Isomers And Carbonyls Flashcards
What is a stereoisomer
Isomers with the same structural formula but different spatial arrangements of atoms
When does optical isomerism occur
When a carbon atom has 4 different functional groups attached to it
What are enantiomers
2 compounds that are optical isomers of each other (non superimposeable mirror images )
How do optical isomers work
They have similar physical and chemical properties but they rotate plane polarised light by the same amount but in opposite directions
What is a race mate / racemic mixture
A mixture containing a 50/50 mixture of 2 enantiomers
Why are racemic mixtures not detected by polarimeters
They don’t rotate plane polarised light
How is a race mate formed
When a reactant or intermediate has a original planar group in the molecule and is approached from both sides by an attacking species
There is an equal chance of it being attacked from both sides so an equal amount of each enantiomer is formed
What are 2 reactions that form racemates
An unsymmetrical alkene with HBr in Electrophilic addition
Nucleiphilic addition of HCN to aldehydes and unsymmetrical ketones
What are crabonyls
Compounds with the C=O bond
Why are smaller carbonyl soluble in water
They can form hydrogen bonds with the water
Why do carbonyls not undergo addition reactions easily
How do they attract nuceliphiles
The C=O is strong
The bond is polarised as O is more electronegative than carbon
What do primary alcohols oxidise to
Aldehydes then carboxylic acids
What do secondary alcohols oxidise to
Ketones
What is the oxidising agent used to oxidise alcohols
Acidified potassium dichromate solution
Or potassium dichromate solution and dilute sulfuric acid
How do you test for aldehydes
Heat gently with tollens reagent and silver mirror forms
Heat gently with fehlongs solution and brick red precipitate forms
What is the reducing agent for reducing carbonyls
NaBH4
What are aldehydes reduced to
Primary alcohol
What are ketones reduced to
Secondary alcohols
What is the mechanism for reducing alcohols
Nucleophilic addition
What is another way carbonyls can be reduced
Catalytic hydrogenation
Using hydrogen and a nickel catalyst
At a high pressure
How are hydroxinitriels formed
What are the conditions
What is the mechanism
Reacting carbonyls with HCN ( dilute sukfiric acid and CN source )
Room temp and pressure
Nuecliphikic addition
What type of acids are carboxylic acids in terms of strength (2)
They are weak acids as they only slightly dissociate in water
But they are strong enough to displace carbon dioxide from carbonates
Why do carboxylic acids dissolve in water
They form hydrogen bonds with water molecules
How do carboxylic acids differ in strength based on chain length
The alkyl groups are electron releasing, a bigger chain lengths makes it more negative and less stable
So acids are weaker as they get biggger
