1. Chapter 13 Aldehydes and Ketones Denniston Topping Caret 5th Edition
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Chapter 13
Aldehydes and Ketones
Denniston Topping Caret
5th Edition

2. Carbonyl Compounds Short forms Aldehydes:
Contain the carbonyl group C=O
Aldehydes:
R may be hydrogen, usually a carbon containing group
Ketones:
R contains carbon
Short
forms

3. Structures of Aldehydes and Ketones

4. 13.1 Structure and Physical Properties
Aldehydes and ketones are polar compounds
The carbonyl group is polar
The oxygen end is electronegative
Can hydrogen bond to water
Cannot form intermolecular hydrogen bond
Hydrogen
bond

5. Hydrogen Bonding in Carbonyls
13.1 Structure and Physical Properties
Bonding with H2O Intermolecular

6. 13.1 Structure and Physical Properties
Carbonyls boil at
Higher temperatures than:
Hydrocarbons
Ethers
Lower temperatures than:
Alcohols
13.1 Structure and Physical Properties

7. 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

8. 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 – 4-methyl
13.2 Nomenclature and Common Names 5 4 3 2 1
4-methylpentanal

9. 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
g-chlorovaleraldehyde

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

11. 13.2 Nomenclature and Common Names
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
13.2 Nomenclature and Common Names

12. IUPAC Naming of Ketones
Rules directly analogous to those for aldehydes
Base name: longest chain with the C=O pent
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 3 5 4 2 1
4-chloro-2-pentanone

13. 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
Methyl ethyl ketone or
Ethyl methyl ketone
Dimethyl ketone

14. 13.3 Important Aldehydes and Ketones
Methanal (b.p. –21oC) is a gas used in aqueous solutions as formalin to preserve tissue
Ethanal is produced from ethanol in the liver causing hangover symptoms
Propanone (Acetone) is the simplest possible ketone
Miscible with water
Flammable
Both acetone methyl ethyl ketone (MEK or butanone) are very versatile solvents

15. 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
Vanillin
Vanilla beans
2-octanone
Mushroom flavor

16. Other Important Carbonyls
13.3 Important Aldehydes and Ketone

17. 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
It is considered an oxidative elimination reaction

18. Distinguishing Types of Alcohol Oxidation
Upper box shows oxidation of a 1º alcohol
Must use a mild oxidizing agent or a carboxylic acid will be formed
Lower box oxidation of a 2º alcohol to a ketone
Tertiary alcohols cannot be oxidized
13.4 Reactions Involving Aldehydes and Ketones

19. Reactions of Aldehydes and Ketones
Redox
Aldehydes: oxidized to carboxylic acids
Aldehydes and ketones are reduced to alcohols: aldehydes to primary alcohols and ketones to secondary alcohols
Addition
Hydrogen to give alcohols
Alcohols to give hemiacetals, acetals, hemiketals, and ketals
Aldehydes/ketones to give aldol (b-hydroxy carbonyl) products
13.4 Reactions Involving Aldehydes and Ketones

20. Oxidation of Aldehydes
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
Susceptible to air oxidation even at room temperature
Cannot be stored for long periods
13.4 Reactions Involving Aldehydes and Ketones

21. 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

22. Distinguishing Aldehydes From Ketones
Benedict’s Test
Reagent is a buffered aqueous solution of copper(II) hydroxide and sodium citrate
Reacts with aldehydes, but not generally 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

23. Reduction of Carbonyls
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
Occurs with heat and pressure
13.4 Reactions Involving Aldehydes and Ketones

24. 13.4 Reactions Involving Aldehydes and Ketones
Addition Reactions
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

25. Formation of Hemiacetal or Hemiketal
Product of the addition reaction is a hemiacetal (above) or a hemiketal (below)
13.4 Reactions Involving Aldehydes and Ketones
Hemiacetal (ketal) carbons are part of both alcohol and ether functions and are a new functional group

26. Recognizing Hemiacetals, Acetals, Hemiketals, and Ketals
13.4 Reactions Involving Aldehydes and Ketones

27. 13.4 Reactions Involving Aldehydes and Ketones
Keto-enol Tautomers
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

28. 13.4 Reactions Involving Aldehydes and Ketones
Aldol Condensation
Self-addition or condensation
Uses two molecules of the same aldehyde or ketone
The a carbon of the second molecule adds to the carbonyl carbon of the first molecule
Strong base such as hydroxide catalyzes the reaction
Very complex reaction occurring in multiple steps
13.4 Reactions Involving Aldehydes and Ketones

29. Condensation of an Aldehyde
An aldol has an –OH b to the carbonyl group
carbonyl carbon of first molecule becomes
alcohol carbon in aldol
a C, 2nd molecule
original
a C
13.4 Reactions Involving Aldehydes and Ketones

30. Aldol Condensation: Aldolase
Dihydroxyacetone phosphate +
D-glyeraldehyde-3-phosphate
13.4 Reactions Involving Aldehydes and Ketones
Bond formed
D-fructose-1,6-bisphosphate
a carbon (3) adds to carbonyl carbon (4)

31. Reaction Schematic Carbonyl Oxidation Addition Reduction If aldehyde
Carboxylic
Acid
Reduction
If aldehyde
If ketone
If aldehyde
Hemiacetal - Acetal
2º Alcohol
1º Alcohol
If ketone
Hemiketal - Ketal

32. Summary of Reactions 1. Aldehydes and ketones
a. Oxidation of an aldehyde
b. Reduction of aldehydes and ketones
c. Addition reactions
i. Hemiacetal and acetal
ii. Hemiketal and ketal
2. Keto-enol tautomerization
3. Aldol condensation

33. Summary of Reactions