Carbonyl Compounds ✅

Question 1

What makes a compound a carbonyl

Answer 1

C=O functional group
Aldehyde C=O at end
Ketones C=O joined by 2 C atoms

Question 2

How do you oxidize an aldehyde what forms

Answer 2

Oxidized under reflux with Cr2O7^2-/H+ eg potassium dichromate

Forms an acid EG butanol to butanoic acid

Question 3

What happens in nucleophilic addition reactions

Answer 3

As C=O bond is polar, the nucleophile id attracted to slightly positive C and is added across the double bond

Question 4

What is produced with alehyde and warming NAbH4 in a nucleophilic addition reaction

Answer 4

Primary alcohol

Eg butanol + 2[H]———> butanol-1-ol

Question 5

Describe the reaction between ketones and NaBH4

Answer 5

Form secondary alcohol

Eg propanone to pro propan-2-ol

Question 6

Describe the mechanism of:
propanone + 2[H]—————> propan-2-ol
NaBH4/H2O

Answer 6

The nucleophile is OH- ion from H2O

Lone pair is attracted to slightly positive C and forms a dative covalent bond

The Pi-bond breaks by heterolytic fission and forms a negatively charged intermediate

The intermediate is protanated by a H atom in a water molecule to form an alcohol and OH-

Question 7

What happens with propanal and hydrogen cyanide (HCN) give equation with propanal

Answer 7

Propanal + HCN—————-> hydroxynitrile
H2SO4/NaCN

HCN adds across C=O bond. Acidified sodium cyanide used to provide it indirectly (too dangerous if not)

C=O ———> C-OH, CN, H

Question 8

Explain the mechanism of propanal and HCN

Answer 8

The nucleophile is CN-

Lone pair is attracted to slightly positive C and forms a dative covalent bond

The Pi-bond breaks by heterolytic fission and forms a negatively charged intermediate

This is then protonated by water or H+ ions to form hydroxynitrile

Question 9

What are the test for carbonyl groups

Answer 9

2,4-dinitrophenylhadrazine is used to detect presence of carbonyl group in an organic compound
Positive result= oranje/yellow precipitate, melting point of derivate can then be compared to reference samples to determine identity

Question 10

How can ketones and aldehydes be differentiated

Answer 10

By tollens reagent, or ammonia silver nitrate.

Aldehydes oxidize to carboxylic acids and silver ions reduce to silver; a distinctive silver mirror is produced