Organic Chemistry - Module 2 Flashcards
Which two chemical processes can be used to make ethanol?
The hydration of ethene and the fermentation of sugars.
Which catalyst is used for the hydration of ethene?
Phosphoric acid - H3PO4
When hydrating ethene, why is only 5% of the ethene converted into ethanol?
It is a reversible reaction.
In fermentation, carbohydrates are converted into which two products?
Ethanol and carbon dioxide.
Which two things are usually used as the carbohydrate source in fermentation?
Sugar or starch.
Why is yeast used during fermentation?
It contains an enzyme called zymase which catalyses the reaction.
Why can’t fermentation take place at temperatures above 37 degrees?
The enzyme in the yeast begins to denature and lose efficiency.
Why does the toxicity of the alcohol limit the concentration of ethanol that can be made?
The enzyme in the yeast ceases to function above an alcohol concentration of 14%.
Why does fermentation need to take place in the absence of air?
It prevents ethanol being oxidised into undesirable compounds like ethanal or ethanoic acid, which would affect the flavour.
Why do alcohols have higher boiling points than alkanes?
Because of the presence of hydrogen bonds in alcohols, which are strong.
Why do alcohols dissolve in water?
Because hydrogen bonds form between the O-H groups of the alcohols and the water molecules, because both of them are polar.
Define a primary alcohol.
When the O-H group of the alcohol is only attached to a carbon atom with no alkyl groups or is attached to one alkyl group.
Define a secondary alcohol.
When the O-H group of the alcohol is attached to two alkyl groups.
Define a tertiary alchol.
When the O-H group of the alchol is attached to three alkyl groups.
Which products are formed when alcohols burn completely?
Carbon dioxide and water.
Which type of alcohol is resistant to oxidation?
Tertiary alcohols.
Which type of product is formed by the oxidation of both primary and secondary alcohols?
Aldehydes.
Which type of product is formed by the further oxidation of secondary alcohols?
Ketones.
When oxidising primary alcohols, why must you distill the aldehyde immediately?
To stop it from being oxidised further into a carboxylic acid.
Define reflux.
The continual boiling and condensing of a mixture.
How are esters formed?
When alcohols are warmed with a carboxylic acid in the presence of an acid catalyst.
Which acid is often used as the acid catalyst for esterification?
Concentrated sulphuric acid.
Explain what happens during esterification.
The O-H bond of the alcohol is broken and the H atom forms a water molecule using the O-H of the carboxylic acid. This leaves an ester and water as the products.
Which products are formed by the dehydration of an alcohol?
An alkene and water.
What type of reaction is the dehydration of an alcohol an example of?
An elimination reaction.
Define halogenoalkane.
A compound where a halogen atom has replaced at least one hydrogen atom in an alkane chain.
Why do halogenoalkanes only contain single bonds?
Because they are based the alkane homologous series.
What is the general formula for a halogenoalkane?
CnH2n+1X (X represents the halogen atom)
Why are carbon-halogen bonds polar?
Because halogen atoms are more electronegative than carbon atoms, causing the bonded electrons to be more attracted to it, giving the carbon a slightly positive charge, and the halogen a slightly negative charge.
Does the electronegativity of halogens increase or decrease down the group?
Decrease.
