Aldehydes and Ketones ( A-level ) Flashcards
what is a carbonyl group?
C=O
what is the functional group and general formula for and aldehyde?
RCHO( C double bonded to O, single bond to H and R )
what is the functional group for a ketone?
RCOR’ ( C double bonded to O )
how do you name aldehydes?
-al suffix
how do you name ketones?
-one suffix
what kind of intermolecular forces do molecules with the carbonyl group have? why?
Permanent dipole-dipole due to the polar C=O bond
are they soluble are they in water? what influences solubility?
Yes- because they can form hydrogen bonds between water molecules and oxygen of C=O. as the carbon chain length increases the solubility decreases.
what bond in carbonyl compounds is usually involved in reactions? why?
C=O due to the polarity of the bond ( large difference in electronegativity between carbon and oxygen )
why is the addition of HCN important?
increases the length of the carbon chain by one carbon atom- very useful
will the product of HCN added to a carbonyl compound have optical isomers? why?
yes they will. in the aldehyde/ketone, the carbonyl group is planar, so the :CN- can attack from either above or below, forming two enantiomers
what is the name of the product when HCN is added to a carbonyl compound?
Hydroxynitriles
what is Fehlings solution? what colour is it?
Copper complex ions, blue
what happens when an aldehyde is added to Fehlings solution?
reduced to C+ ions –> colour change to brick red ppt
what happens when a ketone is added to Fehlings solution?
no visible change –.> stays blue
what is tollens reagent?
silver complex ions, colourless solution
what happens when an aldehyde is added to tollens reagent?
silver mirror forms as Ag+ is reduced to Ag
what happens when an ketone is added to tollens reagent?
no visible change
what is another oxidising agent for alcohols and aldehydes? what change in colour does this undergo?
acidified potassium dichromate (VI) H2SO4 and K2Cr2O7. colour change from orange to green
what is a reducing agent for aldehydes and ketones? what ions does this release in solution?
NaBH4
releases an H- ion
write an equation for the reduction of pentan-2-one
CH3COHCH2CH2CH3 + [H] —> CH3CH(OH)CH2CH2CH3
