Carboxylic Acids and Carboxylic Acid Derivatives

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Carboxylic Acids and Carboxylic Acid Derivatives

• Chapter 15
• Pages 408-438

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Structure of Carboxylic Acids

• The carboxyl group is shown in red and may be
  written in the condensed form -COOH.
• The term carboxylic is taken from the terms
  carbonyl and hydroxyl, the two structures that
  make up the carboxyl group.

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Properties of Carboxylic Acids

• Very polar compounds
• Can hydrogen bond to one another and to water
• Boil at higher temperatures than aldehydes,
  ketones, or alcohols
• Smaller carboxylic acids are soluble in water
• Lower molecular weight acids have sharp, sour
  tastes and unpleasant aromas
• Longer chain carboxylic acids are called fatty
  acids and are important components of biological
  membranes

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Naming Carboxylic Acids - IUPAC

• Determine the name of the parent compound, the
  longest continuous chain containing the carboxyl
  group.
• Replace the e ending with the suffix oic acid.
  If there are two carboxyl groups, the suffix is
  dioic acid.
• Number the chain so the carboxyl carbon is number
  1.
• Name and number substituents.

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Naming carboxylic acids of cycloalkanes

• Add the suffix carboxylic acid to the name of the
  cycloalkane or substituted cycloalkane.
• The carboxyl group is always numbered 1.
• Other substituents are named and numbered as
  usual.

Cyclopentanecarboxylic acid
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Name the following.
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Name the following.
2,4-dimethylpentanoic acid
2-ethylcyclopentanecarboxylic acid
3-methylcyclohexanecarboxylic acid
2,4-dichlorobutanoic acid
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Common Carboxylic Acids
Name Structure Source
Formic acid HCOOH Ants
Acetic acid CH3COOH Vinegar
Propionic acid CH3CH2COOH Swiss Cheese
Butyric acid CH3(CH2)2COOH Rancid butter
Stearic acid CH3(CH2)16COOH Beef fat
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Draw structures for the following.

• 2,3-dihydroxybutanoic acid
• 2-bromo-3-chloro-4-methylhexanoic acid
• 1,4-cyclohexanedicarboxylic acid
• 4-hydroxycyclohexanecarboxylic acid
• Formic acid
• Acetic acid

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Naming Aromatic Carboxylic Acids

• These are usually named as derivatives of benzoic
  acid.
• Generally, the oic acid or ic acid suffix is
  attached to the appropriate prefix.

o-bromobenzoic acid
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Naming Aromatic Carboxylic Acids

• Often, the phenyl group is treated as a
  substituent.

2-phenylethanoic acid
4-phenylpentanoic acid
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Draw structures for the following.

• 2,4,6-tribromobenzoic acid
• 2,2,2-triphenylethanoic acid
• 3-phenylhexanoic acid
• 3-phenylcyclohexanecarboxylic acid

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Preparation of Carboxylic Acids

• As discussed in Ch 14, carboxylic acids can be
  prepared from the oxidation of primary alcohols
  and/or aldehydes.
• 1º alcohol ? Aldehyde ? Carboxylic acid
• Examples
• 1-propanol
• 2-methylbutanal

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Carboxylic acid - ACID

• Carboxylic acids act as acids because they are
  proton (H) donors. They are weak acids that
  dissociate to form a carboxylate ion and a
  hydrogen ion as shown
• carboxylic acid carboxylate anion
  hydrogen ion

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Acid/Base Reaction

• Since a carboxylic acid acts as an acid, it will
  neutralize a strong base like NaOH or KOH to form
  water and the salt of the carboxylic acid.
• Acid Base
  Salt water

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Acid/Base Reaction

• Naming the Salt of the Carboxylic Acid
• Replace the ic acid suffix with ate
• Place the name of the metal cation from the base
  first
• EX CH3COOH KOH CH3COO -K H2O
• ethanoic acid potassium
  ethanoate

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Examples

• Write a balanced equation and name the products
  that are formed.
• Acetic acid sodium hydroxide ?
• Benzoic acid potassium hydroxide ?

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YOU TRY THESE!

• Propanoic acid potassium hydroxide ?
• Ethanol
• Butanedial
• Hexanoic acid sodium hydroxide ?

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Structure of Esters

• Esters are carboxylic acid derivatives.
• They are formed from the reaction of a carboxylic
  acid with an alcohol.

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Formation of an EsterEsterification
H, heat
Carboxylic acid alcohol Ester
Water
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Properties of Esters

• Mildly polar
• Have pleasant aromas
• Found in natural foodstuffs (banana oil,
  pineapples, raspberries, etc.)
• Boil at approximately the same temperature as
  aldehydes or ketones of similar molecular weights
• Simpler ones are somewhat soluble in water

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Naming Esters

• Use the alkyl portion of the alcohol as the first
  name.
• Remove the ic acid ending of the carboxylic acid
  and replace it with ate.
• The same naming rules apply if the common name of
  the carboxylic acid is used.

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Examples of Ester Names
Methyl ethanoate (methyl acetate)
Propyl ethanoate (propyl acetate)
Methyl benzoate
Methyl m-bromobenzoate
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You Try These!
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Answers to You Try These!

• Cyclopentyl ethanoate
• (cyclopentyl acetate)
• Ethyl cyclohexanecarboxylate
• Methyl p-nitrobenzoate
• Methyl butanoate

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Esterification Reactions
H, heat
Ethanoic acid ethanol (Acetic Acid)
Ethyl ethanoate (Ethyl acetate)
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Esterification

• Butanoic Acid Methanol
• How would you make ethyl propanoate from only
  alcohols?

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Esterification

• Fats and oils are triesters of the alcohol
  glycerol.
• Carboxylic acid alcohol
  ester water

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Formation of Soap - Saponification

• When esters are hydrolyzed by saponification, the
  products are soaps.

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Saponification

• Base-catalyzed hydrolysis of esters
• Ester water OH C.A. salt alcohol
• SOAP is a salt of long-chain carboxylic acids
  AKA Fatty Acid Salts
• Lower molecular weight salts (lt12 carbons) have
  high water solubility and large bubbles
• K salts are more water soluble than Na salts

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Saponification

• Ester water base C.A. salt alcohol
• O O
• CH3CH2COCH3 H2O KOH CH3CH2COK
• Methyl ethanoate potassium ethanoate
• CH3OH
• methanol

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Acid Chlorides
IUPAC name - Replace the oic acid ending of the
IUPAC name with oyl chloride. Common name
Replace the ic acid ending of the common name
with yl chloride.
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Examples of Acid Chlorides
Ethanoyl chloride (acetyl chloride)
3-bromopropanoyl chloride
p-chlorobenzoyl chloride (4-chlorobenzoyl
chloride)
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Properties of Acid Chlorides

• Noxious, irritating chemicals
• Slightly polar
• Boil at approximately the same temperature as
  aldehydes or ketones of similar molecular weights
• React violently with water

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Formation of Acid Chlorides
Carboxylic acid Acid
Chloride ( inorganic products)
Ethanoic acid Ethanoyl chloride (acetic
acid) (acetyl chloride)
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Hydrolysis of Acid Chlorides
Acid chloride water Carboxylic acid
Hydrochloric acid
Ethanoyl chloride ethanoic acid (acetyl
chloride) (acetic acid)
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Acid Anhydrides
An acid anhydride is two carboxylic acids with a
water molecule removed. Anhydride means without
water.
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Formation of Acid Anhydrides
Carboxylic acid
Carboxylic acid
Water
Acid anhydride