C3 Topic 5 - Organic Chemistry Flashcards
What is the general formula for alkanes?
CnH2n+2
Define homologous series.
A homologous series is a group of compounds with the same general formula. They all have very similar molecular structures and properties, and contain the same elements.
Their physical properties however slowly change as the compounds increase in size. E.g. Boiling points increase
What is the general formula for alkenes?
CnH2n
What is the general formula for alcohols?
CnH2n+1OH
What is the general formula for carboxylate acids?
Cn-1H2n+1COOH
How can ethanol be made from fermentation?
What are the conditions for optimal ethanol production?
C6H12O6 ->(+yeast)-> 2C2H5OH + 2CO2
Glucose -> Ethanol + Carbon Dioxide
The glucose usually comes from sugar cane or sugar beet.
Yeast acts as a catalyst as the have enzymes which convert the glucose into ethanol.
30-40^oC as this is the optimal temperature for the enzymes in the yeast.
Add water to make the mix of glucose and yeast liquid because otherwise they won’t react.
Make sure no oxygen gets into the reaction or vinegar will be produced rather than ethanol.
A concentration of 15% ethanol will be made as it kills off the yeast.
How can concentration of ethanol higher than 15% be obtained?
Fractional distillation:
Ethanol has a lower boiling point than water and so the mixture is heated so that the ethanol evaporates. It is passed through a Liebig condenser and is collected in a separated beaker.
How can ethanol be made from ethane?
Ethene is reacted with steam to make ethanol:
C2H4 + H2O -> C2H5OH
Ethene + Steam -> Ethanol
It is a very cheap process as ethane is cheap and there is not a lot of waste produced.
The ethanol produced is very concentrated and does not require much processing afterwards. If produced industrially, the reaction can be continuous.
The only problem with this is that ethane comes from crude oil which is starting to run out so it may become a very expensive process in the future.
How can alcohol affect society and the body?
Ethanol reduces the activity in the nervous system, leading to slower reactions, impaired judgement, poor balance and coordination, unconsciousness and eventually even a coma.
It can cause dehydration in the brain, which damages the brain cells, which can lead to long-term memory loss.
People who are drunk are also more likely to start fights are behave irresponsibly. Drink driving causes death and serious injury as alcohol impairs a person’s ability to drive.
How can ethane be made from ethanol?
Ethanol can be dehydrated to make ethene.
C2H5OH -> C2H4 + H2O
Ethanol -> Ethene + Water
The ethanol is passed over a hot aluminium oxide catalyst to make ethene and water.
Ethene is useful as it can be used to make polymers.
How can you make ethanol can acid from ethanol?
Ethanol + Oxygen -> Ethanoic Acid (Vinegar) + Water
C2H5OH + O2 -> CH3COOH + H2O
What are the products of a carboxylic acid and a:
Metal
Base
Carbonate
Metal:
Ethanoic Acid + Magnesium -> Hydrogen + Magnesium Ethanoate
2CH3COOH + Mg -> H2 + (CH3COO)2Mg
Base:
Ethanoic Acid + Sodium Hydroxide -> Sodium Ethanoate + Water
CH3COOH + NaOH -> CH3COOHNa + H2O
Carbonate:
Ethanoic Acid + Sodium Carbonate -> Sodium Ethanoate + Carbon Dioxide + Water
2CH3COOH + Na2CO3 -> 2CH3COOHNa + CO2 + H2O
What is an ester and how are they made?
An ester is formed when an alcohol reacts with a carboxylic acid:
Ethanoic Acid + Ethanol -> Ethylene Ethanoate + Water
CH3COOH + C2H5OH -> CH3COOC2H5 + H2O
What are esters used for and why?
Perfumes - many aromas
Flavourings - many flavours
Making polyesters and fabrics - long chains of esters
How is soap made?
Ester + Alkali -> Soap
OR
Oil/fat + Alkali -> Glycerol + Water + Soap
