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A-level Chemistry > PL - Carboxylic acids, esters and acyl chlorides > Flashcards

PL - Carboxylic acids, esters and acyl chlorides Flashcards

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1
Q

What do carboxylic acids contain?

A

-COOH the carboxyl functional group.

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2
Q

How do you name a carboxylic acid?

A

You find and name the longest alkane chain, take off the ‘e’ and add ‘-oic acid’.

It is the most important functional group so all the other functional groups in the molecule are numbered starting from this carbon.

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3
Q

Where is the carboxyl group in a carboxylic acid?

A

Always at the end of the molecule.

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4
Q

What do dicarboxylic acids contain?

A

2 -COOH functional groups.

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5
Q

Where are the carboxyl groups in dicarboxylic acids?

A

At either end of the molecule.

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6
Q

What is the smallest dicarboxylic acid?

A

Ethanedioc acid.

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7
Q

What do all the names of dicarboxylic acids end in?

A

-dioic acid.

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8
Q

What is different about naming dicarboxylic acids compared to carboxylic acids?

A

You don’t lose the ‘e’ off the alkane name.

If there are other functional groups in the molecule then you need to number the carbon atoms to name it. There’s a rule to decide which of the carboxyl carbons should be number 1 - use the lowest possible numbers for the side chains.

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9
Q

What is the rule when naming dicarboxylic acids?

A

If there are other functional groups in the molecule then you need to number the carbon atoms to name it. There’s a rule to decide which of the carboxyl carbons should be number 1 - use the lowest possible numbers for the side chains.

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10
Q

What are carboxylic acids?

A

Weak acids.

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11
Q

What happens to carboxylic acids in water?

A

They are weak acids so they partially dissociate into carboxylate ions and H+ ions in water.

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12
Q

Which way does the equilibrium lie when carboxylic acids are added to water?

A

To the left because most of the molecules don’t dissociate.

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13
Q

What do carboxylic acids react with?

A

Metals, carbonates and alkalis.

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14
Q

What type of metals do carboxylic acids react with?

A

The more reactive metals.

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15
Q

In what type of reaction do carboxylic acids react with metals?

A

A redox reaction.

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16
Q

What are salts of carboxylic acids called?

A

Carboxylates.

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17
Q

What are carboxylates?

A

Salts of carboxylic acids.

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18
Q

What do the names of carboxylates end with?

A

-oate

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19
Q

What is produced when carboxylic acids react with metals?

A

Salt and hydrogen gas.

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20
Q

What is the general formula of a carbonate?

A

CO3 2-

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21
Q

What is produced when carboxylic acids react with carbonates?

A

Salt, CO2 and water.

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22
Q

What are carboxylic acids neutralised by?

A

Aqueous alkalis.

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23
Q

What is formed when carboxylic acids are neutralised by aqueous alkalis?

A

Salts and water.

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24
Q

How can you test for carboxylic acids?

A

If you react a carbonate with an unknown organic compound, and CO2 gas is produced, then the compound is a carboxylic acid.

To be sure, you can check that the gas is CO2 by bubbling it through limewater and seeing if the limewater goes cloudy.

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25
Q

What is the equation for when carboxylic acids react with metals?

A

CA + Metal –> Salt + Hydrogen

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26
Q

What is the equation for when carboxylic acids react with carbonates?

A

CA + Carbonate –> Salt + CO2 + Water

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27
Q

What is the equation for when carboxylic acids react with aqueous alkalis?

A

CA + Alkali –> Salt(s) + Water

28
Q

How is an ester made?

A

By reacting an alcohol with a carboxylic acid (or some carboxylic acid derivatives).

29
Q

What is the name of an ester made up of?

A

Two parts - the first bit comes from the alcohol, and the second bit from the carboxylic acid (or its derivative).

30
Q

How do you name an ester?

A

Look at the alkyl group that came from the alcohol for the first part of the name - e.g. propyl.

Now look at the part that came from the carboxylic acid. Swap its ‘-oic acid’ ending for ‘oate’ to get the second bit of the name - e.g. ethanoic acid –> ethanoate.

Then put the two part together to give you the full systematic name - e.g. propyl ethanoate.

31
Q

How do you number the carbons when naming an ester?

A

You number the carbons counting from the ester link in the middle.

32
Q

What is formed when you hydrolyse an ester?

A

An alcohol.

33
Q

What are the two ways to hydrolyse an ester?

A

Using acid hydrolysis or base hydrolysis.

34
Q

How does acid hydrolysis work to form an alcohol from an ester?

A

It splits the ester into a carboxylic acid and an alcohol.

You have to reflux the ester with a dilute acid, such as HCL or H2SO4.

35
Q

How do you do acid hydrolysis of an ester?

A

You have to reflux the ester with a dilute acid, such as HCL or H2SO4.

36
Q

What are the products of acid hydrolysis of an ester?

A

It splits the ester into a carboxylic acid and an alcohol.

37
Q

What is the general equation for acid hydrolysis of an ester?

A

Ester + Water (+H+ and reflux) CA + Alcohol

38
Q

Is acid hydrolysis of an ester a reversible or irreverible reaction?

A

Reversible

39
Q

What does the fact that acid hydrolysis of an ester is a reversible reaction mean in terms of the shifting of the equilibrium?

A

You need lots of water to push the equilibrium over to the right.

40
Q

Is base hydrolysis of an ester a reversible or irreversible reaction?

A

Irreversible.

41
Q

How does base hydrolysis work to form an alcohol from an ester?

A

You have to reflux the ester with a dilute alkali, such as sodium hydroxide.

You get a carboxylate salt and an alcohol.

The reaction is irreversible.

42
Q

What difference is there in the products of acid hydrolysis of an ester and base hydrolysis of an ester?

A

In acid hydrolysis a carboxylic and and an alcohol are produced but in base hydrolysis, a carboxylate salt and an alcohol are produced.

43
Q

What similarity is there in the products of acid hydrolysis of an ester and base hydrolysis of an ester?

A

They both produce an alcohol.

44
Q

How do you do base hydrolysis of an ester?

A

You have to reflux the ester with a dilute alkali, such as sodium hydroxide.

45
Q

What are the products of base hydrolysis of an ester?

A

You get a carboxylate salt and an alcohol.

46
Q

What is the general equation for base hydrolysis of an ester?

A

Ester + Dilute alkali (+Reflux) –> Carboxylate salt + alcohol.

47
Q

What are acyl chlorides?

A

Carboxylic acid derivatives.

48
Q

How do you name acyl chlorides?

A

They all end in ‘-oyl chloride’ and the carbon atoms are numbered from the end with the acyl functional group (this is the same as with carboxylic acids).

49
Q

What do acyl chlorides contain?

A

-COCl functional group.

50
Q

What do acyl chlorides easily lose?

A

Their chlorine.

51
Q

What do acyl chlorides react with?

A

Alcohols and amines.

52
Q

Describe what you would observe in the reaction between an acyl chloride and an alcohol.

A

A vigorous reaction at room temperature.

53
Q

In what conditions do acyl chlorides react with alcohols?

A

Room temperature.

54
Q

What is produced when acyl chlorides react with alcohols?

A

An ester and HCl.

55
Q

Is the reaction between an acyl chloride and an alcohol reversible or irreversible?

A

Irreversible.

56
Q

What is the difference between reacting an acyl chloride with an alcohol to produce an ester compared to reacting an alcohol with a carboxylic acid to produce an ester?

A

The reaction is a much easier and faster way to produce an ester than the second way.

57
Q

What is the general equation for reacting an acyl chloride with an alcohol?

A

Acyl chloride + Alcohol –> Ester + HCl

58
Q

Describe what you would observe in the reaction between an acyl chloride and an amine.

A

A violent reaction at room temperature.

59
Q

In what conditions do acyl chlorides react with amines?

A

Room temperature.

60
Q

What is produced when acyl chlorides react with amines?

A

A secondary amide and HCl.

61
Q

Is the reaction between an acyl chloride and an amine reversible or irreversible?

A

Irreversible.

62
Q

What is the general equation for reacting an acyl chloride with an amine?

A

Acyl chloride + Amine –> Secondary amide + HCl

63
Q

What is Cl substituted by when an acyl chloride reacts?

A

An oxygen or nitrogen group.

64
Q

What fumes are given off when an acyl chloride reacts?

A

Hydrogen chloride fumes.

65
Q

What type of reactions are the reactions between acyl chlorides and alcohols/amines?

A

Nucleophilic substitution (or condensation) reactions.

66
Q

How can you test whether an organic compound is an acyl chloride?

A

By slowly adding an alcohol to it in a fume hood. Of cloudy white fumes are given that turn a piece of damp blue litmus paper red, then the compound is an acyl chloride.

A-level Chemistry (51 decks)

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