1. ORGANIC CHEMISTRY 13
Aldehydes and Ketones
General, Organic, and Biochemistry 9th Edition
Katherine J. Denniston
Joseph J. Topping
Danaè R. Quirk Dorr
Robert L. Caret
Copyright © 2017 McGraw-Hill Education.  Permission required for reproduction or display

2. 13.1 Structures and Physical Properties

3. 13.1 Structure and Physical Properties
Aldehydes and ketones are polar compounds
The carbonyl group is polar
The oxygen end is electronegative 1

4. Hydrogen Bonding in Carbonyls
Aldehydes and ketones cannot form intermolecular hydrogen bonds
However, water can form hydrogen bonds to them
13.1 Structure and Physical Properties

5. Physical Properties Carbonyls boil at Higher temperatures than:
Hydrocarbons
Ethers
Lower temperatures than:
Alcohols

6. 13.2 Nomenclature and Common Names
Naming Aldehydes
Locate the parent compound
Longest continuous carbon chain
Must contain the carbonyl group
Replace the final –e of the parent with –al
Number the chain with the carbonyl carbon as 1
Number and name all substituents

7. 13.2 Nomenclature and Common Names
Naming Aldehydes
What is the name of this molecule?
Parent chain – 5 carbons = pentane
Change suffix – pentanal
Number from carbonyl end – L to R
Number / name substituents – 2-methyl
13.2 Nomenclature and Common Names 5 4 3 2 1
2-methylpentanal

8. Common Names of Aldehydes
These names are taken from Latin roots as are the first 5 carboxylic acids
Greek letters are used to indicate the position of substituents with the carbon atom adjacent or bonded to the carbonyl carbon being the a carbon
13.2 Nomenclature and Common Names

9. IUPAC and Common Names With Formulas for Several Aldehydes
13.2 Nomenclature and Common Names

10. Examples of Ketones
Simplest ketone MUST have 3 carbon atoms so that the carbonyl group is interior
Base name: longest chain with the C=O
Replace the –e of alkane name with –one
Indicate position of C=O by number on chain so that C=O has lowest possible number 2

11. IUPAC Naming of Ketones2
Rules directly analogous to those for aldehydes
Base name: longest chain with the C=O hept
Replace the –e of alkane name with –one
Indicate position of C=O by number on chain so that C=O has lowest possible number 2
13.2 Nomenclature and Common Names 5 4 3 2 1
4-methyl-2-heptanone

12. Common Names of Ketones
Based on the alkyl groups that are bonded to the carbonyl carbon
Alkyl groups are prefixes (2 words) followed by the word ketone
Order of alkyl groups in the name
Alphabetical
Size – smaller to larger
13.2 Nomenclature and Common Names

13. 13.3 Important Aldehydes and Ketones
Methanal (formaldehyde) - gas used in aqueous solutions as formalin to preserve tissue
Ethanal (acetaldehyde) - produced from ethanol in the liver causing hangover symptoms
Propanone (Acetone) - simplest possible ketone
Miscible with water
Flammable
Both acetone and methyl ethyl ketone (butanone) are very versatile solvents

14. Important Uses of Carbonyl Compounds
Used in many industries
Food chemicals
Natural food additives
Artificial additives
Fragrance chemicals
Medicines
Agricultural chemicals
13.3 Important Aldehydes and Ketone

15. Vanillin and 2-Octanone
13.3 Important Aldehydes and Ketone

16. Benzaldehyde and Cinnamaldehyde
13.3 Important Aldehydes and Ketone

17. Citral and α-Demascone
13.3 Important Aldehydes and Ketone

18. 13.4 Reactions Involving Aldehydes and Ketones
Preparation of aldehydes and ketones
Principal means of preparation is oxidation of the corresponding alcohol
Primary alcohol produces an aldehyde
Secondary alcohol produces a ketone
Tertiary alcohol does not oxidize
This oxidation process removes two hydrogens

19. 13.4 Reactions Involving Aldehydes and Ketones
1° Alcohol Oxidation
An aldehyde is formed 4
13.4 Reactions Involving Aldehydes and Ketones

20. 13.4 Reactions Involving Aldehydes and Ketones
2° Alcohol Oxidation 4
A ketone is formed
13.4 Reactions Involving Aldehydes and Ketones

21. 13.4 Reactions Involving Aldehydes and Ketones
3° Alcohol 4
3o alcohols cannot undergo oxidation:
13.4 Reactions Involving Aldehydes and Ketones

22. Reactions of Aldehydes and Ketones
Oxidation and Reduction
Aldehydes: oxidized to carboxylic acids
Aldehydes and ketones are reduced to alcohols: aldehydes to primary alcohols and ketones to secondary alcohols
Addition
Alcohols to give hemiacetals and acetals,
13.4 Reactions Involving Aldehydes and Ketones

23. Oxidation of Aldehydes5
Aldehydes are easily oxidized to carboxylic acids by almost any oxidizing agent
So easily oxidized that it is often difficult to prepare them as they continue on to carboxylic acids
13.4 Reactions Involving Aldehydes and Ketones

24. Visually Distinguishing Aldehydes From Ketones
Visual tests for the aldehyde functional group based on its easy oxidation are:
Tollen’s Test
Silver ion is reduced to silver metal
Use a basic solution of Ag(NH3)2+
The silver metal precipitates and coats the container producing a smooth silver mirror
13.4 Reactions Involving Aldehydes and Ketones

25. 13.4 Reactions Involving Aldehydes and Ketones
Tollen’s Test
13.4 Reactions Involving Aldehydes and Ketones

26. 13.4 Reactions Involving Aldehydes and Ketones
Benedict’s Test
Benedict’s Test
Reagent is a buffered aqueous solution of Cu(OH)2 and sodium citrate
Reacts with aldehydes, but not with ketones
Cu2+ is reduced to Cu+
Solution of Cu2+ is a distinctive blue color
Color fades during the reaction as Cu+ precipitates as the red solid, copper(I) oxide, Cu2O
13.4 Reactions Involving Aldehydes and Ketones

27. Benedict’s Test on Glucose
13.4 Reactions Involving Aldehydes and Ketones

28. Reduction of Carbonyls7
Both aldehydes and ketones are readily reduced to alcohols
Reduction occurs with hydrogen as the reducing agent
Classical reaction is hydrogenation
React with hydrogen gas
Requires a catalyst – Ni, Pt, Pd
13.4 Reactions Involving Aldehydes and Ketones

29. 13.4 Reactions Involving Aldehydes and Ketones
Addition Reactions 7
Principal reaction is the addition reaction across the polar C=O double bond
Very similar to the addition hydrogenation of alkenes
Requires catalytic acid in the solution
Product of the reaction is a hemiacetal
Hemiacetals are quite reactive
Undergo a substitution reaction with the –OH group of the hemiacetal is exchanged for another –OR group from the alcohol
Reaction product is an acetal
This reaction is reversible
13.4 Reactions Involving Aldehydes and Ketones

30. Hemiacetal and Acetal Formation7
13.4 Reactions Involving Aldehydes and Ketones
Generalized structure of a hemiacetal
Generalized structure of an acetal

31. Aldehyde and Alcohol Reaction
Product of the addition reaction is a hemiacetal followed by formation of an acetal
13.4 Reactions Involving Aldehydes and Ketones

32. Ketone and Alcohol Reaction
13.4 Reactions Involving Aldehydes and Ketones

33. Intramolecular Hemiacetal Formation
The aldehyde and alcohol functional groups can both be parts of the same molecule in an intramolecular reaction
13.4 Reactions Involving Aldehydes and Ketones

34. Hemiacetals and Carbohydrates
This reaction is important in the chemistry of carbohydrates, where hemiacetals are readily formed:
13.4 Reactions Involving Aldehydes and Ketones

35. Acetals and Carbohydrates
The acetal is formed between the hemiacetal hydroxyl group in blue with the alcohol hydroxyl group in red on a second molecule
13.4 Reactions Involving Aldehydes and Ketones

36. 13.4 Reactions Involving Aldehydes and Ketones
Keto-Enol Tautomers 8
Tautomers are isomers which differ in the placement of:
A hydrogen atom
A double bond
The keto form has a C=O while the enol form has a C=C.
The keto form is usually the most stable
13.4 Reactions Involving Aldehydes and Ketones

37. Reaction Schematic

38. Summary of Aldehyde and Ketone Reactions
1. Aldehydes and ketones
a. Oxidation of an aldehyde
b. Reduction of aldehydes and ketones
c. Addition reactions
Hemiacetal and acetal
Cyclic Hemiactetal and acetal
2. Keto-enol tautomerization

39. Summary of Reaction Equations