Chapter SeventeenCarboxylic Acids and Their

Derivatives

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Goals• Be able to describe and compare the structures,

reactions, and physical properties of carboxylic acids, esters, and amides.

• Be able to name the simple members of these families and write their structures, given the names.

• Be able to identify the general occurrence and some important members of each family.

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Goals Contd.

• Be able to describe and predict the products of the ester- and amide-forming reactions of carboxylic acids and the hydrolysis of esters and amides.

• Be able to recognize and write the structures of phosphate esters and their ionized forms.

Carboxylic Acids and Their Derivatives: Properties and NamesCarboxylic acids have an –OH group

bonded to the carbonyl C atom.

Polar & form hydrogen bonds High boiling points.

Amides

Amides have :• NH2, • NH-R, or• –NR2

• bonded to the carbonyl C atom

Substitution reactions

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1. Carboxylic acids and their derivatives undergo carbonyl-group substitution reactions, in which the group bonded to the carbonyl C atom is replaced.

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• Carboxylic acids behave as weak acids. • They surrender the hydrogen of

the carboxyl group, COOH, to bases and establish acid–base equilibria in aqueous solution.

► Like alcohols, carboxylic acids form hydrogen bonds with each other so that even formic acid (HCOOH), the simplest carboxylic acid, is a liquid at room temperature with a boiling point of 101ºC.

Long Chain Carboxylic acids

• saturated straight-chain R groups of up to 9 C’s are volatile liquids

• Saturated chains up to 4 C’s are water soluble.

• solubility falls off as the size of the hydrophobic, alkane-like portion increases.

• Acids with larger saturated R groups are waxy, odorless solids.

Naming Carboxylic acids

• Replacing the final -e of the alkane name with -oic acid.– If other functional groups are present, number beginning

at the –COOH end.

Common names and systematic names

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• Common names of many of the carboxylic acids are used far more often than their IUPAC names, primarily because carboxylic acids were among the first organic compounds to be isolated and purified.

• When using common names, the carbon atoms attached to the –COOH group are identified by Greek letters rather than numbers.

IUPAC Names• Unsaturated acids are named systematically

in the IUPAC system with the ending -enoic.

• Dicarboxylic acids, contain two –COOH groups, are named by adding the ending -dioic acid to the alkane name.

The acyl group name

• When a carboxylic acid loses its –OH is named by replacing the -ic at the end of the name with -oyl. An exception is the acyl group from acetic acid, which is traditionally called an acetyl group.

Copyright © 2010 Pearson Education, Inc. Chapter Seventeen 14

Esters do not form Hydrogen bonds

• Simple esters are therefore lower boiling than the acids from which they are derived. • Esters are colorless, volatile liquids with

pleasant odors, and many of them contribute to the natural fragrance of flowers and ripe fruits.

Esters

when the OH of the carboxyl group is converted to an OR group (ester) the ability to hydrogen bond to each other is lost

Esters have lower boiling points that carboxylic acids

Esters have an -OR group bonded to the carbonyl C atom..

Naming EstersFirst name the R group, .

Second: name the parent acid, replace the ic ending with ate

Ethyl acetate

Which has a higher boiling pointAmides or Amines?

They are both

...

Amides are hig...

Amines are hig...

It depends o

n ...

0% 0%0%0%

1. They are both high

2. Amides are higher

3. Amines are higher

4. It depends on the length of the chain

Amids

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• Unsubstituted amides form 3 strong hydrogen bonds to other amide molecules. They are higher melting and higher boiling than the acids from which they are derived.

• Except for the simplest amide (formamide, a liquid), low molecular- weight unsubstituted amides are solids, and are soluble in both water and organic solvents.

Amids

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• Monosubstituted amides can also form hydrogen bonds to each other,

• Disubstituted amides cannot form hydrogen bonds to each other and have lower boiling.

Amides • The nitrogen atom is bonded to a carbonyl-group

carbon in an amide, but not in an amine.• The positive end of the carbonyl group attracts the

unshared pair of electrons on nitrogen strongly enough to prevent it from acting as a base by accepting a hydrogen atom.

• As a result, amides are NOT basic like amines.

Copyright © 2010 Pearson Education, Inc. Chapter Seventeen 22

• Unsubstituted amides are named by replacing the -ic acid or -oic acid of the corresponding carboxylic acid name with -amide.

• If the N atom of the amide has alkyl substituents on it, the compound is named by first specifying the N-alkyl group and then identifying the amide name.

Copyright © 2010 Pearson Education, Inc. Chapter Seventeen 23

17.2 Some Common Carboxylic Acids

• Formic acid, HCOOH: Chemical that is present in the sting of ants.

• Acetic acid, CH3COOH: dilute (5%) aqueous acetic acid is known as vinegar.

• Butyric acid, CH3CH2CH2COOH: Chemical responsible for odor of rancid butter.

• Caproic acid, CH3CH2CH2CH2CH2COOH: First isolated from the skin of goats-which has a distinct smell.

• Citric acid: Present in citrus fruits and blood.

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Acidity of Carboxylic Acids

Carboxylic acids are weak acids that establish equilibria in aqueous solution with carboxylate ions, The carboxylate ions are named by replacing the -ic ending in the carboxylic acid name with –ate.

Copyright © 2010 Pearson Education, Inc. Chapter Seventeen 25

To Review

• Esters and Amides are made from carboxylic acids - and can be converted back again

• simple acids and esters are liquids• unsubstituted amides are solids

• Carboxylic acids give ==> acidic solutions• Esters and Amides==> neutral• Amines==> basic

pH and Structure

Esters and Amides==> neutral

Carboxylic acids give ==> acidic solutions

Amines==> basic

Reactions of Carboxylic Acids: Esterification

• Ester formation (esterification), is carried out by warming a carboxylic acid with an alcohol in the presence of a strong-acid catalyst.

.

This reaction is reversible, the production of the ester is favored either by using a large excess of the alcohol or by continuously removing one of the products..

• Unsubstituted amides are formed by the reaction of carboxylic acids with ammonia.

• Substituted amides are produced in reactions between primary or secondary amines and carboxylic acids.

Aspirin and Other Over-the-Counter Carboxylic Acid Derivatives

Aspirin is a white, crystalline solid. Chemically, aspirin is acetylsalicylic acid, an ester formed between acetic acid and the –OH group of salicylic acid.

Aspirin and Other Over-the-Counter Carboxylic Acid Derivatives

• Bayer began marketing aspirin in July 1899. It was marketed alongside another of Hoffmann's products, an acetylated derivative of morphine called 'Heroin' that he invented 11 days after aspirin

• Heroin was initially the more successful of the two painkillers and it was common belief that it was healthier than aspirin.- but the addictive effects were soon discovered

Chapter Seventeen

• An alternative to aspirin for pain relief is acetaminophen (better known as Tylenol), an amide that also contains a hydroxyl group. • Acetaminophen reduces fever, but unlike aspirin it is

not an anti-inflammatory agent. The major advantage of acetaminophen over aspirin is that it does not induce internal bleeding.

Ibuprofen is a nonsteroidal anit-inflammatory drug which is said to have the lowest incidence of adverse side effects

• Benzocaine (topical) used in many over-the-counter topical preparations for such conditions as cold sores, poison ivy, sore throats, and hemorrhoids. • It works by blocking the transmission of impulses by

sensory nerves. • Lidocaine is commonly administered by injection to

prevent pain during dental work. (Because benzocaine is less soluble than lidocaine, it cannot be used in this manner)

Why is benzocaine is less soluble than lidocaine?

Hydrogen bondi...

Hydrogen bondi...

The le

ngth of ..

.

0% 0%0%

1. Hydrogen bonding by benzocane

2. Hydrogen bonding by lidocane

3. The length of the the lidocaine chain

Hydrolysis of Esters and AmidesAn ester is treated with water in the presence of a strong acid causes hydrolysis to take place.

Acid-catalyzed hydrolysis is the reverse of the esterification

An excess of water pushes the equilibrium to the right.

Saponification : Making Soap

Ester hydrolysis by reaction with a base(frequently NaOH or KOH) .

The product of saponification is a carboxylate anion; rather than a free carboxylic acid.

Hydrolysis of AmidesAmides undergo hydrolysis with heating in the presence of acids or bases.Under acidic conditions, the carboxylic acid and amine salt are obtained,

This is similar to the cleavage of proteins that takes place in digestion

• Under basic conditions, the neutral amine and carboxylate anion are produced

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Polyamides and Polyesters• Nylons are polyamides

produced by reaction of diamines with diacids.

• Nylon 66 is made by heating a six-carbon dicarboxylic acid with a six-carbon diamine) at 280°C.

► Nylon being pulled from the interface between adipoyl chloride and hexamethylenediamine.

• Diacids and dialcohols react to yield polyesters. The most widely used polyester is made by the reaction of terephthalic acid with ethylene glycol. • As a clothing fiber, has the trade name Dacron Under the

name Mylar it is used in plastic film and recording tape.• Its chemical name, poly(ethylene terephthalate) or PET, is

usually applied when it is used in clear, flexible soft-drink bottles.

Phosphoric Acid Derivatives• Phosphoric acid is an inorganic acid with

three ionizable hydrogen atoms (red), allowing it to form three different anions.

• Just like a carboxylic acid, phosphoric acid reacts with alcohols to form phosphate esters. It may be esterified at one, two, or all three of its groups by reaction with an alcohol.

Phosphate esterFormed by reaction of an alcohol with phosphoric acid;

May form MonoesterDiester or a Triester

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• If two molecules of phosphoric acid combine to lose water, they form a phosphoric acid anhydride. • The resulting acid reacts with yet another phosphoric

acid molecule to give triphosphoric acid.• These acids can also form esters, which are known

as diphosphates and triphosphates.

Biochemical Reactions: ATPADP

• Transfer of phosphoryl groups from one molecule to another (phosphorylation) is used in the regulation of metabolic cycles

Phosphoryl groups are often provided by adenosine triphosphate, ATP, which is converted to ADP in a reaction accompanied by the release of energy