Aldehydes and Ketones Page Reference: 49-56#1-9
Aldehydes and Ketones:
Functional Group:
Name:
Structure:
Difference between Aldehydes and Ketones:
Rules for Naming:
• Find longest continuous chain of carbons to which the =O is bonded.
• If it is on an end carbon it is an aldehyde. Name it as an alkane, changing the ending to –al.
Groups are added as in alkanes.
• If it is on an interior carbon, it is a ketone. Number the chain so that the =O is on the lowest possible
number.
• Name the compound changing the ending to –one. Location of =O is indicated with a number
before the name. Groups are added as in alkanes.
Examples:
CH3-CH2-CH2=O
propanal (No number is needed since it must be a 1)
-------------------------------------------------------------------------------------------------------------------CH3
or
-Contains a = O on an inner C so it is an ketone
-Longest chain: 4 carbons  butanone
|
Number to get OH on lowest (O on 2nd C) 2-butanone
CH3 -CH-C=O
Side groups: CH3 on 3rd C  3-methyl-2-butanone
|
CH3
Or
--Contains a =O on an end C so it is an
aldehyde
-Longest chain: 5 C  pentanal
-side group: ethyl on 2nd C 2-ethylpentanal
Questions:
1. In the last example above, explain why we did not call it an hexanal, even though there is a 6
carbon chain.
2. How can you tell the difference between an aldehyde and a ketone.
3. Describe the physical properties of aldehydes and ketones as compared to their parent alkanes
and alcohols: boiling point, solubility in water. Explain these physical properties.
4. Describe the following reactions involving aldehydes and ketones and write an example of each:
a. Preparation from alcohols
b. Conversions to alcohols
c. Combustion
5. Explain why primary secondary and tertiary alcohols produce different substances from an
oxidation reaction.