Chemistry: Aldehydes and Ketones
This flashcard set introduces aldehydes and ketones, highlighting their shared general formula and the presence of a carbonyl (=O) group. It distinguishes them based on the position of the carbonyl group—at the end of the chain in aldehydes and in the middle for ketones.
general formula aldehydes and ketones
CnH2nO
Key Terms
general formula aldehydes and ketones
CnH2nO
fuctional group
aldehydes and ketones both contain the carbonile bond (=O)
where is the functional carbonie bond on an aldehyde
end of chain
where is the functional carbonile bond on ketones
middle of chain
what are aldehydes and ketones with the same number of carbon atoms, in relation to eachother
functional group isomers
how can aldehydes and ketones be prepared
oxidation of alcohols
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| Term | Definition |
|---|---|
general formula aldehydes and ketones | CnH2nO |
fuctional group | aldehydes and ketones both contain the carbonile bond (=O) |
where is the functional carbonie bond on an aldehyde | end of chain |
where is the functional carbonile bond on ketones | middle of chain |
what are aldehydes and ketones with the same number of carbon atoms, in relation to eachother | functional group isomers |
how can aldehydes and ketones be prepared | oxidation of alcohols |
what are aldehydes readily oxidised to | carboxylic acids |
what 3 reagents can be used to oxidise an aldehyde to a carboxylic acid |
|
what observations with acidified potassium dichromate and warm and aldehyde | orange>green |
what observations with fehlings solutions and warm and aldehyde | blue solution>brick red ppt |
what observations with tollens reagent and warm and adlehyde | silver mirror |
what are tollens reagent and fehings solutions used as | chemical tests to distinguish between aldehydes and ketones |
how are tollens and fehlings used to distinguish between aldehydes and ketones | ketones cannot be further oxidised and will not react with either tollens reagent/fehlings solution |
what complex ion does tollens reagent contain | Ag(NH3)2+ |
why is a silver mirror seen when an aldehyde is warmed with tollens | the aldehyde is oxidised to a carboxylic acid and the silver ions are reduced to silver metal |
| RCOH+(O)>RCOOH Ag+aq>Ags |
what does (O) represent in equation for aldehyde and tollens | oxidising agent- tollens |
which ions does fehlings solution contain | cu2+ |
why is a brick red ppt seen when an aldehyde is warmed with fehlings | aldehyde is oxidised to a carboxylic acid and the copper ions are reduced to copper 1 oxide (cu2o) |
what does the presence of the delta+ c atom in aldehydes and ketones mean | theyre susceptible to attack by nucleophiles |
why do aldehydes and ketones have a delta+ c atom | polar C=O bond |
what is a nucleophile | an electron pair donor |
how can the nucleophile attach the delta+ carbon | forming a new covalent bond, an addition reaction then occurs across the double bond |
what can aldehydes and ketones be reduced to | alcohols |
how does the reduction of aldehydes and ketones occur | via a nucleophilic addition mechanism |
reagent for reduction of aldehydes and ketones | NaBH4 |
conditions for reduction of aldehydes and ketones | aqueous solution |
GENERAL EQUATION FOR REDUCTION OF ALDEHYDES | RCOH + 2[H] > RH2COH |
what are aldehydes reduced to form | primary alcohols |
what is the reducing agent often simplified as in balanced equations | [H] |
general equation for reduction of ketones | RCOR + 2[H] > RCHOHR |
name of mechanism for reduction of aldehydes/ketones | nucleophilic addition |
nucleophile for reduction of aldehydes/ketones | hydride ion H- |
how can aldehydes and ketones be converted into hydroxynitriles | addition of HCN |
mechanism for addition of HCN to aldehyde/ketone | nucleophilic addition |
reagents for addition of HCN | KCN followed by dilute acid |
general equation for addition of HCN to aldehydes | RCOH + HCN > RCHOHCN |
general equation for addition of HCN to ketones | RCOR + HCN > RCOHRCN |
what will reacting an aldehyde/ketone with cyanide increase | the length of the carbon chain |
nucleophile in addition of HCN to aldehyde/ketone | cyanide ion CN- |
why is KCN used as opposed to HCN | HCN TOXIC GAS | KCN ALSO TOXIC BUT IS AN IONIC SOLID- READILY DISSOLVES TO FORM SOLUTION |
what forms when aldehydes and unsymmetrical ketones undergo reaction with KCN followed by dilute acid | a racemic mixture of 2 enantiomers |
racemic mix | a mixture of equal amounts of the two enantiomers |
what are enantiomers | optical isomers |
optical isomers | non superimposable mirror imahes |
how does the shape of the aldehyde/unsymmetrical ketone lead to a mixture with equal amounts of the two enantiomers being formed | trig planar- attack from each side equally likely |