UNIT 2 : Functional Groups Occurring in

Natural Compounds

2.1 Classes of organic compounds and functionality

2.2 Hydrocarbons

2.3 Alcohols and ethers

2.4 Aldehydes and ketones

2.5 Carboxylic acids and esters

2.6 Amines and amides

2.1 Classes of organic compounds and functionality

 Organic compounds are classified as hydrocarbons, alcohols, ethers,

aldehydes, ketones, carboxylic acids, esters, amines and amides …etc

 A functional group is defined as an atom or a group of atoms that gives

some properties to an organic compound. A functional group is attached
to the Carbon chain through its free valency or valencies. It acts as the
reactive site of the molecule.
 A functional group is a specific group of atoms or bonds within
a compound that is responsible for the characteristic chemical
reactions of that compound.
 Every class of an organic compound is recognized by its functional
group
 The same functional group will behave in a similar fashion, by undergoing
similar reactions, regardless of the compound of which it is a part.
 Functional groups also play an important part in organic compound
nomenclature; combining the names of the functional groups with the
names of the parent alkanes provides a way to distinguish compounds.
 Functional groups play a significant role in directing and controlling organic
reactions.
 In organic chemistry, the most common functional groups are carbonyls
(C=O), alcohols
(-OH), carboxylic acids (CO2H), esters (CO2R), and amines (NH2). ..etc. It is
important to be able to recognize the functional groups and the physical and
chemical properties that they afford compounds.
Summary of the various classes of organic compounds and their functional groups
 2.2 Hydrocarbons

 organic compounds containing only the elements carbon and hydrogen are called
hydrocarbons. The hcs are broadly divided into aliphaic hcs and aromatic hcs.
 We use hydrocarbons every day, mainly as fuels, such as natural gas, acetylene,
propane, butane, and the principal components of gasoline, diesel fuel, and heating
oil. The familiar plastics polyethylene, polypropylene, and polystyrene are also
hydrocarbons.

Classification of hydrocarbons

 Hydrocarbons are further broadly classified into aliphatic and aromatic hydrocarbons

 Aliphatic hydrocarbons ( saturated and unsaturated hydrocarbons):

Alkanes, alkenes, alkynes

 Aromatic hydrocarbons: benzene and benzene derivative compounds

2.2.1 Saturated Hydrocarbons- Alkanes

 Alkanes : are Saturated hydrocarbons. These hydrocarbons contain single bonds

of carbon-carbon and carbon-hydrogen. These hydrocarbons form chain structures
that are open in nature. These hydrocarbons don’t contain any double or triple
bonds. Saturated hydrocarbons are known as the simplest hydrocarbons.
 The general formula for saturated hydrocarbons is CnH2n+2.
 Alkanes, or saturated hydrocarbons, contain only single covalent bonds between
carbon atoms. Each of the carbon atoms in an alkane has sp3 hybrid orbitals and is
bonded to four other atoms, each of which is either carbon or hydrogen.
 The structures of alkanes and other organic molecules may also be represented in
a less detailed manner by condensed structural formulas (or simply, condensed
formulas). Instead of the usual format for chemical formulas in which each
element symbol appears just once, a condensed formula is written to suggest the
bonding in the molecule
Condensed structural formulas for methane, ethane and pentane are shown at the
figure below
The first ten alkanes
Properties of Some Alkanes
Isomers are substances with the same molecular formula but different structures
Example : n-butane and 2-methylpropane are isomers. Both have the molecular
formula C4H10
 The compounds n-butane and 2-methylpropane are structural isomers (the term

constitutional isomers are also commonly used). Constitutional isomers have the

same molecular formula but different spatial arrangements of the atoms in their

molecules.

 The n-butane molecule contains an unbranched chain, meaning that no carbon

atom is bonded to more than two other carbon atoms.

 We use the term normal, or the prefix n, to refer to a chain of carbon atoms

without branching. The compound 2–methylpropane has a branched chain (the

carbon atom in the center of the Lewis structure is bonded to three other carbon

atoms)
The Basics of Organic Nomenclature: Naming Alkanes
 The International Union of Pure and Applied Chemistry (IUPAC) has devised a
system of nomenclature that begins with the names of the alkanes and can be
adjusted from there to account for more complicated structures.
 The nomenclature for alkanes is based on rules:
IUPAC Rules for Alkane Nomenclature
1.Find and name the longest continuous carbon chain.
2. Identify and name groups attached to this chain.
3. Number the chain consecutively, starting at the end nearest a substituent group.
4. Designate the location of each substituent group by an appropriate number and
name.
5. Assemble the name, listing groups in alphabetical order.
6. The prefixes di, tri, tetra etc., are used to designate several groups of the same
kind.
Alkyl Groups

 An alkyl group is formed by removing one hydrogen from the alkane chain and is

described by the formula CnH2n+1. The removal of this hydrogen results in a stem

change from -ane to -yl. Take a look at the following examples. R stands for any

alkyl group
The names and formulas for various alkyl groups formed by the removal of hydrogen
atoms from different locations are given below.
Give the IUPAC name of the following structure

5,7-diethyl-3,4,7-trimethyl-5-propyldecane
 The identical substituents are grouped by first specifying the number of their
positions, and then by adding a prefix to denote the number of groups: di for two,
tri for three, tetra for four, penta for five, etc. The compound below is correctly
named by IUPAC rules as 2,2,4-trimethylhexane. The numbers must be separated
by commas and followed by a hyphen.
1.

2.
Chemical reactions of alkanes

a) Combustion

 Alkanes burn in the presence of oxygen, a highly exothermic oxidation-

reduction reaction that produces carbon dioxide and water.

CH4(g)+2O2(g)⟶CO2(g)+2H2O(g)

 As a consequence, alkanes are excellent fuels.

For example, methane, CH4, is the principal component of natural gas.

 Butane, C4H10, used in camping stoves and lighters is an alkane

 Gasoline is a liquid mixture of continuous- and branched-chain alkanes,each

containing from five to nine carbon atom

b) Substitution reaction
 In a substitution reaction one or more of the alkane’s hydrogen atoms is
replaced with a different atom or group of atoms. No carbon-carbon bonds
are broken in these reactions, and the hybridization of the carbon atoms
does not change.
 For example, the reaction between ethane and molecular chlorine depicted
here is a substitution reaction:
 2.2.2 Unsaturated hydrocarbons (Alkenes and Alkynes)

 Unsaturated hydrocarbons are organic compounds that are entirely made up of

carbon and hydrogen atoms and consist of a double or a triple bond between two
adjacent carbon atoms.
 Unsaturated Hydrocarbons — contain carbon - carbon double or triple bonds (more
hydrogens can be added).

Alkenes
Carbon atoms linked by a double bond are bound together by two bonds, one σ
bond and one π bond.

Ethene, C2H4, is the simplest alkene. Each carbon atom in ethene, commonly
called ethylene, has a trigonal planar structure. The second member of the series
is propene (propylene) .

A few common alkenes

IUPAC Nomenclature of Alkenes
 Step 1. Identify and name the longest continuous chain of C atoms which
contains the double bond(s) (#C + -ene).
 Step 2. Number the longest chain so that the C’s joined by the double bond
have the lowest numbers possible. If the double bond has the same position
starting from either end, use the positions of the substituents to determine
beginning of the chain.
 Step 3. Locate the double bond by the lower numbered carbon atom joined by
the double bond (e.g., 1-butene).
 Step 4. Locate and name attached groups.
 Step 5. Combine the names for the attached groups and the longest chain into
the name.
Chemical Reactions Involving Alkenes
 Alkenes are more reactive than alkanes due to the exposed pi-bonding electrons.
 There are four types of common rxns:
1. Combustion Reactions
2. Addition Reactions
3. Oxidation Reactions of Alkenes
4. Polymerization of Alkenes

1. Combustion Reactions
CnH2n + 1.5nO2 ---> n CO2 + n H2O

C2H4 + 3 O2 ---> 2 CO2 + 2 H2O

C3H6 + 4.5 O2 ---> 3 CO2 + 3 H2O

As with alkanes, combustion of alkenes with insufficient oxygen also produces CO.
2. Addition Reactions
a. Addition of Hydrogen = Hydrogenation

 Hydrogenation generally requires a catalyst such as Pt, Pd and may also require
heat and / or pressure.

 Hydrogenation is used to convert liquid oils to solid fats. As the number of

double bonds is reduced, the melting point of the fat increases. This type of
reaction is called hardening. Pt is a common catalyst.
b. Addition of Halogens = Halogenation

 The double bond reacts rapidly at room temp with either Cl2 or Br2. No catalyst is
needed. F>> Cl > Br >>> I (iodine hardly reacts, fluorine reacts explosively).
 Halogenation can be used as a qualitative test for alkenes
Suspect compound + dilute solution of Br2. If red color disappears then the
compound is probably an alkene.
 c. Addition of water = Hydration
In the presence of acid, water adds to an alkene double bond.

Addition of water to an alkene follows Markovnikov’s rule.

It states that when an unsymmetrical molecule such as HCl or H 2O adds to a double
bond, the double-bonded carbon with the most hydrogens gets the additional
hydrogen.
d. Addition of Hydrogen Halides = Hydrohalogenation

Addition of a hydrogen halide (HX, X = Br, Cl, or I) to an alkene also follows

Markovnikov’s rule.
3. Oxidation Reactions of Alkenes
Oxidation can be defined as either
a) the addition of oxygen to a molecule, or
b) the removal of hydrogen from a molecule.
Common oxidizing agents: oxygen, O2, ozone, O3, potassium permanganate,

KMnO4, potassium dichromate, K2Cr2O7.

Reaction of an alkene with dilute aqueous solution of KMnO4 produces a

dihydroxy alcohol.
Ethylene + KMnO4 -----> CH2(OH)CH2OH [ethylene glycol - used in antifreeze]

Oxidation of an alkene with potassium permanganate, KMnO4, can be a

qualitative test. Suspect compound + aqueous solution of KMnO 4. If purple

color disappears then the compound is probably an alkene
4. Polymerization of Alkenes
 Certain alkenes undergo self-addition reactions in the presence of specific catalysts to
produce molecules called polymers. A polymer is a very large molecule (macromolecule)
made up of repeating units.
 The reaction involves double bonds being converted to single bonds as hundreds or
thousands of molecules bond and form long chains. The large number of molecules bonding
is represented by "n" in the following example polymerization of ethene to form
polyethylene.
heat, pressure
n CH2=CH2 --------------------> (-CH2-CH2-)n
ethene catalysts polyethylene
The word "polymer" comes from the Greek "poly" (many) and "mer" (parts). An addition
polymer is a polymer formed by linking together many alkene molecules through addition
reactions. The monomer is the starting material that becomes the repeating units of polymers. It
is not possible to give an exact formula for a polymer produced by a polymerization reaction
because the individual polymer molecules vary in size. Polymers made from alkenes result in a
very long-chain alkane. As a result, it has the chemical inertness of alkane
Examples of Addition Polymers
Alkynes
 Hydrocarbon molecules with one or more triple bonds are called alkynes;
they make up another series of unsaturated hydrocarbons. Two carbon
atoms joined by a triple bond are bound together by one σ bond and two π
bonds. The sp-hybridized carbons involved in the triple bond have bond
angles of 180°, giving these types of bonds a linear, rod-like shape.
 The simplest member of the alkyne series is ethyne, C2H2, commonly called
acetylene.
Examples of alkynes
Nomenclature of alkynes

 The IUPAC nomenclature for alkynes is similar to that for alkenes except that the
suffix -yne is used to indicate a triple bond in the chain.
For example, CH3CH2C≡CH is called 1-butyne.
Chemical reactions of alkynes
 Chemically, the alkynes are similar to the alkenes.
1. Addition Reactions
 The principal reaction of the alkynes is addition across the triple bond to form
alkanes. These addition reactions are analogous to those of the alkenes.
 Since the C≡C functional group has two π bonds, alkynes typically react even
more readily, and react with twice as much reagent in addition reactions. The
reaction of acetylene with bromine is a typical example:
 a) Hydrogenation. Alkynes undergo catalytic hydrogenation with the same
catalysts used in alkene hydrogenation: platinum, palladium, nickel, and
rhodium.
Hydrogenation proceeds in a stepwise fashion, forming an alkene first, which
undergoes further hydrogenation to an alkane.

b) Halogenation.
 The addition of halogens to an alkyne proceeds in the same manner as halogen
addition to alkenes. The halogen atoms add to an alkyne molecule in a stepwise
fashion, leading to the formation of the corresponding alkene, which undergoes
further reaction to a tetrahaloalkane.
c) Hydrohalogenation.
 Hydrogen halides react with alkynes in the same manner as they do with alkenes.

 Both steps in the above addition follow the Markovnikov rule. Thus, the addition
of hydrogen bromide to 1‐butyne gives 2‐bromo‐1‐butene as the major product
of the first step.
d) Hydration.
 The addition of the elements of water across the triple bond of an alkyne leads to
the formation of aldehydes and ketones.
 Water addition to terminal alkynes leads to the generation of aldehydes, while
nonterminal alkynes and water generate ketones.

 Water adds across the triple bond of an alkyne via a carbocation mechanism.
 Dilute mineral acid and mercury(II) ions are needed for the reaction to occur.
2.Oxidation.
 Alkynes are oxidized by the same reagents that oxidize alkenes.
 Disubstituted alkynes react with potassium permanganate to yield vicinal diketones
(Vic‐diketones or 1,2‐diketones) or, under more vigorous conditions, carboxylic
acids.
3. Combustion .
 Alkynes, like other hydrocarbons, undergo combustion, producing carbon
dioxide and water (with complete combustion) or mixtures of carbon dioxide,
carbon monoxide, carbon, and water (with incomplete combustion).

4. Polymerization.
 Alkynes can be polymerized by both cationic and free‐radical methods. The
reactions and mechanisms are identical with those of the alkenes.
 2.2.3 Aromatic Hydrocarbons
 Benzene, C6H6, is the simplest member of a large family of hydrocarbons, called
aromatic hydrocarbons.

 Aromatic rings (also known as aromatic compounds or arenes) are hydrocarbons

which contain benzene, or some other related ring structure. Benzene, C6H6, is often

drawn as a ring of six carbon atoms, with alternating double bonds and single bonds:
 Carbon-carbon single bonds are longer than carbon-carbon double bonds, so if there were
"real" single and double bonds in the molecule, the shape of the benzene molecule would be a
distorted hexagon:

 What is actually found is that all of the bond lengths in the benzene rings are
1.397A , which is roughly intermediate between the typical lengths of single bonds
(~1.5A) and double bonds (~1.3 A) .
 All of the carbon atoms in the benzene rings are sp2-hybridized: the overlap of
the sp2 orbitals around the ring produces a framework of six sigma bonds, while the
unhybridized p-orbitals which are perpendicular to this plane overlap in a side-to-
side fashion to form three pi-bonds.
 These pi-bonds are delocalized around the ring, leading to an unusual stability for
the benzene ring compared to other alkenes.
 Thus benzene contain ring structures and exhibit bonding that must be described
using the resonance hybrid concept of valence bond theory or the delocalization
concept of molecular orbital theory. The resonance structures for benzene, C6H6 ,
are:
 There are many derivatives of benzene. The hydrogen atoms can be replaced by
many different substituents.
 Aromatic compounds more readily undergo substitution reactions than addition
reactions; replacement of one of the hydrogen atoms with another substituent will
leave the delocalized double bonds intact.
 The following are typical examples of substituted benzene derivatives:

Toluene and xylene are important solvents and raw materials in the chemical
industry. Styrene is used to produce the polymer polystyrene.
A few another derivatives of benzene
Reactions of Benzene and Its Derivatives

Reactions of Benzene Reactions of Benzene

 The most characteristic reaction of aromatic compounds is substitution at a
ring carbon:
2.3 Alcohols and Ether

 Incorporation of an oxygen atom into carbon- and hydrogen-containing molecules

leads to new functional groups and new families of compounds. When the oxygen
atom is attached to carbon by single bonds, the molecule is either an alcohol or
ether.
a) Alcohols
 Alcohols are derivatives of hydrocarbons in which an –OH group has replaced a
hydrogen atom.
 Alcohols are covalent molecules; the –OH group in an alcohol molecule is attached
to a carbon atom by a covalent bond.
 Ethanol, CH3CH2OH, also called ethyl alcohol, is a particularly important alcohol for
human use.
Most people are familiar with ethyl alcohol (ethanol), the active ingredient in
alcoholic beverages-the alcohol found in beer, wine and other consumed sprits, but
this compound is only one of a family of organic compounds known as alcohols.

Ethanol is the alcohol produced by some species of yeast that is found in wine, beer,
and distilled drinks. It has long been prepared by humans harnessing the metabolic
efforts of yeasts in fermenting various sugars.
 Large quantities of ethanol are synthesized from the addition reaction of
water with ethylene using an acid as a catalyst

ethylene
ethanol
 Alcohols containing two or more hydroxyl groups can be made. Examples
include 1,2-ethanediol (ethylene glycol, used in antifreeze) and 1,2,3-
propanetriol (glycerine, used as a solvent for cosmetics and medicines):
Classification of Alcohols
• Alcohols are classified as primary (1°), secondary (2°), or tertiary (3°) according to
how many carbon groups are attached to the carbon bearing the OH group:

• The number of hydrogens on the carbon bearing the OH group does affect some
chemical properties.
Numenclature of alcohols
The following is list of some common alcohols based on the IUPAC naming
system

Name Molecular Formula

Methanol (methyl alcohol) CH3OH
Ethanol (ethyl alcohol) C2H­­5OH
Propanol C3H7OH
Butanol C4H9OH
Pentanol C5H11OH
Hexanol C6H13OH
Heptanol C7H15OH
Octanol C8H17OH
Name the following alcohol
Reactions of Alcohols

Dehydration of Alcohols to Produce Alkenes

• Heating alcohols in concentrated sulfuric acid (H2SO4) at 180°C removes the OH
group and a H from an adjacent carbon to produce an alkene, with water as a by-
product. Since water is “removed” from the alcohol, this reaction is known as a
dehydration reaction (or an elimination reaction):
Dehydration of Alcohols to Produce Ethers
• Heating alcohols (R—OH) in concentrated sulfuric acid (H2SO4) at 140°C removes
a molecule of water from two alcohol molecules, causing the two “R” groups to
become attached to an oxygen atom, forming an ether functional group:
Oxidation of Alcohols to Carbonyl Compounds
• An oxidation reaction occurs when a molecule loses electrons. This is usually
manifested as an increase in the number of oxygen atoms or a decrease in the
number of hydrogen atoms.
• Some common oxidizing agents include potassium permanganate (KMnO4),
chromic acid (H2CrO4), sodium dichromate (Na2Cr2O7), and other Cr6+ salts.
• Alcohols can be oxidized by removing two H atoms from the molecule; the exact
products of the reaction will depend on the type of alcohol.
Oxidation of Alcohols to Carbonyl Compounds
• Primary or secondary alcohols can be oxidized to produce compounds containing
the carbonyl group (a carbon-oxygen double bond, C=O):
Oxidation of 1° Alcohols
• Primary alcohols are oxidized first to aldehydes, but the aldehydes are then
usually oxidized into carboxylic acids.

In the body, oxidation of ethanol to acetaldehyde takes place in the liver; the
acetaldehyde is further oxidized to acetyl coenzyme A, which can be used to
synthesize fat or eventually be oxidized to water and carbon dioxide.
Oxidation of 2° Alcohols
• Secondary alcohols are oxidized to ketones, which cannot be oxidized any further:
Oxidation of 3° Alcohols
• Tertiary alcohols, because there is by definition no hydrogen on the alcoholic
carbon, cannot be oxidized:
b) Ethers

 Ethers are compounds that contain the functional group –O–. Ethers do
not have a designated suffix like the other types of molecules we have
named so far.
 In the IUPAC system, the oxygen atom and the smaller carbon branch
are named as an alkoxy substituent and the remainder of the molecule
as the base chain, as in alkanes. As shown in the following compound,
the red symbols represent the smaller alkyl group and the oxygen atom,
which would be named “methoxy.” The larger carbon branch would be
ethane, making the molecule methoxyethane.
 Many ethers are referred to with common names instead of the IUPAC
system names. For common names, the two branches connected to the
oxygen atom are named separately and followed by “ether.”
Naming Ethers
Provide the IUPAC and common name for the ether shown here:

Solution
IUPAC: The molecule is made up of an ethoxy group attached to an ethane chain,
so the IUPAC name would be ethoxyethane.
Common: The groups attached to the oxygen atom are both ethyl groups, so the
common name would be diethyl ether.
Ethers can be obtained from alcohols by the elimination of a molecule of water from
two molecules of the alcohol. For example, when ethanol is treated with a limited
amount of sulfuric acid and heated to 140 °C, diethyl ether and water are formed:
In the general formula for ethers, R—O—R, the hydrocarbon groups (R) may be
the same or different. Diethyl ether, the most widely used compound of this
class, is a colorless, volatile liquid that is highly flammable. It was first used in
1846 as an anesthetic, but better anesthetics have now largely taken its place.
Diethyl ether and other ethers are presently used primarily as solvents for
gums, fats, waxes, and resins.
2.4 Aldehydes and Ketones
 Both aldehydes and ketones contain a carbonyl group, a functional group with a
carbon-oxygen double bond.

 The names for aldehyde and ketone compounds are derived using similar
nomenclature rules as for alkanes and alcohols, and include the class-identifying
suffixes -al and -one, respectively:
 In an aldehyde, the carbonyl group is bonded to at least one hydrogen atom.

 In a ketone, the carbonyl group is bonded to two carbon atoms

Example of an aldehyde and ketone
 The importance of molecular structure in the reactivity of organic compounds is
illustrated by the reactions that produce aldehydes and ketones. We can prepare
a carbonyl group by oxidation of an alcohol for organic molecules, oxidation of a
carbon atom is said to occur when a carbon hydrogen bond is replaced by a
carbon-oxygen bond.
Preparation of aldehydes and ketones

Aldehydes are commonly prepared by the oxidation of alcohols whose –OH functional
group is located on the carbon atom at the end of the chain of carbon atoms in the
alcohol

Alcohols that have their –OH groups in the middle of the chain are necessary to
synthesize a ketone, which requires the carbonyl group to be bonded to two other
carbon atoms:
Formaldehyde

 It is an aldehyde with the formula HCHO. It is a colorless gas with a pungent and

irritating odor. It is sold in an aqueous solution called formalin, which contains

about 37% formaldehyde by weight. Formaldehyde causes coagulation of

proteins, so it kills bacteria (and any other living organism) and stops many of

the biological processes that cause tissue to decay.

 Thus, formaldehyde is used for preserving tissue specimens and embalming

bodies. It is also used to sterilize soil or other materials.

 Formaldehyde is used in the manufacture of Bakelite, a hard plastic having high

chemical and electrical resistance.

Dimethyl ketone (acetone)

 Dimethyl ketone, CH3COCH3, commonly called acetone, is the simplest ketone.

It is made commercially by fermenting corn or molasses, or by oxidation of 2-

propanol.

 Acetone is a colorless liquid. Among its many uses are as a solvent for lacquer

(including fingernail polish),cellulose acetate, cellulose nitrate, acetylene,

plastics, and varnishes; as a paint and varnish remover; and as a solvent in the

manufacture of pharmaceuticals and chemicals.

2.5 Carboxylic Acids and Esters
 Both carboxylic acids and esters contain a carbonyl group with a second oxygen
atom bonded to the carbon atom in the carbonyl group by a single bond.
 In a carboxylic acid, the second oxygen atom also bonds to a hydrogen atom.

 In an ester, the second oxygen atom bonds to another carbon atom.

 An ester is an organic compound that is a derivative of a carboxylic acid in which

the hydrogen atom of the hydroxyl group has been replaced with an alkyl group.
Nomenclature of Carboxylic Acids
• Select the longest carbon chain containing the carboxyl group. The -e
ending of the parent alkane name is replaced by the suffix -oic acid.
• The carboxyl carbon is always numbered “1” but the number is not
included in the name.
• Name the substituents attached to the chain in the usual way.
• Aromatic carboxylic acids (i.e., with a CO2H directly connected to a
benzene ring) are named after the parent compound, benzoic acid.
Names of carboxylic acids
Carboxylic acids are weak acids. Generally only about 1% of the molecules of a

carboxylic acid dissolved in water are ionized at any given time. The remaining

molecules are undissociated in solution.

Preparation of carboxylic acids and esters

We prepare carboxylic acids by the oxidation of aldehydes or alcohols whose –OH

functional group is located on the carbon atom at the end of the chain of carbon

atoms in the alcohol:

Carboxylic acids are organic molecules containing the carboxyl functional group, -
COOH. This is made up of the carbonyl group, C=O, and the hydroxyl group, -OH.
Carboxylic acids are weak acids, meaning they only partially dissociate in solution.
When they dissociate, they lose a proton to form a negative carboxylate ion. The
charge delocalises across the molecule and makes both C-O bonds equal.
Carboxylic acids are formed by oxidising primary alcohols under reflux, hydrolysing
nitriles or hydrolysing esters.
 Carboxylic acids occur widely in nature. The fatty acids are components of
glycerides, which in turn are components of fat.
 Hydroxyl acids, such as lactic acid (found in sour-milk products) and citric acid
(found in citrus fruits), and many keto acids are important metabolic products
that exist in most living cells.
 Proteins are made up of amino acids, which also contain carboxyl groups.
 Compounds in which the ―OH of the carboxyl group is replaced by certain other
groups are called carboxylic acid derivatives, the most important of which are acyl
halides, acid anhydrides, esters, and amides.
Carboxylic Acid Reactions
1. Reaction with Metals
The reaction of carboxylic acids with metals like K, Na, Mg, and Ca results in the
formation of salts. A proton will be released from the carboxyl group of the carboxylic
acid where the metal substation will occur during the reaction phase. H2 gas is
produced as a result of the reaction.
2CH3COOH + 2Na → 2CH3COONa + H2
2. Reaction with Alkalis
The reaction of carboxylic acids with alkalis results in the formation of salts and water.
CH3COOH + NaOH → CH3COONa + H2O
3. Reaction with Carbonates and Bicarbonates
Carboxylic acids decompose with carbonates and bicarbonates to produce salts, vapor,
and carbon dioxide gas.This reaction can also be used to check for carboxyl groups.
Carboxylic acids react with a saturated sodium bicarbonate solution to create
effervescence, which is caused by the release of CO2.
2CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2
2CH3COOH + NaHCO3 → CH3COONa + H2O + CO2
4. Formation of Acyl Chlorides
 Acid chlorides are formed when carboxylic acids react with thionyl chloride
(SOCl2), phosphorus penta chloride (PCl5),
RCOOH + SOCl2 → RCOCl + SO2 + HCl
3RCOOH + PCl5 → 3RCOCl + POCl + HCl

5. Formation of Esters (Esterification)

 When carboxylic acids and alcohols are heated in the presence of concentrated
sulphuric acid or dry hydrochloric acid, fruity esters are formed.

 The dehydrating agent in this reaction is concentrated sulphuric acid. An

equilibrium reaction is exemplified by this reaction.
6. Formation of Amide
Ammonium salts are formed by treating carboxylic acids with ammonia. Ammonium
salts lose a water molecule when heated, resulting in the formation of amides.

7. Decarboxylation
Decarboxylation reaction occurs when soda lime (NaOH + CaO) is distilled with
sodium salts of carboxylic acids, resulting in alkanes.
8. Formation of Anhydrides
Acid anhydrides are formed when two molecules of carboxylic acid are heated with
a dehydrating agent such as phosphorus pentoxide.
2RCOOH ⇢ RCO-O-RCO + H2O
Esters are produced by the reaction of acids with alcohols. For example, the ester

ethyl acetate, CH3CO2CH2CH3, is formed when acetic acid reacts with ethanol:
 The simplest carboxylic acid is formic acid, HCO2H, known since 1670. Its name
comes from the Latin word formicus, which means “ant”; it was first isolated by
the distillation of red ants.
 It is partially responsible for the pain and irritation of ant and wasp stings, and is
responsible for a characteristic odor of ants that can be sometimes detected in
their nests.
 Acetic acid, CH3CO2H, constitutes 3–6% vinegar. Cider vinegar is produced by
allowing apple juice to ferment without oxygen present. Yeast cells present in
the juice carry out the fermentation reactions.
 The fermentation reactions change the sugar present in the juice to ethanol, then
to acetic acid. Pure acetic acid has a penetrating odor and produces painful burns.
It is an excellent solvent for many organic and some inorganic compounds, and it is
essential in the production of cellulose acetate, a component of many synthetic
fibers such as rayon.

Esters

 Esters are present in a many biologically important molecules, which have a wide
range of effects.
 Esters include compounds such as fats, waxes, Vitamin C, Cocaine, Novacaine, oil
of wintergreen, and aspirin.
Esters are compounds often the sources of the pleasant aromas of many fruits.
Mthylethanoate Ethylbutanoate
 The distinctive and attractive odors and flavors of many flowers, perfumes,

and ripe fruits are due to the presence of one or more esters.

 Among the most important of the natural esters are fats (such as lard,

tallow, and butter) and oils (such as linseed, cottonseed, and olive oils),

which are esters of the trihydroxyl alcohol glycerine, C3H5(OH)3, with large

carboxylic acids, such as palmitic acid, CH3(CH2)14CO2H, stearic

acid,CH3(CH2)16CO2H, and oleic acid,CH3(CH2)7CH=CH(CH2)7CO2H.

 Oleic acid is an unsaturated acid; it contains a C=C double bond.

 Palmitic and stearic acids are saturated acids that contain no double or triple

bonds.
 Reactions of Esters
1. Conversion of Esters to Carboxylic Acids:
Hydrolysis

 Esters can be cleaved back into a carboxylic acid and an alcohol through reaction
with water and a catalytic amount of strong acid. This reaction represents the
reverse of the acid catalyzed esterification of a carboxylic acid and an alcohol
Conversion of Esters to Carboxylic Acids: Saponification
 Esters can also be cleaved into a carboxylate and an alcohol through reaction
with water and a base. The reaction is commonly called a saponification from
the Latin sapo which means soap. This name comes from the fact that soap
used to me made by the ester hydrolysis of fats.
 Saponification reaction utilize a better nucleophile (hydroxide) and are typically
faster than an acid catalyzed hydrolysis. The carboxylation ions produced by
saponification are negatively charged and very unreactive toward further
nucleophilic substitution which makes the reaction irreversible.
Conversion of Ester to Amides: Aminolysis
It is possible to convert esters to amides through direct reaction with ammonia or
amines. However, these reactions are not commonly used because the formation of an
amide using an acid chloride is a much simpler reaction.
2.6 Amines and Amides
a) Amines
 Amines are molecules that contain carbon-nitrogen bonds. The nitrogen atom
in an amine has a lone pair of electrons and three bonds to other atoms, either
carbon or hydrogen. Various nomenclatures are used to derive names for
amines, but all involve the class-identifying suffix –ine as illustrated here for a
few simple examples:
In some amines, the nitrogen atom replaces a carbon atom in an aromatic
hydrocarbon.
Pyridine is one such heterocyclic amine. A heterocyclic compound contains
atoms of two or more different elements in its ring structure.
Like ammonia, amines are weak bases due to the lone pair of electrons on their
nitrogen atoms:
 The basicity of an amine’s nitrogen atom plays an important role in much of the

compound’s chemistry.

 Amine functional groups are found in a wide variety of compounds, including

natural and synthetic dyes, polymers, vitamins, and medications such as penicillin

and codeine.

 They are also found in many molecules essential to life, such as amino acids,

hormones, neurotransmitters, and DNA.

Amides
Amides are molecules that contain nitrogen atoms connected to the carbon atom of
a carbonyl group. Like amines, various nomenclature rules may be used to name
amides, but all include use of the class-specific suffix -amide
 Amides can be produced when carboxylic acids react with amines or ammonia

in a process called amidation.

 A water molecule is eliminated from the reaction, and the amide is formed from

the remaining pieces of the carboxylic acid and the amine (note the similarity to

formation of an ester from a carboxylic acid and an alcohol discussed in the

previous section)

:
 The reaction between amines and carboxylic acids to form amides is biologically

important.

 It is through this reaction that amino acids (molecules containing both amine and

carboxylic acid substituents) link together in a polymer to form proteins.