carboxylic acids and carboxylic acid derivatives chapter 14

Carboxylic Acids and Carboxylic Acid DerivativesChapter 14

14.1 Carboxylic Acids•Structure and Physical Properties

▫The carboxyl group of the carboxylic acid consists of a carbonyl group and a hydroxyl group

▫Both are very polar ▫This means carboxylic acids are polar▫They bond to each other through H-bonding

as well as to water molecules▫Because of the strong intermolecular bonds

of the H-bonds, they boil at higher temps than aldehydes, ketones or alcohols of similar molecular mass

14.1 Carboxylic Acids

•Structure and Physical Properties

Carbonyl Hydroxyl


•Structure and Physical Properties▫Compare boiling points on page 453

▫Much like alcohols, the smaller the carboxylic acid, the more soluble it is in water.

▫ As the carbon chain grows on the carboxylic acid, solubility decreases because it becomes more like a hydrocarbon and therefore, less polar.

14.1 Carboxylic Acids•Structure and Physical Properties

▫Carboxylic acids with lower molecular masses have a very sour taste and bad smells

▫Formic acid is what causes the burning when you are bit by an ant!

▫Acetic acid is found in vinegar▫Propionic acid gives swiss cheese its tangy

flavor▫Butyric acid causes the smell associated with

rancid butter and gas gangrene▫http://www.nlm.nih.gov/medlineplus/ency/artic

le/000620.htm

14.1 Carboxylic Acids•Nomenclature (IUPAC)

▫Determine the parent compound (the longest continuous carbon chain containing the carboxyl group.)

▫Number the chain so that the carboxyl carbon is carbon-1.

▫Replace the –e ending of the parent alkane with the suffix –oic acid. If there are 2 carboxyl groups, the suffix –dioic acid is used.

▫Name and number the substituents the usual way.


•Nomenclature (IUPAC)▫A carboxylic acid with 1 carboxyl group

Butanoic Acid

▫A carboxylic acid with 2 carboxyl groups

Butanedioic Acid


•Nomenclature (IUPAC)▫Name the following:


•Nomenclature (IUPAC)▫Carboxylic acid derivatives of cycloalkanes

are named by adding the suffix carboxylic acid to the name of the cycloalkane or substituted cycloalkane.

▫The carboxyl group with always be on carbon-1 and the other substituents named and numbered as usual.


•Nomenclature (IUPAC)▫Name the following:


•Nomenclature (Common)▫Table 14.1 on page 456 shows sources of

common names▫Common names end in –ic rather than –oic.▫In this system , substituted carboxylic acids

are named as derivatives of the parent compound.

▫Greek letters are used to indicate position of the substituent. The carbon bonded to the carboxyl carbon is the alpha carbon, the next is beta…and so on.


•Nomenclature (Common)▫Alpha (α)▫Beta (β)▫Gamma (γ)▫Delta (δ)▫Epsilon (Ε)▫Zeta (ζ)


•Nomenclature (Aromatic Carboxylic acids)▫Benzoic acid is the simplest aromatic

carboxylic acid▫Can be named using either system as

derivatives of benzoic acid▫The –oic acid or –ic acid is attached to the

appropriate prefix▫Common names are frequently used (See

page 458)


•Nomenclature (Aromatic Carboxylic acids)▫The phenyl group is often treated as the

substituent and the name comes from the parent chain attached to the benzene (alkanoic parent chain)

14.1 Carboxylic Acids• Some Important Carboxylic Acids

▫Larger carboxylic acids have very strong, foul odors

▫Pentanoic (valeric) acid from the valerian plant has an aroma described to be like over-ripe cheese or a wet dog

▫Extracts of it have been used for thousands of years as a sedative

▫Hexanoic (caproic) acid was first isolated from goats and said to smell like goats.

▫Heptanoic (enanthic) acid is said to smell like rancid oil.


•Some Important Carboxylic Acids▫When carboxylic acids react with alcohols

they produce esters which create the fragrance and flavor of many fruits.

▫More pages 461-462


•Reactions Involving Carboxylic Acids▫Preparation of carboxylic acids (oxidation

reaction)▫Carboxylic acids are produced by the

oxidation of a primary alcohol or aldehydes.▫Chromic acid is a common oxidizing agent.


•Preparation of carboxylic acid▫Write the mechanism (equation) for the

oxidation of butanol to butanoic acid.

14.1 Carboxylic Acids•Acid-Base Reactions

▫Carboxylic acids behave as acids because they donate protons.

▫They are weak acids that dissociate to form a carboxylate ion and a hydrogen ion

▫Carboxylic acids do not completely dissociate (only 5% ions created)


•Acid-Base Reactions▫When strong bases are added to carboxylic

acid, neutralization occurs.▫The hydrogen ions from the acid and

hydroxide ions from the base form water.▫Carboxylic acid salt is also formed.

+ NaOH → + H2O

Butyric acid Sodium Sodium butyrate Waterhydroxide


•Acid-Base Reactions▫Notice that the carboxylic acid salt

changed from –ic to –ate.▫Acetic acid would become acetate, benzoic

acid would become benzoate.▫In the front of the name, you place the

cation, in this case it was sodium.


•Esterification▫Carboxylic acids react with alcohol to form

esters and water▫R and R1 represent alkyl groups (can be

the same or different) Acid

Carboxylic Alcohol EsterWater

Acid

14.2 Esters

•Structure and Physical Properties▫Mildly polar, pleasant aromas▫Found in natural foods (banana oil,

pineapple, raspberries…etc.)▫Boils at approx. same temperature as

aldehydes and ketones of similar mass▫Somewhat soluble in water

14.2 Esters

•Nomenclature▫Esters are carboxylic acid derivatives

(organic compounds that come from carboxylic acids)

▫Formed from the reaction of a carboxylic acid and an alcohol

▫1. Use the alkyl or aryl portion of the alcohol name as the first name

▫2. The –ic acid ending of the carboxylic acid is replaced with –ate and follows the first name

14.2 Esters

•Nomenclature▫Examples

Ethyl Butanoate

14.2 Esters

•Reactions Involving Esters▫Preparation of Esters (Esterification)

Dehydration reaction Requires heat & small amount of acid

Acid

Carboxylic Alcohol EsterWater

Acid

14.2 Esters

•Esterification ▫Example

Write an equation showing the esterification of propyl ethanoate.

14.2 Esters

•Reactions Involving Esters▫Hydrolysis of Esters

Hydration reaction (adding water)

Ester Water C.A. Alcohol

Requires heat (a small amount of acid may also be added)

Reverse of esterification

14.2 Esters

•Hydrolysis of Esters▫Example

Ethyl methanoate Methanoic

Ethanolacid

14.2 Esters

•Saponification▫When you use a base instead of an acid as a

catalyst, you make carboxylic acid salt.

14.2 Esters

•Saponification ▫Examples

Propyl ethanoate + water

Propyl hexanoate + water

14.2 Esters

•Saponification▫Fats and oils are triesters of the alcohol,

glycerol (they have 3 esters in their structure) AKA triglycerides- solid fats from animals or

liquid oils from plants

14.2 Esters•Saponification

▫Saponification is when esters are hydrated (water added)

▫Soap is produced (soaps are the salts of long chain carboxylic acids- fatty acid salts)

▫Roman Legend!- Soap was discovered by washerwomen after a heavy rain on Mons Sapo “Mount Soap.” The rain mixed with the remains of animal sacrifices, wood ash & animal fat. The ingredients of soap accidently came together (H2O, fat & K2CO3/KOH from the ash). The soap ran into the Tiber River where its value was quickly realized.

14.2 Esters•Saponification

▫We still make soap the same way Water, strong base, fats/oils from animals or plants Solubility of the soap is determined by the C-chain

length Up to 12 carbons is good (has lower mass) and

gives larger bubbles Higher mass carbon chains (14-20 carbons) are

less soluble in water and create smaller bubbles and a fine lather

Solubility is also affected by the cation used, whether KOH or NaOH. K+ is more soluble than Na+ when formed with the carboxylic acid.

14.2 Esters

•Saponification▫How does soap remove oil/grease?

The long hydrocarbon chain of soaps resembles alkanes & they dissolve other nonpolar compounds (oil/grease- “like dissolves like”).

Large hydrocarbon- hydrophobic Carboxylate end- hydrophilic When soap dissolves in water, the carboxylate

end dissolves the carbon chain is repelled so a thin layer of soap forms on the surface (chains protrude out).

14.2 Esters

•Saponification▫How does soap remove oil/grease?

When soap comes into contact with oil or grease the C-chaindissolves in the oil/grease but the polar carboxylate groupremains dissolved in water

14.2 Esters• Saponification

▫ How does soap remove oil/grease? When soap molecules

form around oil/grease, you get micelles. Micelles repel each

other because they are surrounded by the carboxylate ions in the water.

Mechanical action is what creates the micelles and removes them.

14.2 Esters

•Condensation Polymers▫Recall from chapter 11

A polymer is a macromolecule made from the combination of smaller monomers

Can be made from a single polymer (same)- “homopolymers.”

OR 2 different monomers- “heteropolymers”

14.2 Esters

•Condensation Polymers▫Polyesters are heteropolymers- also called

condensation polymers▫Formed by polymerization of monomers in

a reaction that forms water or alcohol.▫This reaction is created using a

dicarboxylic acid and a dialcohol (diol).▫DO NOT NEED TO KNOW REACTION

14.2 Esters

•Polyesters▫When formed as fibers, polyesters are used

as fabric for clothing.▫Trendy in the 70’s during the disco era, it

lost popularity after that.▫Along with other synthetic fibers, it has

become more popular since the introduction of microfiber technology.

•Polyester▫Can be created into fibers half the diameter

of silk. This creates a fabric that drapes, retains its shape, is lightweight, wrinkle resistant & strong.

▫Polyester is used to make mylar (balloons) Formed into thin sheets & coated with

aluminum foil. Also used as the base for recording tapes and photo film.

14.2 Esters

14.3 Acid Chlorides and Acid Anhydrides•Acid Chlorides

▫Carboxylic acid derivative

•Nomenclature▫Replace the –ic acid ending of the common

name with the –yl chloride OR replace the –oic acid ending of the IUPAC name of the carboxylic acid with –oyl chloride.

Butanoyl Chloride


▫Nomenclature Examples


▫Noxious, irritating chemicals▫Slightly polar▫Boil at approx. the same temperature as

aldehydes and ketones of similar mass▫React violently with water▫Only use is to make esters and amides

14.3 Acid Chlorides and Acid Anhydrides•Synthesis of Acid Chlorides

+ Inorganic products

Carboxylic acid Acid Chloride

▫The carboxylic acid must react with one of 3 Inorganic acid chlorides seen above and below the reaction arrow.

14.3 Acid Chlorides and Acid Anhydrides•Synthesis of Acid Chlorides

▫Example

Inorg. Acid chlor.

+ Inorganic products

Benzoic acid Benzoyl Chloride

14.3 Acid Chlorides and Acid Anhydrides•Acid Anhydrides

▫2 carboxcylic acids with awater removed.

▫Anhydride means “withoutwater”

•Nomenclature▫Symmetrical if both acyl groups are the

same.▫Name by replacing the acid ending of the

carboxylic acid with the word anhydride

14.3 Acid Chlorides and Acid Anhydrides•Acid Anhydride

▫Nomenclature example Ethanoic Anhydride

14.3 Acid Chlorides and Acid Anhydrides•Acid Anhydride

▫Nomenclature Unsymmetrical anhydrides have 2 different acyl

groups Name by arranging the names of the 2 parent

carboxylic acids followed by the word anhydride Can arrange by size or alphabetical

butanoic pentanoic anhydride

14.3 Acid Chlorides and Acid Anhydrides•Synthesis of Acid Anhydrides

▫Cannot form in a reaction with a carboxylic acid.▫See pg 479 for mechanism▫Acid chloride reacts with a carboxylate ion to

form an acid anhydride and a chlorine ion.

Carbox. ion

+ Cl-

Ethanoyl chloride Ethanoic anhydride

carboxylic acids and carboxylic acid derivatives chapter 14

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