Aldhydes And Ketones(optical isomerism Flashcards
What does partial oxidation of primary alcohol form
It results an aldehyde forming
What does oxidation of a secondary alcohol
Results in a forming a ketone
What is the oxidizing agent used in the oxidation primary alcohol and secondary alcohol and aldehydes
Potassium dichromate in sulphuric acid (gentle warming needed)
What happens to the potassium dichromate
The orange colour reduced to green
What is the symbol for oxidation
[O]
Give the simplified equations for oxidation reactions
R-CH2OH+[O]–R-CHO +H2O
Give the oxidation reaction for secondary alcohol
R1-CH(OH)-R2+[O]–R1-CO-R2+ H2O
When oxidised further what do aldehydes produce
Carboxylic acid
What two tests can help distinguish between aldehydes and ketones
Tollens reagent
Feelings solution
What occurs when aldehydes and ketones react with tollens reagent
Aldehydes- tollens reagent is reduced and a grey silver mirror forms (carboxylic acid formed)
Ketones-no reaction
What happens when fehlings solution reacts with an aldehyde or ketone
Aldehydes- it’s reduced from the blue copper to red brick red precipitate on gentle warming
Ketone- no reaction
What reducing agent is used to reduce aldehydes and ketones to alcohols
NaBH4 sodium tetrahydroborate
What symbol shows reduction
[H]
2[H] in equation
Give the simplified equation for the reduction of aldehyde
R-CHO + 2[H]-> R-CH2OH(primary alcohol)
Give a simplified equation for reduction of ketone
R1-CO-R2 +2[H]->R1-CH(OH)-R2 (secondary alcohol)
What reducing agent is used to reduce carboxylic acids
LiAlH4
What reactions do carbonyls undergo
Nucleophilic addition
What nucleophile undergoes nucleophillic addition with carbonyls in reduction
HCN
Give the simplified equation for when HCN is reacted with carbonyls in reduction
R1-CO-R2 + HCN->R1-C(CN)(OH)-R2
What is produced when carbonyls undergo reduction with HCN
Hydroxynitrile
Write out equation for reduction by NaBH4 to make alcohols
R1-CO-R2+ 2[H]->R1-CH(OH)-R2
What is chirality
When 4 different groups are attached to one carbon
What are optical isomers (enantiomers)
They are two non superimposable mirror images
How can optical isomers be distinguished
By passing plane polarised light through a liquid containing a chiral molecule
What do chiral molecules do to plane polarised light
They cause it to rotate equally but in opposite directions
One in clockwise rotation
One in anti-clockwise rotation
Define optically active
A substance which can rotate plane polarised light
What is a racemic mixture
When optical isomers are found together in equal amounts
What reactions do chiral substances undergo
Electrophillic addition
Nucleophillic addition
Nucleophillic substitution
When a chiral substance is produced by an addition reaction what is it
It’s a racemic mixture
Why is a racemic mixture produced when by an addition reaction
As the attacking nucleophile or electrophile will attack the polar C-O bond planar molecule above and below in equal proportions
What happens when a chiral substance undergoes nucleophillic substitutions
It only produces a single enantimor as the attacking species only attacks from one side
Give the reagents involved in nucleophilic addition of carbonyl
KCN
HCL
Room temperature
Why is HCn generated insitu and give the equation
As it’s a very toxic gas
KCN +HCl->HCN KCL
