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A2 Chemistry Unit 1 > Carboxylic Acids > Flashcards

Carboxylic Acids Flashcards

1
Q

What is the general formula for Carboxylic Acids?

A

CnH2nO2

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2
Q

Describe the process of naming Carboxylic Acids

A
  1. Select longest chain containing -COOH
  2. Change the ‘e’ suffix to ‘-oic acid’
  3. No number needed as it’s always at the end
  4. If substituent present then name C stretched to -COOH as C1
  5. For dicarboxylic Acids use suffix ‘-edioic acid
  6. For complex Carboxylic acids use suffix ‘carboxylic acid’
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3
Q

Describe the physical properties of Carboxylic acids

A
  • Polar due to presence of O atoms
  • low RMM = water soluble
  • pungent, sharp, irritating odours
  • in pure liquid state they are H-bonded dimers
  • H bonding is stronger than in alcohols
  • higher b.ps than alcohols
  • more soluble than alcohols, aldehydes or ketones
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4
Q

When and Why do Carboxylic acids exist as H-bonded dimers

A
  1. In the pure liquid state in non-aqueous solvents

2. Due to polar OH group which allows H bonding between molecules

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5
Q

Why do Carboxylic acids have higher boiling points in comparison to alcohols?

A

Stronger intermolecular forces

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6
Q

What happens when water is the solvent for Carboxylic acids

A
  • the dimers are broken up as the polar OH group allows for H-bonds with water molecules
  • Each Carboxylic acids can form up to 3 H-bonds with water molecules
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7
Q

Why are Carboxylic acids more soluble than alcohols

A

Each Carboxylic acid molecule can form up to 3 H-bonds with water molecules

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8
Q

Draw the H-bonding in pure ethanoic acid

A

See pg 136

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9
Q

Draw the H-bonding in aqueous ethanoic acid

A

See page 136

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10
Q

Name the 3 ways to prepare Carboxylic acids

A
  1. Oxidation of primary alcohols or aldehydes
  2. Hydrolysis of esters
  3. Hydrolysis of Nitriles
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11
Q

Describe briefly how to prepare propanoic acid

A

Heat under reflux propan-1-ol or propanal with acidified potassium dichromate (VI) solution

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12
Q

Write the structural equations for the preparation of a Carboxylic acid using oxidation of propan-1-ol and pronanal

A

See page 136

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13
Q

What are the two types of hydrolysis of esters?

A
  1. Acid catalysed hydrolysis

2. Base catalysed hydrolysis

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14
Q

Describe how to prepare a Carboxylic acid via acid catalysed hydrolysis. Why is this a poor method

A
  1. Reflux ester with an excess of water and dilute HCl

2. Reversible and some ester left unhydolysed

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15
Q

Draw the equation for acid catalysed hydrolysis of an ester. What are the products

A

See notes

Products are Carboxylic acid and alcohol

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16
Q

Describe base catalysed hydrolysis (saponification). Why is it a good method for producing Carboxylic acid

A
  1. Reflux ester with NaOH(aq)
  2. Sodium salt of acid produced
  3. Acid liberated from salt via addition of strong acid

Good because irreversible

17
Q

Draw the equations for base catalysed hydrolysis of ester. State the products

A

See notes for equation

Products = salt of acid and alcohol and NaCl

18
Q

Describe acid based hydrolysis of nitriles

A

Heat under Reflux with strong acid (HCl)

Water

19
Q

Write the equation for acid catalysed hydrolysis of nitriles and state the products

A

See notes

Products = Carboxylic acid ammonium salt

20
Q

Describe alkaline catalysed hydrolysis of nitriles

A
  1. Reflux with strong alkali
  2. Produces salt and ammonium
  3. Acid liberated from salt by addition of strong acid
21
Q

Write the method for carrying out test tube reactions of a Carboxylic acid with sodium carbonate, sodium hydroxide and aqueous ammonia and measure pH changes

A
  1. 1cm^3 Carboxylic acid in boiling tube
  2. Record pH (pH paper)
  3. Add spatula measure of sodium carbonate and record obs
  4. Record pH (pH paper)
  5. Repeat but with 1cm^3 sodium hydroxide
  6. Repeat using 1cm^3 aqueous ammonia
22
Q

Write the general equation for Carboxylic acid with sodium carbonate. State the observations

A

Acid + Carbonate ➡️ salt + water + CO2

Obvs: bubbles of gas
Carbonate disappears to form colourless solution

23
Q

Write the general equation of Carboxylic acid with sodium hydroxide. State the observations

A
  1. Acid + alkali ➡️ salt + water

2. Heat released, colourless solution

24
Q

Write the product and observations when a Carboxylic acid is reacted with ammonia

A
  1. Ammonia salt formed

2. Heat released and all is colourless

25
Q

State the conditions and general equation of Carboxylic acid with alcohol

A
  1. Excess alcohol, reflux, conc sulfuric acid

2. Acid + alcohol ➡️ ester + water

26
Q

State the general equation for Carboxylic acid with PCl5. State the observations and conditions

A

⚫️ Acid + PCl5 ➡️ acyl chloride + POCl3 + HCl
⚫️ obvs: misty fumes (HCl)
Vigorous
Heat evolved
⚫️ acid must be anhydrous as PCl5 hydrolysis in water

27
Q

What happens when Carboxylic acid is reacted with lithal

A

⚫️ Acid is reduced to primary alcohol

⚫️ cannot be stopped at aldehyde stage

28
Q

State the conditions of a reaction of Carboxylic acid with lithal and write the equation

A

Reflux ether solution of lithal with acid

See notes for equation (4H in lithal)

29
Q

What happens if a dibasic/tribasic acid reacts with excess reagent

A

All COOH groups react

30
Q

What is the method for preparing a liquid Ester from carboxylic acid and alcohol

A

See notes

A2 Chemistry Unit 1 (9 decks)

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