Chapter 18- Aldehydes and Ketones

Question 1

Why are aldehydes more reactive than ketones?

Answer 1

Aldehydes are more polarized than ketones, allowing for better attack by Nu on the carbonyl carbon

Ketones are more sterically hindered bc they have two R groups whereas aldehydes have an H

Question 2

What is trioxane? How do you convert it to formaldehyde? What state of matter is formaldehyde at room temp? How do you convert formaldehyde to formalin? What is formalin?

Answer 2

Trioxane- cyclic trimer of formaldehyde
Trioxane + heat --> formaldehyde 
Formaldehyde- gas at room temp
Formaldehyde + H2O --> formalin
Formalin- 40% aqueous solution

Question 3

Describe the BP and solubility of ketones and aldehydes

Answer 3

BP: Higher BP than alkanes or ethers because more polar, but lower BP than alcohols because no hydrogen bonding

Solubility: Good solvents for alcohols, can have hydrogen bonding with O-H or N-H, acetone and acetaldehyde are miscible in water

Question 4

What are the six classes of carbonyl compounds?

Answer 4

Ketones
Carboxylic Acids
Esters
Aldehydes
Acid Chlorides
Amides

Question 5

The C and O of the carbonyl group have what hybridization? How do CO double bond compare to CC double bond?

Answer 5

Sp2 hybridized, and CO bond is shorter, stronger, and more polar than CC double bond in alkenes

Question 6

What are the major and minor resonance contributors of the carbonyl group? Which one is better? Which one reacts an electrophile?

Answer 6

Major- double bond b/w C and O
Minor- partial - on O and partial + on C

Major is better because all the atoms complete the octer and there are no charges

The partial positive carbon on the minor contributor reacts an electrophile

Question 7

What are the seven ways to synthesize ketones?

Answer 7

1. Oxidize secondary alcohols
2. Ozonolysis
3. Hydration of Alkynes
4. Organometallics and Carboxylic Acids
5. F-C Acylation
6. Nitriles and Grignard Reagent
7. Acid Chlorides and Lithium dialkylcuprate

Question 8

What are the seven ways to synthesize aldehydes?

Answer 8

1. Oxidize primary alcohols
2. Gatterman- Koch Formylation
3. Hydroboration-Oxidation of Alkynes
4. Reduction of Nitriles
5. Reduction of Acid Chlorides
6. Reduction of Esters
7. Ozonolysis

Question 9

What is the normal chemical shift for an aldehyde on an NMR spec? What about a methyl ketone?

Answer 9

Aldehyde- 9-10

Methyl ketone- 2.1

Question 10

Conugated carbonyl compounds have characteristic _____ absorbtion in the UV spectrum

An additional conugated CC double bond increases the lambda max about ___ nm, and an additional alkyl group increases it about ___ nm

Answer 10

Pi- pi*

30, 10