Reactions of Carbonyl Compounds Flashcards
what are the reactions of carbonyl compounds?
- oxidation of aldehydes to form carboxylic acids
- nucleophilic addition reactions
what is the suitable oxidising agent to oxidise aldehydes?
- acidified dichromate (H+/CR2O7^2-)
- which is made by mixing potassium dichromate and sulfuric acid
what is the colour change for potassium dichromate?
orange(Cr2O7-) to green(Cr3+)
how should the oxidation be carried out?
carried out at reflux
what are the differences between alkene and carbonyls?
- alkenes have a double bond between 2 carbon atoms whereas carbonyls have a double bond between carbon and oxygen atoms
- alkenes have no difference in electronegativity whereas carbonyls have a difference in electronegativity
- the alkenes do not have a polarised bond and carbonyls do have a polarised bond
- alkenes react with electrophiles whereas carbonyls react with nucleophiles
what is the structure of a C=O bond?
- p orbitals overlap
- difference in electronegativity between carbon and oxygen
- creates a dipole in the C=O bond
what is an aldehyde?
- carbon on carbonyl group is attached to one carbon atom
- suffix = ‘-al’
what is a ketone?
- carbon on carbonyl group is attached to two other hydrogen atoms
- suffix = ‘-one’
what is the suitable reducing agent when reducing aldehydes and ketones?
- NaBH4
- sodium borohydride
what does NaBH4 generate?
- it readily generates hydride ions (H-)
- hydride ions are negatively charged ions with a lone pair of electrons
what are aldehydes reduced to form?
- primary alcohols
what are ketones reduced to form?
- secondary alcohols
what does the mechanism of nucleophilic addition need?
protonation
- using H2O when forming alcohols
- using H+ ion when forming hydroxynitriles
what is used to form hydroxynitriles from carbonyl groups?
- NaCN or KCN followed by the addition of dilute HCl
- -C triple bond N
- H+ used in protonation
what are the two uses of nitriles?
1) formations of carboxylic acids
2) reduction
what is the use of nitriles to form carboxylic acids?
- hydrolysis of nitriles with aqueous acid forms carboxylic acids
- catalysts are HCl
what is the use of nitriles in reduction?
- nitriles can be reduced to form amines by using hydrogen with a nickel catalyst
