Carbonyl Chemistry

Question 0

Why do compounds containing the carbonyl group have a higher b.p.t than alkanes?

Answer 0

Because molecules of the compound have dipole-dipole interactions, which alkanes do no have.

Question 1

What is the carbonyl group?

Answer 1

\
C = O
/

Question 2

Why are carbonyl compounds able to form hydrogen bonds with water in spite of the fact no hydrogen is bonded to the oxygen in the carbonyl group?

Answer 2

Because the delta positive hydrogen atoms in the water are attracted to the lone pair on the oxygen.

Question 3

Why are carbonyl compounds susceptible to nucleophilic attack?

Answer 3

Because the oxygen in the carbonyl group withdraws electron density from the carbon, creating a positive dipole on that carbon. This attracts nucleophiles, which are species which have a lone pair of electrons available for donation to another species.

Question 4

What are short-chain aldehydes and ketones used for?

Answer 4

Scenting soap and nail varnish remover.

Question 5

Why are hydroxynitriles not made in the lab using hydrogen cyanide?

Answer 5

Because hydrogen cyanide is toxic.

Question 6

How can a hydroxynitrile be formed?

Answer 6

By reacting a ketone or aldehyde with acidified potassium cyanide.

Question 7

What is the mechanism for the formation of a hydroxynitrile?

Answer 7

Addition - the C=O bond is broken.

Question 8

Describe a test for asserting the presence of an aldehyde in solution.

Answer 8

Fehling’s test: Contains Cu²⁺ ions, an alkali and a completing agent.
If an aldehyde is present when the solution is warmed with Fehling’s a brick-red p.p.t will form (Cu₂O).

Question 9

Describe a test for asserting the presence of a ketone in a solution.

Answer 9

Tollens’ reagent: formed by reacting ammonia with silver nitrate.
NH₃ +AgNO₃ —> [Ag(NH₃)₂]⁺
Reduction by an aldehyde:
Forms Ag and 2NH₃
The silver colors the solution.

Question 10

How is it possible to form a primary alcohol from a carbonyl-containing compound?

Answer 10

By reducing an aldehyde with sodium tetrahydridoborate (NaBH₄) in solution.

RCHO + 2[H] —> RCH₂OH

Question 11

Why are esters more volatile than carboxylic acids?

Answer 11

Because esters do not form hydrogen bonds - carboxylic acids do. Weaker IMFs between ester molecules mean that less energy is required to initiate the state change.

Question 12

What is a fat/oil?

Answer 12

A long-chain ester formed from glycerol.

Question 13

What are the steps in the hydrolysis of methyl ethanoate with a sodium hydroxide catalyst?

Answer 13

H₂O + CH₃COOCH₃ —> CH₃COOH + CH₃OH

CH₃COOH + NaHCO₃ —> CH₃COO⁻Na⁺ + H₂O + CO₂

Question 14

What is the IUPAC name for glycerol?

Answer 14

Propane - 1,2,3 - triol.

Question 15

What is a sodium salt of a fat?

Answer 15

A sodium carboxylate. (I.e. An ester with a sodium group rather than an alkyl group)

Question 16

What is a use of sodium carboxylates formed by boiling sodium hydroxide with fats?

Answer 16

Soap.

Question 18

What are some uses of glycerol?

Answer 18

Plasticizer - allows polymers to slip over one another.
Solvent - toothpaste and food coloring.
Hydrating agent - used in pharmaceuticals.

Question 19

How, in words, can biodiesel be formed?

Answer 19

By reacting long-chain triglycerides and methanol in the presence of a potassium hydroxide catalyst.

Question 20

How can an ester be converted to its parent acid and alcohol?

Answer 20

By refluxing the ester with a dilute acid - acid hyrolysis.

By refluxing the ester with dilute alkali - this forms the salt of the acid and the reaction can go to completion.

Question 21

Why are fats solid, but oils not?

Answer 21

Fats are saturated hydrocarbons - they tessellate and have strong Van der Waals between molecules.
Oils are unsatuated hydrocarbons, meaning that they do not tessellate and have weak Van der Waals.

Question 22

How is it possible to form glycerol and a sodium carboxylate from a fat?

Answer 22

By boiling the fat with sodium hydroxide.

Question 23

How can a sodium carboxylate be converted to an acid?

Answer 23

By reacting the sodium salt with an acid.

Question 24

Why is biodiesel not carbon neutral?

Answer 24

Fossil fuels are sometimes burned when making fertilizer and planting, harvesting and converting the oil.

Question 25

What is the suffix for the acyl chloride functional group?

Answer 25

-oyl chloride

Question 26

What is formed in the reaction between water and an acyl chloride?

Answer 26

A carboxylic acid and HCl gas.

Question 27

How is it possible to determine that a reaction is between ammonia/water/an alcohol and an acyl chloride?

Answer 27

By observing whether the reaction gives off fumes - HCl gas.

Question 28

What temperature is the reaction between an acyl chloride and alcohol conducted at?

Answer 28

Room temperature, same as with all acyl chloride + nucleophile reactions.

Question 29

Why is it preferable to use an acid anhydride over an acyl chloride in industry?

Answer 29

Acid anhydrides are cheaper, less corrosive, react less violently and do not produce toxic HCl gas.

Question 30

What mechanism are the reactions between acyl chlorides and a nucleophile?

Answer 30

Nucleophilic addition-elimination reactions.

Question 31

What is aspirin? How is it produced?

Answer 31

An ester. It is produced by reacting salicyclic acid with ethanoic anhydride.

Question 32

What is the byproduct in the production of aspirin?

Answer 32

Ethanoic acid.