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A level Chemistry Paper 2- Organic Chemistry & Analysis > Carboxylic acids and Esters > Flashcards

Carboxylic acids and Esters Flashcards

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1
Q

What are carboxylic acids?

A

Organic compounds containing both a carbonyl (C=O) and a hydroxy group (-OH) attached to the same carbon, known as the carboxyl group.

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2
Q

How can the carboxylic acid functional group be represented?

A

It can be represented in the following ways:
* RCOOH
* R
* 0-H
* Skeletal Formula
* Displayed Formula
* Structural Formula

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3
Q

What does ‘R’ represent in the carboxylic acid formulas?

A

The rest of the chain, which could be an alkyl group including a mixture of branches and/or other functional groups.

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4
Q

How do you name a carboxylic acid?

A

Start with the alkane, remove the ‘e’ and replace it with ‘oic acid’.

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5
Q

What is the numbering convention for carbon atoms in carboxylic acids?

A

The carbon atom that is part of the carboxylic acid functional group is always carbon 1.

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6
Q

What is the name of the compound with the formula CH3COOH?

A

Propanoic acid

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7
Q

How is 3-chlorobutanoic acid structured?

A

It has a chlorine atom on the third carbon of a butanoic acid structure.

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8
Q

What is the name of the compound with the structure CH3(CH2)4COOH?

A

Octanoic acid

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9
Q

Fill in the blank: To name a carboxylic acid, you replace the ‘e’ in the alkane name with ______.

A

oic acid

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10
Q

True or False: The carbon atom in the carboxylic acid functional group is always counted as carbon 2.

A

False

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11
Q

What is the significance of the carboxyl group in carboxylic acids?

A

It defines the functional properties of the acid, influencing its reactivity and solubility.

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12
Q

What type of acid are carboxylic acids classified as?

A

Weak acids
Carboxylic acids only partially dissociate in water.

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13
Q

What is the product of the reaction between ethanoic acid and sodium hydroxide?

A

Sodium ethanoate and water

Reaction: CH3COOH(aq) + NaOH(aq) → CH3COONa(aq) + H2O

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14
Q

What gas is produced when ethanoic acid reacts with sodium carbonate?

A

Carbon dioxide

Reaction: 2 CH3COOH(aq) + Na2CO3(aq) → 2 CH3COONa(aq) + H2O + CO2(g)

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15
Q

What is the result of the reaction between ethanoic acid and sodium metal?

A

Sodium ethanoate and hydrogen gas

Reaction: CH3COOH(aq) + Na(s) → CH3COONa(aq) + ½H2(g)

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16
Q

What is the name of the ion formed when carboxylic acids react under alkaline conditions?

A

Carboxylate ion

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17
Q

What is the relationship between carboxylic acids and carboxylate salts?

A

Carboxylate salts are formed when metal ions are present with carboxylate ions.

Carboxylate salts are ionic compounds.

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18
Q

Fill in the blank: The carboxylate ion is named after the carboxylic acid that forms it by replacing ‘-oic acid’ with ‘-______’.

A

oate

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19
Q

What are the physical properties of carboxylate salts?

A
  • Soluble in water
  • Good electrical conductivity in aqueous solution
  • Relatively high melting point compared to the carboxylic acid
    These properties are due to their ionic nature.
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20
Q

What do carboxylic acids react with alcohols to form?

A

esters

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21
Q

What are the two main functional groups present in esters?

A

Carbonyl (C=O) and alkyl (O-R) groups

Esters are characterized by the presence of these two functional groups.

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22
Q

How can esters be formed?

A

From the reaction between:
* Carboxylic acid and alcohol
* Acid anhydride and alcohol
* Acyl chloride and alcohol

These reactions are typical methods for synthesizing esters.

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23
Q

What is the naming convention for esters?

A

Named ‘back to front’, starting with the alkyl part and ending with the acid

This naming convention reflects the components that form the ester.

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24
Q

What is the ester formed from propanoic acid and ethanol?

A

Ethyl propanoate

The name is derived from the alcohol (ethyl) and the acid (propanoate).

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25
Q

Fill in the blank: The carbonyl group in esters is represented as _______.

A

C=O

The carbonyl group is a key feature of esters.

26
Q

Fill in the blank: Esters can be formed from an acid anhydride and an _______.

A

Alcohol

This is one of the methods for ester formation.

27
Q

True or False: The alkyl part of an ester is derived from the carboxylic acid.

A

False

The alkyl part comes from the alcohol, while the acid part comes from the carboxylic acid.

28
Q

What is formed when an alcohol and carboxylic acid are warmed in the presence of concentrated sulphuric acid?

A

An ester is formed

The reaction is known as esterification.

29
Q

What type of reaction occurs between an alcohol and a carboxylic acid to form an ester?

A

The reaction is both slow and reversible

This means that the ester can break down back into the reactants under certain conditions.

30
Q

Fill in the blank: When ethanoic acid reacts with methanol in the presence of concentrated sulphuric acid, an _______ is produced.

A

ester

31
Q

What is the role of concentrated sulphuric acid in the esterification process?

A

It acts as a catalyst

Catalysts speed up the reaction without being consumed.

32
Q

True or False: The esterification reaction is irreversible.

A

False

The reaction is reversible, meaning the products can revert to reactants.

33
Q

What are the two main reactants involved in the esterification process?

A

Alcohol and carboxylic acid

34
Q

What are acid anhydrides?

A

Derivatives of carboxylic acids where the H of the hydroxy group has been replaced with a carbonyl group

Acid anhydrides are used in the formation of esters through reactions with alcohols.

35
Q

What products are formed when an acid anhydride reacts with an alcohol?

A

An ester and a carboxylic acid

This reaction is a common method for synthesizing esters.

36
Q

Do phenols readily react with carboxylic acids to form esters?

A

No

Phenols do not react readily with carboxylic acids, but they do react with acid anhydrides and acyl chlorides.

37
Q

Which reagents can phenols react with to form esters?

A

Acid anhydrides and acyl chlorides

These reagents are effective due to the reactivity of the carbonyl group.

38
Q

Why do phenols not react readily with carboxylic acids?

A

Due to the comparative non-availability of the lone electron pair on the O atom of the OH group

This non-availability affects the reactivity of phenols in ester formation.

39
Q

What effect does the increased electron density on the phenol ring have?

A

Makes phenol more susceptible to electrophilic attack

This increased susceptibility is crucial for the reactivity of phenols with certain reagents.

40
Q

What are the products of ester hydrolysis?

A

Carboxylic acid and alcohol

Esters can be hydrolyzed using water.

41
Q

What is the catalyst used in acid hydrolysis of esters?

A

Hot aqueous acid

The acid acts as a catalyst in the reaction.

42
Q

Is the reaction of acid hydrolysis of esters reversible?

A

Yes

The reaction can be reversed under certain conditions.

43
Q

What type of hydrolysis uses hot aqueous alkali?

A

Base hydrolysis

This method is different from acid hydrolysis.

44
Q

Is base hydrolysis of esters reversible?

A

No

This reaction is not reversible.

45
Q

What is produced instead of carboxylic acid during base hydrolysis?

A

Carboxylate salt

This occurs in alkali conditions.

46
Q

What is the process of hydrolyzing large esters found in fats and oils called?

A

Saponification

The sodium salt produced is similar to those found in soap.

47
Q

Fill in the blank: Concentrated acid is used to make an ester, while _______ is used to hydrolyze it.

A

Dilute acid

This distinction is important for the hydrolysis process.

48
Q

What are acyl chlorides?

A

Derivatives of carboxylic acids where the hydroxyl group is replaced by a chlorine atom

Acyl chlorides are characterized by their polar carbonyl bonds.

49
Q

How do acyl chlorides react with other molecules?

A

They react readily due to very polar carbonyl bonds and form permanent dipole interactions

This reactivity is a key feature of acyl chlorides.

50
Q

Give an example of an acyl chloride.

A

Ethanoyl chloride

Ethanoyl chloride is a common example used in organic synthesis.

51
Q

How can acyl chlorides be prepared?

A

From carboxylic acids using thionyl chloride (SOCk)

Thionyl chloride is also known as sulfur dichloride oxide.

52
Q

Fill in the blank: Acyl chlorides are derivatives of carboxylic acids where the hydroxyl group has been replaced by a _______.

A

Chlorine atom

53
Q

True or False: Acyl chlorides do not have polar carbonyl bonds.

A

False

54
Q

How does ammonia react with acyl chlorides to form primary amides?

A
55
Q
A

ammonia is basic so will react with the HCl formed to make a salt.
-We use two ammonia molecules in the equation -
-the first reacts with the acyl chloride to produce the amide and HCl.
-The second NH3 mops up the HCl produced forming the salt NH4Cl

56
Q

What are the reagents and conditions for the reaction with ammonia and acyl chloride?

A

Acyl chloride and excess ammonia

57
Q

How do amines react with acyl chlorides to form secondary amides?

A

react with acyl chlorides in a similar way to ammonia, again products
salt from the reaction of the amine starting material with HCl produced in the reaction.

58
Q

What does acylation refer to?

A

producing a molecule which contains an acyl group

59
Q

What can act as acylation agents?

A

-Esters
-Amides
-Carboxylic acids

60
Q

When is it not possible to use aldehydes or ketones as acylating agents?

A

under normal conditions

A level Chemistry Paper 2- Organic Chemistry & Analysis (4 decks)

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