Chapter 4 and

Chapter 4 Aldehydes and Ketones

Chapter Objectives: • Learn to recognize the and functional groups. • Learn the IUPAC system for naming aldehydes and ketones. The • Learn the important physical properties of the aldehydes and ketones. • Learn the major of aldehydes and ketones, and learn how to predict the products of , oxidation, and addition of reactions. • Learn to recognize the , , ketal, and hemiketal group, and how these are related to aldehydes and ketones.

Mr. Kevin A. Boudreaux Angelo State University CHEM 2353 Fundamentals of Organic Organic and for Today (Seager & Slabaugh) 2

The Carbonyl Group Functional Groups Containing Carbonyls • The carbonyl group (C=O) is found in aldehydes, ketones, and many other organic functional groups. O O • The and in the carbonyl group are C C sp2-hybridized, with bond angles of 120°. RR' RH ketone aldehyde O O O O O O sp2 C C C HCR' C C the carbonyl group RO RO ROR' •In ketones, two carbon groups are attached to the carboxylic acid anhydride carbonyl carbon, while in aldehydes at least one is attached to the carbon. O O O C H RN C C RHRR' H 3 4 aldehyde ketone

Some Common Aldehydes and Ketones O O O

C C C H H CH3 CH3 CH3 H Methanal 2-Propanone Ethanal () () () Gas at room temperature; 1 billion pounds used annually Product of oxidation of in 35-40% solution in water, called in U.S.; good for most the liver; consuming large quantities formalin, used to preserve organic compounds, and is of ethanol causes acetaldehyde to biological specimens, sterilize also soluble in water; solvent build up in bloodstream faster than Nomenclature of instruments, and embalm for coatings such as fingernail it can be consumed in the liver to cadavers; present in wood , polish and enamel , etc. make other products, leading to and helps to preserve smoked nausea, sweating, reduced blood meats by killing bacteria. pressure, etc. Aldehydes and Ketones O

C O H C CH3 CH2CH3 2- (Methyl ethyl ketone, MEK) Causes the of almonds Common industrial solvent 5 and cherries, and is also found 6 in apricots and . Chapter 4 Aldehydes and Ketones

Nomenclature of Aldehydes Nomenclature of Ketones • Select the longest carbon chain containing the • Select the longest carbon chain containing the carbonyl carbon. carbonyl carbon. • The -e ending of the parent name is replaced • The -e ending of the parent alkane name is replaced by the suffix -al. by the suffix -one. • The carbonyl carbon is always numbered “1.” (It is • Number the chain starting with the end closest to the not necessary to include the number in the name.) ketone group (the carbonyl carbon should have the lowest possible number). The location # for the • Name the attached to the chain in the ketone group precedes the name for the longest chain. usual way. • Name the substituents attached to the chain in the O usual way. O O O CH CCH3 CH3CH2CH2 CH CH3CH2CH2 CCH3 CH CH CCH CH3 CH2 CH CH2 CH3 3 2 2 CH3

7 8 CH2 CH2 CH2 CH3

Examples: Naming Aldehydes and Ketones Other Nomenclature Rules • Name the following compounds: • 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 Br O O CH3 counterclockwise to give the lowest number for the next . CH3CHCH2 CH H C CH2 CH CH CH3 • Molecules with more than one ketone group are CH3 named by preceding the suffix with a counting prefix (dione, trione, etc.); position numbers must be used for each ketone group. CH O O 3 • Aromatic aldehydes (containing an aldehyde group CH CH CH C CH CH CCHCHCH directly attached to a ring) are named after 3 3 3 2 3 the parent compound benzaldehyde. (The carbon to which the aldehyde group is attached is carbon “1”). CH3 CH2CH3

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Examples: Naming Aldehydes and Ketones Examples: Naming Aldehydes and Ketones • Name the following compounds: • Name the following compounds:


CH CH 3 3 C CH3 C H H

Br CH3


CH3 CH CH 11 2 3 12 Chapter 4 Aldehydes and Ketones

Examples: Naming Aldehydes and Ketones Examples: Naming Aldehydes and Ketones • Draw structural formulas for the following molecules: • Draw structural formulas for the following molecules: – 3-ethyl-2-pentanone – 4-chloro-2-phenylpentanal

– 2,4,6-trimethylheptanal – para-nitrobenzaldehyde

– 3-ethylcyclopentanone – 3-ethyl-2-butanone (what’s wrong with this name?)

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The Polarity of the Carbonyl Group • Carbonyl compounds are polar, containing a dipole along the carbon-oxygen .  O

C Physical Properties of  • This creates weak attractive forces between carbonyl Aldehydes and Ketones compounds, but these attractions are not as strong as those that result from hydrogen-bonding.

      CO CO CO

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The Boiling Points of Aldehydes and Ketones The Boiling Points of Aldehydes and Ketones • Since there is no hydrogen on the carbonyl oxygen, aldehydes and ketones do not form hydrogen bonds with themselves. • Aldehydes and ketones therefore have boiling points that are in between those of and of the same molecular weight: – Alcohols form hydrogen bonds, and have high boiling points. – Hydrocarbons are nonpolar, and have low boiling points. – Aldehydes and ketones are polar, so they have higher boiling points than hydrocarbons, but they are not as polar as molecules which can . 17 18 Chapter 4 Aldehydes and Ketones

Physical Properties of 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 Boiling Points: Water Solubility: the carbonyl oxygen. Alcohols Alcohols • Low-molecular weight aldehydes and ketones are Aldehydes/Ketones Aldehydes/Ketones water-soluble; water solubility decreases as the size Ethers of the molecule increases. Alkanes

    Name Molecular Boiling Solubility  O  weight point in water H H    O O  58 g/mol 0°C Insoluble propanal 58 g/mol 49°C Soluble C C   R  R' R  R' acetone 58 g/mol 56°C Soluble 1-propanol 60 g/mol 97°C Soluble 19 20

Examples: Predicting Boiling Points • Arrange the following compounds in order of increasing : – 2-pentanone – 2-methylpentane – 2-pentanol

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Important Aldehydes and Ketones HO C CH2OH


HO C H HO C H Some Important H C OH H C OH H C OH H C OH Aldehydes and Ketones CH OH 2 CH2OH

Glucose One of the most important of the Another important ; a , which are polyhydroxy major component of corn syrup; found aldehydes and ketones; the in , syrups, and preserves; in of is a major source of energy combination with glucose it forms the for living organisms sucrose.

23 24 Chapter 4 Aldehydes and Ketones

Important Aldehydes and Ketones O


Dihydroxyacetone 2-Heptanone Active ingredient in "bronzers" that Found in oil of clove; also present in provide fake suntan coloration; reacts Used in perfurmery, and as an organic the odor of many fruits and dairy CH3 with dead, outer skin cells to produce solvent; also used in the synthesis of products, and is also responsible for O a darker color; fades as the dead skin some pharmeceuticals the odor of blue cheese. cells slough off. O O Isolated by steam from the camphor tree CH3 of China and Japan. Camphor is a counter-irritant CH3O (produces a superficial inflammation to reduce deeper CH3O inflammation) and antipruritic (anti-itching) H medication; it appears to selectively stimulate cold sensors. It also stimulates the respiratory systems and inspires deep breathing, but can cause convulsions HO O HO Zingerone (vanillyl acetone) and respiratory collapse in larger doses. The pungent, hot component of ginger CH CHCH flavoring in Vanilla beans 3 3 Menthone (parent compound of the vanniloids) 25 26

O O O HO H H O H 3-(para-Hydroxyphenyl)- Produced from the breakdown of Hyacinthin 2-butanone in meat during cooking; the Found in hyacinth Responsible for the odor acrid smell of this compound is obvious The flavoring in oil of cinnamon; obtained by of ripe raspberries. during barbeques. It also contributes to steam distillation from the bark of the the of caramel, where it is produced cinnamon tree; has a carminative action by decomposing sucrose (releases hydrogen , , and hydrogen from the intestine) CH3 Methyl 2-pyridyl ketone O Found in the odor of O popcorn O N 2-Methylundecanal CH3 H One of the first of the synthetic H , introduced by Coco Chanel in 1921 as Chanel No. 5 O O Citronellal Vitamin K1 Found in citronella oil; A soluble vitamin btained from green leafy vegetables, cabbage, cauliflower, kale, 27 28 used as an insect repellant spinach, pork liver; also made by intestinal bacteria. Essential for blood clotting.


CH3 Responsible for the odor of Butanedione nucleus freshly picked raspberries, A volatile yellow liquid compound violets (and the extract, oil of with the odor of cheese; gives violets), and sun-dried hay. its characteristic flavor. It also O contributes to the odor of armpits and O O unwashed feet by the action of bacteria O A male sex hormone which ferment the compounds in CH3 H OH C C perspiration. CH3 OH CH3 C

Humulone CH3 HO OH A component of hop resin, a viscous yellow material obtained from the blossoms of the female hop plant (Humulus lupulus); it adds to O the bitter taste of some beers. O Norethynodrel 29 A female sex hormone Active ingredient in birth-control pills 30 Chapter 4 Aldehydes and Ketones

Oxidation of Alcohols to Produce Carbonyls • Aldehydes, like primary alcohols, can be oxidized to produce carboxylic : H O O [O] [O] RCOH C C RH ROH Reactions of H aldehyde 1° alcohol • Secondary alcohols can be oxidized to produce Aldehydes and Ketones ketones, which are not further oxidized: H O [O] RCOH C RR' R' ketone 31 2° alcohol 32

Examples: Oxidation Reactions Examples: Oxidation Reactions • Complete the following reactions: • Complete the following reactions: O CH3 OH C [O] CH CHCH CH CH H [O] 3 2 3


CH3 O [O] [O] CH3CHCH2 C H

O [O] CH3 CCH3 33 34

Oxidation of Aldehydes: The Tollens' Test Examples: The Tollens’ Test • Tollens’ reagent is a mild • What observations would be made in the following composed of silver in an aqueous basic solution reactions? of . O Tollen's • Aldehydes are oxidized to salts (since CH CH C H the solution is basic), and the silver ions are reduced 3 2 reagent to solid silver, which coats the bottom of the test O tube with a “silver mirror.” Tollen's CH C CH • Ketones are not oxidized, so no silver mirror forms. 3 3 reagent O O O

- + C RCH ++++2 Ag(NH3)2(OH)2 RCO NH4 3NH3 2Ag H2O aldehyde Tollen's reagent a carboxylate salt silver H Tollen's reagent O

RCR + 2 Ag(NH ) (OH) NR 3 2 2 Tollen's 35 36 ketone Tollen's reagent Unknownreagent silver ppt Chapter 4 Aldehydes and Ketones

Hydrogenation of Aldehydes and Ketones Examples: Hydrogenation Reactions • Hydrogenation of aldehydes and ketones with • Complete the following reactions: hydrogen gas and a platinum catalyst produces alcohols: O OOH Pt CH3CH2 CH+ H2 Pt RCH+ H2 RCH an aldehyde O H Pt H a CH3 CCH3 + 2

OOH O Pt RCR'+ H2 RCR' a ketone H Pt + H2 a secondary alcohol 37 38

Addition of Alcohols to Aldehydes Addition of Alcohols to Ketones • Aldehydes react with alcohols first to form • Ketones react with alcohols first to form , which then react with excess alcohol to hemiketals, which then react with excess alcohol to produce . produce ketals. OOHOR'' O OH OR''' + + H H + + RCH RCH RCH H H R' OH R'' OH RCR' RCR' RCR' aldehyde R'' OH R''' OH OR' OR' ketone OR'' OR'' hemiacetal acetal hemiketal ketal


Hemiacetals, Acetals, Hemiketals, and Ketals Examples: Identifying Acetals and Ketals (oh my) • Identify the following compounds as being acetals, ketals, hemiacetals, or hemiketals. OH OCH hemiacetal carbon 3 acetal carbon OH OCH3 CH3 CH CH3 CH CH3OCHCH3 CH3OCH2CH2OH CH3CH2OCCH3 OCH3 OCH3 CH3 a hemiacetal an acetal

OH OCH CH3O OCH3 hemiketal carbon 3 ketal carbon OH

CH3 CCH3 CH3 CCH3 OO OCH3 OCH3 OCH3 a hemiketal a ketal 41 42 Chapter 4 Aldehydes and Ketones

Examples: Identifying Acetals and Ketals Examples: Formation of Acetals and Ketals • Identify the following compounds as being acetals, • Complete the following reactions. ketals, hemiacetals, or hemiketals. CH3 O H+ CH CH C H + CH OH OH OCH OOCH 3 3 O O 3 3




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Intramolecular Addition Reactions Intramolecular Addition Reactions • In molecules which have both OH and C=O groups • These kinds of reactions are very important in on different carbon , an intramolecular carbohydrate chemistry: can occur, producing a cyclic hemiacetal or hemiketal: O H O C1 H OH 6CH2OH C H HOHC2 H C H C5 O OH 2 H+ O OH + H HOHC3 H C4 OH H C1 H2C CH2 HOC H C 4 H H2 HO C3 C2 H OH H OCH H C5 OH 3 H OH

6 CH2OH -D-glucose O H+ O + CH3OH + H2O D-glucose 45 46

Hydrolysis of Acetals and Ketals Examples: of Acetals and Ketals • Under acidic conditions, water can be used to • Complete the following reactions. reverse the previous reaction, and regenerate the OCH3 original aldehyde or ketone from the acetal or ketal. H+ + H O • This is an example of a hydrolysis reaction, in CH3 CH 2 which water causes a compound to be split into its component substances. OCH3 OR' O + H OCH CH RCH+ H2O RCH+ 2 R'—OH 2 3 + aldehyde alcohol H OR' CH3 CCH2CH2CH3 + H2O acetal OR'' O OCH2CH3 H+ RCR'+ H2O RCR'+ 2 R''—OH ketone alcohol OR'' ketal 47 48 Chapter 4 Aldehydes and Ketones

Reactions of Aldehydes and Ketones 5. Addition of an Alcohol to an Aldehyde to form an Acetal O OH OR

1. Oxidation of Aldehydes to give Carboxylic Acids + + H H O O RCHRCH RCH aldehyde ROH ROH [O] OR OR RCHRCOH hemiacetal acetal aldehyde carboxylic acid 6. Addition of an Alcohol to a Ketone to form a Ketal 2. Oxidation of Ketones — No Reaction O OH OR O + + RCRRCH R H RCR [O] RCR NR ketone ROH ROH OR OR ketone hemiketal ketal 3. Hydrogenation of Aldehydes to give Primary Alcohols 7. Hydrolysis of an Acetal to give an Aldehyde O O H OR O Pt + RCHRC+ H H H 2 RCH + H2O RCH + 2 ROH aldehyde aldehyde alcohol H OR primary alcohol acetal 4. Hydrogenation of Ketones to give Secondary Alcohols 8. Hydrolysis of a Ketal to give a Ketone O O H OR O + Pt H RCRRC+ H2 R RCR + H2O RCR + 2 ROH ketone ketone alcohol H OR secondary alcohol 49 ketal 50

The End