Alcohols Flashcards
What is the general formula of alcohols?
CnH2n+1OH
A carbonyl group
the name when a carbon forms a double bond to an oxygen atom
Aldehyde
a compound which contains a carbonyl group at the end of a carbon chain
Aldehydes suffix
‘al’
Ketone
contain a carbonyl group somewhere in the middle of a carbon chain
Formula of aldehydes
RCHO
Formula of ketones
RCOR’
Suffix of ketones
‘one’
Carboxylic acids
compound that contains a carbonyl group and a hydroxyl group both at the end of a carbon chain
Formula of carboxylic acids
RCOOH
Suffix of carboxylic acids
‘oic acid’
Physical properties of alcohols due to hydrogen bonding
As alcohols have an OH group they have hydrogen bonding between molecules. For this reason alcohols have higher melting and boiling points than alkanes of similar chain length. Hydrogen bonds form about the OH group, but not about the alkyl chain of the molecule. For this reason short alcohol molecules dissolve well in polar solvents like water, but longer alcohol molecules dissolve better in non-polar solvents such as hexane.
Ethanol uses
- As an intermediate in the synthesis of other organic chemicals.
- As a solvent in cosmetics and perfumes.
- In the manufacture of drugs, detergents, and inks.
- It is also the alcohol found in alcoholic drinks.
What are the two different methods of producing ethanol?
- producing ethanol from crude oil
- producing ethanol by fermentation
Producing ethanol from crude oil
Ethene is made when crude oil fractions are cracked to form an alkane and an alkene. Ethene is then hydrated by adding water in the presence of a concentrated phosphoric catalyst.
Producing ethanol from crude oil (reaction name)
Hydration
Producing ethanol from crude oil (equation)
CH2=CH2 + H2O(g) -> CH3CH2OH
Producing ethanol from crude oil (conditions)
Conc H3PO4 catalyst, Steam 450⁰C temperature, 50-100atm pressure
What mechanism is the hydration reaction (producing ethanol from crude oil) ?
electrophilic addition
Producing ethanol by fermentation
In this process carbohydrates in plants are converted into sugars, which are then fermented into ethanol using enzymes found in yeast. The carbohydrates can come from crops such as sugar cane, sugar beet etc.
Producing ethanol by fermentation (reaction name)
Fermentation/Anaerobic respiration
Producing ethanol by fermentation (equation)
C6H12O6(aq) -> 2CH3CH2OH(aq) + 2CO2(g)
Producing ethanol by fermentation (conditions)
Yeast enzymes (zymase), temp ~ 35 degrees C, no oxygen
Why should no oxygen be present when producing ethanol by fermentation?
ethanol formed may oxidise to ethanoic acid
Advantages of Hydration of Ethene
- Large scale production method
- High purity product made
- Readily available raw material
- High rate of reaction
- Continuous production method
Disadvantages of Hydration of Ethene
- High temp and pressure needed which increases costs
- Expensive and high tech equipment needed
- Crude oil is non-renewable
Advantages of Fermentation
- Uses renewable resources
- Low tech method – suitable for developing
countries as little expensive eqpt needed.
- Readily available and renewable raw
materials from plants - Low cost
Disadvantages of Fermentation
- Slow rate of reaction
- Impure ethanol made needs distilling
- Causes food prices to rise if crops are used to produce alcohol instead of food.
- Batch production method. Less efficient.
What is the reagent in the dehydration of alcohols to form alkenes?
concentrated sulfuric acid or concentrated phosphoric acid
What condition is required for the dehydration of alcohols to form alkenes?
hot/temperature in range 150 - 200 degrees C
