Week # 6: Aldehydes and Ketones
Lectures - 15, 16, 17
Concepts:
Carbonyl group - pi bond
Boiling points, polarity, solubility
Chiral Molecules (definition), mirror images, Fischer projection,D amd L glyceraldehyde, biological and drug examples.
Enantiomer, diasteroisomer
Hemiacetal and acetal as functional groups, ring hemiacetals
Reaction Summary: Write the word equations.
(first four are review)
Oxidation of primary alcohol:
Oxidation of secondary alcohol:
Oxidation of tertiary alcohol:
Oxidation of aldehyde:
Reduction or hydrogenation of aldehyde or ketone:
Synthesis of Hemiacetal:
Synthesis of Acetal:
Ques.1. Summarize the definitions of the three classes of alcohols including
an example of each, using 4 carbons.
Definition Example
Primary:
Secondary:
Tertiary:
Ques. 2. a. Rank the compounds by boiling point (lowest to highest) and by polarity. First write out the structures.
propanone, propanol, propane, methyl ethyl ether, and propanal
b. Are aldehyde and ketones able to hydrogen bond? What explains their relative high polarity compared to alkanes or ethers?
Ques. 3. Which compound is more soluble in water? Explain your reason.
a. butanone or butane
b. 3-hexanone or propanone
c. 1-butanol or butanal
Ques. 4.a. Which of the following compounds contains at least one chiral carbons. Circle that carbon.
b. Write the structures of D and L glyceraldehyde.
Ques. 5. Explain why both mirror images of a compound are not effective as drugs? Use the L-dopa and D-dopa as examples. Draw out the structures centered on the chiral carbons to show the mirror images.
Review - Subtraction Reactions - Dehydration and Oxidation
Reaction Name / Word Equation / Example8. Oxidation - pri. alcohol / Pri. Alcohol + (O)
à aldehyde + water / 1-propanol + (O) à propanal
9. Oxidation - sec. alcohol / Sec. Alcohol + (O)
à ketone + water / 2-propanol + (O) à
2-propanone
10. Oxidation - aldehyde / Aldehyde + (O) à Acid / Propanal + (O) à propanoic acid
Ques. 6. Write the structures and names of the reactants and products.
a) CH3CH2OH + (O) ----->
b) CH3CH2CH2OH + (O) ----->
c) + (O) ----->
d) + (O) ----->
Ques. 7: Write the names of the structures below.
Ques. 8: Write the names of the reactant structures:
a.
b.
c.
Addition Reactions
6. Reduction (H2) / Aldehyde or ketone + hydrogenà alcohol / Propanal + hydrogen
Propanone + hydrogen
Ques. 9. Write the structures and names of the reactants and products.
Ques. 10: Write the name of the reactants and the structures of the products.
a.
b.
c.
d.
Hemiacetal and acetal Functional Groups
In the simplest form, the hemiacetal is really the combination of two
functional groups.
A hemiacetal is an alcohol and ether ATTACHED TO THE
SAME CARBON.
An acetal is two ether groups ATTACHED TO THE SAME CARBON.
Hemiacetal Formation:
The aldehyde and alcohol approach each other as follows because of the
attraction of opposite charges on the polar groups. The reaction is written as an equilibrium because the hemiacetal is unstable and reverts back to the original aldehyde and alcohol.
1. The alcohol oxygen becomes bonded to the carbonyl carbon to form the
ether.
2. The carbon double bond oxygen electrons are used to bond the alcohol
hydrogen to the carbonyl oxygen
3. The alcohol oxygen-hydrogen bond is broken
The whole process can be remembered by saying: The aldehyde or ketone
oxygen becomes an alcohol. The alcohol oxygen becomes an ether.
Ques. 11: Identify the structures below as hemiacetals or acetals:
à hemiacetal / Ethanal + methanol
15. Acetal Synthesis
(ether synthesis) / Alcohol + hemiactal
à acetal + water / Hemiacetal (above) + methanol
Ques. 12:
a. If butanone reacts with one molecule of methanol, what is the structure formed?
b. If butanone reacts with two molecules of methanol, what is the structure formed?
Ques. 13. Write the structures and names of the reactants and products.