TABLE OF CONTENT

Contents
Chemical Reaction: ................................................................................................................................. 2
Types of Chemical reactions: ............................................................................................................. 2
1. Addition Reaction:.................................................................................................................. 2
2. Substitution Reaction: ............................................................................................................ 3
3. Elimination Reaction: ............................................................................................................. 4
4. Rearrangement Reaction: ...................................................................................................... 5
5. Series reaction: ....................................................................................................................... 7
6. Parallel Reaction:.................................................................................................................... 8
7. Catalytic Reaction:.................................................................................................................. 9
8. Non-Catalytic Reaction: ....................................................................................................... 11
HOMOGENEOUS AND HETROGENEOUS REACTON ............................................................................. 12
1. Homogeneous Reaction: .......................................................................................................... 12
2. Heterogeneous Reaction:......................................................................................................... 12
CATALYST AND CATALYSIS ................................................................................................................... 14
1 Catalyst: .................................................................................................................................... 14
Types of Catalysts with Examples .................................................................................................... 14
i. Positive Catalysts: ........................................................................................................... 14
ii. Negative Catalysts: .......................................................................................................... 14
2. Catalysis: ................................................................................................................................... 16
Types of Catalysis ............................................................................................................................. 16
i. Homogeneous catalysis: ................................................................................................. 16
ii. Heterogeneous catalysis: ..................................................................................................... 17
iii. Autocatalysis: ....................................................................................................................... 17

1
 Assignment No.1
Chemical Reaction:
A chemical reaction is a process in which one or more substances (reactants) are transformed
into one or more different substances (products) through the breaking and forming of
chemical bonds.
➢ Chemical reactions involve the rearrangement of atoms, resulting in the formation of
new compounds with different properties from the original substances. These
reactions typically involve changes in energy, such as the release or absorption of heat,
light, or electricity. Chemical reactions play a fundamental role in all aspects of
chemistry and are essential for understanding various natural and synthetic processes,
including metabolism, combustion, and industrial production.

Types of Chemical reactions:

Chemical reactions in a reactor can be classified into various types based on different criteria.
Some common types of reactions that occur in reactors included as:
1. Addition Reaction.
2. Substitution Reaction.
3. Elimination Reaction.
4. Rearrangement Reaction.
5. Series Reaction.
6. Parallel Reaction.
7. Catalytic Reaction.
8. Non-Catalytic Reaction.

1. Addition Reaction:
An addition reaction is a type of chemical reaction where two or more reactants combine to
form a single product.
➢ In such reactions, atoms or groups of atoms are added to a molecule, resulting in the
formation of a larger molecule. Addition reactions often involve the breaking of
multiple bonds and the formation of new bonds. These reactions are common in
organic chemistry and are used in the synthesis of various compounds.

2
The general equation for an addition reaction can be represented as:

Reactant 1 + Reactant 2 → Product

Example of an Addition Reaction.

Hydrogenation of Alkenes:
In this reaction, hydrogen gas (H2) is added across the carbon-carbon double bond (C=C) of
an alkene, resulting in the formation of a saturated alkane.

Equation:
Alkene + Hydrogen → Alkane

Example:

Ethene (C2H4) +Hydrogen (H2) → Ethane (C2H6)

In this example, ethene (C2H4), which is an alkene with a carbon-carbon double bond,
undergoes addition reaction with hydrogen gas (H2) in the presence of a catalyst (such as
platinum or palladium) to form ethane (C2H6), which is a saturated alkane.
This addition reaction is important industrially, particularly in the production of margarine
from vegetable oils and in the hydrogenation of unsaturated fats to make them solid at room
temperature (e.g., in the production of shortening and certain types of cooking oils).

2. Substitution Reaction:
A substitution reaction is a type of chemical reaction in which an atom or group of atoms in a
molecule is replaced by another atom or group of atoms.

➢ The substitution typically occurs at a specific position within the molecule, resulting in
the formation of a new compound. Substitution reactions are common in organic
chemistry and are often categorized as either nucleophilic or electrophilic
substitutions, depending on the nature of the reactants involved.
The general equation for a substitution reaction can be represented as:
Reactant + Reagent → Product

3
Here's an example of a nucleophilic substitution reaction:

Nucleophilic Substitution in Haloalkanes:

In this reaction, a halogen atom (such as chlorine, bromine, or iodine) in a haloalkane (alkyl
halide) is replaced by a nucleophile, resulting in the formation of a new compound.

Equation:
Haloalkane+Nucleophile→Product

Example:
Chloroethane (C2H5Cl) +Hydroxide ion (OH−)→Ethanol (C2H5OH) +Chloride ion (Cl−)

In this example, chloroethane ((C2H5Cl)) reacts with a hydroxide ion (OH-) in a nucleophilic
substitution reaction. The chlorine atom in chloroethane is replaced by the hydroxide ion,
resulting in the formation of ethanol (C2H5OH) and chloride ion ((Cl-). This reaction is known
as the hydrolysis of haloalkanes, and it is an important method for preparing alcohols from
haloalkanes.
Substitution reactions are also prevalent in other areas of chemistry, including inorganic and
coordination chemistry, where ligands may be substituted around a central metal ion in a
complex.

3. Elimination Reaction:
An elimination reaction is a type of chemical reaction where a molecule loses one or more
atoms or groups of atoms, resulting in the formation of a new molecule with fewer
substituents than the reactant molecule.

4
 ➢ Elimination reactions often involve the removal of small molecules like water,
hydrogen halides, or other simple molecules.
The general equation for an elimination reaction can be represented as:

Reactant → Product
Here's an example of an elimination reaction:

Dehydration of Alcohols:
In this reaction, an alcohol molecule loses a molecule of water, resulting in the formation of
an alkene.

Equation:
Alcohol → Alkene + Water

Example:
Ethanol (C2H5OH) → Ethene (C2H4) + Water

In this example, ethanol (C2H5OH) undergoes elimination reaction, specifically dehydration,

to form ethene (C2H4) and water. The -OH group and a hydrogen atom from adjacent carbon
atoms are eliminated, resulting in the formation of a carbon-carbon double bond in ethene.
Elimination reactions are also common in organic chemistry in reactions such as the
dehydrohalogenation of alkyl halides to form alkenes and in the elimination of water from
vicinal diols to form alkenes, among others.

4. Rearrangement Reaction:
A rearrangement reaction is a type of chemical reaction in which the atoms within a molecule
are rearranged to form a new structural isomer of the original molecule, without adding or
removing any atoms.
➢ These reactions involve the migration of atoms or groups of atoms within the
molecule, resulting in the formation of a different molecular structure.

5
The general equation for a rearrangement reaction can be represented as:

Reactant →Product

Here's an example of a rearrangement reaction:

Hydride Shift in Carbocation Rearrangement:

In this reaction, a carbocation undergoes rearrangement by migration of a hydride ion (H⁻)
from one carbon atom to another, leading to the formation of a more stable carbocation.

Equation:
Carbocation → Rearranged Carbocation

Example:
1-Butyl Carbocation→2-Butyl Carbocation
I. Starting with 1-Butyl Carbocation (1-Butyl cation):

H H
| |
H3C–C–C⁺–CH2
| |
H H
II. Starting with 1-Butyl Carbocation (1-Butyl cation):
H H
| |
H3C–C⁺–CH2–H
| |
H H
III. Formation of 2-Butyl Carbocation (2-Butyl cation):
H H
| |
H3C–C⁺–CH2–H
| |
H H

6
In this example, the 1-butyl carbocation, which is relatively less stable due to the presence of
a secondary carbocation, rearranges to form the more stable 2-butyl carbocation through a
hydride shift. In the process, a hydrogen atom migrates from the carbon atom adjacent to the
positively charged carbon to the carbon bearing the positive charge, resulting in a more stable
tertiary carbocation.
Rearrangement reactions are common in organic chemistry and often occur in reactions
involving carbocations, radicals, or other reactive intermediates. These reactions are essential
for understanding reaction mechanisms and predicting the outcomes of various synthetic
transformations.

5. Series reaction:
Series reaction refers to a sequence of two or more chemical reactions that occur
sequentially, with the product of one reaction serving as a reactant for the subsequent
reaction.

➢ Each step in the series typically involves different reactants and/or catalysts and leads
to the formation of intermediate products before reaching the final desired product.
The general equation for a series reaction involving (n) steps can be represented as:

Reactant Step 1→ Intermediate Step2 → Intermediate2 Step3→ …

… →Step (n−1)
Intermediaten−1 Step n →Product

Here's a simplified example of a series reaction involving two steps:

Example:
Consider the decomposition of hydrogen peroxide (H2O2) in the presence of manganese
dioxide (MnO2) as a catalyst, followed by the reaction of the resulting oxygen gas (O2) with
iron (Fe) to form iron oxide (Fe2O3):

Step 1:
H2O2 →Decomposition → H2O +O2

In this step, hydrogen peroxide decomposes into water (H2) and oxygen gas (O2), catalyzed by
manganese dioxide (MnO2).

7
Step 2:
2Fe+3O2→Fe2O3
In this step, oxygen gas (O2) reacts with iron (Fe) to form iron oxide (Fe2O3).
Overall, the series reaction involves the decomposition of hydrogen peroxide (H2O2) in the
first step, followed by the reaction of the resulting oxygen gas (O2) with iron (Fe) in the second
step to produce iron oxide (Fe2O3).
Series reactions are commonly encountered in many chemical processes, including organic
synthesis, industrial manufacturing, and biochemical pathways. Understanding the sequence
of reactions and the intermediates involved is crucial for designing efficient reaction pathways
and optimizing chemical processes.

6. Parallel Reaction:
Parallel reactions occur when multiple chemical reactions proceed simultaneously using the
same reactants but producing different products.
➢ These reactions can compete with each other for the available reactants, and the
relative rates of the parallel reactions determine the distribution of products formed.
Parallel reactions can occur in both homogeneous and heterogeneous systems.
The general equation for parallel reactions involving (n) different reactions can be
represented as:

Here's an example of parallel reactions:

8
Consider the combustion of methane (CH4) in the presence of excess oxygen (O2):
Parallel Reaction 1:

CH4+2O2→CO2+2H2O
In this reaction, methane reacts with oxygen to form carbon dioxide and water.

Parallel Reaction 2:

2CH4+3O2→2CO+4H2O
In this reaction, methane reacts with oxygen to form carbon monoxide and water.
In this example, both parallel reactions involve the combustion of methane with oxygen,
resulting in the formation of different products. Depending on the reaction conditions, such
as temperature, pressure, and the presence of catalysts, the relative rates of these parallel
reactions may vary, leading to different distributions of products.

Parallel reactions are commonly encountered in many chemical systems, including

combustion processes, industrial catalysis, and biochemical reactions. Understanding the
kinetics and mechanisms of parallel reactions is essential for predicting product yields and
optimizing reaction conditions in various chemical processes.

7. Catalytic Reaction:

A catalytic chemical reaction is a type of reaction in which a substance known as a catalyst

facilitates the reaction without being consumed itself.
➢ Catalysts lower the activation energy required for the reaction to occur, thereby
increasing the rate of the reaction without being chemically changed at the end of the
process. They provide an alternative reaction pathway that allows reactant molecules
to convert into product molecules more easily.

9
The general equation for a catalytic chemical reaction can be represented as:
Reactant + Catalyst → Product
Reactant + Catalyst ───────────────────> Product + Regenerated Catalyst

(Starting Material) (Catalyst) (Final Product)

Here's an example of a catalytic chemical reaction:

Example:

Hydrogenation of Alkenes
The hydrogenation of alkenes is a catalytic chemical reaction that involves the addition of
hydrogen (H2) across the carbon-carbon double bond (C=C) in an alkene to form a saturated
alkane. This reaction is widely used in the food industry for the hydrogenation of unsaturated
fats and oils to make them solid at room temperature, thereby producing products like
margarine.

Equation:
Alkene + Hydrogen → Alkane
For example, the hydrogenation of ethene (C2H4) to form ethane (C2H6) can be represented
as:

In this reaction, a catalyst such as platinum (Pt), palladium (Pd), or nickel (Ni) is used to
facilitate the addition of hydrogen across the double bond of ethene, resulting in the
formation of ethane.

Catalytic reactions play a vital role in various industrial processes, including petroleum
refining, chemical synthesis, and environmental remediation, by enabling more efficient and
selective production of desired products.

10
 8. Non-Catalytic Reaction:
A non-catalytic chemical reaction is a type of reaction in which the conversion of reactants
into products occurs without the involvement of a catalyst.
➢ Unlike catalytic reactions, non-catalytic reactions do not require an additional
substance to facilitate the reaction, and the reactants themselves spontaneously
undergo the desired transformation.

The general equation for a non-catalytic chemical reaction can be represented as:
Reactant → Product
Here's an example of a non-catalytic chemical reaction:

Example:

Combustion of Methane:
The combustion of methane (CH4) in the presence of oxygen (O2) to produce carbon dioxide
(CO2) and water (H2O) is a common example of a non-catalytic chemical reaction.
Equation:

CH4 + 2O2 → CO2 + 2H2O

In this reaction, methane reacts directly with oxygen to form carbon dioxide and water
without the need for a catalyst. The reaction occurs spontaneously under suitable conditions,
such as the presence of sufficient oxygen and ignition.

Non-catalytic reactions are ubiquitous in nature and play a crucial role in various processes,
including combustion, chemical synthesis, and biochemical reactions. These reactions often
occur without the need for external intervention and proceed according to the inherent
chemical properties of the reactants involved.

11
HOMOGENEOUS AND HETROGENEOUS REACTON
1. Homogeneous Reaction:
A homogeneous reaction is a type of chemical reaction in which all reactants are present in
the same phase i.e., either all in the gas phase, all in the liquid phase, or all in the solid phase.
Homogeneous reactions can occur in various phases, including gas-phase reactions, liquid
phase reactions, and solid-phase reactions. However, in the context of solution-phase
chemistry, homogeneous reactions most commonly refer to reactions that take place in a
liquid phase, where all reactants and products are dissolved in a solvent.

Here are some examples of homogeneous reactions in different phases:

1. Gas-Phase Homogeneous Reactions:

- Example:
2NO2(g) → 2NO(g) + O2(g)

2. Liquid-Phase Homogeneous Reactions:

- Example:
2H2O2(aq) →2H2O(l) + O2(g)
In this reaction, hydrogen peroxide (H2O2 decomposes into water (H2O and oxygen O2 in the
liquid phase.

3. Solid-Phase Homogeneous Reactions:

- Example:
2Fe(s) + 3O2(g) →2Fe_2O3(s)
- In this reaction, iron Fe reacts with oxygen O2 to form iron(III) oxide Fe2O3 in the solid
phase.

In solution-phase chemistry, homogeneous reactions are commonly studied in liquid

solutions where reactants and products are dissolved in a solvent. These reactions often
involve ions or molecules reacting with each other in a well-mixed solution. Examples include
acid-base reactions, redox reactions, and many organic reactions that occur in solution.

2. Heterogeneous Reaction:
A heterogeneous reaction is a type of chemical reaction in which the reactants are present in
different phases (i.e., in different physical states or in distinct regions of a heterogeneous
mixture) before the reaction occurs.
Unlike homogeneous reactions, where all reactants are in the same phase, heterogeneous
reactions involve reactants that are in different phases.

12
Here are some common examples of heterogeneous reactions:

1. Gas-Solid Heterogeneous Reactions:

- Example:
Fe(s) + O2(g) →Fe2O3(s)
- In this reaction, solid iron Fe reacts with gaseous oxygen O2 to form solid iron(III) oxide
Fe2O3 .

2. Gas-Liquid Heterogeneous Reactions:

- Example:
CO(g) + H2O(l) → CO2(g) + H2(g)
This is an example of the water-gas shift reaction, where carbon monoxide CO reacts with
water H2O in the presence of a catalyst to produce carbon dioxide CO2 and hydrogen gas H2

3. Solid-Liquid Heterogeneous Reactions:

- Example:
CaCO3(s) + 2HCl →CaCl2(aq) + CO2(g) + H2O(l)
In this reaction, solid calcium carbonate CaCO3 reacts with aqueous hydrochloric acid 2HCl
to form aqueous calcium chloride CaCl2(aq) carbon dioxide gas CO2(g) and liquid water H2O.

Difference between Homogeneous And Heterogeneous Mixtures:

13
CATALYST AND CATALYSIS
1. Catalyst:
A catalyst is a substance that increases the rate of a chemical reaction without itself being
consumed in the reaction. Catalysts work by providing an alternative reaction pathway with
lower activation energy, thereby accelerating the conversion of reactants into products.
Catalysts remain unchanged in chemical composition and physical state at the end of the
reaction, allowing them to participate in multiple reaction cycles.

Here are some key characteristics and functions of catalysts:

1. Speeding up Reactions: Catalysts enhance the rate of chemical reactions by lowering
the activation energy barrier required for the conversion of reactants into products. This
allows reactions to occur more rapidly under milder conditions, such as lower temperatures
or pressures.
2. Providing Alternative Reaction Pathways: Catalysts facilitate reactions by providing
alternative pathways with lower activation energies. These pathways often involve the
formation of temporary intermediate species that stabilize the transition state and promote
the conversion of reactants into products.
3. Specificity: Catalysts are selective in the reactions they catalyze, often promoting the
formation of specific products while leaving other reaction pathways unaffected. This
selectivity is crucial for controlling reaction outcomes and minimizing unwanted side
reactions.
4. Reusability: Catalysts can be used repeatedly in multiple reaction cycles without being
consumed or significantly altered. They can be recovered from the reaction mixture and
reused in subsequent reactions, making them economically and environmentally beneficial.
5. Homogeneous and Heterogeneous Catalysis: Catalysts can be classified based on
their physical state and interaction with reactants. Homogeneous catalysts are in the same
phase as the reactants, while heterogeneous catalysts are in a different phase. Both types
play important roles in various industrial processes and chemical reactions.

Types of Catalysts with Examples

Depending on the needs or requirements of the chemical process, various types of catalysts
may be used.
1. Positive Catalysts:
Positive catalysts are those that increase the rate of a chemical reaction. It accelerates the
reaction by lowering the activation energy barriers, allowing a large number of reaction
molecules to be converted into products, increasing the percentage of product yield.
Example: Iron oxide acts as a positive catalyst in Haber’s process, increasing the yield of
ammonia despite less nitrogen reaction.
2. Negative Catalysts:
Catalysts that slow down the rate of the reaction, as well as negative catalysts It reduces the
rate of reaction by increasing the activation energy barrier, which reduces the number of
reactant molecules that can be converted into products and thus the rate of reaction.

14
Example: the decomposition of hydrogen peroxide into water and oxygen is slowed by the
use of acetanilide, which acts as a negative catalyst to slow the rate of hydrogen peroxide
decomposition.

Difference between a Positive catalyst and a Negative catalyst:

Examples of Catalysts:
Catalysts can be metals (e.g., platinum, palladium), metal oxides (e.g., titanium dioxide),
enzymes (biological catalysts), acids (e.g., sulfuric acid), or bases (e.g., sodium hydroxide),
among others. Each catalyst has specific properties that make it suitable for particular
reactions.
Industrial Applications:
Catalysts are widely used in industrial processes, including petroleum refining, chemical
synthesis, environmental remediation, and pharmaceutical production. They enable the
efficient production of essential chemicals and materials while minimizing energy
consumption and waste generation.

Overall, catalysts play a crucial role in advancing chemical transformations and enabling the
development of sustainable and efficient chemical processes. Their ability to accelerate
reactions while remaining unchanged makes them indispensable tools in chemistry and
industry.

15
 2. Catalysis:
Catalysis is the process by which a substance, known as a catalyst, increases the rate of a
chemical reaction by lowering the activation energy required for the reaction to proceed.
Catalysts facilitate the conversion of reactants into products without being consumed
themselves, allowing them to participate in multiple reaction cycles. Catalysis is a
fundamental concept in chemistry with broad applications in various fields, including
industrial processes, environmental remediation, and biological systems.

Here are some key aspects and principles of catalysis:

1. Role of Catalysts:
- Catalysts provide an alternative reaction pathway with a lower activation energy
compared to the uncatalyzed reaction. This allows reactant molecules to overcome the
energy barrier more easily, leading to faster reaction rates.

2. Activation Energy:
- Activation energy is the minimum energy required for a chemical reaction to occur.
Catalysts lower the activation energy by stabilizing the transition state or by providing an
alternative reaction pathway with lower energy barriers.

3. Reaction Mechanisms:
- Catalysis can occur through various mechanisms, including adsorption of reactants onto
the catalyst surface, formation of transient complexes, and activation of specific functional
groups in the reactants. Understanding the reaction mechanism is crucial for designing
effective catalysts and optimizing reaction conditions.

Types of Catalysis
On the basis of nature and the physical state of the substance employed in the chemical
reaction, catalysis is of three types:
• Homogeneous catalysis
• Heterogeneous catalysis
• Autocatalysis

1. Homogeneous catalysis:
Homogeneous catalysis occurs when the reactants and the catalyst are in the same phase.
Some examples of homogeneous catalysis are as follows:
• In the lead chamber process, sulfur dioxide is oxidized to sulfur trioxide with dioxygen
in the presence of nitrogen oxides as the catalyst. All of the reactants, sulfur dioxide
and oxygen, as well as the catalyst, nitric oxide, are in the same phase.
2SO2 (g) + O2(g) → 2SO3 (g) (in the presence of gaseous NO)
• H ions supplied by hydrochloric acid catalyze the hydrolysis of methyl acetate. The
+

reactants and catalyst are both in the same phase.

CH3COOCH3 (l) + H2O(l) → CH3COOH (aq) + CH3OH (aq) (in the presence of aqueous HCl)

16
 2. Heterogeneous catalysis:
Heterogeneous catalysis refers to the catalytic process in which the reactants and catalysts
are in different phases. The following are some examples of heterogeneous catalysis:
• In the presence of Pt, sulfur dioxide is oxidized to sulfur trioxide. The reactant is in a
gaseous state, while the catalyst is solid.
2SO2 (g) → 2SO3 (g) (in presence of Pt(s))
• In Haber’s process, dinitrogen and dihydrogen combine to form ammonia in the
presence of finely divided iron. The reactants are in a gaseous state, while the catalyst
is solid.
4NH3 (g) + 5O2 (g → 4NO(g) + 6H2O(g) (in presence of Pt(s))
• Hydrogenation of vegetable oils with finely divided nickel as a catalyst. One of the
reactants is in a liquid state, the other is in a gaseous state, and the catalyst is solid.
Vegetable oils(l) + H2 (g) → vegetable ghee (s) (in the presence of solid Nickel)

3. Autocatalysis:
In the autocatalytic reaction, no specific catalyst is added. Instead, one of the products acts
as a catalyst and increases the rate of formation of products.
Example: Decomposition of Arsine (AsH3) is formed by the Arsenic formed in the reactor as
“auto catalyst”.
2AsH3 → 2As + 3H2
In this process, As acts as a catalyst.

Applications:
Catalysis plays a vital role in various industrial processes, including petroleum refining,
chemical synthesis, polymerization, and environmental clean-up. It enables the production of
essential chemicals and materials with higher efficiency, lower energy consumption, and
reduced environmental impact.

17