Grade 11
  1. Basic concepts of chemistry  1.1. Importance of Chemistry  1.2. Nature and scope of chemistry  1.3. laws of chemical combination  1.3.1. Law of conservation of mass  1.3.2. Law of definite proportions  1.3.3. Law of multiple proportions  1.3.4. Law of gaseous volume  1.3.5. Avogadro's Law  1.4. Dalton's atomic theory  1.5. Mole concept and molar mass  1.6. Percent composition  1.7. Empirical and molecular formula  1.8. Stoichiometry and Stoichiometric Calculations  1.9. Limiting reagent concept
  2. Structure of the atom  2.1. Discovery of the electron, proton, and neutron  2.2. Atomic Model  2.2.1. Thomson's model  2.2.2. Rutherford's model  2.2.3. Bohr's model  2.3. Quantum mechanical model of the atom  2.4. Dual nature of matter and radiation  2.5. Heisenberg's uncertainty principle  2.6. Quantum numbers  2.7. Atomic orbitals and their shapes  2.8. Electronic configuration of elements  2.9. Aufbau principle  2.10. Pauli's exclusion principle  2.11. Hund's maximum multiplicity rule  2.12. de Broglie's hypothesis  2.13. Photoelectric effect
  3. Classification of elements and periodicity in properties  3.1. Historical development of the periodic table  3.2. Modern Periodic Law and Periodic Table  3.3. Periodic trends in properties  3.3.1. Atomic and Ionic Radius  3.3.2. Ionization enthalpy  3.3.3. Electron gain enthalpy  3.3.4. Electronegativity  3.3.5. Valency  3.3.6. Metallic and Non-Metallic Properties  3.3.7. Oxidation states  3.4. Unusual Properties of the First Elements
  4. Chemical Bonding and Molecular Structure  4.1. Kossel–Lewis approach to chemical bonding  4.2. Ionic or electrovalent bond  4.3. Covalent bond and its features  4.4. Bond parameters  4.5. VSEPR Theory  4.6. Valence bond theory  4.7. Hybridization and its types  4.8. Molecular orbital theory  4.8.1. Bond order and stability  4.9. Hydrogen bonding
  5. States of matter  5.1. Intermolecular forces  5.2. Gas Laws  5.2.1. Boyle's law  5.2.2. Charles's Law  5.2.3. Avogadro's Law  5.2.4. Dalton's law of partial pressure  5.2.5. Graham's law of spread  5.3. Ideal Gas Equation and Applications  5.4. Real gases and deviations from ideal behaviour  5.5. Kinetic molecular theory of gases  5.6. Liquefaction of gases  5.7. Properties of Liquids  5.8. Surface tension and viscosity
  6. Thermodynamics  6.1. System and environment  6.2. Types of systems in thermodynamics  6.3. Types of procedures  6.4. First law of thermodynamics  6.5. Internal energy and enthalpy  6.6. Heat capacity and specific heat  6.7. Hess's law of constant heat summation  6.8. Bond dissociation enthalpy  6.9. Enthalpy of formation and combustion  6.10. Enthalpy of solution and neutralization  6.11. Spontaneity and the second law of thermodynamics  6.12. Gibbs free energy and its applications
  7. Balance  7.1. The concept of balance  7.2. Equilibrium constant and its applications  7.3. Le Chatelier's principle  7.4. Ionic equilibrium in solutions  7.5. Acid and Base Theory  7.5.1. Arrhenius concept  7.5.2. Bronsted-Lowry concept  7.5.3. Lewis concept  7.6. pH Scale and pOH  7.7. Common ion effect  7.8. Hydrolysis of salts  7.9. Buffer solutions and their mechanism of action  7.10. Solubility equilibrium of sparingly soluble salts
  8. Redox reactions  8.1. Oxidation and reduction concepts  8.2. Oxidation number and its applications  8.3. Redox reactions in terms of electron transfer  8.4. Balancing redox reactions (oxidation number and ion-electron methods)  8.5. Types of redox reactions  8.6. Electrochemical Cells and Redox Reactions
  9. Hydrogen  9.1. Position of Hydrogen in the Periodic Table  9.2. Isotopes of hydrogen  9.3. Preparation of Hydrogen  9.4. Properties of Hydrogen  9.5. Hydrides and their classification  9.6. Water and heavy water  9.7. Hydrogen peroxide and its properties  9.8. Uses of Hydrogen and Its Compounds
  10. S-block elements (alkali and alkaline earth metals)  10.1. Group 1 Elements - Properties and Trends  10.2. Group 2 Elements - Properties and Trends  10.3. Unusual properties of lithium and beryllium  10.4. Important compounds of sodium and their uses  10.5. Important Compounds of Magnesium and Calcium
  11. Some p-block elements  11.1. General Introduction to p-Block Elements  11.2. Group 13 Elements  11.2.1. Boron and its compounds  11.3. Group 14 Elements  11.3.1. Carbon and its allotropes  11.3.2. Important Compounds of Carbon and Silicon
  12. Organic Chemistry - Some Basic Principles and Techniques  12.1. Classification and Nomenclature of Organic Compounds  12.2. Structural representation of organic compounds  12.3. Classification of organic reactions  12.4. Electronic Effects in Organic Chemistry  12.4.1. Inductive effect  12.4.2. Resonance effect  12.4.3. Hyperconjugation  12.5. Reaction mechanism and intermediate species  12.6. Purification and qualitative analysis of organic compounds
  13. Hydrocarbons  13.1. Hydrocarbons  13.1.1. Preparation and Properties of Alkenes  13.2. alkene  13.2.1. Preparation and Properties of Alkenes  13.2.2. Electrophilic addition reactions  13.3. Alkynes  13.3.1. Preparation and Properties of Alkynes  13.4. Aromatic hydrocarbons  13.4.1. Structure and properties of benzene  13.4.2. Electrophilic substitution reactions of benzene
  14. Environmental Chemistry  14.1. Environmental Pollution  14.2. Atmospheric pollution and the greenhouse effect  14.3. Water pollution and treatment methods  14.4. Soil pollution and its effects  14.5. Industrial waste and its treatment  14.6. Strategies for pollution control

Grade 11 → Hydrocarbons ↓


alkene


In the world of chemistry, hydrocarbons are particularly fascinating compounds made of hydrogen and carbon. Among the different types of hydrocarbons, alkanes stand out due to their unique chemical properties. The aim of this lesson is to provide a detailed description of alkanes, their structure, properties, and importance in both academic studies and practical applications.

What are alkenes?

Alkanes are types of hydrocarbons that contain at least one carbon-carbon double bond ( -C=C- ). This double bond is the defining characteristic that distinguishes alkanes from other types of hydrocarbons such as alkenes, which contain only single bonds, and alkynes, which contain triple bonds. Because of the double bond, alkanes are also known as unsaturated hydrocarbons.

Chemical structure of alkenes

The general molecular formula of an alkene is C n H 2n . For example, if an alkene has four carbon atoms, following the formula will give C 4 H 8 The simplest alkene is ethene, also known as ethylene, which has the chemical formula C 2 H 4 .

      HH
       ,
        C=C
       ,
      HH

Nomenclature of alkenes

The naming of alkenes follows the IUPAC nomenclature system, where the suffix "-ene" is used to indicate the presence of a double bond. The location of the double bond must also be specified in the name. Here is a step-by-step guide to naming alkenes:

  1. Identify the longest carbon chain that contains a double bond. This becomes the parent chain.
  2. Number the carbon atoms in the parent chain starting at the end nearest the double bond.
  3. Use the number of the first carbon atom involved in the double bond as a locator before the radical name.
  4. List the prefixes alphabetically and numbered, if present.

As an example, consider the following compound:

        CH 3
         ,
      CH 3 -CH-CH=CH-CH 2 -CH 3

The longest chain with a double bond has five carbon atoms, making it "pentene." Since the double bond starts at the second carbon, the compound is named 2-methyl-2-pentene.

Isomerism in alkynes

Alkenes show two main types of isomerism:

Structural isomerism

This happens when the molecular formula of the alkene is the same but the structural arrangement of the atoms is different. For example, C 4 H 8 can be but-1-ene or but-2-ene.

    But-1-ene: CH 2 =CH-CH 2 -CH 3
    But-2-ene: CH3 -CH=CH- CH3

Cis-trans isomerism

This type of isomerism is typical for alkenes because of the restricted rotation around the double bond. In cis isomers, the substituents are on the same side of the double bond. In trans isomers, they are on opposite sides. Let's consider but-2-ene:

    cis-but-2-ene:
          CH 3 H
           ,
        HC=C-CH 3
          
    trans-but-2-ene:
          H CH 3
           ,
        CH 3 -C=CH

The double bond prevents free rotation in alkenes, which gives rise to specific configuration and properties in them.

Physical properties of alkenes

The physical properties of alkenes are similar to those of alkanes, but some differences are worth noting:

  • Boiling point: The boiling point of alkenes is generally similar to that of alkenes of comparable size, affected slightly by the presence of the double bond. The increased polarity from the double bond can lead to a slightly higher boiling point.
  • Solubility: Like alkanes, alkenes are nonpolar and insoluble in water, but are soluble in other nonpolar solvents.
  • Density: Alkenes are less dense than water, which means they would float on water if they were liquid at room temperature.

Chemical properties of alkenes

The presence of the double bond makes alkenes more reactive than alkanes. This double bond can undergo different reactions, some of which are as follows:

Hydrogenation

In this reaction, hydrogen gas (H 2) is added to the double bond, converting it into a single bond. This reaction is used industrially to convert unsaturated fats into saturated fats.

    CH 2 =CH 2 + H 2 → CH 3 -CH 3

Halogenation

Alkenes react with halogens (such as Cl 2 or Br 2) to form dihaloalkanes.

    CH 2 =CH 2 + Br 2 → CH 2 Br-CH 2 Br

Hydration

In the presence of an acidic catalyst, water can be added to an alkene to form an alcohol:

    CH 2 =CH 2 + H 2 O → CH 3 -CH 2 OH

Synthesis of alkenes

Alkenes can be synthesized in several ways:

Dehydration of alcohol

Alcohols can be converted to alkane by removing a water molecule. This usually requires an acid catalyst and heat:

    CH 3 -CH 2 OH → CH 2 =CH 2 + H 2 O

Cracking of alkenes

Larger alkanes can be broken down into smaller alkanes through cracking, a process used in the petroleum industry.

Applications and importance of alkenes

Alkenes play an important role in both nature and industry:

  • Polymerization: Alkenes are the building blocks of many polymers, such as polyethylene and polypropylene, which are important in the manufacture of plastics.
  • Pheromones: Many insects use alkanes as pheromones for communication.
  • Natural products: Alkanes are found in a variety of essential compounds in plants and animals, such as vitamins and hormones.

Conclusion

Alkenes, with their characteristic carbon-carbon double bonds, are a distinctive and important class of hydrocarbons. Their unique reactivity and physical properties make them important in a wide range of chemical processes and industries. Understanding the structure and behavior of alkenes is important in many areas of chemistry, from organic synthesis to the development of new materials and the study of biological systems.


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alkene

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