Section 6 homologous series Flashcards
Homologous series definitions
A family of chemicals with the same general formula and similar chemical properties.
Alkanes general formula
CnH2n+2
Alkenes general formula
CnH2n
Cycloalkanes general formula
CnH2n
Naming hydrocarbons
Branch chain position (numbers)
Number of branch chains (prefix)
Name branch chains
Name of main chain
Position of any functional groups.
saturation test
Add bromine water to the hydrocarbon, if the colour remains orange, the chemical is saturated.
Unsaturation test
Add bromine water to the hydrocarbon, if the colour goes from orange to colourless, the chemical is unsaturated.
Why is bromine water used in bromine water test
It has the best colour change/ most distinctive colour change.
Alkanes saturation
Saturated
Alkenes saturation
Unsaturated
Cycloalkanes saturation
Saturated
Alkene addition reaction types
Hydrogenation
Hydration
Halogenation
Saturated definition
Where a molecule has only single bonds between the carbon atoms.
UnSaturated definition
Where a molecule contains a carbon to carbon double/triple bond.
Addition definition
Where a molecule reacts with a unsaturated molecule, breaking apart the carbon to carbon double/ triple bond and saturating the molecule.
Hydration definition
Where a water molecule is added to an unsaturated chemical, breaking apart the carbon to carbon double/ triple bond and saturating the molecule.
Hydrogenation definition
Where a hydrogen molecule is added to an unsaturated molecule, breaking apart the carbon to carbon double / triple bond and saturating the molecule.
Halogenation definition
Where a halogen molecule is reacted to an unsaturated molecule to break apart the carbon to carbon double / triple bond and saturate the molecule.
Alkene hydration
Alkene + water —> alcohol
Alkene hydrogenation
Alkene + hydrogen —-> alkane
Alkene Halogenation
Alkene + halogen —-> saturated dihalogen Alkane
Isomer definition
A molecule with the same general formula but a different structural formula and different chemical properties.
Rules of hydrocarbon boiling point
As the length of the chain increases the number of electrons increases, which increases the force of the London dispersion forces, meaning more heat energy is required to break the intermolecular forces .meaning the melting and boiling point increases
Volatility
The measure of how easily something evaporates
Hydrocarbons volatility rule
As the chain length increases the number of electrons increases, this increases the force of the London dispersion forces, which means that more heat energy is required for the molecule to evaporate, decreasing the volatility.
Solubility rule hydrocarbons
Hydrocarbons are non polar molecules, since they do not have PD -PD intermolecular forces, and don’t contain hydrogen bonding either, meaning they don’t dissolve in water but do in non polar liquids/ solutions.
Functional group definition
The part of a molecule which is responsible for the molecules chemical properties.
Alkenes functional group
Carbon to carbon double bond
Alcohols functional group
Hydroxyl
General formula of alcohols
(Alkanols)
CnH2n+1OH
General formula of alcohols
(Alkanols)
CnH2n+1OH
Alcohol boiling point rule
As the number of carbons in the chain increases the London dispersion forces increases, due to the increase in the number of electrons, meaning the MP and BP increase due to more energy being required to break apart these intermolecular forces.
Alcohols also have higher melting and boiling points than other homologous series, due to the hydroxyl containing PD PD and Hydrogen bonding van def waals
Volatility of alcohols
Have lower volatility than other homologous series due to hydroxyl group and hydrogen bonding and PD PD van der waals
What are diols and triols
Where an alcohol has more hydroxyl functional groups -2and3 - making them more soluble in water, have a higher mp and bp and less volatile.
Alcohols solubility in water
Soluble because of hydrogen bonding in the hydroxyl group
As number of hydroxyls increases the solubility increases
As the chain length increases the hydroxyl group becomes less significant and the solubility decreases.
Primary alcohols
Alcohols where the carbon bonded to the hydroxyl group is only bonded to one other carbon.
Secondary alcohols
Alcohols where the carbon bonded to the hydroxyl group is only bonded to two other carbons.
Tertiary alcohols
Alcohols where the carbon attached to the hydroxyl group is bonded to three other carbon atoms.
Functional group of carboxylic acids
COOH (carboxyl)
General formula of carboxylic acids
CnH2n+1COOH
Carboxylic acids solubility
In water
They are soluble due to the hydroxyl group in the carboxyl functional group, which contains hydrogen bonding and PDPD van der waals
Carboxylic acids volatility
They are less volatile than other homologous series due to the carboxyl functional group containing PDPD and hydrogen bonding.
As the length of a chain increases the volatility decreases due to London dispersion forces.
Carboxylic acids volatility
They are less volatile than other homologous series due to the carboxyl functional group containing PDPD and hydrogen bonding.
As the length of a chain increases the volatility decreases due to London dispersion forces.
Carboxylic acid boiling point rule
As the carbon chain increases the
boiling point increases due to London dispersion forces getting stronger, since there is more electrons.
It has higher boiling point than other homologous series due to the carboxyl group.
Carboxylic acid reactions with metal oxides
Propanoic acid + sodium oxide —-> sodium propanoate + water
Carboxylic acid reaction with metal hydroxide
Propanoic acid + sodium hydroxide —-> sodium propanoate + water
Carboxylic acid reaction with metal carbonate
Propanoic acid + sodium carbonate —-> sodium propanoate + carbon dioxide + water
Oxidation in carbon compounds
An increase in the oxygen to hydrogen ratio within a carbon compound.
Reduction in carbon compounds
A decrease in the oxygen to hydrogen ratio within a carbon compound.
Primary alcohol oxidation
Aldehydes and then carboxylic acids
Secondary alcohol oxidation
Ketones
Aldehyde and ketone functional group
Carbonyl (C=O)
Difference between an aldehyde and a ketone
Aldehydes are formed by oxidation of primary alcohols, whereas ketones are formed by oxidation of secondary alcohols
Aldehydes have the carbonyl functional group at the end of the chain, ketones have their functional group in the middle of the chain.
Aldehydes can be oxidised further whereas ketones cannot be oxidised further.
Aldehydes suffix
Al
Ketones suffix
One
Ketones homologous series
Alkanones
Aldehydes homologous series
Alkanals
Alcohols oxidising agents
Acidified dichromate (orange -blue/green)
heated copper oxide (black to orange)
Tertiary alcohols oxidation
Cannot oxidise
Oxidising agents for distinguishing between aldehydes and ketones
Fehlings solution (blue to red/brown in aldehydes)
Tollen’s reagent (clourless to silver mirror in aldehydes)
Acidified dichromate ions (orange to green/blue in aldehydes)
