Chapter 17.1, 17.2 & 17.3 - Chirality, Carbonyls & Carboxylic acids (L)
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What are carbonyl compounds?
Compounds with a C=O bond
What are the two types of carbonyl compounds?
Aldehydes and ketones
What is the structural difference between aldehydes and ketones?
In aldehydes, there is a hydrogen bonded to the carbonyl group, in ketones there is not
Where are aldehydes always found and what does this mean locant-wise?
They are always found at the start or end of the chain. This means they do not require a locant
Where can’t ketones be found?
At the end or start of the chain
What’s the difference between C=C and C=O bonds?
Carbon and oxygen have different electronegativities, meaning the C=O bond is a polar bond
What does the fact that C=O is a polar bond mean for reactions?
It means the delta positive carbon can be attacked by nucleophiles
How does the smell of aldehydes vary?
Short aldehydes = unpleasant smells Long aldehydes = pleasant smells
What is the smell of short ketones?
Solvents
Out of alcohols, carbonyl compounds and alkanes, what is the order of boiling point?
Highest Alcohols Carbonyl compounds Alkanes Lowest
Why do carbonyl compounds have a higher boiling point than alkanes?
Carbonyl compounds have both London and dipole-dipole intermolecular forces, whereas alkanes only have London forces
Why do carbonyl compounds have dipole-dipole forces and alkanes do not?
Because carbonyl compounds are polar, and alkanes are non-polar
Why do alcohols have the highest boiling point?
Because they can form hydrogen bonds between each other, as well as having London and dipole-dipole
Why can’t carbonyl compounds form hydrogen bonds despite being polar?
Because there are no hydrogen atoms attached directly to the oxygen
Why are small carbonyl compounds soluble?
Because they can form hydrogen bonds with water
What is the trend in solubility as carbonyl chain length increases and why?
As the chain gets longer, solubility decreases. This is because the greater number of London forces interferes with the formation of hydrogen bonds
Which is easier to oxidise aldehydes or ketones and why?
Aldehydes are very easy to oxidise because of the hydrogen atom attached to the carbonyl group. On the contrary, ketones are hard to oxidise as they have no hydrogen attached
How many polar bonds are present in carboxylic acids?
3 C=O C-O O-H
When are carboxylate ions formed?
When a carboxylic acid loses the H from the O-H bond
What is meant by chirality?
A molecule is called chiral if it cannot be superimposed on its mirror image by any combination of rotations and translations
How can you identify a chiral centre?
A carbon with 4 different atoms or groups attached
What is polarimetry?
The use of a polarimeter to measure the amount of optical activity
What does a polariser do?
Converts unpolarised light into plane polarised light
What is the structure of a carboxylate ion?
O - C O There are two identical carbon-oxygen bonds