Derivatives of Carboxylic acids Flashcards
What are the derivatives of Carboxylic acids
Esters, fats and acyl chlorides
What is the ester functional group?
-COO-
How are esters formed
Formed from the condensation reaction between a carboxylic acid and alcohol or from the elimination reaction between an alcohol and acyl chloride.
What are some properties of esters?
Esters are liquids with a fruity odour, immiscible and mostly non polar.
How are esters named?
Esters names are based on the alcohol converted to acyl chloride and the acid converted to the salt name
e.g. Ethanol and Propanoic acid → ethyl propanoate
Methanol and Ethanoic acid → Methyl ethanoate
What happens to the solubility of esters as chain length increases
Solubility decreases as chain length increases. There are H bonds between the carbonyl group and water molecules but as the chain length increases the bonds are less effectively formed.
What happens to boiling point as chain length increases?
As ester chain length increases boiling point increases, greater number of electrons, more induced dipoles therefore stronger Van der Waals forces of attraction between molecules.
What are the two ways esters can be formed?
- Formed from an alcohol and carboxylic acid.
2. Formed from an alcohol and an acyl chloride
Draw the formation of an ester from ethanol and propanoic acid and describe
in book
Concentrated sulfuric acid is added to remove water and promote the formation of the ester
The mixture is heated and distilled and the ester collected
Draw the formation of an ester from ethanol and propanoyl chloride and describe
in book
This reaction produces a much higher yield of the ester, as the HCl is gaseous and removed.
What are the two ways esters can be hydrolysed
Acid catalysed hydrolysis - heated under reflux with dilute HCl
Base catalysed hydrolysis - heated under reflux with sodium hydroxide solution
Write the eqn for the acid catalysed hydrolysis of methyl ethanoate
in book
Write the eqn for the base catalysed hydrolysis of ethyl methanoate
in book
What is the method of preparation of ethyl ethanoate
- Place a mixture of the alcohol and concentrated sulfuric acid in a pear shaped flask
- Add a mixture of the alcohol and carboxylic acid slowly form a dropping funnel
- Swirl the mixture
- Add antibump granules and arrange the apparatus for distillation
- Heat the mixture gently and collet the distillate 2ºC pf the boiling point
- Place in a separating funnel and rinse with Sodium carbonate solution
- Remove lower aqueous layer and add anhydrous calcium chloride to the upper organic layer
- Filter to remove calcium chloride
- Redistill and collect distillate 1ºC either side of the BP
How are acyl chlorides produced
Produced when a carboxylic acid reacts with phosphorus pentachloride. All are highly reactive
What happens when you react an acyl chloride with water?
The corresponding carboxylic acid and hydrogen chloride is produced.
What are the observations when ethanoyl chloride is reacted with water
Fizzes, misty fumes produced.
What are some proerties of ethanoyl chloride?
It is a colourless, corrosive liquid. An open bottle of ethanoyl chloride fumes in contact with moist air and HCl is produced
What are fats?
Fats are triesters of propane-1,2,3-triol (glycerol) and fatty acids.
What is the structure of glycerol?
in book
What are fatty acids?
Carboxylic acids with long hydrocarbon chains
What is Stearic acid?
CH3(CH2)16COOH. It is saturated as it contains no C=C, and its systematic name is Octadecanoic acid
What is Oleic acid?
CH3(CH2)7CH=CH(CH2)7COOH. Unsaturated as it contains C=C. It is a Z isomer. Its systematic name is (9Z)-octadec-9-enoic acid
How is a fat formed?
1 mol of glycerol reacts with 3 mol of fatty acids to form 1 mol of fat and 3 moles of water
Show the formation of a fat from glyerol and fatty acids
in book
Show the formation of gylceryl tristearate
in book
How do fats and oils come about?
If a fat has a large proportion of C=C bonds it will be an oil. The more C=C the weaker the Van der Waals
Saturated fats in the diet
LDL, provide energy and insulation, increase risk of CHD
Unsaturated fats in the diet
HDL, reduces risk of CHD,
What are the two reactions of fats and oils
- Hydrogenation of unsaturated fats
2. Hydrolysis of fats
What are the conditions for the hydrogenation of fats
They react with hydrogen in the present of finely divided nickel catalyst at 180ºC
How many moles of H2 does it take to saturated an unsaturated fat?
It takes 1 mol of H2 per C=C
What are two ways fats can be hydrolysed?
Acid or base, base is the most common and it is called saponification
What does saponification produce?
Produced glycerol and the sodium or potassium salt of the fatty acid.
Draw the saponification of glyceryl tristearate
in book
What is transesterification
The process of swapping an alkyl group in an ester for a different alkyl group.
What can transesterification be between?
An ester and an alcohol or an ester and carboxylic acid.
What does transesterification produce ?
Margarine or a biodiesel
Draw the transesterification between triglyceride and methanol (excess)
in book
Draw intramolecular exchange and intermolecular exchange
in book
What are the conditions for inter/intramolecular exchange
Occurs at 400K in the presence of an alkali (NaOH), glycerol and a catalyst (Sodium methoxide, CH3ONa)
