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Chemistry Module 5 and 6 > Carbonyls and Carboxylic acids > Flashcards

Carbonyls and Carboxylic acids Flashcards

1
Q

What is the carbonyl group?

A

C=O

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2
Q

What kind of intermolecular forces do molecules with carbonyl group have?

A

Permanent dipole-dipole due to the polar C=O bond

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3
Q

How can an aldehyde be oxidised to a carboxylic acid?

A

Refluxed with K2Cr2O7/H2SO4

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4
Q

Can ketones be oxidised?

A

No due to the lack of reactivity

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5
Q

How do carbonyl groups undergo nucleophilic addition?

A
  • Due to the polarity of the C=O bond, aldehydes and ketones react with some nucleophiles
  • The nucleophile is attracted to the slightly positive carbon
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6
Q

What reducing agent is used to reduce ketones and aldehydes?

A

NaBH4/H2O

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7
Q

What symbol is used as a reducing agent in the reaction?

A

2[H]

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8
Q

What symbol is used as an oxidising agent in the reaction?

A

[O]

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9
Q

What is the product of the reaction of a carbonyl compound with HCN?

A

A hydroxynitrile

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10
Q

What is the reacting agent used in the reaction of a carbonyl compound with HCN?

A

H2SO4/NaCN

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11
Q

Why is the reaction of a carbonyl compound and HCN useful?

A

It provides a mean of increasing the length of the carbon chain

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12
Q

What is the test for detecting carbonyl compounds?

A

2,4-DNP (Brady’s reagent)

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13
Q

What is the method for detecting an aldehyde and a ketone using 2,4-DNP?

A
  1. Add 5cm of 2,4-DNP to a test tube
  2. Use a dropping pipette add 3 drops of the unknown compound
  3. If no crystals form, add a few drops of H2SO4
  4. A yellow/orange precipitate should form indicating the presence of either an aldehyde/ketone
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14
Q

Following the 2,4-DNP how do you distinguish between aldeyhdes and ketones?

A

Tollen’s reagent

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15
Q

How do you prepare a Tollen’s reagent?

A
  1. Add 3cm of aq silver nitrate to a test tube
  2. Add aq sodium hydroxide to the silver nitrate until a brown precipitate of silver oxide is formed
  3. Add dilute ammonia solution until the brown precipitate dissolves to form a colourless solution
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16
Q

What is the method for carrying out the test for an aldehyde using Tollen’s reagent?

A
  1. Pour 2cm of the unknown solution into a test tube
  2. Add an equal volume of Tollen’s reagent
  3. Leave the test tube to stand in a 50 degrees water bath then observe whether any silver mirror is formed
17
Q

What is the method for identifying an aldehyde or ketone by melting point?

A
  1. Filter the yellow/orange solid precipitate
  2. Re-crystallise the solid
  3. The melting point of the purified 2,4-DNP is measured and recorded
18
Q

Describe the solubility in carboxylic acid?

A
  • Carboxylic acids with up to 4 carbon atoms are soluble in water
  • As the number of carbon atoms increases, the solubility decreases as the non-polar chain has a greater effect on the overall polarity
19
Q

What are the strength of carboxylic acids?

A

They are classified as weak acids

20
Q

What are the products of a carboxylic acid reacting with a metal in a redox reaction?

A

A carboxylate and hydrogen gas

21
Q

What are the products of carboxylic acids with metal oxides?

A

Salt and water

22
Q

What is used to test for carboxyl groups?

A

Carboxylic acid and a carbonate, as the carboxylic acid is sufficiently acidic enough to react with carbonates

23
Q

What is an acyl group?

A

C=O attached to an R group

24
Q

How do you name an acyl chloride?

A

-anoyl chloride

25
Q

How is an acid anhydride formed?

A

By the removal from water from two carboxylic acids

26
Q

How do you name 2 molecules of ethanoic acid?

A

Ethanoic anhydride

27
Q

What is esterification?

A

The reaction of can alcohol with a carboxylic acid to form an ester

28
Q

What are used to hydrolyse esters?

A

Aq acid or alkali

29
Q

What is acid hydrolysis of an ester and how is it carried out?

A
  • Acid hydrolysis is the reverse of esterification
  • The ester is heated under reflux with aq acid and is broken down by water
30
Q

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

A

Ester + H2O ⇌ OH + COOH
- in aq acid

31
Q

What is alkaline hydrolysis of an ester and how is it carried out?

A
  • Known as saponification and is irreversible
  • Ester is heated under reflux with aq hydroxide ions
32
Q

What is the equation for the alkaline hydrolysis of an ester?

A

Ester + OH- → carboxylate ion + OH

33
Q

What is reacted to form an acyl chloride?

A

A carboxylic acid and thionyl chloride, SOCl2, to form -anoyl chloride + SO2 + HCl

34
Q

What does ethanoyl chloride and propan-1-ol make?

A

Propyl ethanoate + HCl

35
Q

What does ethanoyl chloride and phenol make?

A

Phenyl ethanoate + HCl

36
Q

What does an acyl chloride and H2O make?

A

A carboxylic acid and HCl

37
Q

What is the product of butanal and Tollen’s reagent?

A

Butanoic acid

Chemistry Module 5 and 6 (5 decks)

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