Define carboxyl group

A carboxyl group is the functional group –COOH, consisting of a carbonyl (C=O) and a hydroxyl (O–H) attached to the same carbon atom. It is the defining feature of carboxylic acids.

What is the general formula of a carboxylic acid?

General formula of a carboxylic acid is C n H 2n+1 COOH, often written as RCOOH where R represents the hydrocarbon chain.

How is a carboxylic acid named from its parent alkane?

Replace the '-e' ending of the alkane with '-oic acid', giving the pattern alkan-oic acid (e.g. propane → propanoic acid). No locant is needed because the –COOH group is always on carbon 1.

Carboxylic acids have relatively high boiling points because the O–H bond allows them to form .......... .

Carboxylic acids have relatively high boiling points because the O–H bond allows them to form hydrogen bonds .

How does the solubility of carboxylic acids in water change as the hydrocarbon chain length increases?

Solubility falls as chain length increases. The longer hydrocarbon chain forces its way between water molecules, breaking hydrogen bonds between them, reducing overall solubility.

True or False? Carboxylic acids have two polarised groups: C=O and O–H.

True. Both the C=O and O–H bonds are polarised. This gives carboxylic acids strong intermolecular forces, resulting in high melting and boiling points.

At approximately what chain length do carboxylic acids become solid at room temperature?

Carboxylic acids with more than eight carbon atoms are solids at room temperature. They are very slightly soluble in cold water but become more soluble in hot water.

True or False? Shorter-chain carboxylic acids are soluble in water.

True. Shorter-chain carboxylic acids are soluble in water because they can form hydrogen bonds with water molecules via their –COOH group.

What two classes of organic compound can be oxidised to form a carboxylic acid?

Primary alcohols Aldehydes Both are oxidised using acidified K 2 Cr 2 O 7 or acidified KMnO 4 under reflux.

What are the reagents and conditions for oxidising a primary alcohol to a carboxylic acid?

Acidified K 2 Cr 2 O 7 or acidified KMnO 4 with reflux . Reflux ensures the carboxylic acid cannot escape and allows full oxidation.

What colour change is observed when acidified K 2 Cr 2 O 7 oxidises a primary alcohol to a carboxylic acid?

The solution changes from orange to green . The dichromate ions (Cr 2 O 7 2- ) are reduced to Cr 3+ ions as the organic compound is oxidised.

What colour change is observed when acidified KMnO 4 is used to oxidise a primary alcohol to a carboxylic acid?

The solution changes from purple to colourless . The manganate ions (MnO 4 - ) are reduced to Mn 2+ ions.

Carboxylic acids can be prepared by hydrolysis of a nitrile using either .......... or dilute alkali followed by acidification.

Carboxylic acids can be prepared by hydrolysis of a nitrile using either dilute acid or dilute alkali followed by acidification.

What are the products of hydrolyising a nitrile with dilute acid?

A carboxylic acid and an ammonium salt . The –CN group is converted to a –COOH group.

What are the two steps needed to obtain a carboxylic acid from nitrile hydrolysis using dilute alkali?

Hydrolyse the nitrile with dilute alkali to form a sodium carboxylate salt and ammonia. Acidify the carboxylate salt to convert –COO - to –COOH.

True or False? Distillation is used to oxidise a primary alcohol to a carboxylic acid.

False. Reflux is used, not distillation. Reflux keeps the mixture at boiling point while preventing loss of volatile products, ensuring complete oxidation to the carboxylic acid.

In the hydrolysis of a nitrile, the .......... group at the end of the hydrocarbon chain is converted to a –COOH group.

In the hydrolysis of a nitrile, the –CN group at the end of the hydrocarbon chain is converted to a –COOH group.

Define weak acid (in the context of carboxylic acids)

A weak acid is one that only partially ionises in aqueous solution. For carboxylic acids, the equilibrium lies to the left, giving a low concentration of H + ions compared to the undissociated acid.

How can you test for the presence of a carboxylic acid using sodium carbonate?

Add aqueous sodium carbonate to the sample. Effervescence of CO 2 (g) confirms a carboxylic acid is present: 2RCOOH + Na 2 CO 3 → 2RCOO - Na + + CO 2 + H 2 O.

Carboxylic acids react with sodium hydrogen carbonate to produce a carboxylate salt, water and .......... .

Carboxylic acids react with sodium hydrogen carbonate to produce a carboxylate salt, water and carbon dioxide .

What are the products when ethanoic acid reacts with magnesium oxide?

Magnesium ethanoate and water . The equation is: 2CH 3 COOH (aq) + MgO (s) → (CH 3 COO) 2 Mg (aq) + H 2 O (l).

What reagent reduces a carboxylic acid to a primary alcohol, and what conditions are required?

Lithium tetrahydridoaluminate (LiAlH 4 ) suspended in dry ether at room temperature. Water is added at the end to destroy any excess LiAlH 4 .

What are the products when a carboxylic acid reacts with potassium carbonate?

A potassium carboxylate salt , water and carbon dioxide (g) . For example: 2CH 3 COOH (aq) + K 2 CO 3 (s) → 2CH 3 COOK (aq) + H 2 O (l) + CO 2 (g).

Define esterification

Esterification is the condensation reaction between a carboxylic acid and an alcohol, using concentrated H 2 SO 4 as a catalyst, to form an ester and water.

What product is formed when propanoic acid reacts with phosphorus(V) chloride, and what observation is made?

Propanoyl chloride , phosphorus trichloride oxide (POCl 3 ) and hydrogen chloride (g) are formed. Steamy fumes of HCl are observed. The liquid products are separated by fractional distillation.

True or False? Propanol and ethanoic acid form the ester propyl ethanoate.

True. The first part of the ester name comes from the alcohol (propanol → propyl) and the second part from the carboxylic acid (ethanoic acid → ethanoate).

When a carboxylic acid reacts with potassium hydroxide, the products are a potassium .......... salt and water.

When a carboxylic acid reacts with potassium hydroxide, the products are a potassium carboxylate salt and water.

An acyl chloride is a derivative of a carboxylic acid in which the –OH group has been replaced by a chlorine atom, giving the functional group –COCl. They are named using the suffix –oyl chloride.

Define acid anhydride

An acid anhydride is a carboxylic acid derivative formed by substitution of the –OH group by an alkanoate group. Acid anhydrides are named using the suffix –oic anhydride.

What are the products of the hydrolysis of an acyl chloride with water?

A carboxylic acid and HCl . Water acts as the nucleophile, adding across the C=O bond, then HCl is eliminated.

What type of reaction mechanism do acyl chlorides undergo with nucleophiles?

Acyl chlorides undergo nucleophilic addition-elimination reactions. The nucleophile adds across the C=O bond, then a small molecule (HCl) is eliminated.

When an acyl chloride reacts with an alcohol, an .......... is formed and HCl is eliminated.

When an acyl chloride reacts with an alcohol, an ester is formed and HCl is eliminated.

What are the products when propanoyl chloride reacts with excess ammonia?

Propanamide (a primary amide) and ammonium chloride . The overall equation is: CH 3 CH 2 COCl + 2NH 3 → CH 3 CH 2 CONH 2 + NH 4 Cl.

True or False? Two molecules of ammonia are needed to react with one acyl chloride molecule.

True. The first molecule of ammonia forms the amide . The second molecule neutralises the HCl produced, forming ammonium chloride.

What are the products when ethanoyl chloride reacts with methylamine (CH 3 NH 2 )?

A secondary (substituted) amide (N-methylethanamide) and methylammonium chloride . Equation: CH 3 COCl + 2CH 3 NH 2 → CH 3 CONHCH 3 + CH 3 NH 3 Cl.

True or False? Acyl chlorides react with tertiary amines to form amides.

False. Acyl chlorides do not react with tertiary amines. Only primary and secondary amines undergo nucleophilic addition-elimination with acyl chlorides to form amides.

Define hydrolysis (of esters)

Hydrolysis is the reverse of esterification: an ester is broken down using water (with either acid or alkali) to reform the original carboxylic acid and alcohol, or a carboxylate salt and alcohol.

What are the products of acid hydrolysis of an ester?

A carboxylic acid and an alcohol . The reaction is reversible, so an equilibrium mixture is established when the ester is heated under reflux with dilute acid.

What are the products of alkaline hydrolysis of an ester?

A carboxylate salt and an alcohol . The reaction is irreversible because the ester is fully hydrolysed. Further acidification is needed to convert the carboxylate ion to a carboxylic acid.

True or False? Acid hydrolysis of an ester is an irreversible reaction that goes to completion.

False. Acid hydrolysis is reversible and establishes an equilibrium mixture. It is alkaline hydrolysis that is irreversible and goes to completion.

Alkaline hydrolysis of an ester produces a carboxylate salt. Acidification is then needed to convert the .......... ion into a carboxylic acid.

Alkaline hydrolysis of an ester produces a carboxylate salt. Acidification is then needed to convert the carboxylate ion into a carboxylic acid.

Name the products and write the equation for the acid hydrolysis of ethyl ethanoate.

Products: ethanoic acid and ethanol . CH 3 COOCH 2 CH 3 + H 2 O ⇌ CH 3 COOH + CH 3 CH 2 OH

Name the products and write the equation for the alkaline hydrolysis of methyl propanoate with NaOH.

Products: sodium propanoate and methanol . CH 3 CH 2 COOCH 3 + NaOH → CH 3 CH 2 COONa + CH 3 OH

What conditions are used for both acid and alkaline hydrolysis of esters?

Both use heat under reflux . Acid hydrolysis uses dilute acid (e.g. H 2 SO 4 ) and alkaline hydrolysis uses dilute alkali (e.g. NaOH or KOH).

Define condensation polymerisation

Condensation polymerisation is a type of polymerisation in which monomers join together by repeated condensation reactions, eliminating a small molecule (such as water) at each step.

What are polyesters ?

Polyesters are condensation polymers in which monomers are linked by ester bonds . They are formed from a diol and a dicarboxylic acid, or from a single hydroxycarboxylic acid monomer.

What two types of monomer are required to form a polyester?

A diol (containing two –OH groups) and a dicarboxylic acid (containing two –COOH groups). The groups react at both ends of each monomer, allowing the polymer chain to grow.

When a polyester is formed, the H atom on the diol and the –OH of the –COOH group are expelled as a .......... molecule.

When a polyester is formed, the H atom on the diol and the –OH of the –COOH group are expelled as a water molecule.

What is PET and what are its alternative names?

PET is poly(ethylene terephthalate), a polyester formed from a diol and a dicarboxylic acid. It is also known by the brand names Terylene and Dacron .

True or False? A hydroxycarboxylic acid can act as a single monomer to form a polyester.

True. A hydroxycarboxylic acid contains both an –OH group and a –COOH group, so it can undergo condensation polymerisation with itself to produce a polyester.

How can condensation polymers be distinguished from addition polymers?

Condensation polymers are formed with elimination of a small molecule (e.g. water) at each step. Their monomers are linked by ester or amide bonds , unlike addition polymers which have no such linkages.

International A Level (IAL)ChemistryEdexcelFlashcards4: Rates, Equilibria & Further Organic ChemistryOrganic Chemistry: Carboxylic Acids

Organic Chemistry: Carboxylic Acids (Edexcel International A Level (IAL) Chemistry): Flashcards

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Define carboxyl group

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Define carboxyl group
A carboxyl group is the functional group –COOH, consisting of a carbonyl (C=O) and a hydroxyl (O–H) attached to the same carbon atom. It is the defining feature of carboxylic acids.
What is the general formula of a carboxylic acid?
General formula of a carboxylic acid is C_nH_2n+1COOH, often written as RCOOH where R represents the hydrocarbon chain.
How is a carboxylic acid named from its parent alkane?
Replace the '-e' ending of the alkane with '-oic acid', giving the pattern alkan-oic acid (e.g. propane → propanoic acid). No locant is needed because the –COOH group is always on carbon 1.
Carboxylic acids have relatively high boiling points because the O–H bond allows them to form ...........
Carboxylic acids have relatively high boiling points because the O–H bond allows them to form hydrogen bonds.
How does the solubility of carboxylic acids in water change as the hydrocarbon chain length increases?
Solubility falls as chain length increases. The longer hydrocarbon chain forces its way between water molecules, breaking hydrogen bonds between them, reducing overall solubility.
True or False?
Carboxylic acids have two polarised groups: C=O and O–H.
True.
Both the C=O and O–H bonds are polarised. This gives carboxylic acids strong intermolecular forces, resulting in high melting and boiling points.
At approximately what chain length do carboxylic acids become solid at room temperature?
Carboxylic acids with more than eight carbon atoms are solids at room temperature. They are very slightly soluble in cold water but become more soluble in hot water.
True or False?
Shorter-chain carboxylic acids are soluble in water.
True.
Shorter-chain carboxylic acids are soluble in water because they can form hydrogen bonds with water molecules via their –COOH group.
What two classes of organic compound can be oxidised to form a carboxylic acid?
1. Primary alcohols
2. Aldehydes
Both are oxidised using acidified K₂Cr₂O₇ or acidified KMnO₄ under reflux.
What are the reagents and conditions for oxidising a primary alcohol to a carboxylic acid?
Acidified K₂Cr₂O₇ or acidified KMnO₄ with reflux. Reflux ensures the carboxylic acid cannot escape and allows full oxidation.
What colour change is observed when acidified K₂Cr₂O₇ oxidises a primary alcohol to a carboxylic acid?
The solution changes from orange to green. The dichromate ions (Cr₂O₇^2-) are reduced to Cr³⁺ ions as the organic compound is oxidised.
What colour change is observed when acidified KMnO₄ is used to oxidise a primary alcohol to a carboxylic acid?
The solution changes from purple to colourless. The manganate ions (MnO₄^-) are reduced to Mn²⁺ ions.
Carboxylic acids can be prepared by hydrolysis of a nitrile using either .......... or dilute alkali followed by acidification.
Carboxylic acids can be prepared by hydrolysis of a nitrile using either dilute acid or dilute alkali followed by acidification.
What are the products of hydrolyising a nitrile with dilute acid?
A carboxylic acid and an ammonium salt. The –CN group is converted to a –COOH group.
What are the two steps needed to obtain a carboxylic acid from nitrile hydrolysis using dilute alkali?
1. Hydrolyse the nitrile with dilute alkali to form a sodium carboxylate salt and ammonia.
2. Acidify the carboxylate salt to convert –COO^- to –COOH.
True or False?
Distillation is used to oxidise a primary alcohol to a carboxylic acid.
False.
Reflux is used, not distillation. Reflux keeps the mixture at boiling point while preventing loss of volatile products, ensuring complete oxidation to the carboxylic acid.
In the hydrolysis of a nitrile, the .......... group at the end of the hydrocarbon chain is converted to a –COOH group.
In the hydrolysis of a nitrile, the –CN group at the end of the hydrocarbon chain is converted to a –COOH group.
Define weak acid (in the context of carboxylic acids)
A weak acid is one that only partially ionises in aqueous solution. For carboxylic acids, the equilibrium lies to the left, giving a low concentration of H⁺ ions compared to the undissociated acid.
How can you test for the presence of a carboxylic acid using sodium carbonate?
Add aqueous sodium carbonate to the sample. Effervescence of CO₂ (g) confirms a carboxylic acid is present: 2RCOOH + Na₂CO₃ → 2RCOO^-Na⁺ + CO₂ + H₂O.
Carboxylic acids react with sodium hydrogen carbonate to produce a carboxylate salt, water and ...........
Carboxylic acids react with sodium hydrogen carbonate to produce a carboxylate salt, water and carbon dioxide.
What are the products when ethanoic acid reacts with magnesium oxide?
Magnesium ethanoate and water. The equation is: 2CH₃COOH (aq) + MgO (s) → (CH₃COO)₂Mg (aq) + H₂O (l).
What reagent reduces a carboxylic acid to a primary alcohol, and what conditions are required?
Lithium tetrahydridoaluminate (LiAlH₄) suspended in dry ether at room temperature. Water is added at the end to destroy any excess LiAlH₄.
What are the products when a carboxylic acid reacts with potassium carbonate?
A potassium carboxylate salt, water and carbon dioxide (g). For example: 2CH₃COOH (aq) + K₂CO₃ (s) → 2CH₃COOK (aq) + H₂O (l) + CO₂ (g).
Define esterification
Esterification is the condensation reaction between a carboxylic acid and an alcohol, using concentrated H₂SO₄ as a catalyst, to form an ester and water.
What product is formed when propanoic acid reacts with phosphorus(V) chloride, and what observation is made?
Propanoyl chloride, phosphorus trichloride oxide (POCl₃) and hydrogen chloride (g) are formed. Steamy fumes of HCl are observed. The liquid products are separated by fractional distillation.
True or False?
Propanol and ethanoic acid form the ester propyl ethanoate.
True.
The first part of the ester name comes from the alcohol (propanol → propyl) and the second part from the carboxylic acid (ethanoic acid → ethanoate).
When a carboxylic acid reacts with potassium hydroxide, the products are a potassium .......... salt and water.
When a carboxylic acid reacts with potassium hydroxide, the products are a potassium carboxylate salt and water.
Define acyl chloride
An acyl chloride is a derivative of a carboxylic acid in which the –OH group has been replaced by a chlorine atom, giving the functional group –COCl. They are named using the suffix –oyl chloride.
Define acid anhydride
An acid anhydride is a carboxylic acid derivative formed by substitution of the –OH group by an alkanoate group. Acid anhydrides are named using the suffix –oic anhydride.
What are the products of the hydrolysis of an acyl chloride with water?
A carboxylic acid and HCl. Water acts as the nucleophile, adding across the C=O bond, then HCl is eliminated.
What type of reaction mechanism do acyl chlorides undergo with nucleophiles?
Acyl chlorides undergo nucleophilic addition-elimination reactions. The nucleophile adds across the C=O bond, then a small molecule (HCl) is eliminated.
When an acyl chloride reacts with an alcohol, an .......... is formed and HCl is eliminated.
When an acyl chloride reacts with an alcohol, an ester is formed and HCl is eliminated.
What are the products when propanoyl chloride reacts with excess ammonia?
Propanamide (a primary amide) and ammonium chloride. The overall equation is: CH₃CH₂COCl + 2NH₃ → CH₃CH₂CONH₂ + NH₄Cl.
True or False?
Two molecules of ammonia are needed to react with one acyl chloride molecule.
True.
The first molecule of ammonia forms the amide. The second molecule neutralises the HCl produced, forming ammonium chloride.
What are the products when ethanoyl chloride reacts with methylamine (CH₃NH₂)?
A secondary (substituted) amide (N-methylethanamide) and methylammonium chloride. Equation: CH₃COCl + 2CH₃NH₂ → CH₃CONHCH₃ + CH₃NH₃Cl.
True or False?
Acyl chlorides react with tertiary amines to form amides.
False.
Acyl chlorides do not react with tertiary amines. Only primary and secondary amines undergo nucleophilic addition-elimination with acyl chlorides to form amides.
Define hydrolysis (of esters)
Hydrolysis is the reverse of esterification: an ester is broken down using water (with either acid or alkali) to reform the original carboxylic acid and alcohol, or a carboxylate salt and alcohol.
What are the products of acid hydrolysis of an ester?
A carboxylic acid and an alcohol. The reaction is reversible, so an equilibrium mixture is established when the ester is heated under reflux with dilute acid.
What are the products of alkaline hydrolysis of an ester?
A carboxylate salt and an alcohol. The reaction is irreversible because the ester is fully hydrolysed. Further acidification is needed to convert the carboxylate ion to a carboxylic acid.
True or False?
Acid hydrolysis of an ester is an irreversible reaction that goes to completion.
False.
Acid hydrolysis is reversible and establishes an equilibrium mixture. It is alkaline hydrolysis that is irreversible and goes to completion.
Alkaline hydrolysis of an ester produces a carboxylate salt. Acidification is then needed to convert the .......... ion into a carboxylic acid.
Alkaline hydrolysis of an ester produces a carboxylate salt. Acidification is then needed to convert the carboxylate ion into a carboxylic acid.
Name the products and write the equation for the acid hydrolysis of ethyl ethanoate.
Products: ethanoic acid and ethanol.
CH₃COOCH₂CH₃ + H₂O ⇌ CH₃COOH + CH₃CH₂OH
Name the products and write the equation for the alkaline hydrolysis of methyl propanoate with NaOH.
Products: sodium propanoate and methanol.
CH₃CH₂COOCH₃ + NaOH → CH₃CH₂COONa + CH₃OH
What conditions are used for both acid and alkaline hydrolysis of esters?
Both use heat under reflux. Acid hydrolysis uses dilute acid (e.g. H₂SO₄) and alkaline hydrolysis uses dilute alkali (e.g. NaOH or KOH).
Define condensation polymerisation
Condensation polymerisation is a type of polymerisation in which monomers join together by repeated condensation reactions, eliminating a small molecule (such as water) at each step.
What are polyesters?
Polyesters are condensation polymers in which monomers are linked by ester bonds. They are formed from a diol and a dicarboxylic acid, or from a single hydroxycarboxylic acid monomer.
What two types of monomer are required to form a polyester?
A diol (containing two –OH groups) and a dicarboxylic acid (containing two –COOH groups). The groups react at both ends of each monomer, allowing the polymer chain to grow.
When a polyester is formed, the H atom on the diol and the –OH of the –COOH group are expelled as a .......... molecule.
When a polyester is formed, the H atom on the diol and the –OH of the –COOH group are expelled as a water molecule.
What is PET and what are its alternative names?
PET is poly(ethylene terephthalate), a polyester formed from a diol and a dicarboxylic acid. It is also known by the brand names Terylene and Dacron.
True or False?
A hydroxycarboxylic acid can act as a single monomer to form a polyester.
True.
A hydroxycarboxylic acid contains both an –OH group and a –COOH group, so it can undergo condensation polymerisation with itself to produce a polyester.
How can condensation polymers be distinguished from addition polymers?
Condensation polymers are formed with elimination of a small molecule (e.g. water) at each step. Their monomers are linked by ester or amide bonds, unlike addition polymers which have no such linkages.
True or False?
Polyesters are classified as addition polymers.
False.
Polyesters are condensation polymers. They are formed by repeated condensation reactions with elimination of water, not by addition across C=C double bonds.

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