Aldehydes and Ketones - K. A. Boudreaux, Angelo State University, Lecture notes of Chemistry

Download Aldehydes and Ketones - K. A. Boudreaux, Angelo State University and more Lecture notes Chemistry in PDF only on Docsity! Chapter 4 Aldehydes and Ketones Chapter Objectives: • Learn to recognize the aldehyde and ketone functional groups. • Learn the IUPAC system for naming aldehydes and ketones. • Learn the important physical properties of the aldehydes and ketones. • Learn the major chemical reaction of aldehydes and ketones, and learn how to predict the products of hydrogenation, oxidation, and addition of alcohol reactions. • Learn to recognize the acetal, hemiacetal, ketal, and hemiketal group, and how these are related to aldehydes and ketones. Chapter 4 Aldehydes and Ketones The Carbonyl Group 2 Mr. Kevin A. Boudreaux Angelo State University CHEM 2353 Fundamentals of Organic Chemistry Organic and Biochemistry for Today (Seager & Slabaugh) Chapter 4 Aldehydes and Ketones The Carbonyl Group • The carbonyl group (C=O) is found in aldehydes, ketones, and many other organic functional groups. • The carbon and oxygen in the carbonyl group are sp2-hybridized, with bond angles of 120°. • In ketones, two carbon groups are attached to the carbonyl carbon, while in aldehydes at least one hydrogen is attached to the carbon. C O sp2 C O the carbonyl group C R R' O C R H O ketonealdehyde 3 Functional Groups Containing Carbonyls C R R' O C R H O C R O O H C R O O R' C R O O C R' O C R N O H H ketone aldehyde carboxylic acid ester acid anhydride amide 4 Chapter 4 Aldehydes and Ketones Examples: Naming Aldehydes and Ketones • Name the following compounds: CH3CHCH2 C H OBr CH3CHCHCH2C CH3 CH3 O H CH3 CH CH C CH3 CH3 CH3 O CH3 C CHCH2CH3 O CH2CH3 9 Other Nomenclature Rules • In cyclic ketones, the carbonyl group is always numbered “1”; this does not need to be included in the name. The numbering continues clockwise or counterclockwise to give the lowest number for the next substituent. • Molecules with more than one ketone group are named by preceding the suffix with a counting prefix (dione, trione, etc.); position numbers must be used for each ketone group. • Aromatic aldehydes (containing an aldehyde group directly attached to a benzene ring) are named after the parent compound benzaldehyde. (The carbon to which the aldehyde group is attached is carbon “1”). 10 Chapter 4 Aldehydes and Ketones Examples: Naming Aldehydes and Ketones • Name the following compounds: O O CH3 CH3 C C CH3 OO O CH3 CH2 C C CH3 OO CH3 CH CH3 CH2CH CH3 11 Examples: Naming Aldehydes and Ketones • Name the following compounds: C H O CH3 CH3C H O Br C H O CH2CH3 CH3 12 Chapter 4 Aldehydes and Ketones Examples: Naming Aldehydes and Ketones • Draw structural formulas for the following molecules: – 3-ethyl-2-pentanone – 2,4,6-trimethylheptanal – 3-ethylcyclopentanone 13 Examples: Naming Aldehydes and Ketones • Draw structural formulas for the following molecules: – 4-chloro-2-phenylpentanal – para-nitrobenzaldehyde – 3-ethyl-2-butanone (what’s wrong with this name?) 14 Chapter 4 Aldehydes and Ketones Physical Properties of Aldehydes and Ketones • Carbonyl compounds cannot hydrogen-bond to each other, but they can hydrogen-bond to water through the carbonyl oxygen. • Low-molecular weight aldehydes and ketones are water-soluble; water solubility decreases as the size of the molecule increases. R C R' O H O R' C R O H        19 Physical Properties of Aldehydes and Ketones Name Molecular weight Boiling point Solubility in water butane 58 g/mol 0°C Insoluble propanal 58 g/mol 49°C Soluble acetone 58 g/mol 56°C Soluble 1-propanol 60 g/mol 97°C Soluble Boiling Points: Alcohols Aldehydes/Ketones Ethers Alkanes Water Solubility: Alcohols Aldehydes/Ketones Ethers Alkanes 20 Chapter 4 Aldehydes and Ketones Examples: Predicting Boiling Points • Arrange the following compounds in order of increasing boiling point: – 2-pentanone – 2-methylpentane – 2-pentanol 21 22 Chapter 4 Aldehydes and Ketones Some Important Aldehydes and Ketones 23 Important Aldehydes and Ketones H C C OH Glucose One of the most important of the carbohydrates, which are polyhydroxy aldehydes and ketones; the metabolism of glucose is a major source of energy for living organisms C C C CH2OH HHO OHH OHH H O CH2OH C O C C C CH2OH HHO OHH OHH Fructose Another important carbohydrate; a major component of corn syrup; found in honey, syrups, and preserves; in combination with glucose it forms the disaccharide sucrose. 24 Chapter 4 Aldehydes and Ketones Humulone A component of hop resin, a viscous yellow material obtained from the blossoms of the female hop plant (Humulus lupulus); it adds to the bitter taste of some beers. O HO O OH OH Ionone Responsible for the odor of freshly picked raspberries, violets (and the extract, oil of violets), and sun-dried hay. O Butanedione A volatile yellow liquid compound with the odor of cheese; gives butter its characteristic flavor. It also contributes to the odor of armpits and unwashed feet by the action of bacteria which ferment the compounds in perspiration. O O 29 A Few Steroids Steroid nucleus OH CH3 CH3 O Testosterone A male sex hormone C CH3 CH3 O CH3 O Progesterone A female sex hormone OH CH3 O C C H Norethynodrel Active ingredient in birth-control pills 30 Chapter 4 Aldehydes and Ketones Reactions of Aldehydes and Ketones 31 Oxidation of Alcohols to Produce Carbonyls • Aldehydes, like primary alcohols, can be oxidized to produce carboxylic acids: • Secondary alcohols can be oxidized to produce ketones, which are not further oxidized: R C H H O H C O R H C O R OH [O][O] aldehyde 1° alcohol carboxylic acid R C H R' O H C O R R' [O] 2° alcohol ketone 32 Chapter 4 Aldehydes and Ketones Examples: Oxidation Reactions • Complete the following reactions: C H O [O] CH3 C CH3 [O] O CCH3CHCH2 O H CH3 [O] 33 Examples: Oxidation Reactions • Complete the following reactions: OH [O] CHCH3CHCH2 OH CH3 CH3 [O] 34 Chapter 4 Aldehydes and Ketones Addition of Alcohols to Aldehydes • Aldehydes react with alcohols first to form hemiacetals, which then react with excess alcohol to produce acetals. R C H R' OH R C H OR' R'' OH R C H OR' hemiacetal acetal aldehyde H+H+ O OH OR'' CH3 C H CH3OH CH3 C H OCH3 CH3 C H OCH3 CH3OH H+ H+ O OH OCH3 39 Addition of Alcohols to Ketones • Ketones react with alcohols first to form hemiketals, which then react with excess alcohol to produce ketals. R C R' R'' OH R C R' OR'' R''' OH R C R' OR'' hemiketal ketal ketone H+H+ OR'''OHO CH3 C CH3 CH3 C CH3 OCH3 CH3 C CH3 OCH3 H + CH 3 OH H + CH 3 OH O OH OCH3 40 Chapter 4 Aldehydes and Ketones Hemiacetals, Acetals, Hemiketals, and Ketals (oh my) CH3 C H a hemiacetal hemiacetal carbon OH OCH3 CH3 C H OCH3 an acetal acetal carbon OCH3 CH3 C CH3 OCH3 a hemiketal hemiketal carbon OH CH3 C CH3 OCH3 a ketal ketal carbon OCH3 41 Examples: Identifying Acetals and Ketals • Identify the following compounds as being acetals, ketals, hemiacetals, or hemiketals. CH3OCHCH3 OH CH3OCH2CH2OH CH3CH2OCCH3 OCH3 CH3 OH OCH3 OCH3CH3O O O 42 Chapter 4 Aldehydes and Ketones Examples: Identifying Acetals and Ketals • Identify the following compounds as being acetals, ketals, hemiacetals, or hemiketals. O OH CH3 O OCH3 CH2CH3 O OCH3 H O H OH O OCH3 CH2CH2CH3 O CH2CH3 CH2CH2CH3 43 Examples: Formation of Acetals and Ketals • Complete the following reactions. +CH C H H+ O CH3 CH3 CH3OH +CH C CH3 H+ O CH3 CH3 CH3CH2OH 44