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13.4 Carbonyl compounds

CARBONYL COMPOUNDS
Organic Chemistry
12 March 2024
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Slide 1: Diapositive
ChemistrySecondary EducationAge 12,13

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CARBONYL COMPOUNDS
Organic Chemistry
12 March 2024

Slide 1 - Diapositive

Cet élément n'a pas d'instructions


  • participate in the hinge-point discussion
  • explain the mechanism of the reactions in this session
  • formulate a conclusion from a set of reactions
Learning expectations

Slide 2 - Diapositive

Cet élément n'a pas d'instructions

CARBONYL COMPOUNDS
Organic Chemistry
12 March 2024

Slide 3 - Diapositive

Cet élément n'a pas d'instructions

Identify one concept you
learned from the
previous sessions.

Slide 4 - Carte mentale

Cet élément n'a pas d'instructions

CARBONYL COMPOUNDS
Organic Chemistry
12 March 2024

Slide 5 - Diapositive

Cet élément n'a pas d'instructions


  • Compounds that contain the C=O (carbonyl) group
CARBONYL COMPOUNDS

Slide 6 - Diapositive

Cet élément n'a pas d'instructions

Slide 7 - Diapositive

Cet élément n'a pas d'instructions

EXAMPLES

Slide 8 - Diapositive

Cet élément n'a pas d'instructions

CARBONYL COMPOUNDS
Organic Chemistry
12 March 2024

Slide 9 - Diapositive

Cet élément n'a pas d'instructions


  • have higher boiling points than the alkanes with similar Mr 
  • boiling points increase with increasing carbon atoms
  • permanent dipole-dipole forces are also present due to carbonyl compounds being polar
  • Methanal and ethanal are gases at room temperature, while others are liquids.
  • soluble in water = decreases with increasing carbon atoms
Properties of Carbonyl compounds

Slide 10 - Diapositive

Cet élément n'a pas d'instructions

CARBONYL COMPOUNDS
Organic Chemistry
12 March 2024

Slide 11 - Diapositive

Cet élément n'a pas d'instructions

Which of these could be the best oxidising agent?
acid. potassium manganate (VII)
acid. potassium dichromate
hydrochloric acid

Slide 12 - Sondage

Cet élément n'a pas d'instructions


  • Aldehydes and ketones can be made by oxidising primary and secondary alcohol. The oxidising agent used is either acidified potassium dichromate(VI), K2Cr2O7 or acidified potassium manganate(VII), KMnO4.
Preparation of Aldehydes and Ketones

Slide 13 - Diapositive

Cet élément n'a pas d'instructions


  • The primary alcohol used must be in excess and heated under reflux with acidified K2Cr2O7/KMnO4. The aldehyde formed must be distilled off as soon as possible.
  • Under these conditions, a primary alcohol is oxidised to an aldehyde. 
Preparation of aldehydes

Slide 14 - Diapositive

because 
______________ involves heating the chemical reaction for a specific amount of time, while continually cooling the vapour produced back into liquid form, using a condenser.
A
In situ
B
Reflux
C
In vitro

Slide 15 - Quiz

Cet élément n'a pas d'instructions


  • The secondary alcohol is heated under reflux with acidified K2Cr2O7/KMnO4.
  • Under these conditions, a secondary alcohol is oxidised to a ketone.  
Preparation of ketones

Slide 16 - Diapositive

Cet élément n'a pas d'instructions

CARBONYL COMPOUNDS
Organic Chemistry
12 March 2024

Slide 17 - Diapositive

Cet élément n'a pas d'instructions


  • C=O bond of the carbonyl group = highly polarised due to oxygen atom being more electronegative
  • carbonyl compounds = undergo nucleophilic addition
Reactivity of carbonyl compounds

Slide 18 - Diapositive

Cet élément n'a pas d'instructions

CARBONYL COMPOUNDS
Organic Chemistry
12 March 2024

Slide 19 - Diapositive

Cet élément n'a pas d'instructions


  • Reduction
  • Oxidation
  • Reaction with Hydrogen cyanide, HCN
Reactions of Aldehydes and Ketones

Slide 20 - Diapositive

Cet élément n'a pas d'instructions

  • Reagent : Lithium tetrahydridoaluminate, LiAlH4 or sodium tetrahydridoborate, NaBH4
  • Condition : For LiAlH4 - in dry ether; For NaBH4 - in aqueous alcoholic solution
  • Product : Aldehyde - primary alcohol; Ketone - secondary alcohol
REDUCTION

Slide 21 - Diapositive

it can also happen with water molecule as a nucleophile
REDUCTION
Aldehyde
Ketone

Slide 22 - Diapositive

Due to the reactivity of LiAlH4, it cannot be used in the presence of water or
alcohol. It must be carried out in solution in a carefully dried ether such as ethoxyethane(diethyl ether).
CARBONYL COMPOUNDS
Organic Chemistry
12 March 2024

Slide 23 - Diapositive

Cet élément n'a pas d'instructions

  • Reagent : Acidified potassium dichromate(VI), K2Cr2O7 or acidified potassium manganate(VI), KMnO4
  • Condition : Heat under reflux
  • Product : Aldehyde - Carboxylic acid; Ketone - Will not be oxidised.
OXIDATION
Aldehyde
Ketone

Slide 24 - Diapositive

Cet élément n'a pas d'instructions

  • Reagent : Sodium/potassium cyanide, NaCN and a little sulfuric acid, H2SO4
  • Condition : Room temperature
  • Product : Hydroxynitriles
REACTION WITH HYDROGEN CYANIDE
Aldehyde
Ketone

Slide 25 - Diapositive

Hydrogen cyanide is not used alone because it is a poisonous gas. Instead, it is produced from the reaction between sodium/potassium cyanide and sulfuric acid. The solution will contain hydrogen cyanide and some free cyanide ions.

Reaction mechanism

Slide 26 - Diapositive

Hydrogen cyanide is not used alone because it is a poisonous gas. Instead, it is produced from the reaction between sodium/potassium cyanide and sulfuric acid. The solution will contain hydrogen cyanide and some free cyanide ions.

CARBONYL COMPOUNDS
Organic Chemistry
12 March 2024

Slide 27 - Diapositive

Cet élément n'a pas d'instructions

  • Reagent : Brady's reagent = solution of the 2,4-dinitrophenylhydrazine in methanol and sulfuric acid
Test for Carbonyl Group

Slide 28 - Diapositive

2,4-dinitrophenylhydrazine or 2,4-DNPH can be used to detect the presence of carbonyl group, C=O. 
  • Reagent : Tollens' reagent = diamminesilver(I) ions, [Ag(NH3)2]+
Test for Aldehydes
  • When a few drops of aldehyde are added to the freshly prepared Tollens' reagent and warmed in a water bath for a few minutes, a grey precipitate or a silver mirror is observed only if aldehyde is present.

Slide 29 - Diapositive

Aldehydes will reduce the diamminesilver(I) ions to metallic silver, aldehyde itself is oxidised to a salt of carboxylic acid.

Since ketones will not be oxidised, it will not reduce it to metallic silver.

Slide 30 - Diapositive

it can also happen with water molecule as a nucleophile
  • Reagent : Fehling's solution =  copper(II) ions complexed with tartrate ions in sodium hydroxide solution
Test for Aldehydes

Slide 31 - Diapositive

Complexing the copper(II) ions with tartrate ions prevents precipitation of copper(II) hydroxide. It is a blue solution.

CARBOXYLIC ACIDS AND DERIVATIVES
Organic Chemistry
12 March 2024

Slide 32 - Diapositive

Cet élément n'a pas d'instructions


  • compounds that contain the -COOH group
Carboxylic Acids

Slide 33 - Diapositive

Cet élément n'a pas d'instructions


  • have higher melting and boiling points than the corresponding alcohols
  • boiling points increase with increasing carbon atoms
  • soluble in water = decreases with increasing carbon atoms
Properties of Carboxylic acids

Slide 34 - Diapositive

Cet élément n'a pas d'instructions

CARBOXYLIC ACIDS AND DERIVATIVES
Organic Chemistry
12 March 2024

Slide 35 - Diapositive

Cet élément n'a pas d'instructions


There are three ways to produce carboxylic acids: 
  • Oxidation of primary alcohol.
  • Oxidation of aldehyde.
  • Acidic/alkaline hydrolysis of nitrile.
Preparation of carboxylic acids

Slide 36 - Diapositive

Cet élément n'a pas d'instructions


  • When nitrile is heated under reflux with a dilute acid such as dilute hydrochloric acid, carboxylic acid will be formed.
Acidic hydrolysis of nitriles

Slide 37 - Diapositive

Cet élément n'a pas d'instructions


  • When nitrile is heated under reflux with an alkali such as sodium hydroxide, salt of carboxylic acid (carboxylate salt) is produced.
  • Ethanoate ion can be converted to ethanoic acid by the addition of acid. 
 Alkaline hydrolysis of nitrile

Slide 38 - Diapositive

Cet élément n'a pas d'instructions

CARBOXYLIC ACIDS AND DERIVATIVES
Organic Chemistry
12 March 2024

Slide 39 - Diapositive

Cet élément n'a pas d'instructions


  • Acidic, because they can donate a proton to form carboxylate ions and hydroxonium ions. The presence of hydroxonium ions makes the solution acidic.
  • Weakly acidic
Acidity of carboxylic acids

Slide 40 - Diapositive

Cet élément n'a pas d'instructions

CARBOXYLIC ACIDS AND DERIVATIVES
Organic Chemistry
12 March 2024

Slide 41 - Diapositive

Cet élément n'a pas d'instructions


  • Reaction with bases
  • Reaction with metals
  • Reaction with carbonates and hydrogencarbonates
  • Converting carboxylic acids to acyl chlorides 
Reactions of Carboxylic acids

Slide 42 - Diapositive

Cet élément n'a pas d'instructions

  • Reagent : a base such as sodium hydroxide
  • Product : a carboxylate salt and water
Reaction with bases

Slide 43 - Diapositive

it can also happen with water molecule as a nucleophile
  • Reagent : reactive metals such as sodium
  • Product : a carboxylate salt and hydrogen gas
Reaction with metals

Slide 44 - Diapositive

it can also happen with water molecule as a nucleophile
  • Reagent : carbonates and hydrogencarbonates
  • Product : a carboxylate salt, carbon dioxide gas and water
Reaction with carbonates and hydrogencarbonates

Slide 45 - Diapositive

it can also happen with water molecule as a nucleophile

  • have the -OH in the -COOH group of the carboxylic acid replaced by chlorine
  • very reactive and can be used to produce a range of other organic compounds
What are ACYL CHLORIDES?
Example

Slide 46 - Diapositive

Cet élément n'a pas d'instructions


  • Reaction with phosphorus(III) chloride, PCl3
  • Reaction with phosphorus(V) chloride, PCl5
  • Reaction with thionyl chloride, SOCl2.
Three methods to produce acyl chlorides 

Slide 47 - Diapositive

Cet élément n'a pas d'instructions

 Reaction with phosphorus(III) chloride, PCl3 

Slide 48 - Diapositive

Cet élément n'a pas d'instructions

 Reaction with phosphorus(V) chloride, PCl5

Slide 49 - Diapositive

Cet élément n'a pas d'instructions

 Reaction with thionyl chloride, SOCl2

Slide 50 - Diapositive

Cet élément n'a pas d'instructions

CARBOXYLIC ACIDS AND DERIVATIVES
Organic Chemistry
12 March 2024

Slide 51 - Diapositive

Cet élément n'a pas d'instructions

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