Unit 3.4.5 - Carbonyl groups Flashcards
What functional group do aldehydes and ketones share?
=O
What is the difference between aldehydes and ketones?
Aldehydes have the =O at the end of the carbon chain Ketones have the =O in the middle of the carbon chain
How can aldehydes be made?
By oxidising primary alcohols
How can ketones be made?
By oxidising secondary alcohols
What suffix is used to name aldehydes?
-al
What suffix is used to name ketones?
-one
Other than the suffix used what is the difference between naming aldehydes and ketones?
With ketones you have to say the number of the carbon the functional group comes off
What can you oxidise an aldehyde too?
Carboxylic acid
What can you oxidise a ketone too?
It can’t be oxidised
Name three tests to distinguish between aldehydes and ketones.
You heat with …… Tollen’s reagent, Benedict’s solution or Fehling’s solution
What do all the tests for distinguishing between aldehydes and ketones work on?
The fact an aldehyde can be oxidised but a ketone can’t
What is Tollen’s reagent?
Colourless solution of silver nitrate dissolved in aqueous ammonia
What are the results when a ketone and aldehyde is mixed with Tollen’s reagent?
Ketone - no visible change Aldehyde - silver mirror forms
What is the equation for when diamine silver ions are reduced, when they are used as Tollen’s reagent?
[Ag(NH₃)₂]⁺ + e⁻ → Ag + 2NH₃
What is Fehling’s solution?
Blue solution of a complexed copper (II) ions dissolved in sodium hydroxide
What are the results when a ketone and aldehyde is mixed with Fehling’s solution?
Ketone - no visible change Aldehyde - brick red precipitate
What is the equation for when copper(II) ions are reduced, when used as Fehling’s solution?
Cu²⁺ + e⁻ → Cu⁺
What is Fehling’s solution similar too?
Benedict’s solution
What are the results when a ketone and aldehyde is mixed with Benedict’s solution?
Ketone - no visible change Aldehyde - brick red precipitate
What can you reduce an aldehyde too?
Primary alcohol
What can you reduce a ketone too?
Secondary alcohol
Give an example of a reducing agent used to reduce a aldehyde to a primary alcohol.
Sodium borohydride - NaBH₄
What is usually used to represent a reducing agent?
[H]
What is the mechanism called for when an aldehyde is reduced to a primary alcohol?
Nucleophilic addition
What from the reducing agent acts as a nucleophile for the mechanisms of an aldehyde being reduced to a primary alcohol
H⁻
What are the five steps in the mechanism for the reaction between an aldehyde and H⁻?
1.) The C=O bond is polar so the carbon is slightly positive and attracts the negative lone pair of electrons on the H⁻ ion 2.) The H⁻ ion attacks the slightly positive carbon and donates its pair of electrons forming a bond with the carbon 3.) As the carbon can only have four bonds this causes one of the carbon-oxygen bonds to break, forcing a lone pair of electrons from the C=O double bond onto the oxygen 4.) The oxygen then donates its lone pair of electrons to a H⁺ ion (which has come from from or a weak acid) 5.) And so a primary alcohol is produced
How can you produce hydroxynitriles?
By reacting aldehyde or ketones with hydrogen cyanide
What is produced when you react aldehydes or ketones with hydrogen cyanide?
Hydroxynitriles
What are hydroxynitriles?
Molecules which contain a hydroxyl group (OH) and a nitrile group (CN)
How do you name hydroxynitriles?
The nitrile group takes priority and so you name that with the suffix -nitrile, the carbon in the nitrile group is then carbon-1, you then name the hydroxyl group with the prefix hydroxyl- along with the number of the carbon atom it comes off
What is the mechanism called for when an aldehyde or ketone reacts with hydrogen cyanide to produce a hydroxylnitrile?
Nucleophilic addition
What are the six steps in the mechanism for when hydrogen cyanide reacts with an aldehyde or ketone?
1.) HCN is a weak acid so partially dissociates in water to form H⁺ ions and CN⁻ ions 2.) The C=O bond is polar so the carbon is slightly positive and attracts the negative lone pair of electrons on the CN⁻ ion 3.) The CN⁻ ion attacks the slightly positive carbon and donates its pair of electrons forming a bond with the carbon 4.) As the carbon can only have four bonds this causes one of the carbon-oxygen bonds to break, forcing a lone pair of electrons from the C=O double bond onto the oxygen 5.) The oxygen then donates its lone pair of electrons to a H⁺ ion 6.) A hydroxylnitrile is produced
What is often used instead of HCN? and why?
Acidified KCN HCN is extremely toxic and so KCN is used to reduce the risk and it is also easier to store Acidified to provide the H⁺ ions for the reaction
How should you heat aldehydes and ketones and why?
In a water both because they are very flammable
What functional group do carboxylic acids contain
-COOH
What suffix is used to name carboxylic acids?
-oic acid
What type of acids are carboxylic acids?
Weak
Why are carboxylic acids only weak acids?
They only partially dissociate into carboxylate ions and H⁺ ions
What do carboxylic acids react with carbonates or hydrogen carbonates to form?
A salt, carbon dioxide and water
What is the symbol for a carbonate ion?
CO₃²⁻
What is the symbol for a hydrogen carbonate ions?
HCO₃⁻
What can you react with a carboxylic acid to form a salt, carbon dioxide and water?
Carbonates or hydrogen carbonates
What is the equation for ethanoic acid reacting with sodium carbonate?
2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂
What is the equation for ethnic acid reacting with sodium hydrogen carbonate?
CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂
What is CH₃COONa?
Sodium ethanoate
How can you produce an ester from a carboxylic acid?
Heat in with an alcohol with a concentrated acid catalyst
What is produced when you heat a carboxylic acid with an alcohol and a concentrated acid catalyst?
Ester
How are esters named?
You name the first part with the alkyl group that came from the alcohol and then add the name of the carboxylic acid swapping the -oic acid for -oate
How do you name other functional group on esters?
Away from the C-O-C bond with both of these carbons being carbon-1
Name four uses of esters.
Perfumes, flavourings, solvents, plasticisers
Why are esters used in perfumes and as flavourings?
They can have a pleasant sweet smell
Why are esters used as solvents?
They are polar liquids so lots of polar organic compounds with dissolve in them, they also have a low boiling point so they an evaporate easily from the mixture
How are esters used as plasticisers?
They are added to plastics during polymerisation to make the plastics more flexible
What is hydrolysis?
When a substance is split up using water
What is the name for the reaction between an alcohol and carboxylic acid?
Esterification
As hydrolysis of an ester is often slow what is added to speed up the reaction?
An acid or alkali
What are the two types of hydrolysis called?
Acid hydrolysis and base hydrolysis
What is acid hydrolysis the reverse of?
Esterification
How do you carry out acid hydrolysis?
Reflux an ester with dilute acid
What does acid hydrolysis produce?
A carboxylic acid and alcohol
Why do you need a lot of water for acid hydrolysis?
The reactions are reversible so you need lots of water to push the equilibrium over to the right so you get more products
How do you carry out base hydrolysis?
Reflux an ester with a dilute alkali
What does base hydrolysis produce?
A carboxylate ion and alcohol
Name a common naturally occurring ester?
Fats and oil
What are fats and oils esters of?
Glycerol and fatty acids
What are fatty acids?
Long chain carboxylic acids
What is the actual name of glycerol?
propan-1,2,3-triol
How many fatty acids bond to glycerol to make fats and oils?
3
Where do most of the properties of fats and oils come from? And why?
The long chain fatty acid as it is what makes up most of the fat or oil
What are two types of fatty acids?
Saturated or unsaturated
What is meant by saturated?
No double bonds
What is meant by unsaturated?
Double bonds
What type of hydrocarbon (fatty acid) tail to fats have?
Saturated
Why are fats solid at room temperature?
They can fit closely together increasing the van der Waals forces between them, therefore a higher temperature is needed to overcome the forces and melt them so they are solid at room temperature
What type of hydrocarbon (fatty acid) tail to oils have?
Unsaturated
What is the difference between fats and oils?
Oils are unsaturated and so contain double bonds where as fats are unsaturated so only contain single bonds
Why are oils liquid at room temperature?
The double bonds means the chains are bent and so they don’t pack well together, decreasing the effect of the van der Waals forces, meaning they are easier to overcome and they melt at lower temperatures and so are liquid at room temperature
What type of hydrolysis can be used to used to split fats or oils?
Base hydrolysis
What do you heat fats and oils with to split them?
Sodium hydroxide
What is produced when you heat a fat or oil with sodium hydroxide?
Alcohol and a sodium salt (the carboxylate ion reacts with the Na⁺)
What is a use of sodium salt?
As salt
How can you convert a sodium salt back into a long chain carboxylic acid?
By adding an acid such as HCl, as the H⁺ ions displace the Na⁺ ions in the salt forming a carboxylic acid
What is biodiesel a mixture of?
Methyl esters of long chain carboxylic acids
What do you have to do with vegetable oils to produce biodiesel?
React them with methanol using a strong alkali as as catalyst, to produce a mixture of methyl esters which is the biodiesel and glycerol
What is biodiesel thought to be carbon neutral?
When the crops grow they absorb the same amount of CO₂ as they produce when they are burnt
Why isn’t biodiesel carbon neutral?
Energy is used to make fertiliser to grow the crops, during planting, during harvesting and when converting the crop into oil, this energy comes from burning fossil fuels which release carbon dioxide
What functional group do acyl chlorides have?
-COCl
What is another name for acyl chlorides?
Acid chlorides
What suffix is used to name acyl chlorides?
-oyl chloride
Name four things acyl chlorides react with?
Cold water, alcohols, ammonia and amines
What is a common product when acyl chlorides are reacted with cold water, alcohols, ammonia and amines ?
Hydrogen chloride
How do you know hydrogen chloride has been produced?
You will see misty fumes
What is produced when you react an acyl chloride with cold water?
Carboxylic acid and hydrogen chloride
What is produced when you react an acyl chloride with an alcohol?
Ester and hydrogen chloride
What is produced when you react an acyl chloride with ammonia?
Amide and hydrogen chloride
What is produced when you react an acyl chloride with an amine?
N-substituted amide and hydrogen chloride
What do you react an acyl chloride with to produce an ester?
Alcohols
What do you react an acyl chloride with to produce a carboxylic acid?
Cold water
What do you react an acyl chloride with to produce an amide?
Ammonia
What do you react an acyl chloride with to produce an N- substituted amide?
Amines
What is the name of the mechanism for the reaction between acyl chlorides and cold water, alcohols, ammonia or amines ?
Nucleophilic addition-elimination
What are the two general steps during acyl chloride nucleophilic addition-elimination reactions?
1.) The nucleophile adds onto the acyl chloride displacing the Cl⁻ ions 2.) The Cl⁻ ion steals a hydrogen ion from the nucleophile to eliminate HCl
What are acid anhydrides?
Two identical carboxylic acids joined together via an oxygen
How do you name acid anhydrides?
Take away the acid from the carboxylic acid it is made from and add anhydride
What is the difference between the reactions of acyl chlorides and acid anhydrides?
Acid anhydrides react less vigorously and a carboxylic acid is formed instead of HCl
What is produced when you react an acid anhydride with cold water?
Two of the same carboxylic acids
What is produced when you react an acid anhydride with an alcohol?
Ester and carboxylic acid
What is produced when you react an acid anhydride with ammonia?
Amide and carboxylic acid
What is produced when you react an acid anhydride with an amine?
N substituted amide and carboxylic acid
What do you react an acid anhydride with to produce an N- substituted amide?
Amine
What do you react an acid anhydride with to produce an amide?
Ammonia
What do you react an acid anhydride with to produce an ester?
Alcohol
What do you react an acid anhydride with to produce an two carboxylic acids?
Cold water
What else is released when you turn a carboxylic acid into an acid anhydride?
Water
Name an ester used as a drug?
Aspirin
How is aspirin made?
By reacting salicylic acid with either ethanoic anhydride or ethanoyl chloride
What is more commonly used to make aspirin: ethanoic anhydride or ethanol chloride? And why?
Ethanoic anhydride is used more often because it is cheaper and safer because it is less corrosive, reacts more slowly with water and doesn’t produce dangerous hydrogen chloride fumes
What is the functional group of amides?
-CONH₂
Why do amides behave differently from amines?
The carbonyl group pulls electron density away from the NH₂ group so they behave differently
What suffix is used to name amides?
-amide
What are n-substituted amides?
Where one of the hydrogens attached to the nitrogen has been substituted for an alkyl group
What to do you name N-substitued amides?
N-whatever alkyl group have been added to the nitrogen
Draw the general structure of aldehydes and ketones.
Draw the general equation for for the oxidation of an aldehyde.
Draw the general equation for reducing an aldehyde.
Draw the generla equation for reducing a ketone.
Draw the general structure of a hydroxynitrile.
Draw the general structure of a carboxylic acid.
Draw the equation for how a carboxylic acid pratially dissociates.
Draw the general reaction between an alcohol and a carboxylic acid.
Draw the general equation for acid hydrolysis.
Draw the general equation for base hydrolysis.
Draw the general strcuture of a fat or oil.
Draw the rest of this reaction.
Draw the general equation for the foramtion of biodiesel.
Draw the reaction between ethanoic anhydride and ammonia.
Draw the reaction between ethanoic anhydride and methylamine.
Draw the general structure of an amide.
Draw the reaction between ethanoic acid and methanol.
Draw the reaction between ethanoic anhydride and water.
Draw the reaction between ethanoyl chloride and methylamine.
Draw the reaction between ethanoyl chloride and ammonia.
Draw the reaction between ethanoyl chloride and methanol.
Draw the reaction between ethanoyl chloride and water.
