Alcohols Flashcards
What affects an alcohol’s physical properties?
The ability to form hydrogen bonds between the the OH groups of neighbouring molecules
What is volatility?
The ease that a liquid turns into a gas
What is the general trend between volatility and boiling point?
Volatility increases as boiling point decreases
Why can alcohols dissolve in water?
The OH group can hydrogen bond with water
Why does solubility decrease as chain length increases?
A larger part of the alcohol molecule is made up of non polar hydrocarbon chain
The hydrocarbon chain does not form hydrogen bonds with water molecules
How do you classify an alcohol?
By looking at the carbon where the functional group is attached to and counting the number of alkyl groups attached to determine whether the alcohol is primary, secondary or tertiary
Why does the boiling point increase as chain length increases?
The van der Walls’ forces will increase as chain length increases
Why do alcohols have higher boiling points than alkanes?
Alcohols have hydrogen bonding
What to draw when drawing hydrogen bonding
Show lone pairs
Show charges
Show hydrogen bond as a line of horizontal lines
Make sure the the O-H-O is drawn at 180 degrees
What is required to ensure that complete combustion occurs?
An excess of oxygen
How are alcohols oxidised?
An oxidising agent is made from potassium dichromate and sulfuric acid
When an oxidising agent is added to a primary or secondary alcohol, the solution will turn green from orange
What is the symbol for an oxidising agent?
[O]
What is produced at each stage of oxidation?
Primary -> Water is produced
Secondary -> No water is produced
What set up is used for primary oxidation and why?
Simple distillation
What is the equation for the fermentation of glucose to make alcohols?
C6H12O6 -> 2CH3CH2OH + 2CO2
What is the equation for the direct hydration of ethene
H2C=CH2 +H2O -> CH3CH2OH
What are the conditions for the direct hydration of ethene?
The water has to be in the form of steam
Phosphoric acid catalyst
300 degrees
60 atm
What are the conditions needed for the ferementation of glucose?
Yeast (zymase)
37 degrees
Absence of air
Why does the fermentation process have to be derpived of oxygen?
To prevent the oxidation of ethanol into other products such as ethanal or ethanoic acid
Why can ethanol produced by fermentation only be up to 14% alcohol concentration?
The enzyme zymase ceases to function at higher levels of alcohol concentration
What percentage of ethene is hydrated at any one time?
5%
What happens to the unreacted ethene once it has passed through the reactor?
The gases are recycled and fed back into the system
Uses of ethanol
Alcoholic beverages
Perfumes/aftershave
Fuel
Methylated spirits
Uses of methanol
Clean burning fuel
Feedstock for the chemical industry
What are the four key reactions of alcohols?
Combustion
Elimination
Oxidation
Esterfication
What makes ethanol a good fuel?
Renewable source of energy
Burns more cleanly
Can reduce emissions
What are the conditions needed for the dehydration of an alcohol?
Concentrated phosphoric or sulfuric acid
Heated under reflux
What is dehydration?
An elimination reaction in which water is removed from a saturated molecule to make an unsaturated molecule
What is reflux?
The continual boiling and condensing of a reaction mixture to ensure that the reaction takes place without the contents of the flask boiling off
What atoms are lost during a dehydration reaction?
The OH group from one carbon atom
An H atom from the adjacent carbon atom
What is an elimination reaction?
A reaction where two molecules are made from one molecules
When is distillation used?
When oxidising alcohols to form aldehydes
The aldehyde would react again to form a carboxylic acid if left in mixture, therefore it must be boilied off to avoid further oxidation
What is esterification?
The reaction of an alcohol with a carboxylic acid to produce and ester and water
How to name an ester
The alcohol provides the alkyl prefix while the carboxylic acid provides the alkanoate prefix
What are the reasgents needed for making an ester?
An alcohol
A carboxylic acid
What are the conditions for esterification?
Warmed
Concentrated sulfuric acid to act as a catalyst
How to prepare an ester
Add equal amounts of alcohol and carboxylic acid into boiling tube and add conc sufluric acid
Place boiling tube in hot water bath for five minutes at 80 degrees
Pour product into cold water
You will see an oil floating on the water that is the ester
What atoms react during esterification to make an ester?
The OH group from the carboxylic acid and the H on the OH group of the alcohol
What are esters used for in the chemical industry?
Adhesives
Solvents
Food fragrances
Perfume
What is a carbonyl group?
A functional group that consists of a carbon atom double bonded to a oxygen atom
