Chapter 14 Flashcards
What is the general formula for an alcohol?
CnH2n+1OH
What functional group to alcohols contain?
A OH functional group.
What are the properties of alcohols?
They have high melting and boiling points, so a less volatile and have a greater water solubility than alkanes.
Why have alcohols got a high melting and boiling point?
As alcohols are polar molecules due to the O – H polar bond there is a difference in electronegativity between oxygen and hydrogen. The intermolecular forces are weak London forces as well as strong hydrogen bonds between the polar groups. Therefore they require more energy to overcome and break the bonds.
Why are they soluble in water?
They are soluble in water due to the influence of the OH group in the hydrocarbon chain as hydrogen bonds form between the OH and the water molecule.
What happens to the solubility as the chain length increases?
As the hydrocarbon chain increases the influence of the OH group becomes relatively smaller and the solubility of the longer chain becomes less soluble (solubility decreases).
Are they more or less soluble than alkanes?
They are more soluble than alkanes due to alkanes being non polar so can’t form hydrogen bonds with water whereas alcohols can form hydrogen bonds with water meaning they are soluble in water.
Why do they have a low volatility?
In the liquid state hydrogen bonds hold the alcohol together, bonds need to be broken to change its state which requires more energy than breaking a weak bonds found in alkanes. Alcohols have a lower volatility than alkanes.
What is viscosity?
It is the measure of a fluid resistance to flow
What is a primary alcohol?
The OH group is attached to 2 hydrogens or one carbon atom.
What is a secondary alcohol?
The OH group is attached to a carbon atom that is attached to one hydrogen or two other carbon atoms.
What is the tertiary alcohol?
The OH group is attached to no hydrogens on the carbon atom and three carbon atoms
What happens as the chain length increases in terms of the quantity of heat released.
The quantity of heat release per mole increases.
What is the usual oxidising mixture?
Potassium dichromate acidified with dilute sulphuric acid.
What happens in terms of a colour change if the alcohol is oxidised?
It changes colour from an orange solution to a green solution as it has been reduced. The orange solution contains dichromate ions and the reduced solution contains chromium ions.
