Undergraduate
  1. General chemistry  1.1. Introduction to Chemistry  1.2. Atomic Structure  1.2.1. Subatomic particles  1.2.2. Atomic Model  1.2.3. Quantum numbers  1.2.4. Electron Configuration  1.2.5. Periodic trends  1.2.6. Isotopes and their applications  1.3. Chemical bond  1.3.1. Ionic bond  1.3.2. Covalent bonds  1.3.3. Metal Bond  1.3.4. Hybridization  1.3.5. Molecular geometry and VSEPR theory  1.3.6. Bond polarity and dipole moment  1.4. Stoichiometry  1.4.1. Mole concept  1.4.2. Empirical and molecular formula  1.4.3. Limiting reactant and excess reactant  1.4.4. Percent Yield and Purity  1.4.5. Dilution calculation  1.5. States of matter  1.5.1. Gas Laws  1.5.2. Matter and Intermolecular Forces  1.5.3. Solid and Crystal Structures  1.5.4. Phase diagram  1.5.5. Plasma and supercritical fluid  1.6. Chemical reactions  1.6.1. Types of Chemical Reactions  1.6.2. Balancing Chemical Equations  1.6.3. Thermochemical reactions  1.6.4. Reaction energy profiles  1.7. Solutions and Mixtures  1.7.1. Concentration units  1.7.2. Syndrome properties  1.7.3. Solubility and Solubility Rules  1.7.4. Henry's Law and Raoult's Law  1.7.5. Partition coefficient  1.8. Chemical equilibrium  1.8.1. Law of mass action  1.8.2. Le Chatelier's principle  1.8.3. Reaction quotient  1.8.4. To use this online calculator for Equilibrium Constant, enter Equilibrium Constant (Eq.) and hit the calculate button. Here is how the Equilibrium Constant calculation can be explained with given input values -> 0.05 = 0.05/0.  1.8.5. Acid-base balance  1.9. Acids and bases  1.9.1. Arrhenius, Brønsted–Lowry, and Lewis definitions  1.9.2. pH and pOH  1.9.3. Acid-base titration  1.9.4. Buffer Solution  1.9.5. Acid-base indicator  1.9.6. Polyprotic Acids and Bases  1.10. Electrochemistry  1.10.1. redox reactions  1.10.2. Galvanic and Electrolytic Cells  1.10.3. Nernst equation  1.10.4. Electrolysis  1.10.5. Faraday's laws of electrolysis  1.11. Thermodynamics  1.11.1. Laws of Thermodynamics  1.11.2. Enthalpy, entropy and Gibbs free energy  1.11.3. Spontaneity of reactions  1.11.4. Thermodynamic cycles (Hess's law, Carnot cycle)  1.12. Kinetics  1.12.1. Rate law and reaction order  1.12.2. Activation Energy and Catalyst  1.12.3. Collision theory  1.12.4. Reaction mechanism  1.12.5. Transition state theory
  2. Organic chemistry  2.1. Structure and relationships  2.1.1. Hybridisation in Carbon Compounds  2.1.2. Resonance and aromatization  2.1.3. Molecular orbitals  2.1.4. Inductive and mesomeric effects  2.2. Hydrocarbons  2.2.1. Hydrocarbons  2.2.2. Alkene  2.2.3. Alkynes  2.2.4. Aromatic compounds  2.2.5. Cycloalkanes and Conformation  2.3. Functional Group  2.3.1. Alcohols and phenols  2.3.2. Ethers and epoxides  2.3.3. Aldehyde and ketone  2.3.4. Carboxylic acids and derivatives  2.3.5. Amin  2.3.6. Esters and amides  2.3.7. Thiols and sulfides  2.4. Stereoscopic  2.4.1. Isomerism in Stereochemistry  2.4.2. Chirality and optical activity  2.4.3. Structural analysis  2.4.4. Diastereomers and Enantiomers  2.5.1. Substitution reactions  2.5.2. Elimination reactions  2.5.3. Addition reactions  2.5.4. Radical reactions  2.5.5. Rearrangement reactions  2.5.6. Pericyclic Reactions  2.6. Spectroscopy and structural analysis  2.6.1. Infrared Spectroscopy  2.6.2. Nuclear magnetic resonance spectroscopy  2.6.3. Mass Spectrometry  2.6.4. UV-visible spectroscopy  2.6.5. X-ray crystallography  2.7. Polymer chemistry  2.7.1. Addition and Condensation Polymers  2.7.2. Polymerization mechanism  2.7.3. Biodegradable Polymer  2.7.4. Conducting and smart polymers
  3. Inorganic chemistry  3.1. Coordination chemistry  3.1.1. Ligands and coordination compounds  3.1.2. Crystal field theory  3.1.3. Molecular Orbital Theory in Coordination Compounds  3.1.4. Jahn–Taylor distortion  3.2. Main Group Chemistry  3.2.1. Alkali and alkaline earth metals  3.2.2. Halogens and Noble Gases  3.2.3. Transition metals and their complexes  3.2.4. Lanthanides and Actinides  3.3. Solid state chemistry  3.3.1. Crystal lattices and unit cells  3.3.2. Defects in solids  3.3.3. Electrical and magnetic properties  3.3.4. Superconductivity  3.4. Bio-inorganic chemistry  3.4.1. Metal ions in biology  3.4.2. Enzymatic reactions with metals  3.4.3. Metal poisoning and detoxification  3.4.4. Metalloproteins and Metalloenzymes
  4. Physical chemistry  4.1. Quantum Chemistry  4.1.1. Wave–particle duality  4.1.2. Schrödinger Equation  4.1.3. Quantum Numbers and Orbitals  4.1.4. Atomic and molecular spectroscopy  4.2. Statistical mechanics  4.2.1. Maxwell–Boltzmann distribution  4.2.2. Partitioning functions  4.2.3. Bose–Einstein and Fermi–Dirac statistics  4.3. Chemical thermodynamics  4.3.1. Gibbs Free Energy  4.3.2. Phase transition  4.3.3. Thermodynamic efficiency  4.4. Surface chemistry  4.4.1. Absorption and Catalysis  4.4.2. Colloids and Emulsions
  5. Analytical Chemistry  5.1. Classical methods  5.1.1. Gravimetric Analysis  5.1.2. titrimeter  5.2. Instrumental methods  5.2.1. Chromatography  5.2.2. Spectroscopy  5.2.3. Electroanalytical methods  5.2.4. X-ray diffraction
  6. Industrial Chemistry  6.1. Petrochemistry  6.2. Chemical engineering principles  6.3. Green Chemistry  6.4. Pharmaceuticals and Drug Synthesis
  7. Biochemistry  7.1. Carbohydrates  7.2. Proteins and enzymes  7.3. Lipids and membranes  7.4. Nucleic acids  7.5. Metabolism and Bioenergetics  7.6. Enzyme kinetics and mechanism

Undergraduate → Organic chemistry → Hydrocarbons ↓


Alkene


Alkenes are a fascinating group of hydrocarbons in organic chemistry, characterized by the presence of at least one carbon-carbon double bond. This double bond places alkenes in a separate category, distinct from alkenes, and gives them unique properties and reactions. In this comprehensive exploration, we will delve deep into the world of alkenes, covering their structure, properties, nomenclature, occurrence, preparation methods, reactions, and importance. By the end of this exploration, you will have a complete understanding of alkenes and appreciate their role in both nature and industry.

Structure of alkenes

The defining feature of an alkene is the carbon-carbon double bond. This bond consists of a sigma bond and a pi bond. The presence of the pi bond prevents rotation around the double bond, leading to the formation of stereoisomers.

        C=C

Because of this structure, alkenes exhibit remarkable features:

  • Planar geometry around the double bond
  • Bond angle of approximately 120°

Example of ethene

H H H H

Ethene, the simplest alkene, has two carbon atoms linked by a double bond, with each carbon also bonded to two hydrogen atoms.

Nomenclature of alkenes

The naming of alkenes follows the IUPAC nomenclature system. The parent name is based on the longest carbon chain containing a double bond. The position of the double bond is represented by the smallest possible number:

Example: CH 3 CH=CH 2

Name: Propane

Long chains and substituents are named similarly, paying attention to numbering:

Example: CH 3 CH 2 CH=CH 2

Name: 1-Butene

The concept of cis-trans isomers arises due to restricted rotation:

        cis-2-butene: CH 3 CH=CHCH 3 (with methyl group on the same side)
        trans-2-butene: CH 3 CH=CHCH 3 (with methyl groups on opposite sides)

Properties of alkenes

The presence of a double bond gives alkenes characteristic physical and chemical properties:

Physical properties

  • Boiling and melting point: Generally lower than alkanes. These points increase with increasing molecular weight.
  • Solubility: Alkenes are insoluble in water but soluble in organic solvents.
  • Density: Less dense than water.

Chemical properties

  • Addition Reactions: Due to the double bond, alkenes easily participate in addition reactions.
  • Polymerization: Alkenes serve as monomers in the formation of polymers such as polyethylene.
  • Oxidation: Alkenes can be oxidized to form alcohols, ketones, or carboxylic acids.

Occurrence and natural sources

Alkenes are naturally occurring and are found in a variety of plants and organisms. Ethylene, a simple alkene, acts as a plant hormone that regulates processes such as fruit ripening and the response to stress.

Method of preparation

Alkenes can be synthesized in several ways:

  • Dehydration of Alcohols: In this method, alcohols are dehydrated in the presence of sulphuric acid or alumina to give alkenes.
  • Dehydrohalogenation of alkyl halides: Alkyl halides treated with strong base such as potassium hydroxide can form alkene.

Reactions of alkenes

Alkenes are highly reactive because of their double bonds. Some common reactions are as follows:

1. Hydrogenation

Adding H 2 to alkenes in the presence of a catalyst converts them into alkenes. This reaction reduces unsaturation.

2. Halogenation

Dihalogenated compounds are formed by the addition of halogens such as bromine to alkenes:

        R-CH=CH 2 + Br 2 → R-CHBr-CH 2 Br

3. Hydrohalogenation

In this, alkyl halides are formed by adding hydrogen halides (e.g., HCl, HBr) to alkenes:

        CH 2 =CH 2 + HBr → CH 3 -CH 2 Br

4. Hydration

By adding water in the presence of an acidic catalyst, alcohol is obtained:

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

Importance of alkenes

Alkenes are of great importance in industrial and chemical processes. For example, ethylene is essential in the production of various plastics and chemicals. Their reactivity allows alkenes to participate in a wide range of chemical reactions forming the building blocks for many compounds.

Conclusion

Understanding alkenes paves the way for a better understanding of organic chemistry. Their role in a variety of natural and synthetic processes is enormous. Equipped with knowledge about their structure, properties, and reactions, students and chemists can harness the potential of these compounds in countless applications, thereby promoting innovation and understanding in chemistry.


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Alkene

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