Carbonyl And Carboxylic Acids

Question 1

Why does heating under reflux give a high yield

Answer 1

Mixture evaporated but can’t escape so goes back into the round bottomed flask

Question 2

Apparatus needed for distillation

Answer 2

Still head
Receiver
Pear shaped flask
Condenser

Question 3

Carbonyl group formula equation

Answer 3

HnH2nO

Question 4

What are carbonyls used for

Answer 4

Preservation
Nail polish remover
Almond flavour

Question 5

Why is the carbon atom of a carbonyl group open to nucleophilic attack

Answer 5

The carbon has a lower electronegativity compared to the oxygen and the bond is polar

Question 6

Conditions for the reduction of the carbonyl group

Answer 6

Reducing agent- aqueous NaBH4

Reaction is warmed

Question 7

Equation for the reduction of carbonyl group

Answer 7

Aldehyde/ketone +2[H] —> alcohol

Question 8

What does the C=O bond undergo

Answer 8

Attacked by nucleophile
Polar
Undergoes addition
Difference in electronegativity

Question 9

What does the C=C bond undergo

Answer 9

Electrophilic Addition

Question 10

Physical properties of carboxylic acids

Answer 10

Miscible in water (hydrogen bonding)
Higher melting point relative to the similar alcohol
Weak acid

Question 11

Reactions of carboxylic acids

Answer 11

Reacts with
Metals
Bases
Carbonates

Question 12

Products of sodium and propanoic acid

Answer 12

Sodium propanoate
Hydrogen
C2H5COO-Na+
0.5 H2

Question 13

Reaction to form Ester and conditions needed

Answer 13

Condensation reaction between an alcohol and carboxylic acid 
Conc H2SO4 (catalyst)

Question 14

Describe esters volatility

Answer 14

Have no free OH

No hydrogen bonds so only London forces present (weaker) so more volatile

Question 15

Describe how to obtain a sample of an ester

Answer 15

Combine 2cm3 of alcohol with 2cm3 of carboxylic acid
Add drop of CONC H2SO4 (catalyst)
Heat in hot water bath at 80°C for 5 minutes
Add NaCO3 to the top of the test tube

Question 16

Why are esters used in the manufacture of foods

Answer 16

Flavouring

Question 17

How is an acyl chloride formed and other products

Answer 17

Carboxylic acid + thionyl chloride (SOCl2) —> acyl chloride + SO2 +HCl

Question 18

Uses of acyl chlorides (equations)

Answer 18

Acyl chloride + alcohol —> Ester +
HCl
Acyl chloride + water —> carboxylic acid + HCl

Question 19

Why are acyl chlorides and acid anhydride useful in organic synthesis

Answer 19

Can be easily converted into carboxylic acid derivatives such as esters and amides, with good yields

Question 20

Why are acyl chlorides and acid anhydrides useful for esterifying phenols

Answer 20

Carboxylic acids are not reactive enough to form esters with phenols, acyl chlorides and acid anhydrides are much more reactive so don’t need an acid catalyst

Question 21

Define hydrolysis chemical breakdown of a compound in the presence of water

Answer 21

chemical breakdown of a compound in the presence of water

Question 22

How to hydrolyse Ester with hot acid

Answer 22

Carboxylic acid and alcohol

Question 23

How to hydrolyse Ester with hot alkali

Answer 23

Carboxylate ion and alcohol

Question 24

Similarity in the conditions needed for hot aq acid/alkali

Answer 24

Heated under reflux

Question 25

Difference in the conditions needed for hot aq acid/alkali

Answer 25

Acid is reversible | Alkaline is irreversible

Question 26

What is an acid anhydride

Answer 26

OCOCO | product of a dehydration reaction between 2 carboxylic acid molecules

Question 27

What is an acyl group

Answer 27

O=C-(not C/H) -R

Question 28

How to test for an aldehyde/ketone using 2,4-DNP

Answer 28

Add 5cm of 2,4-DNP Add 3 drops of unknown compound If no crystals form add few drops of sulfuric acid A yellow/orange precipitate will form if present

Question 29

How to make tollen’s reagent

Answer 29

Add 3cm of aqueous silver nitrate Add aqueous NaOH until a brown precipitate of silver oxide forms Add dilute ammonia until brown precipitate dissolves to form a clear colourless solution

Question 30

How to test for an aldehyde using Tollen’s reagent

Answer 30

Pour 2cm of unknown into test tube Add equal volume of tollens Leave to stand in a beaker of warm water at about 50°C for 10-15 mins and a silver mirror will form if present

Question 31

How is a silver mirror formed with tollens

Answer 31

Silver ions are reduced to silver as the aldehyde is oxidised go a carboxylic acid

Question 32

conditions for the reduction of carbonyl groups

Answer 32

aqueous NaBH4 | reaction mixture warmed

Question 33

what did Schlesinger find

Answer 33

found NaBH4 was a good reducing agent for carbonyl groups

Question 34

describe the reaction of a carbonyl group

Answer 34

undergoes nucleophilic addition due to the difference in electronegativity

Question 35

what reaction do aldehydes and ketones undergo

Answer 35

nucleophilic addition

Question 36

do C=C and C=O show chemical similarity

Answer 36

the C=C and C=O groups might be expected to show chemical similarity but in fact they show very little

Question 37

similarities and differences between C=C and C=O

Answer 37

similarities- unsaturated/undergoes addition reactions differences- alkenes react with electrophiles carbonyl group is attacked by nucleophiles