1 Announcements & Agenda (03/30/07) Quiz on Wednesday (Chirality & Ch 13) Will hand out HW practice on Monday Schedule for rest of semester on M or W <10 people at review on Wed  Great place for help! Great place for help!Today Fisher projections (12.6) Fisher projections (12.6) Carboxylic acids (13.1, 13.2) Carboxylic acids (13.1, 13.2) Esters (13.3) Esters (13.3)

2 Fischer Projections of Chiral Molecules (12.6) are a 2-dimensional representation of a 3-D molecule.are a 2-dimensional representation of a 3-D molecule. places the most oxidized group at the top.places the most oxidized group at the top. uses vertical lines in place of dashes for bonds that go back.uses vertical lines in place of dashes for bonds that go back. uses horizontal lines in place of wedges for bonds that come forward.uses horizontal lines in place of wedges for bonds that come forward.

3 Drawing Fischer Projections

4 D and L Notations By convention, the letter L is assigned to the structure with the —OH on the left.By convention, the letter L is assigned to the structure with the —OH on the left. The letter D is assigned to the structure with the —OH on the right.The letter D is assigned to the structure with the —OH on the right. FYI: Other conventions exist too…FYI: Other conventions exist too…

5 Learning Check Indicate whether each pair is a mirror image that cannot be superimposed (enantiomers). Yes Yes No No

6 Carboxylic Acids (13.1)

7 Ch 13 Practice Problems 13.01, 13.07, 13.09, 13.11, 13.13, 13.15, 13.17, 13.19, 13.21, 13.25, 13.29, 13.31, 13.33, 13.37, 13.39, 13.41, 13.43, 13.49, 13.55, 13.57, 13.59, 13.63, 13.65, 13.67, 13.69, 13.71, 13.73, 13.74, 13.75, 13.76

8 A carboxylic acid contains a carboxyl group, which is a carbonyl group (C=O) attached to a hydroxyl group (—OH).is a carbonyl group (C=O) attached to a hydroxyl group (—OH). O O   CH 3 — C—OHhydroxyl group carbonyl group carbonyl group Will also see a carboxylic acid written as CH 3 COOH Carboxylic Acids

9 The IUPAC names of carboxylic acids: Replace the -e in the alkane name with -oic acid.Replace the -e in the alkane name with -oic acid. CH 4 methane HCOOH methanoic acid CH 3 —CH 3 ethane CH 3 —COOH ethanoic acid Number substituents from the carboxyl carbon 1.Number substituents from the carboxyl carbon 1. CH 3 O CH 3 O | ║ | ║ CH 3 —CH—CH 2 —C—OH methylbutanoic acid 3-methylbutanoic acid Recognizing Carboxylic Acids from Names Don’t need to know numbering rules!!!

10 Names & Sources of Some Carboxylic Acids (Know These) By the way, very common in nature: Citric acid, tartaric acid, lactic acid, fatty acids, etc.

11 Polarity of Carboxylic Acids strongly polar because they have two polar groups:strongly polar because they have two polar groups: [hydroxyl ( − OH) and carbonyl (C=O)] form dimers in which hydrogen bonds form between two carboxyl groups.form dimers in which hydrogen bonds form between two carboxyl groups. O H—O O H—O || | || | CH 3 —C C—CH 3 | || | || O—H O O—H O A dimer of acetic acid A dimer of acetic acid have higher boiling points than alcohols, ketones, and aldehydes of similar mass.have higher boiling points than alcohols, ketones, and aldehydes of similar mass. … …

12 Comparison of Boiling Points Compound Molar Mass Boiling Point O ║ CH 3 −CH 2 −C−H5849°C CH 3 −CH 2 −CH 2 −OH6097°C O ║ CH 3 −C−OH60118°C

13 Solubility in Water Carboxylic acids: form hydrogen bonds with many water molecules.form hydrogen bonds with many water molecules. with 1-4 carbon atoms are very soluble in water.with 1-4 carbon atoms are very soluble in water. Water molecules

14 Boiling Points and Solubility

15 Acidity of Carboxylic Acids Carboxylic acids are weak acids.are weak acids. ionize in water to produce carboxylate ions and hydronium ions.ionize in water to produce carboxylate ions and hydronium ions. O O O O ║ ║ ║ ║ CH 3 − C − OH + H 2 O CH 3 − C − O – + H 3 O + ~1%

16 Neutralization of Carboxylic Acids Carboxylic acid salts are a product of the neutralization of a carboxylic acid with a strong base.are a product of the neutralization of a carboxylic acid with a strong base. CH 3 —COOH + NaOH CH 3 —COO – Na + + H 2 O CH 3 —COOH + NaOH CH 3 —COO – Na + + H 2 O acetic acid sodium acetate (carboxylic acid salt) (carboxylic acid salt) are used as preservatives and flavor enhancers.are used as preservatives and flavor enhancers.

17 Learning Check Write the equation for the reaction of propanoic acid with A. water B. KOH CH 3 —CH 2 —COOH + H 2 O CH 3 —CH 2 —COO – + H 3 O + CH 3 —CH 2 —COOH + KOH CH 3 —CH 2 —COO – K + + H 2 O

18 Esters (13.3)

19 Esters In an ester, the H in the carboxyl group is replaced with an alkyl group. O   CH 3 — C—O —CH 3 ester group ester group

20 Esterification: reaction of a carboxylic acid & alcohol in the presence of an acid catalyst to produce an ester. O O  H +  H + CH 3 —C—OH + H—O—CH 2 —CH 3 O   CH 3 —C—O—CH 2 —CH 3 + H 2 O ethyl acetate (an ester) ethyl acetate (an ester) Esterification FYI: The acid half of an ester is called an “acyl” group Also called a condensation reaction!

21 Write the equation for the reaction of propanoic acid and methanol in the presence of an acid catalyst. O  H +  H + CH 3 —CH 2 —C—OH + H—O—CH 3 propanoic acid methanol propanoic acid methanol O   CH 3 —CH 2 —C—O—CH 3 + H 2 O Learning Check

22 Ester Products Aspirin is used to relieve pain and reduce inflammation.is used to relieve pain and reduce inflammation. is an ester of salicylic acid and acetic acid.is an ester of salicylic acid and acetic acid. Oil of wintergreen is used to soothe sore muscles.is used to soothe sore muscles. is an ester of salicylic acid and methanol.is an ester of salicylic acid and methanol.

23 Naming Esters The name of an ester contains the names of the alkyl group from the alcohol.the alkyl group from the alcohol. the carbon chain from the acid with –ate ending.the carbon chain from the acid with –ate ending. methyl ethanoate (acetate) methyl ethanoate (acetate) O O   CH 3 — O—C —CH 3 CH 3 — O—C —CH 3 IUPAC: methyl ethanoate common: methyl acetate -oate: means ester present

24 Esters in Plants Esters give flowers and fruits their pleasant fragrances and flavors.

25 an ester reacts with water to produce a carboxylic acid and an alcohol.an ester reacts with water to produce a carboxylic acid and an alcohol. an acid catalyst is required.an acid catalyst is required. O  H +  H + H—C—O—CH 2 —CH 3 + H 2 O O   H—C—OH + H—O—CH 2 —CH 3 Acid Hydrolysis of Esters

26 is the reaction of an ester with a strong base.is the reaction of an ester with a strong base. produces the salt of the carboxylic acid and an alcohol.produces the salt of the carboxylic acid and an alcohol. O || || CH 3 —C—O—CH 2 —CH 3 + NaOH CH 3 —C—O—CH 2 —CH 3 + NaOH O  CH 3 —C—O – Na + + HO—CH 2 —CH 3  CH 3 —C—O – Na + + HO—CH 2 —CH 3 salt of carboxylic acid alcohol salt of carboxylic acid alcohol Base Hydrolysis (Saponification)

27 Base Hydrolysis of Fatty Acids Produces Soaps

28 Carboxylic acids with lots of carbons are fatty acids (usually even #, 10, 12, 14, 16, 18) Sodium salts of fatty acids are soaps.

29 Cleaning Action of Soap A soap contains a nonpolar end that dissolves in nonpolar fats and oils, and a polar end that dissolves in water.contains a nonpolar end that dissolves in nonpolar fats and oils, and a polar end that dissolves in water. forms groups of soap molecules called micelles that dissolve in water and are washed away.forms groups of soap molecules called micelles that dissolve in water and are washed away.

30 Write the organic products when methyl acetate reacts with A. water and an acid catalyst. O   CH 3 —C—OH + HO—CH 3 CH 3 —C—OH + HO—CH 3 B. KOH. O O   CH 3 —C—O – K + + HO—CH 3 CH 3 —C—O – K + + HO—CH 3 Learning Check