Carboxylic Acids, Esters, Amines, and Amides

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Carboxylic Acids, Esters, Amines, and Amides
Carboxylic acids and esters are two families of
organic molecules that contain a carbonyl group
(CO) singly bonded to an oxygen atom.

• A carboxylic acid contains a carboxyl group
  (COOH).

• An ester contains an alkoxy group (OR) bonded to
  
• the carbonyl carbon.

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Carboxylic Acids, Esters, Amines, and Amides
Amines and amides are nitrogen-containing organic
molecules.

• An amine is an organic nitrogen compound
• formed by replacing one or more hydrogen atoms
• of ammonia (NH3) with alkyl groups.

• An amide is a carbonyl compound that contains a
• nitrogen atom bonded to the carbonyl carbon.

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NomenclatureNaming a Carboxylic Acid (RCOOH)
To name a carboxylic acid using the IUPAC system

• Find the longest chain containing the COOH
• group, and change the -e ending of the parent
  
• alkane to -oic acid.

• Number the chain to put the COOH group at C1,
  but
• omit 1 from the name. Apply all other
• nomenclature rules.

CH3
hexane ? hexanoic acid
CH3CHCHCH2CH2
OH
Answer 4,5-dimethylhexanoic acid
CH3
1
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NomenclatureNaming a Carboxylic Acid (RCOOH)

• Many simple carboxylic acids are referred to by
• their common names. A common name uses the
• suffix -ic acid.

formic acid
acetic acid
benzoic acid
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NomenclatureNaming an Ester (RCOOR)
To name an ester using the IUPAC system

• Name the R' group bonded to the oxygen atom as
• an alkyl group.

• Name the RCO group by changing the -ic acid
• ending of the parent carboxylic acid to the
• suffix -ate.

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NomenclatureNaming an Ester (RCOOR')
Sample Problem 13.2
Give the IUPAC name for the following ester
Name the R group bonded to the O atom as an
alkyl group.
Step 1
methyl group
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NomenclatureNaming an Ester (RCOOR')
Sample Problem 13.2
Step 2
Name the acyl group (RCO-) by

• Changing the -ic acid ending of the
  parent carboxylic acid to -ate.

• This becomes the second part of the name.

Answer methyl butanoate
derived from butanoic acid ? butanoate
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Physical Properties of Carboxylic Acids and Esters

• Carboxylic acids and esters are polar compounds.

• Only carboxylic acids can undergo intermolecular
  
• hydrogen bonding.

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Physical Properties
Carboxylic acids also have higher boiling
points than esters because esters are incapable
of intermolecular hydrogen bonding.
methyl acetate
propanoic acid
Increasing boiling point
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Physical Properties
Carboxylic acids have higher boiling points than
similar alcohols because there are more
hydrogen bonding interactions possible than
alcohols.
Increasing boiling point
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Interesting Carboxylic Acids

• Simple carboxylic acids have foul or biting
  odors.

• Formic acid (HCO2H) is responsible for the sting
• of some types of ants.

• Acetic acid (CH3CO2H) is the sour-tasting
• component of vinegar it can be made by air
• oxidation of ethanol when wine goes bad.

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Focus On Health MedicineSkin Care Products

• Several skin care products purported to smooth
• fine lines contain a-hydroxy acids.

• General structure of an a-hydroxy acid

• These acids work by removing the outer, older
  layer
• of skin cells, revealing the healthier looking,
  new
• cells underneath.

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Focus On Health Medicine Aspirin and
Anti-Inflammatory Agents

• Common pain relievers that are also anti-
• inflammatory agents contain a carboxyl group

aspirin
ibuprofen
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Interesting Carboxylic AcidsAspirin and
Anti-Inflammatory Agents

• Pain relievers work because they block the
• synthesis of prostaglandins, compounds
• responsible for pain responses in the body.

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The Acidity of Carboxylic Acids

• Carboxylic acids are proton (H) donors

• They are weak acids compared to inorganic acids
• like HCl or H2SO4.

• Only a small percentage of a carboxylic acid is
• ionized in aqueous solution.

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The Acidity of Carboxylic AcidsReaction with
Bases

• Carboxylic acids react with bases such as NaOH
• to form water-soluble salts.

• A proton is removed from acetic acid to form its
  
• conjugate base, the acetate anion, which is
  present
• in solution as its sodium salt, sodium acetate.

• Hydroxide (OH-) gains a proton to form neutral
  H2O.

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The Acidity of Carboxylic AcidsCarboxylate
AnionsSalts of Carboxylic Acids

• The salts of carboxylic acids formed by
  acid-base
• reactions are water-soluble ionic solids.

• Thus, the reaction will turn a water-insoluble
• carboxylic acid into a water-soluble carboxylic
• acid salt.

O
O
CH3(CH2)6COH octanoic acid

Na -OH base
CH3(CH2)6CO- Na sodium octanoate
HOH
Water-insoluble
Water-soluble
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The Acidity of Carboxylic AcidsHow Does Soap
Clean Away Dirt?

• Soap has been used by humankind for 2000 years.

• Soaps are salts of carboxylic acids that have
• many C atoms in a long hydrocarbon chain.

• A soap molecule has two parts

1. The ionic end is called the polar head.

1. The carbon chain of nonpolar CC and CH bonds is
   called the nonpolar tail.

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The Acidity of Carboxylic AcidsHow Does Soap
Clean Away Dirt?

• Structure of a soap molecule

polar head ionic end
nonpolar tail nonpolar end
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The Acidity of Carboxylic AcidsHow Does Soap
Clean Away Dirt?

• In water, soap forms micelles, spherical
  droplets
• with the ionic heads on the surface and the
  nonpolar
• tails packed together in the interior.

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The Acidity of Carboxylic AcidsHow Does Soap
Clean Away Dirt?

• Nonpolar hydrocarbon tails trap nonpolar
  material
• like grease and oil.

• The polar head remains on the surface, sealing
• off the grease and oil, and washing away in
• the presence of water.

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Reactions Involving Carboxylic Acidsand Esters

• Carboxylic acids and esters undergo a common
• type of reactionsubstitution.

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Reactions Involving Carboxylic Acidsand
EstersEster Formation

• Carboxylic acids react with alcohols to form
• esters.

• Here, the OR' group replaces the OH group.

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Reactions Involving Carboxylic Acidsand
EstersEster Formation

• Formation of an ester is done by the Fisher
• esterification

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Reactions Involving Carboxylic Acidsand
EstersEster Hydrolysis

• Treatment of an ester (RCOOR') with water in the
  
• presence of an acid catalyst forms a carboxylic
  
• acid (RCOOH) and a molecule of alcohol (R'OH).

• Here, the OH group replaces the OR' group.

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Reactions Involving Carboxylic Acidsand
EstersEster Hydrolysis

• This reaction is a hydrolysis, since bonds are
• cleaved by reaction with water.

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Focus on Health MedicineOlestra, a Synthetic
Fat

• Triacylglycerols, common naturally occurring
• esters, contain three ester groups, each with a
  long
• C chain.

• They are lipids, water-insoluble organic
• compounds, present in fats and oils.

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Focus on Health MedicineOlestra, a Synthetic
Fat

• Animals store energy in the form of
  triacylglycerols.

• Using enzymes called lipases, the three ester
• bonds are hydrolyzed when the triacylglycerol
  is
• metabolized.

• Diets high in fat lead to obesity, so the fake
  fat
• olestra (Olean) was invented to replace some
• triacylglycerols in snack foods.

• The lipase enzymes cannot hydrolyze the olestra,
  
• so it passes through the body unmetabolized,
• providing no calories to the consumer.

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Focus on Health MedicineOlestra, a Synthetic
Fat

• Hydrolysis of a triacylglycerol by lipase

O
HO
C
R
CH2O
R

CH2OH
H2O
R
R
CH O
HO
CH OH

lipase
HO
R
CH2O
R
CH2OH

glycerol
3 long-chain carboxylic acids
The 3 bonds that break are drawn in red.
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Focus on Health MedicineStructure of Olestra
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AminesStructure and Classification

• Amines are organic nitrogen compounds, formed by
• replacing one or more hydrogen atoms of ammonia
  
• (NH3) with alkyl groups.

• Amines are classified by the number of alkyl
  groups
• bonded to the N atom.

• A primary (1o) amine contains
• 1 CN bond, and has the
• general structure RNH2.

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AminesStructure and Classification

• A secondary (2o) amine
• contains 2 CN bonds, and
• has the general structure R2NH.

• A tertiary (3o) amine has
• 3 CN bonds, and has the
• general structure R3N.

• The 1o, 2o, and 3o amine N atom has a lone pair
  of
• e-, which is omitted in condensed structures.

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AminesStructure and Classification

• The amine N has a trigonal pyramidal shape,
• with bond angles of 109.5o.

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AminesStructure and Classification

• The amine N atom can also be part of a ring.

• Morphine and atropine each contains a nitrogen
• atom in a ring.

• They are alkaloidsnaturally occurring amines
• derived from plant sources.

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NomenclatureAmines

• To name a primary (1o) amine, name the alkyl
  group
• bonded to the nitrogen atom and add the
• suffix -amine.

• For 2o and 3o amines with different alkyl
  groups,
• alphabetize the names of the alkyl groups.

• 2o and 3o amines with identical alkyl groups are
  
• named using the prefix di- or tri-

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NomenclatureAmines
Sample Problem 13.8
Name each amine.
a.
For a 1amine, name the alkyl group and add the
suffix -amine.
Answer pentylamine
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NomenclatureSecondary and Tertiary Amines
Sample Problem 13.8
b.
For a 2amine, name each alkyl group, alphabetize
the names, and add the suffix -amine.
Answer ethylmethylamine
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NomenclatureAromatic Amines

• Amines with the N directly bonded to a benzene
• ring are named as derivatives of aniline.

• Use the prefix N- before any alkyl group bonded
  
• to the amine nitrogen.

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Physical Properties

• Many low molecular weight amines have very foul
  
• odors like rotting fish, urine, and bad breath.

• Amines are polar molecules, containing either
• polar CN or polar HN bonds.

• 1o and 2o amines can have intermolecular
• hydrogen bonding

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Physical Properties

• 1o and 2o amines have higher boiling points than
• compounds that do not have intermolecular
• hydrogen bonding.

CH3CH2OCH2CH3 diethyl ether bp 38 oC
CH3CH2CH2CH2NH2 butylamine bp 78 oC
Increasing boiling point
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Physical Properties

• 1o and 2o amines have lower boiling points than
• alcohols, as alcohols have stronger
  intermolecular
• hydrogen bonds.

CH3CH2CH2CH2NH2 butylamine bp 78 oC
CH3CH2CH2CH2OH 1-butanol bp 117 oC
Increasing boiling point
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Physical Properties

• 3o amines have lower boiling points than 1o or
• 2o amines of comparable size because they have
  no
• NH bonds.

Increasing boiling point
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Amines as Bases

• Amines are bases they are proton (H) acceptors.

• This acidbase reaction occurs with 1º, 2º, and
• 3º amines.

• Amines are weak bases compared to inorganic
• bases like NaOH.

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Amines as BasesReactions of Amines with Acids

• Amines react with acids (HCl) to form water-
• soluble salts.

conjugate acid
conjugate base
base
acid
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Amines as BasesAmmonium Salts

• When an amine reacts with an acid, the product
  is an
• ammonium salt.

• The amine forms a positively charged ammonium
• ion and the acid forms an anion.

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Amines as BasesAmmonium Salts
To name an ammonium salt

• Change the suffix -amine of the parent
• amine to the suffix -ammonium.

• Add the name of the anion.

Answer triethylammonium acetate
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Amines as BasesAmmonium Salts

• A water-insoluble amine is converted to a water-
• soluble ammonium salt by treatment with acid.

water-insoluble
water-soluble
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Focus on Health MedicineAmmonium Salts as
Useful Salts

• Many amines with medicinal properties are sold
• as their ammonium salts, which are transported
• through the aqueous bloodstream.

• The antihistimine Benadryl is sold as the salt
• diphenhydramine hydrochloride.

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Amides
Amides contain a carbonyl group bonded to a N
atom.
Amides are classified based on the number of
C atoms bonded to the N atom.

• A primary (1o) amide contains
• 1 CN bond.

• It is abbreviated as RCONH2.

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Amides

• A secondary (2o) amide
• contains two CN bonds,
• and is abbreviated RCONHR'.

• A tertiary (3o) amide
• contains three CN bonds,
• and is abbreviated RCONHR'2.

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NomenclatureNaming an Amide

• All 1o amides are named by replacing the -oic
  acid
• ending of the parent carboxylic acid with
  -amide.

NH2
derived from benzoic acid ? benzamide
derived from acetic acid ? acetamide
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NomenclatureNaming an Amide
To name a 2º or 3º amide

• Name the alkyl group (or groups) bonded to
• the N atom of the amide. Use the prefix N-
• preceding the name of each alkyl group.

• Name the RCO group with the suffix -amide.

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NomenclatureNaming an Amide
Sample Problem 13.12
Name the following amide HCONHCH2CH3
Name the alkyl group on the N atom, and precede
its name with N-.
Step 1
Name N-ethyl
ethyl group
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NomenclatureNaming an Amide
Sample Problem 13.12
Step 2
Name the acyl group with -amide.
derived from formic acid ? formamide
Answer N-ethylformamide
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Physical Properties
1o and 2o amides have higher boiling points
than 3o amides and esters because of
intermolecular hydrogen bonding.
Increasing boiling point
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Hydrolysis of Esters and AmidesAmide Hydrolysis

• Treatment of an amide with water in the presence
• of an acid catalyst (HCl) forms a carboxylic
  acid
• and an ammonium salt.

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Hydrolysis of Esters and AmidesAmide Hydrolysis

• Amides are also hydrolyzed in aqueous base to
• form carboxylate anions and a molecule of
  ammonia
• (NH3) or amine.

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Interesting Amines and AmidesCaffeine and
Nicotine

• Caffeine and nicotine are widely used stimulants
• of the central nervous system that contain
• nitrogen atoms in rings.

• They are alkaloidsnaturally occurring amines
• derived from plants.

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Focus on the Human BodyEpinephrine and Related
Compounds

• A hormone is a compound produced by an
• endocrine gland, which travels through the
  blood-
• stream to a target tissue or organ.

• Epinephrine (adrenaline) is a hormone made from
• norepinephrine, the neurotransmitter.

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Focus on the Human BodyEpinephrine and Related
Compounds

• Danger or emotional stress causes the formation
• of epinephrine.

• The body will metabolize stored carbohydrates
• to form glucose, which is further metabolized
  to
• provide an energy boost.

• The heart rate increases and lung passages are
• dilated.

• This effect is known as a rush of adrenaline
  or
• fight-or-flight response.

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Focus on Health MedicinePenicillin

• The antibiotic properties of penicillin were
  first
• discovered in 1928 by Sir Alexander Fleming.

• Penicillin interferes with the enzyme that
• synthesizes bacterial cell walls, killing the
• bacterium.

• All penicillins contain a ß-lactam

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Focus on Health MedicineCommon Penicillin Used
Today
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