Notebook 2
[Source: Inštrukcije blog, 2025]
STRUCTURE OF MOLECULES OF
ORGANIC COMPOUNDS
Structure of Hydrocarbon
Molecules
,SUMMARY OF CONTENT
Essential Organic Chemistry Notes: From Structure to Reactivity
Are you looking for notes that go beyond mere theory? Our handcrafted and detailed
organic chemistry notes are not just a collection of rich theoretical content—they are
an indispensable tool for problem-solving. They are designed to guide you toward
complete understanding and confidence in tackling chemistry problems.
Why are these notes worth buying?
Our added value lies in the precisely explained solutions to problems. Every key
concept (from determining formulas to hybridization) is supported by solved examples
that offer not just the final answer, but unveil the entire logical process and
chemical rationale.
Content Includes:
• Theory: Clear, organized, and enriched with visual elements.
• Solved Problems: Selected examples are presented as step-by-step
instructions that explain the "why" and "how" behind every solution.
Key Topics Covered in the Notes:
Our notes systematically cover the fundamentals of organic chemistry, with an
emphasis on:
• Nomenclature and Formulas: Application of root-suffix rules, determination of
Molecular and Empirical Formulas (see C4H10 → C2H5).
• Molecular Geometry and Hybridization: Understanding the shape and bond
angles (CH4 -tetrahedral 109,5°; C2H4 – planar 120°; C2H2 – linear 180°).
• Covalent Bonds and Orbital Overlap: Detailed comparison of Sigma (σ) and
Pi (π) bonds, including visualization of orbital overlap (head-on vs. sideways).
• Structure and Stability: Analysis of the aromatic state (benzene),
understanding bond length and strength (triple < double < single bond), and
their impact on reactivity.
• Hydrocarbon Reactivity: Comparison of the reactivity of alkanes (unreactive)
versus alkenes and alkynes (reactive due to π -bonds).
Example of Solution Power (Excerpt from Notes):
Problem (Reactivity): Are alkynes less reactive than alkenes?
,Answer and Explanation: False. Alkynes are more reactive than alkenes because
they have two π-bonds (weaker and more exposed), while alkenes have only one.
The two π-bonds allow alkynes to participate in two sequential addition reactions.
By purchasing these notes, you gain a tool that significantly accelerates your
understanding of organic chemistry and saves you time on complex problem-solving.
Prepare for excellent exam success!
,
,TABLE OF FIGURES
Figure.1: Structural formula and molecular model of
ethane…………………………………………………………………………………………3
Figure 2: Display of π – bonds in the ethene molecule .............................................. 4
Figure 3: A representation of the σ-bond and two π-bonds in an ethyne molecule ... 5
Figure 4: Coal tar ....................................................................................................... 9
Figure 5: A schematic representation of sp2 hybridization and the formation of a
double bond between two carbon atoms. .................................................................. 24
, Organic chemistry notes
1 THEORY
Hydrocarbons are the fundamental building blocks of organic chemistry and are
crucial, as they represent the simplest organic molecules, composed exclusively of
carbon and hydrogen atoms. Their fascinating diversity stems from the ability of
carbon atoms to form various frameworks, which can be chain-like, branched, or
cyclic. For easier understanding and structural representation, hydrocarbons are often
depicted using only their carbon backbone, where free valencies implicitly represent
bonded hydrogen atoms (see the skeletal formula of butane and cyclohexane).
Based on the nature of the bonds between carbon atoms, we divide them into two main
categories:
• Saturated hydrocarbons contain only single bonds within the molecule.
• Unsaturated hydrocarbons also contain multiple bonds – double or triple.
This structural difference is also reflected in their classification into homologous
series with characteristic properties, such as alkanes, alkenes, and alkynes (more
details in subsection 1.1).
Classification and Naming
Additionally, we can classify them based on their shape and saturation:
• Aliphatic hydrocarbons include both saturated (e.g., acyclic and cyclic
alkanes – cycloalkanes) and unsaturated compounds (e.g., acyclic and cyclic
alkenes – cycloalkenes, and acyclic and cyclic alkynes – cycloalkynes).
• Aromatic hydrocarbons, known as arenes, are a specific group of
unsaturated and cyclic compounds with unique properties.
Throughout history, these important groups have also acquired other names that often
reflect their characteristics:
• Alkanes were named paraffins due to their chemical unreactivity (from Latin
parum affinis – "little reactive").
• Alkenes are also called olefins (from French Olefinat – "to form oils"), which
originates from the fact that the simplest alkene, ethene, forms the oily
compound dichloroethane when reacted with chlorine.
1
, Organic chemistry notes
• Alkynes are generally known as acetylenes, a name derived from the shortest
and most well-known representative, ethyne, commonly called acetylene.
Naming and Derivatives of Hydrocarbons
The naming of hydrocarbons follows international agreements, known as Geneva
nomenclature. This system of rules ensures that chemists worldwide understand
which compound is being referred to, regardless of the language. Each compound has
a unique name that precisely describes its structure.
Through the process of substitution*, it's possible to prepare an immense number of
compounds, called derivatives, by replacing one or more hydrogen atoms in
hydrocarbon molecules.
Occurrence and States of Matter
Hydrocarbons are found in natural resources such as coal, petroleum, natural gas,
and plants. Depending on the size of the molecule, hydrocarbons can exist in various
states of matter:
• Gaseous (e.g., methane (CH4), ethane (C2H6))
• Liquid (e.g., hexane (C6H14), heptane (C7H16))
• Solid (e.g., eicosane (C20H42))
Source: Duden, 2008; Graunar, M., Košmrlj, B., 2019
Explanation of the terms*
→ Substitution is a chemical reaction where an atom or group of atoms in a molecule
is replaced by another atom or group. Such a reaction is very characteristic of organic
chemistry, as changing certain parts of a molecule alters (or improves) its properties.
The general formula for substitution is: R−X + Y → R−Y + X
Example of substitution: For instance, if we replace the chlorine atom in a
chloromethane (CH₃Cl) molecule with a hydroxide group (OH−), methanol (CH₃OH) is
formed, an alcohol often used as a solvent and industrial raw material.
Formula for this substitution is: CH3Cl + OH− →CH3OH + Cl−
Source: Duden, 2008; Ads, 2003; Gifford, C., 1993
2
[Source: Inštrukcije blog, 2025]
STRUCTURE OF MOLECULES OF
ORGANIC COMPOUNDS
Structure of Hydrocarbon
Molecules
,SUMMARY OF CONTENT
Essential Organic Chemistry Notes: From Structure to Reactivity
Are you looking for notes that go beyond mere theory? Our handcrafted and detailed
organic chemistry notes are not just a collection of rich theoretical content—they are
an indispensable tool for problem-solving. They are designed to guide you toward
complete understanding and confidence in tackling chemistry problems.
Why are these notes worth buying?
Our added value lies in the precisely explained solutions to problems. Every key
concept (from determining formulas to hybridization) is supported by solved examples
that offer not just the final answer, but unveil the entire logical process and
chemical rationale.
Content Includes:
• Theory: Clear, organized, and enriched with visual elements.
• Solved Problems: Selected examples are presented as step-by-step
instructions that explain the "why" and "how" behind every solution.
Key Topics Covered in the Notes:
Our notes systematically cover the fundamentals of organic chemistry, with an
emphasis on:
• Nomenclature and Formulas: Application of root-suffix rules, determination of
Molecular and Empirical Formulas (see C4H10 → C2H5).
• Molecular Geometry and Hybridization: Understanding the shape and bond
angles (CH4 -tetrahedral 109,5°; C2H4 – planar 120°; C2H2 – linear 180°).
• Covalent Bonds and Orbital Overlap: Detailed comparison of Sigma (σ) and
Pi (π) bonds, including visualization of orbital overlap (head-on vs. sideways).
• Structure and Stability: Analysis of the aromatic state (benzene),
understanding bond length and strength (triple < double < single bond), and
their impact on reactivity.
• Hydrocarbon Reactivity: Comparison of the reactivity of alkanes (unreactive)
versus alkenes and alkynes (reactive due to π -bonds).
Example of Solution Power (Excerpt from Notes):
Problem (Reactivity): Are alkynes less reactive than alkenes?
,Answer and Explanation: False. Alkynes are more reactive than alkenes because
they have two π-bonds (weaker and more exposed), while alkenes have only one.
The two π-bonds allow alkynes to participate in two sequential addition reactions.
By purchasing these notes, you gain a tool that significantly accelerates your
understanding of organic chemistry and saves you time on complex problem-solving.
Prepare for excellent exam success!
,
,TABLE OF FIGURES
Figure.1: Structural formula and molecular model of
ethane…………………………………………………………………………………………3
Figure 2: Display of π – bonds in the ethene molecule .............................................. 4
Figure 3: A representation of the σ-bond and two π-bonds in an ethyne molecule ... 5
Figure 4: Coal tar ....................................................................................................... 9
Figure 5: A schematic representation of sp2 hybridization and the formation of a
double bond between two carbon atoms. .................................................................. 24
, Organic chemistry notes
1 THEORY
Hydrocarbons are the fundamental building blocks of organic chemistry and are
crucial, as they represent the simplest organic molecules, composed exclusively of
carbon and hydrogen atoms. Their fascinating diversity stems from the ability of
carbon atoms to form various frameworks, which can be chain-like, branched, or
cyclic. For easier understanding and structural representation, hydrocarbons are often
depicted using only their carbon backbone, where free valencies implicitly represent
bonded hydrogen atoms (see the skeletal formula of butane and cyclohexane).
Based on the nature of the bonds between carbon atoms, we divide them into two main
categories:
• Saturated hydrocarbons contain only single bonds within the molecule.
• Unsaturated hydrocarbons also contain multiple bonds – double or triple.
This structural difference is also reflected in their classification into homologous
series with characteristic properties, such as alkanes, alkenes, and alkynes (more
details in subsection 1.1).
Classification and Naming
Additionally, we can classify them based on their shape and saturation:
• Aliphatic hydrocarbons include both saturated (e.g., acyclic and cyclic
alkanes – cycloalkanes) and unsaturated compounds (e.g., acyclic and cyclic
alkenes – cycloalkenes, and acyclic and cyclic alkynes – cycloalkynes).
• Aromatic hydrocarbons, known as arenes, are a specific group of
unsaturated and cyclic compounds with unique properties.
Throughout history, these important groups have also acquired other names that often
reflect their characteristics:
• Alkanes were named paraffins due to their chemical unreactivity (from Latin
parum affinis – "little reactive").
• Alkenes are also called olefins (from French Olefinat – "to form oils"), which
originates from the fact that the simplest alkene, ethene, forms the oily
compound dichloroethane when reacted with chlorine.
1
, Organic chemistry notes
• Alkynes are generally known as acetylenes, a name derived from the shortest
and most well-known representative, ethyne, commonly called acetylene.
Naming and Derivatives of Hydrocarbons
The naming of hydrocarbons follows international agreements, known as Geneva
nomenclature. This system of rules ensures that chemists worldwide understand
which compound is being referred to, regardless of the language. Each compound has
a unique name that precisely describes its structure.
Through the process of substitution*, it's possible to prepare an immense number of
compounds, called derivatives, by replacing one or more hydrogen atoms in
hydrocarbon molecules.
Occurrence and States of Matter
Hydrocarbons are found in natural resources such as coal, petroleum, natural gas,
and plants. Depending on the size of the molecule, hydrocarbons can exist in various
states of matter:
• Gaseous (e.g., methane (CH4), ethane (C2H6))
• Liquid (e.g., hexane (C6H14), heptane (C7H16))
• Solid (e.g., eicosane (C20H42))
Source: Duden, 2008; Graunar, M., Košmrlj, B., 2019
Explanation of the terms*
→ Substitution is a chemical reaction where an atom or group of atoms in a molecule
is replaced by another atom or group. Such a reaction is very characteristic of organic
chemistry, as changing certain parts of a molecule alters (or improves) its properties.
The general formula for substitution is: R−X + Y → R−Y + X
Example of substitution: For instance, if we replace the chlorine atom in a
chloromethane (CH₃Cl) molecule with a hydroxide group (OH−), methanol (CH₃OH) is
formed, an alcohol often used as a solvent and industrial raw material.
Formula for this substitution is: CH3Cl + OH− →CH3OH + Cl−
Source: Duden, 2008; Ads, 2003; Gifford, C., 1993
2
