or as a petrol additiveto improve com-
bustion. Most methanol is used as an industrial feedstock, in other words it is
used to make other things such as methanal (formaldehyde), ethanoic acid and
methyl esters. In most cases, these are then turned into other products.Propan-2-ol is another important alcohol, which is used ina variety of ap-
plications as a solvent.Questions- Give the structural formula for propan-2-ol.
- Write a balanced chemical equation for the combustion reaction of ethanol.
- Explain why the alcohols are good solvents.