Isomerism And Carbonyl Compounds Flashcards
What is optical isomerism
Type of stereoisomerism
In optical isomers 4 groups are arranged in 2 different ways around a central carbon atoms so that two different molecules are made
these molecules are non-superimposable mirror images of each other and are called enantiomers or optical isomers
optical isomers differ by their affect on plain polarised light
What is a chiral carbon?
A chiral c atom is a c atom that has 4 diff groups attached to it
What does it mean if a molecule is optically active
Optically active molecules will rotate plane polarised light
Explain why racemic mixtures are not optically active
Racemic mixtures contain equal quantities of two enantiomers
The two enantiomers cancel each other’s light-rotating effect so the mixture doesn’t show any optical activity
What type of compound is produced when an aldehyde is oxidised
Carboxylic acid
Explain why ketones cannot be easily oxidised
Carbonyl group is in the middle of the carbon chain so to oxidise it, a carbon carbon bond would have to be broken, this requires a lot of energy so ketones are not easily oxidised
Describe what you would observe if you use the following to distinguish between an aldehyde and a ketone:
a) tollens’ reagent
b) Fehling’s solution
a) In the presence of an aldehyde a silver mirror is produced in the presence of a Ketone there is no change
b) in the presence of an aldehyde a brick red precipitate is formed in the presence of a Ketone there is no change
Identify a reducing agent which could be used to reduce an aldehyde to a primary alcohol
NaBH4
Butanone reacts with acidified potassium cyanide to produce a mixture of products
draw the structures of the products from this reaction
explain why this reaction doesn’t produce a single product
See page 583
The C=O bond is planar, so nucleophilic attack of the Delta positive carbon can occur from above or below the C= O double bond
depending on which side the nucleophile attacks from, a different optical isomer will form
Whats a hydroxynitrile
A hn is a molecule w a nitrile (cn) group and a hydroxyl (OH) group
Name the mechanism for the production of hydroxynitriles from Carbonyl compounds and acidified KCN
Nucleophillic addition
What are hazards associated with KCN
Toxic
What safety precautions should be taken when using kcn
Should be done in a fume cupboard
If heating Kcn, should be done using a water bath or electric mantle rather than an open flame
