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CH4 > Carboxylic Acids > Flashcards

Carboxylic Acids Flashcards

1
Q

Why is Methanol described as bad at dissociating?

A

Because it’s electron releasing, which prevents the loss of a hydrogen.

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2
Q

What is decarboxylation?

A

The removal of CO2 from an acid

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3
Q

If a hydrogen was swapped for a chlorine in ethanoic acid, the Ka goes up to 1.4x10^-3 Why does this occur?

A

Because the chlorine is very electronegative so it’s very electron withdrawing, which encourages the loss of hydrogen.

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3
Q

Name the reagents used in the halogenation of carboxylic acids.

A

PCl5, PCl3, SOCl2 (thionyl chloride)

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3
Q

What are the steps to dehydrate the ammonium salt of an acid?

A

1) (NH4)2CO3 + RCOOH (arrow) (RCOO)-(NH4)+ + CO2 + H20 2) where RCOOH is an excess acid 3) Heat salt RCOONH4 (heat/arrow) RCONH2 + H2O acid chloride RCOOH + PCl5 (arrow) RCOCl + POCl3 + HCl RCOCl + NH3 (arrow) *RCONH2* +HCl

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3
Q

What is the equation for producing terylene?

A
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4
Q

What’s the general equation for making an amide from an ester using NH3?

A

R1COOR2 + NH3 (arrow) R1CONH2 + R2OH

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5
Q

What would adding hydrogen bonds do to the volatility of a carboxylic acid? What would this do to the boiling points?

A

This would make them less volatile as it would take more energy to get the acid from liquid to gas. This in turn increase the boiling points.

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6
Q
A
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7
Q

How do you make benzoic acid?

A

•Vigorously reflux methyl benzene with alkaline permanganate (KMnO4) and sodium carbonate •this creates sodium benzoate, an acid salt •to form a free acid you need to add hydrochloric acid •this then creates benzoic acid

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8
Q

What is volatility?

A

The ability to evaporate.

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8
Q

Methanoic adic has a Ka = 1.77x10^-4 Ethanoic acid has a Ka = 1.85x10^-5 Which is the stronger acid and why?

A

Methanoic acid is the strongest acid because the Ka value is bigger and the methyl group in ethanoic acid is electron releasing which prevents the loss of hydrogen.

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8
Q

What happens in a positive iron(III) chloride test? What does it show?

A

A positive test is indicated by a colour change from yellow/brown to purple/violet, and is used to show the presence of a phenol group.

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10
Q

What is solubility?

A

The ability to dissolve in water.

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11
Q

List in phenol, water, and carboxylic acid order of most acidic to least acidic.

A

Carboxylic acid, phenol, water.

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12
Q

Show the reaction between 1,4 benzene dicarboxylic acid and ethane 1,2 diol.

A
14
Q

Whats the equilibrium constant for water?

A

Kw = 1.0 x10^-14 mol2dm-6

15
Q

What is ethanoic anhydride used for?

A

To make asprin.

16
Q

How do you get a free acid from an acid salt?

A

By adding hydrochloric acid

17
Q

What does the addition of hydrogen bonds do to the solubility?

A

It increases as there’s a greater chance of the acid to hydrogen bond with the water.

19
Q

What is terylene used for?

A

Clothing and ropes.

20
Q

What are the equations for making benzoic acid?

A
21
Q

What is a chemical test for a carbonyl group, what are the results?

A

Add 2,4-dinitrophenylhydrazine (Brady’s reagent), the result is a orange/yellow precipitate.

22
Q

Name the reagents used in the decarboxylation of carboxylic acids.

A

calcium oxide and sodium hydroxide mix, which is called sodalime.

24
Q

How ionised is water?

A

Weakly.

25
Q

What happens to the anion on a dissociated acid?

A

The C - O and the C=O bond lengths become equal because the negative charge is delocalised across the two oxygen atoms.

26
Q

What is the trend in solubility as the chain length increases?

A

The solubility decreases as there are more hydrophobic elements, such as carbons, are present

28
Q

How does the phenol molecule favour ionisation?

A

Through it having the lone electron pairs in the delocalised Pi-electron system, which leads to excess electron density over the benzine ring. Which makes it able to dissociate.

29
Q

Name two ways to hydrolyse an acid.

A

By using water or an alkaline.

30
Q

What is a dimer?

A

Its when a molecule hydrogen bonds itself to the same type of molecule

CH4 (9 decks)

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