Reactions With Carbonyl Groups Flashcards
What are aldehydes oxidised to?
Carboxylic acids
What symbol represents an oxidising agent?
[O]
What oxidising agent oxidised aldehydes?
Acidified potassium dichromate (VI)
How do we acidify potassium dichromate (VI)?
Add excess dilute sulfuric acid
What two tests distinguish an aldehyde from a ketone?
-Fehlings Test
-Tollens Reagent/Silver Mirror Test
How is Fehlings test used to identify an aldehyde?
- aldehyde warmed with Fehlings solution
- Brick red precipitate formed
- Cu (II) oxidises aldehyde and itself is reduced to Cu (I)
How is Tollens Reagent/ The silver mirror test used to identify an aldehyde?
- Aldehyde warmed with Tollens Reagent
- Metallic silver formed, produced mirror on inside of test tube
- Ag+ reduced to metallic silver
What equation shows how Tollens Reagent is reduced to metallic silver?
[Ag(NH3)2]+ + e- > Ag + 2NH3
What is a hydroxynitrile?
contains hydroxyl and nitrile group
Which is the highest priority group between hydroxyl and nitrile?
C=-N
How do we name hydroxynitriles?
name from nitrile, including C in C=-N bond as the start of the carbon chain
What is the symbol for a cyanide ion?
:CN-
What will the reaction of a cyanide ion and aldehyde produce?
Hydroxynitrile
Racemic mixture of two optical isomers (enantiometers)
Why can nucleophillic addition lead to a racemic mixture with a cyanide ion?
:CN- can attack from above and below planar C=O
How can an optical isomer arise in a hydroxynitrile?
-chiral carbon
-asymmetrical
-two different R groups
What is a chiral carbon?
carbon attached to four different types of atoms
What is a racemic mixture?
equal quantities of each enantiometer in a mixture
What are the shape of double bonds?
Planar
What are the hazards of potassium cyanide?
toxic/poisonous
flammable
As potassium cyanide is flammable what is used instead of a Bunsen burner?
Water Bath
Why is potassium cyanide acidified?
Produce H+ ions
What are the hazards of hydrogen cyanide?
extremely poisonous
flammable
hard to store as gas
How do Carboxylic acids react?
-C+ open to attack from nucleophiles
-O- of C=O attacked by positively charged species (H+)
How is a carboxylate ion formed?
hydrogen of OH group lost leaving a negative carboxylate ion
What do reactions with Carboxylic acids form?
ionic salts / carboxylate ion
Water
Carbon dioxide with a metal carbonate
How do Carboxylic acids form ionic salts?
by reacting with more reactive metals, alkalis, metal oxides or metal carbonates
How does ethanoic acid react with sodium hydroxide?
CH3COOH (aq) + NaOH (aq) >
CH3COONa (aq) + H2O (l)
What is the word equation to show how sodium hydroxide reacts with ethanoic acid?
ethanoic acid + sodium hydroxide >
sodium ethanoate + water
How does ethanoic acid react with sodium carbonate?
2CH3COOH (aq) + Na2CO3 (aq) >
2CH3COONa (aq) + H2O (l) + CO2 (g)
What is the word equation for the reaction between ethanoic acid and sodium carbonate?
ethanoic acid + sodium carbonate >
sodium ethanoate + water + carbon dioxide
How are esters formed?
Carboxylic acid reacts with alcohol alongside strong acid catalyst (concentrated H2SO4)
How is an ester hydrolysed?
C+ attacked by weak nucleophile in carbonyl bond
What does ester hydrolysis form?
Carboxylic acid
Alcohol
What conditions are required for ester hydrolysis?
reflux
strong acid catalyst
lots of water
Why is lots of water needed in ester hydrolysis?
push equilibrium to right
What word equation shows how an ester and base react?
carboxylate ion/ionic salt + alcohol
What are the conditions for a base/ester reaction?
reflux
hydroxide base
reaction in completion
