Carbonyl Compounds Flashcards
The carbonyl group is present in…
Aldehydes and ketones
What is the carbonyl group
C=O
What is the functional group for esters
COO
Esters can be made from what. How are they named
An alcohol and a carboxylic acid
They are named with 2 parts. The first part comes from the alcohol and the second from the carboxylic acid
Uses for esters
Esters are polar liquids, so polar organic compounds will dissolve in them. Also have low boiling points so they evaporate easily from mixtures, making them good solvents in glues and printing inks.
Used in plasticisers, added to plastics during polymerisation to make plastic more flexible. Over time the plasticiser molecules escape, plastic becomes brittle and stiff
Esters are easily hydrolysed to form… What are the 2 types of hydrolysis of esters and what is formed
Alcohols
Acid hydrolysis and base hydrolysis, with both you get an alcohol but the second product is different
Explain acid hydrolysis of esters
Splits the ester into an acid and an alcohol, have to reflux the ester with a dilute acid such as HCl or H2SO4. Is a reversible reaction so need to add plenty of water to move the equilibrium to the right
Explain base hydrolysis of esters
Reflux ester with dilute alkali such as NaOH, get a carboxylate ion and alcohol
Fats and oils are esters of…
Fatty acids and glycerol
Fatty acids are…
Long chain carboxylic acids, they combine with glycerol to make fats and oils. Fatty acids can be saturated or unsaturated.
Most of a fat or oil is made from….properties?
Fatty acid chains
Fats- mainly saturated hydrocarbon chains, fit neatly together, increasing vdw forces between them. Means higher temps needed to melt them, solid at room temp.
Oils- unsaturated hydrocarbon chains, double bonds mean chains are bent and don’t pack together well, decreasing effect of vdw forces. Easier to melt, liquids at room temp.
Biodiesel is a mixture of…
Methyl esters of fatty acids
How is biodiesel made
React oils with methanol using potassium hydroxide as a catalyst
Why is biodiesel not carbon neutral
Energy is used to make the fertiliser to grow the crops, used in planting, harvesting and converting the oil. This energy could come from fossil fuels
Oils and fats can be hydrolysed to…
Glycerol, soap and fatty acids
Aldehydes info
Have their carbonyl group at the end of the carbon chain. Their names end in -al
Ketones info
Have their carbonyl group in the middle of the carbon chain. Their names end in -one, often have a number to show which carbon the carbonyl group is on
What happens with Fehlings solutions and Benedicts solution
They are used as oxidising agents. They are both a deep blue Cu2+ complexes, which recuse to brick red Cu2O when warmed with an aldehyde, remain blue with ketone (as ketones aren’t easily oxidised)
What happens with Tollens reagent
Ammonical silver nitrate, (Ag(NH3)2)+ reduced to silver when warmed with an aldehyde, but not with ketone. Goes from colourless to metallic silver, which will cost the inside of the apparatus to form a silver mirror
You can reduce aldehydes and ketones back to….
Alcohols
NaBH4 dissolved in water with methanol is usually the rescuing agent used. But in equations (H) is often used to indicate a hydrogen from a reducing agent.
What oxidising agent turns alcohols to aldehydes and ketones
Acidified potassium dichromate which goes from Orange to green
Hydrogen cyanide will react with carbonyls by what mechanism…
Nucleophilic addition.
HCN reacts with carbonyl compounds to produce hydroxynitriles.
HCN=weak acid, partially dissolves in water to form H+ ions and CN- ions. The CN- group Attucks partially positive carbon atom and donates a pair of electrons. Both electrons from double bond transfer to the oxygen. H+ (from either HCN or water) bonds to the oxygen to form the hydroxyl group (OH)
A carboxyl group contains which groups
Carbonyl group and a hydroxyl group
Carboxylic acids contain which functional group
Carboxyl -COOH always on end of chain and is more important than other functional groups so all the other functional groups in the molecule are numbered starting from this carbon
To name them you find the longest alkane chain take off the ‘e’ and add ‘oic acid’
Carboxylic acids are ….. acids
Weak, in water they partially dissolve into a carboxylate ion and an H+ ion
Carboxylic acids react with carbonates to form….
Carbon dioxide, a salt, water. CO2 fizzes out of the solution
Carboxylic acids react with alcohols to form…
Esters
If you heat a carboxylic acid with an alcohol in presence of a strong acid catalyst=ester. Called an esterification reaction, also a condensation reaction as water is released. Conc sulfuric acid usually used as acid catalyst
Acyl chlorides have the functional group….
What is their general formula
-COCl
CnH2n-1OCl
Acyl chlorides react with…
Water
Alcohols
Ammonia
Amines
Each time chlorine is substituted by an oxygen or nitrogen group and misty fumes of hydrogen chloride are given off
An acid anhydride is made from…
2 identical carboxylic acid molecules
Acyl chloride reactions are….
Nucleophilic addition elimination
In acyl chlorides both the Cl and O2 atoms draw electrons towards themselves, so carbon has slightest is positive charge so can be attacked by nucleophiles
Why is ethanoic anhydride used in industry instead of ethanol chloride
Cheaper than ethanoyl chloride
Safer to use than ethanoyl chloride as it’s less corrosive, reacts more slowly with water and doesn’t produce dangerous hydrogen chloride fumes
What is the formula for glycerol
1,2,3-propanetriol
Suggest how the rate of reaction of propanone with HCN would compare with the rate of reaction of propanal with HCN when a nucleophile is involved in both reactions
Propanal is a faster reaction as it is easier to attack at the end of the chain.
Propanone is slower as the alkyl group is less exposed in the middle of the chain
