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A-level Chemistry y2 > 10: Carboxylic Acids And Their Derivatives > Flashcards

10: Carboxylic Acids And Their Derivatives Flashcards

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1
Q

Why do carboxylic acids have quite high boiling points

A

They can form hydrogen bonds

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2
Q

Why is the boiling point of a carboxylic acid higher than an alcohol

A
  • The O-H bond in a carboxylic acid is even more polar than in an alcohol because of the adjacent C=O group.
  • Carboxylics acids have a molecular structure that enables them to form more hydrogen bonds than simple alcohols
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3
Q

Are carboxylic acids soluble in water

A

Yes, especially smaller carboxylic acids

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4
Q

Why does the solubility of a carboxylic acid decrease when the molecule gets bigger

A

Only the O-H group can form hydgrogen bonds with water so if the rest of the molecule is large and non-polar then it will be less soluble

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5
Q

How to prepare a carboxylic acid

A

Oxidation of a primary alcohol or and aldehyde

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6
Q

What are the reagents and conditions for oxidation of a primary alcohol or aldehyde

A

Acidified potassium dichromate, heat and under reflux

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7
Q

Write alcohols, carboxylic acids and phenols in order of acidity

A

Alcohol (not acidic)

Phenols (very weakly acidic)

Carboxylic acids (weakly acidic)

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8
Q

What does carboxylic acid + metal produce

A

Salt + hydrogen

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9
Q

What does carboxylic acid + carbonate produce

A

Salt + carbon dioxide + water

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10
Q

What does carboxylic acid + alkali produce

A

Salt + water

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11
Q

What does carboxylic acid + ammonia produce

A

Ammonium salt

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12
Q

Can esters form hydrogen bonds

A

No

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13
Q

How to produce an ester

A

Carboxylic acid + alcohol —> ester + water

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14
Q

What is a condensation reaction

A

Two molecules are joined together to make a larger product molecule but a small molecule is eliminated in the process

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15
Q

What conditions are needed for esterification

A

Concentrated sulphuric acid catalyst and heat.

Works best with reflux

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16
Q

What is an acid anhydride

A

Compound formed by dehydration of carboxylic acids.

17
Q

What is the general formula for acid anhydrides

A

R-COOCO-R

18
Q

How is an acid anhydride formed

A

two carboxylic acids bond together and eliminate the OH from one and the H from the -OH from the other carboxylic acid to form an acid anhydride and water

19
Q

What does acid anhydride + alcohol form

A

ester + carboxylic acid

20
Q

What are the advantages of using anhydrides rather than carboxylic acids for producing esters

A

Anhydrides are more reactive which means:

Milder conditions can be used,

The reaction is irreversible which means that a higher percentage yield can be achieved

21
Q

What does hydrolysis of an ester produce

A

carboxylic acid and alcohol

22
Q

Why would you not just use water for hydrolysis of an ester and what can you use instead

A

It is extremely slow,

An acid or a base

Base is usually preferred

23
Q

What does base catalysed hydrolysis of ester produce

A

Alcohol and the salt of the carboxylic acid (due to the alkaline conditions)

24
Q

What are the conditions for base catalysed hydrolysis of esters

A

Aqueous NaOH and under reflux

25
Q

How to convert the salt formed from the base - catalysed hydrolysis of an ester back into a carboxylic acid

A

Neutralise with aqueous acid to convert the salt into the carboxylic acid

Distil off the carboxylic acid

26
Q

What are the conditions for acid catalysed hydrolysis of esters

A

Reflux the ester with aqueous HCl

27
Q

What is the general form of an acyl chloride

A

RCOCl

28
Q

How to name acyl chlorides

A

Add the ending -oyl chloride

eg. CH₃COCl is ethanoyl chloride

29
Q

What is added to a carboxylic to form an acyl chloride

A

thionyl chloride, SOCl₂

30
Q

Advantages of using acyl chlorides instead of esterifying the carboxylic acid

A

The reaction occurs rapidly, without a catalyst and without heating

Generally high yield

Can be used to esterify phenols

31
Q

How can acyl chlorides be converted into carboxylic acids

A

Reacting with water

32
Q

How can acyl chlorides react with Aromatic compounds

A

Friedel-Crafts

In the presence of a halogen carrier catalyst, the acyl group of an acyl chloride can substitute into an aromatic ring

33
Q

What does acyl chloride + ammonia produce

A

Amides

A-level Chemistry y2 (20 decks)

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