Aldehydes and Ketones

Transcription

1 Reading Chapter 12: , Practice problems: in text problems and 19, 21-24, 28 Carbonyl Compounds II: Reactions of More Reactions of Carboxylic Acid Derivatives The Structure of 1

2 The Structure of Formaldehyde Trigonal-planar geometry Covalent Bonding in Aldehydes and Ketones s bond (overlap of sp 2 orbitals of carbon and oxygen) 2

3 Covalent Bonding in Aldehydes and Ketones p bond (overlap of parallel 2p orbitals) Covalent Bonding in Aldehydes and Ketones Two nonbonding electron pairs in filled sp 2 hybrid orbitals 3

4 Common Names Aldehydes The common name for an aldehyde is derived from the common name of the corresponding carboxylic acid by changing the suffix ic to aldehyde. Nomenclature of IUPAC Nomenclature of Aldehydes Select as the parent compound the longest chain of carbon atoms that contains the functional group. For aldehydes, change the suffix e of the parent name to al. Aldehyde carbon is carbon 1. 4

5 Nomenclature of Aldehydes Nomenclature of Aldehydes The IUPAC system has retained some common or trivial names: 5

6 Name the following compound: Common Names Ketones Common names for ketones are derived by naming the two alkyl or aryl groups attached to the carbonyl group, followed by the word ketone. 6

7 Nomenclature of IUPAC Nomenclature of Ketones Select as the parent compound the longest chain of carbon atoms that contains the functional group. For ketones, change the suffix e of the parent name to one. Number the chain so that the ketone group gets the lowest number. Nomenclature of Ketones 7

8 Nomenclature of Ketones Muscone and Exaltone The macrocyclic ketones, muscone and exaltone, are natural musks found in the scent glands of the male civet cat (Viverra civetta). 8

9 Physical Properties of Oxygen is more electronegative than carbon; therefore, the carbon oxygen bond is polar: Physical Properties of Dipole Dipole Attractions Aldehydes and ketones have higher boiling points and melting points than hydrocarbons of similar molecular weights: Two acetone molecules 9

10 Physical Properties of Hydrogen Bonding Oxygen lone pairs can participate in hydrogen bonding but they can t hydrogen bond with each other. Boiling points and melting points tend to be lower than alcohols of similar molecular weights. Reactions of A carbonyl group, because of its polarity, reacts with both electrophiles and nucleophiles. Site of reaction with nucleophiles Site of reaction with electrophiles 10

11 Reactions of Nucleophilic Addition Reactions of Nucleophilic Addition Remember: Nucleophile Any molecule or anion that can donate a pair of electrons and in the process form a new covalent bond. 11

12 Reactions of Nucleophilic Addition Reactions of Electrophilic Addition 12

13 Reactions of Electrophilic Addition Formaldehyde Addition of Water 13

14 Formaldehyde Addition of Water K eq = 10 3 When formaldehyde is dissolved in water at 20 o C, it is more than 99% hydrated. Acetaldehyde Addition of Water K eq 1 Acetaldehyde is approximately 58% hydrated. For acetaldehyde and most other aldehydes, equilibrium constants for hydration are approximately 1. 14

15 Addition of Water Ketones K eq = For most simple ketones, equilibrium constants for hydration are 10 3 or less. Thus, in aqueous solutions, ketones are almost entirely in the keto form instead of the hydrate. 15