Alcohols Flashcards
What is the functional group of alcohols, and what is the general formula?
-OH
CnH2n+1OH
Explain the difference between a primary, secondary and tertiary alcohol
Primary : ( 1 carbon )
Alcohol bonded to carbon which is bonded to one alkyl group
Secondary : ( 2 carbon )
Alcohol bonded to the carbon which is bonded to 2 alkyl groups
Tertiary : ( 3 carbon )
Alcohol bonded to the carbon which is bonded to 3 alkyl groups
What does the solubility of alcohols depend on why?
It has an OH group so can form hydrogen bonds with water. But, the longer the hydrocarbon chain, the more insoluble the alcohol is. Carbon chain is NON POLAR and HYDROPHOBIC and reduces interaction of alcohol with water
Therefore less water soluble as chain length increases
Why are alcohols polar? What property does this give alcohols?
It has an O-H bond so there is a difference in electronegativity. Slightly positive and negative oxygen. Electrons are therefore pulled towards the ELECTRONEGATIVE oxygen in the covalent bond.
This means alcohols are soluble because the lone pair on oxygen atoms forms a hydrogen bond with water.
Why do alcohols have a high boiling point?
They can hydrogen bond with each other. Hydrogen bonding is the STRONGEST intermolecular force.
Give examples of alcohols which are soluble in water
Smaller carbons, up to 3 carbons. For example, methanol, ethanol, propan-1-ol
What is volatility? Why are alcohols LESS volatile than alkanes?
Volatility is a substances capability of readily changing from a solid/liquid into a gas. More energy is needed to overcome the hydrogen bonds BETWEEN MOLECULES in alcohols than the weaker London forces in alkanes. Hydrogen bonding is STRONGER than London forces.
What is formed when hydrogen hallides react with alcohol? How can we ensure it is a haloalkane? Conditions?
Halogenoalkanes / haloalkanes are made when an alcohol reacts with a halide ion. SUBSTITUTION
Heat under reflux with an acid catalyst is used (sulphuric acid) and a sodium halide. This produces a hydrogen hallide in situ to react with the alcohol.
We can use a pH meter to detect an alkaline solution.
How are alkenes made from alcohols, and state conditions? Give one reason why people would use this reaction in industries?
Dehydration
The removal of water causes an alkene to be formed.
Conditions :
Conc h2so4
170-180 degrees
This is an elimination reaction, where an alkene and water is formed.
This reaction is used to make polymers which are used to make plastics.
Explain how EZ isomers can be formed in dehydration
The double bond can be formed on either side of the carbon that had the hydroxyl group. .
Explain the combustion of alcohols. What use does this give them?
Alcohols are readily combusted and OXIDISED and form CO2 & H2O. They burn readily and with a light blue flame. They can be used as fuels to generate energy.
Exothermic
What are primary alcohols oxidised to?
Aldehydes then carboxylic acids.
What are the three substances alcohols can be oxidised into? What is used for their oxidation?
Aldehydes, ketones and carboxylic acids.
We heat the reaction mixture with mild oxidising acidified agent potassium chromate ( K2Cr2O7 ) - it is REDUCED itself and the alcohols are oxidised. It turns from the orange dichromate ion to the green chromium ion.
Describe the structure of a aldehyde
It has a C-H group and C=O group on the end carbon. It ends in -al and will have CHO in the molecular formula.
Describe the structure of a carboxylic acid
It ends in -oic, it has a C=O and C-OH group. The molecule formula has COOH.