Carbonyl Compounds

Question 1

Why can aldehydes be distinguished from ketones by oxidation tests?

Answer 1

Aldehydes can be oxidized to carboxylic acids or carboxylate ions?

Question 2

List 3 tests used to distinguish aldehydes from ketones

Answer 2

1. Tollen’s Test
2. Fehling’s/ Benedict’s test
3. Jone’s oxidation test

Question 3

Describe Jone’s oxidation reagents and products

Answer 3

Reactants: aldehyde + acidic dichromate solution

Products: Carboxylic acid + Chromium (III) cation

Question 4

Explain the color change in Jone’s oxidation test

Answer 4

1. Orange color due to the presence of dichromate anion

2. Green color of products due to Chromium(III) ion

Question 5

Describe the reagents and products of Fehling’s/ Benedict’s test

Answer 5

Reagents: aldehyde + Copper oxide

Products: carboxylate anion + cuprous oxide

Question 6

Explain the color change of Fehling test/ Benedict’s test

Answer 6

Blue color of reactants due to the Copper Oxide(CuO)

Red precipitate from reaction is Cuprous oxide(Cu2O)

Question 7

What are the reactants and products of Tollen’s test?

Answer 7

Reactants: aldehyde + silver oxide in ammonia to yield a silver mirror

Products: carboxylate anion + silver mirror

Question 8

Give the general formula for esters, amides and acid chlorides

Answer 8

Esters- RCOOR’

Acid chlorides- RCOCl

Amides- RCONH2

Question 9

How does the C=O compare to the C=C in Allende

Answer 9

C=O bond is stronger, shorter and more polar that C=C

Question 10

Name the 2 classifications of carbonyl compounds

Answer 10

1. Aldehydes and ketones

2. Carboxylic acids and its derivatives

Question 11

How do the boiling points of aldehydes and ketones compare to alkanes, ethers and alcohols

Answer 11

Higher than alkanes and ethers due to being more polar, but lower than alcohols because they cannot participate in hydrogen bonding

Question 12

Are smaller aldehydes soluble in water? Why?

Answer 12

Yes, aldehydes and ketones of 5 carbons and under use the doubly bound oxygen to exhibit hydrogen bonding with water

Question 13

Are acetone and aldehyde miscible in water?

Answer 13

Yes

Question 14

Why are aldehydes more reactive than ketones?

Answer 14

• ketones have more steric hindrance than aldehydes
• aldehydes have more partial positive charge than ketones on the carbonyl carbon due to the electron donating alkyl groups( the ketone’s two alkyl group vs the one on aldehydes) making ketones more electrophilic come and less reactive

Question 15

What is often used to oxidize primary alcohols to aldehydes?

Answer 15

Pyridium Chlorochromate?

Question 16

Name 2 methods of oxidizing secondary alcohols to ketone

Answer 16

1. Sodium dichromate in sulfric acid

2. Potassium permanganate

Question 17

What is the name of the process to obtain an aldehyde and ketone from an alkanes?

Answer 17

Ozonlysis

Question 18

What are the reagents and products of ozonlysis?

Answer 18

Reactants: alkene

Catalysts: ozone and dimethyl sulfate

Products: Aldehyde and ketones

Question 19

What are the qualitative test for aldehydes?

Answer 19

Tollens test

Fehlings / Benedict’s test

Jones oxidation

Question 20

What are the reagents for catalytic hydrogenation and products?

Answer 20

Benzene of alkanes and ketone

Catalyst: hydrogen and raney nickel

Product: phenol

Question 21

Why are smaller aldehydes and ketones( less than six carbons) soluble. in water?

Answer 21

Lone pair of electrons on carbonyl group can accept a hydrogen bond on from O-H or N-H

Question 22

Acetone and acetaldehyde are ___________ in water

Answer 22

Miscible

Question 23

________________ is the most reactive aldehyde

Answer 23

Formaldehyde

Question 24

Why is formaldehyde the most reactive aldehyde?

Answer 24

Because the aldehyde has no methyl group attached to it

Question 25

As aldehydes and ketones increase in length and bulkier attached group, what happens?

Answer 25

The positive inductive effect on the carbonyl carbon decreases, making it less reactive

Question 26

Aldehydes are formed from the ____________ of _________ ________ and ________________ is used to selectively used to do this

Answer 26

Oxidation

Primary alcohols

Pyridiminium Chlorochromate

Question 27

Ketones are formed from the ____________ of _________ _____________ using one of the 2 solutions…

Answer 27

Oxidation

Secondary alcohols

Sodium dichromate in sulfric acid

Or

Potassium permanganate