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The Carbonyl Group Nomenclature of Aldehydes and Ketones

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The Carbonyl Group Nomenclature of Aldehydes and Ketones Chapter 4 Aldehydes and Ketones 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. The Carbonyl Group • 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. Mr. Kevin A. Boudreaux Angelo State University CHEM 2353 Fundamentals of Organic Chemistry Organic and Biochemistry for Today (Seager & Slabaugh) www.angelo.edu/faculty/kboudrea 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 carbon and oxygen 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 ester acid anhydride carbonyl carbon, while in aldehydes at least one hydrogen is attached to the carbon. O O O C H RN C C amide 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 (Formaldehyde) (Acetone) (Acetaldehyde) Gas at room temperature; 1 billion pounds used annually Product of oxidation of ethanol in 35-40% solution in water, called in U.S.; good solvent 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 smoke, polish and enamel paints, 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-Butanone Benzaldehyde (Methyl ethyl ketone, MEK) Causes the odor of almonds Common industrial solvent 5 and cherries, and is also found 6 in apricots and peaches. 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 alkane 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 substituents 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 substituent. 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 benzene 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 9 10 Examples: Naming Aldehydes and Ketones Examples: Naming Aldehydes and Ketones • Name the following compounds: • Name the following compounds: O O O O O CH CH 3 3 C CH3 C H H Br CH3 CH3 O O O O CH3 O C CH CCCHCH CH C CH CH CH CCH 3 3 3 2 2 3 H 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?) 13 14 The Polarity of the Carbonyl Group • Carbonyl compounds are polar, containing a dipole along the carbon-oxygen double bond. 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 15 16 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 alcohols and hydrocarbons 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 hydrogen bond. 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 Ethers of the molecule increases. Alkanes Alkanes Name Molecular Boiling Solubility O weight point in water H H O O butane 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 boiling point: – 2-pentanone – 2-methylpentane – 2-pentanol 21 22 Important Aldehydes and Ketones HO C CH2OH H COH CO 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 Fructose One of the most important of the Another important carbohydrate; a carbohydrates, which are polyhydroxy major component of corn syrup; found aldehydes and ketones; the metabolism in honey, syrups, and preserves; in of glucose is a major source of energy combination with glucose it forms the for living organisms disaccharide sucrose. 23 24 Chapter 4 Aldehydes and Ketones Important Aldehydes and Ketones O O O CH3 CH3 CH3 HOCH2 CCH2OH Dihydroxyacetone 2-Heptanone Active ingredient in "bronzers" that Acetophenone 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. Camphor O O Isolated by steam distillation 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. Vanillin 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 Acrolein 3-(para-Hydroxyphenyl)- Produced from the breakdown of Hyacinthin 2-butanone triglycerides in meat during cooking; the Cinnamaldehyde 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 taste of caramel, where it is produced cinnamon tree; has a carminative action by decomposing sucrose (releases hydrogen sulfide, methane, 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 perfumes, introduced by Coco Chanel in 1921 as Chanel No. 5 O O Citronellal Vitamin K1 Found in citronella oil; A fat 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. OH O A Few Steroids CH3 OO CH3 Ionone Responsible for the odor of Butanedione Steroid nucleus freshly picked raspberries, A volatile yellow liquid compound violets (and the extract, oil of with the odor of cheese; gives butter violets), and sun-dried hay. its characteristic flavor. It also O contributes to the odor of armpits and Testosterone 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.
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