Alcohols Flashcards
Organic 1 (45 cards)
What is the first step of alkene hydration
One of the OH groups on a phosphoric acid molecule has an induced dipole and is attracted to the double bond of an alkene
The hydrogen breaks from the phosphoric acid (heterolytic fission) and creates a carbocation and a dihydrogen phosphate ion
What is the second step of alkene hydration
The carbocation reacts with steam (H2O) because the oxygen has 4 free electrons which are attracted to the positive carbon, this creates CH3CH2OH2
What is the third step of alkene hydration
The dihydrogen phosphate ion is attracted to the positive hydrogen on the previous product because it has a negative oxygen, the hydrogen is taken from the product and joins the oxygen to make phosphoric acid and ethanol
What are alcohols with one functional group
Ethane would be ethanol
How do you name alcohols with two functional groups
Ethane would be ethane-1,2-diol and triol for 3 functional groups
What functional groups have higher priority than alcohol
aldehydes, ketones and carboxylic acids
What will the alcohol group be referred to when another functional group has priority
hydroxyl
What is a primary alcohol
The carbon atom bonded to the hydroxyl group is bonded to one other carbon atom
What is a secondary alcohol
The carbon atom bonded to the hydroxyl group is bonded to two other carbon atoms
What is a tertiary alchohol
The carbon atom bonded to the hydroxyl group is bonded to three other carbon atoms
Do alcohols have a higher or lower boiling point than the corresponding alkene
Higher
Why do alcohols have a higher boiling point
Alkanes are non-polar so only van der Waals forces between them
Alcohols are polar because the oxygen atom on the OH is much more electronegative than the hydrogen atoms
Alcohols can have van der Waals forces and hydrogen bonds
What is volatility
How readily a molecule turns into gas
Are alcohols more or less volatile than alkanes
Less
Why does the difference in the boiling point between alcohols and alkanes reduce as the molecules get bigger
In short chain alcohols the hydrogen bonds play a much more significant role than van der Waals forces,
In long chain alcohols there are more van der Waals forces compared to hydrogen bonding so the importance of H bonding is reduced
Are alcohols soluble in water
Yes very, because the alcohol functional group can form hydrogen bonds with water molecules
What happens to alcohol solubility as you increase the chain
They become less soluble
The non-polar chain cannot form bond so as you increase the chain a greater part cannot bond to the water
What is made from the oxidation of a primary alcohol
An aldehyde and water
What is the aldehyde functional group
A double bonded oxygen to one of the carbons
(-COH)
What is a common oxidising agent for primary alcohols
Potassium dichromate with dilute sulfuric acid (acidified potassium dichromate)
K2Cr2O7/H+
What happens to the oxidising agent during the oxidation of primary alcohols
It is reduced from the dichromate (VI) ion which is orange to the chromium (III) ion which is green
Why do you have to remove the aldehyde as soon as it forms
It is very easy to oxidise further so you have to remove it before that happens
Why do aldehydes have low boiling points
They cant form hydrogen bonds
Why is the aldehydes low boiling point useful
Once it forms it can easily be removed by distillation
