11

AnnouncementsAnnouncements & Agenda& Agenda (03/30/07)(03/30/07)

Quiz on Wednesday (Chirality & Ch 13)Quiz on Wednesday (Chirality & Ch 13)

Will hand out HW practice on MondayWill hand out HW practice on Monday

Schedule for rest of semester on M or WSchedule for rest of semester on M or W

<10 people at review on Wed <10 people at review on Wed Great place for help!Great place for help!

TodayToday 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)

22

Fischer Projections of Chiral Molecules Fischer Projections of Chiral Molecules (12.6)(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 uses vertical lines in place of dashes for bonds that go back.go back.

• uses horizontal lines in place of wedges for bonds uses horizontal lines in place of wedges for bonds that come forward.that come forward.

33

Drawing Fischer ProjectionsDrawing Fischer Projections

44

D and L NotationsD and L Notations• By convention, the letter L is assigned to the structure By convention, the letter L is assigned to the structure

with the with the —OH on the left.—OH on the left.• The letter D is assigned to the structure with the —OH on The letter D is assigned to the structure with the —OH on

the right.the right.• FYI: Other conventions exist too…FYI: Other conventions exist too…

55

Learning CheckLearning CheckIndicate whether each pair is a mirror image Indicate whether each pair is a mirror image that cannot be superimposed (enantiomers).that cannot be superimposed (enantiomers).

YesYes

NoNoB.

A.

and

and

Br

CH3 H

CH2OH

C

H

CH3 H

Cl

C

Br

H CH3

CH2OH

C

H

H CH3

Cl

C

66

Carboxylic Acids (13.1) Carboxylic Acids (13.1)

77

Ch 13 Practice ProblemsCh 13 Practice Problems

11 22 33 44 55

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

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A carboxylic acid contains a A carboxylic acid contains a carboxyl groupcarboxyl group, , whichwhich• is a carbonyl group (C=O) attached to a hydroxyl is a carbonyl group (C=O) attached to a hydroxyl

group (group (——OH).OH).

OO

CHCH3 3 —— CC——OHOH hydroxyl grouphydroxyl group

carbonyl groupcarbonyl group

Will also see a carboxylic acid written as CHWill also see a carboxylic acid written as CH33COCOOHOH

Carboxylic Acids Carboxylic Acids

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The IUPAC names of carboxylic acids: The IUPAC names of carboxylic acids:

• Replace the -Replace the -ee in the alkane name with - in the alkane name with -ooic acidic acid..

CHCH44 methan methanee HCOOH methan HCOOH methanoicoic acidacid

CHCH33——CHCH3 3 ethanethanee CH CH33——COOH ethanCOOH ethanoicoic acidacid

• Number substituents from the carboxyl carbon 1.Number substituents from the carboxyl carbon 1.

CHCH3 3 OO | | ║║

CHCH33——CHCH—CH—CH22—C—OH—C—OH 4 3 2 14 3 2 1

3-methylbutanoic acid3-methylbutanoic acid

Recognizing Carboxylic Acids from NamesRecognizing Carboxylic Acids from Names

Don’t need to Don’t need to know numbering know numbering rules!!!rules!!!

1010

Names & Sources of Some Carboxylic Acids Names & Sources of Some Carboxylic Acids (Know These)(Know These)

By the way, very common in nature:By the way, very common in nature:Citric acid, tartaric acid, lactic acid, fatty acids, etc.Citric acid, tartaric acid, lactic acid, fatty acids, etc.

1111

Polarity of Carboxylic Acids Polarity of Carboxylic Acids • strongly polar because they have two polar groups: strongly polar because they have two polar groups:

[hydroxyl ([hydroxyl (−−OH) and carbonyl (C=O)]OH) and carbonyl (C=O)]

• form form dimersdimers in which hydrogen bonds form between two in which hydrogen bonds form between two carboxyl groups.carboxyl groups.

O HO H—O—O |||| | |

CHCH33—C—C C—CH C—CH33

|| ||||

O—H O—H O O A dimer of acetic acidA dimer of acetic acid

• have higher boiling points than alcohols, ketones, and have higher boiling points than alcohols, ketones, and aldehydes of similar mass.aldehydes of similar mass.

…

…

1212

Comparison of Boiling PointsComparison of Boiling Points

CompoundCompound Molar Mass Boiling Point Molar Mass Boiling Point

OO

║║

CHCH33−CH−CH22−C−H−C−H 5858 49°C49°C

CHCH33−CH−CH22−CH−CH22−OH−OH 6060 97°C97°C

OO

║║

CHCH33−C−OH−C−OH 6060 118°C118°C

1313

Solubility in WaterSolubility in Water

Carboxylic acids: Carboxylic acids: • form hydrogen form hydrogen

bonds with many bonds with many water molecules.water molecules.

• with 1-4 carbon with 1-4 carbon atoms are very atoms are very soluble in water.soluble in water.

Water molecules

1414

Boiling Points and SolubilityBoiling Points and Solubility

1515

Acidity of Carboxylic AcidsAcidity of Carboxylic Acids

Carboxylic acids Carboxylic acids • are weak acids.are weak acids.• ionize in water to produce carboxylate ionize in water to produce carboxylate

ions and hydronium ions.ions and hydronium ions.

O O OO ║║ ║║

CHCH33−−CC−−OH + HOH + H22OO CH CH33−−CC−−OO– – + +

HH33OO++

~1%~1%

1616

Neutralization of Carboxylic AcidsNeutralization of Carboxylic Acids

Carboxylic acid saltsCarboxylic acid salts • are a product of the neutralization of a carboxylic acid are a product of the neutralization of a carboxylic acid

with a strong base. with a strong base.

CHCH33——COOH + NaOH CHCOOH + NaOH CH33——COOCOO– – NaNa+ + + H+ H22OO

acetic acidacetic acid sodium acetate sodium acetate

(carboxylic acid salt)(carboxylic acid salt)• are used as preservatives and flavor enhancers.are used as preservatives and flavor enhancers.

1717

Learning CheckLearning Check

Write the equation for the reaction of propanoic acid withWrite the equation for the reaction of propanoic acid with

A. water A. water

B. KOHB. KOH

CHCH33—CH—CH22—COOH + H—COOH + H22O CHO CH33—CH—CH22—COO—COO–– + H + H33OO++

CHCH33—CH—CH22—COOH + KOH CH—COOH + KOH CH33—CH—CH22—COO—COO–– K K++ + H + H22OO

1818

Esters (13.3)Esters (13.3)

1919

EstersEsters

In an In an esterester, the H in the carboxyl group is replaced, the H in the carboxyl group is replacedwith an alkyl group.with an alkyl group.

OO

CHCH3 3 —— CC—O—O —CH—CH33

ester groupester group

2020

EsterificationEsterification: reaction of a carboxylic acid & alcohol : reaction of a carboxylic acid & alcohol in the presence of an acid catalyst to produce an in the presence of an acid catalyst to produce an ester.ester.

OO HH++

CHCH33——CC——OHOH ++ HH——OO——CHCH22——CHCH3 3

OO

CHCH33——CC——OO——CHCH22——CHCH3 3 ++ HH22OO ethyl acetate (an ester)ethyl acetate (an ester)

EsterificationEsterification

FYI: The acid half of an ester is called an “acyl” groupFYI: The acid half of an ester is called an “acyl” group

Also called a condensation reaction!Also called a condensation reaction!

2121

Write the equation for the reaction of propanoic Write the equation for the reaction of propanoic acid and methanol in the presence of an acid acid and methanol in the presence of an acid catalyst. catalyst.

OO HH++

CHCH33——CHCH22——CC——OHOH + + HH——OO——CHCH33

propanoic acid methanolpropanoic acid methanol OO

CHCH33——CHCH22——CC——OO——CHCH3 3 + + HH22OO

Learning CheckLearning Check

2222

Ester ProductsEster Products

AspirinAspirin• is used to relieve pain and is used to relieve pain and

reduce inflammation.reduce inflammation.• is an ester of salicylic acid is an ester of salicylic acid

and acetic acid.and acetic acid.

Oil of wintergreenOil of wintergreen• is used to soothe sore is used to soothe sore

muscles. muscles. • is an ester of salicylic acid is an ester of salicylic acid

and methanol. and methanol.

CH3

O

CO

OH

O

C

OH

CH3O

O

C

2323

Naming EstersNaming Esters

The name of an ester contains the names ofThe name of an ester contains the names of

• the the alkyl groupalkyl group from the alcohol. from the alcohol.

• the carbon chain from the acid with the carbon chain from the acid with ––ateate ending. ending.

methylmethyl ethanoate (acetate)ethanoate (acetate)

OO

CHCH33—— OO——CC —CH—CH33

IUPAC: IUPAC: methylmethyl ethanoateethanoate

common:common: methylmethyl acetateacetate

-oate: means -oate: means ester presentester present

2424

Esters in PlantsEsters in Plants

Esters give flowers and fruits their Esters give flowers and fruits their pleasant fragrances and flavors.pleasant fragrances and flavors.

2525

• an ester reacts with water to produce a an ester reacts with water to produce a carboxylic acid and an alcohol.carboxylic acid and an alcohol.

• an acid catalyst is required. an acid catalyst is required. OO

HH++

HH——CC——OO——CHCH22——CHCH3 3 ++ HH22OO

OO HH——CC——OHOH + + HH——OO——CHCH22——CHCH33

Acid Acid HydrolysisHydrolysis of Esters of Esters

2626

• 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 produces the salt of the carboxylic acid and an alcohol.alcohol. OO

|||| CHCH33——CC—O—O——CHCH22——CHCH3 3 ++ NaOHNaOH

OO CHCH33——CC——OO– – NaNa++ + + HHOO——CHCH22——CHCH33

salt of carboxylic acid alcoholsalt of carboxylic acid alcohol

Base Base HydrolysisHydrolysis (Saponification) (Saponification)

2727

Base Base HydrolysisHydrolysis of Fatty Acids of Fatty Acids Produces SoapsProduces Soaps

2828

Carboxylic acids with lots of carbons are fatty Carboxylic acids with lots of carbons are fatty acids (usually even #, 10, 12, 14, 16, 18)acids (usually even #, 10, 12, 14, 16, 18)

Sodium salts of fatty acids are soaps.

2929

Cleaning Action of SoapCleaning Action of Soap

A A soapsoap• contains a nonpolar end contains a nonpolar end

that dissolves in that dissolves in nonpolar fats and oils, nonpolar fats and oils, and a polar end that and a polar end that dissolves in water.dissolves in water.

• forms groups of soap forms groups of soap molecules called molecules called micellesmicelles that dissolve in that dissolve in water and are washed water and are washed away.away.

3030

Write the organic products when methyl acetate reacts withWrite the organic products when methyl acetate reacts withA. water and an acid catalyst.A. water and an acid catalyst.

OO CHCH33——CC——OH + HOH + HOO——CHCH33

B. KOH.B. KOH. OO

CHCH33——CC——OO– – KK++ + H + HOO——CHCH33

Learning CheckLearning Check