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Physical Properties Affected by the Lone Pair - Hydrogen Bonding

Learning Objective: To study how the presence of a lone pair on the central atom of a molecule contributes to Hydrogen bonding, a type of intermolecular attractive force.

Prerequisites: 

 

Chapter: Fundamentals of Organic Reactions

Sub-topic: Lone Pair

 

Author's Note: Lone pair's involvement in Hydrogen bonding is significant in explaining several observed properties, like why water freezes in a crystalline structure or ice floats on water. It extends beyond chemistry to explain how protein structures in the body hold their shape, an immune response occurs when antigens and antibodies bind using H-bonds, and even explain the solubility of a large number of polar compounds in polar solvents like water, due to which life on earth exists. Still, not all lone pairs form Hydrogen bonds, and for those that do, some aren't strong like the others due to their directionality. This section shows the involvement of the lone pairs in hydrogen bonding that affects various physical properties of Melting/Boiling points, solubility, and more with an example.  

 

 

Physical Properties Affected by the Lone Pair - Hydrogen Bonding

 

Molecules closely associate or interact with the same kind or different using intermolecular forces. One of the prominent intermolecular forces is the H-bonding, which affects the boiling/melting point, solubility, shape, and nature of compounds. Covalent molecules with highly electronegative atoms of Nitrogen (N), Oxygen (O), and Fluorine (F) possessing lone pairs show such a type of H-bonding, hinting at their involvement. 

For example, the water molecule......

The strength of the H-bond is also affected by the lone pair orbital’s directionality.......

 

Subscribe to read how the lone pair participates in Hydrogen bonding and is also responsible for affecting its strength in the chapter Fundamentals of Organic Reactions.

 

Fundamentals of Organic Reactions
Organic Chemistry - Drawing Structures, Concepts, and Examples

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What is Organic Chemistry?

  • Introduction
  • Elements of a Chemical Reaction
  • Components of a Chemical Reaction

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Atom

  • Size of an atom- The world belongs to the tiniest!
  • Power of Protons
  • Mass Number
  • Average Atomic Mass
  • Molecule and Molecular Mass
  • The Electrons- An Atom’s Reactive Component
  • Atomic Orbitals- s, p, d, f
  • Filing of Atomic Orbitals and Writing Electronic Configuration
  • Valence and Core Electrons- How to Determine

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Bonding In Atoms

  • Octet Rule - Introduction and Bonding
  • Limitations of Octet Rule
  • Ionic Bond- Introduction and Formation
  • Formation of Ionic Compound
  • Requirements for Ionic Bonding
  • Appearance and Nature of Ionic Compounds
  • Physical Properties of Ionic Solids- Conductance, Solubility, Melting Point, and Boiling Point
  • Covalent Bond - How it Forms
  • Covalent Bond - Why it Forms?
  • Covalent Bond - Bond Pair (Single, Double, Triple) and Lone Pair
  • Number of Covalent Bonds- Valency
  • Types of Covalent Bonds- Polar and Nonpolar
  • Metallic Bond - Introduction and Nature
  • Significance of Metallic Bonding
  • Impact of Metallic Bonding on the Physical Properties
  • Applications of Metallic Bonding
  • Difference Between Metallic and Ionic Bond

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Covalent Bond

  • Theories on Covalent Bond Formation
  • Valence Bond Theory- Introduction and Covalent Bond Formation
  • Valence Bond Theory- Types of Orbital Overlap Forming Covalent Bonds
  • Applications, Limitations, and Extensions of Valence Bond Theory
  • Hybridization- Introduction and Types
  • sp3 Hybridization of Carbon, Nitrogen, and Oxygen
  • sp2 Hybridization of Carbon, Carbocation, Nitrogen, and Oxygen
  • sp Hybridization of Carbon and Nitrogen
  • Shortcut to Determine Hybridization
  • The shape of sp hybrid orbital - Why is the lobe unequal?
  • VSEPR Theory- Introduction
  • Difference between Electron Pair Geometry and Molecular Structure
  • Finding Electron Pair Geometry and Related Shape
  • Predicting Electron-Pair Geometry and Molecular Structure Guideline
  • Predicting Electron pair geometry and Molecular structure - Examples
  • Finding Electron-Pair Geometry and Shape in Multicentre Molecules
  • Drawbacks of VSEPR Theory
  • Electron Wave Property, LCAO and MOT - Introduction
  • Linear Combination of Atomic Orbitals - Formation of Sigma and Pie bonds using MO Approach
  • The Energetics of Bonding and Antibonding Molecular orbitals
  • Conditions for the Valid Linear Combination of Atomic Orbitals  
  • Features of LCAO Theory
  • Finding the Electronic Configuration of Molecules using MO and Predicting Comparative Stability using Bond Order
  • Setting up the MO diagram for homonuclear diatomic molecules – Second Period Elements
  • Setting up the Molecular Orbital Diagram for Heteronuclear Diatomic Molecules
  • The Non-bonding Molecular Orbitals
  • Weakness of the Molecular Orbital Theory
  • Covalent bond Characteristics - Bond Length
  • Factors affecting Bond Length
  • How does Electron delocalization (Resonance) affect the Bond length?
  • Covalent bond Characteristics- Bond Angle
  • Factors affecting Bond Angle
  • Covalent bond Characteristics - Bond Order
  • How Bond Order Corresponds to the Bond Strength and Bond Length
  • Solved Examples of Bond Order Calculations
  • Covalent Bond Rotation
  • Covalent Bond Breakage
  • Covalent Bond Properties -Physical State, Melting and Boiling Points, Electrical Conductivity, Solubility, Isomerism, Non-ionic Reactions Rate, Crystal structure

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Electronic Displacement in a Covalent Bond

  • Electronegativity- Introduction
  • Factors Affecting Electronegativity- Atomic number, Atomic size, Shielding effect
  • Factors Affecting Electronegativity-s-orbitals, Oxidation state, Group electronegativity
  • Application of Electronegativity in Organic Chemistry
  • Physical Properties Affected by Electronegativity
  • Inductive effect - Introduction, Types, Classification, and Representation
  • Factors Affecting Inductive Effect- Electronegativity
  • Factors Affecting Inductive Effect- Bonding Order and Charge
  • Factors Affecting Inductive Effect- Bonding Position
  • Application of Inductive Effect- Acidity Enhancement and Stabilization of the counter ion due to -I effect
  • Application of Inductive Effect-Basicity enhancement and stabilization of the counter ion due to +I effect
  • Application of Inductive Effect-Stability of the Transition States
  • Application of Inductive Effect-Elevated Physical Properties of Polar Compounds
  • Is the Inductive Effect the same as Electronegativity?
  • Resonance - Introduction and Electron Delocalization
  • Partial Double Bond Character and Resonance Hybrid
  • Resonance Energy
  • Significance of Planarity and Conjugation in Resonance
  • p-orbital Electron Delocalization in Resonance
  • Sigma Electron Delocalization (Hyperconjugation)
  • Significance of Hyperconjugation
  • Resonance Effect and Types
  • Structure Drawing Rules of Resonance (Includes Summary)
  • Application of Resonance
  • Introduction to Covalent Bond Polarity and Dipole Moment
  • Molecular Dipole Moment
  • Lone Pair in Molecular Dipole Moment
  • Applications of Dipole Moment
  • Formal Charges - Introduction and Basics
  • How to Calculate Formal Charges (With Solved Examples)
  • Difference between Formal charges and Oxidation State

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Common Types of Reactions

  • Classification of common reactions based on mechanisms
  • Addition Reactions
  • Elimination Reactions (E1, E2, E1cb)
  • Substitutions (SN1, SN2, SNAr, Electrophilic, Nucleophilic)
  • Decomposition
  • Rearrangement
  • Oxidation-Reduction

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Drawing Organic Structures

  • Introduction
  • Empirical Formula
  • How to Calculate Empirical Formula from percentage composition and atomic masses
  • Related Numerical Problems - Finding Empirical Formula (Solved)
  • Molecular Formula
  • Numerical Problems related to finding molecular formula  (Solved)
  • How to calculate molecular formula from empirical formula and molecular masses
  • Hill Nomenclature - The Empirical and Molecular Formula Writing Rules
  • E/Z Nomenclature -  Structure Writing Rules for Substituted Alkenes
  • Kekulé
  • Condensed
  • Skeletal or Bond line
  • Polygon formula
  • Lewis Structures- What are Lewis structures and How to Draw
  • Rules to Draw Lewis structures- With Solved Examples
  • Lewis structures- Solved Examples, Neutral molecules, Anions, and Cations
  • Limitation of Lewis structures
  • 3D structure representation- Dash and Wedge line
  • Molecular models for organic structure representation- Stick model, Ball-stick, and Space-filling
  • Newman Projection- Introduction and Importance
  • How to Draw Newman Projections from Bond-Line Formula (5 step-by-step solved examples on alkane, substituted alkane, alkene, ketone, and cycloalkane)
  • Drawing Newman Projections to the Bond line Formula (solved examples)
  • Sawhorse Projection

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Functional Groups in Organic Chemistry

  • What are functional groups?
  • Chemical and Physical Properties affected by the Functional Groups
  • Identifying Functional Groups by name and structure
  • Functional Group Categorization- Exclusively Carbon-containing Functional Groups
  • Functional Group Categorization- Functional Groups with Carbon-Heteroatom Single Bond
  • Functional Group Categorization- Functional Groups with Carbon-Heteroatom Multiple Bonds
  • Rules for IUPAC nomenclature of Polyfunctional Compounds
  • Examples of polyfunctional compounds named according to the priority order
  • Examples of reactions wherein the functional group undergoes transformations

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Structural Isomerism

  • Introduction
  • Chain Isomerism
  • Position Isomerism
  • Functional Isomerism
  • Tautomerism
  • Metamerism
  • Ring-Chain Isomerism

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Intermolecular Forces

  • Ion-Dipole Interactions-Introduction and Occurrence
  • Factors Affecting the Ion-Dipole Strength
  • Importance of Ion-Dipole Interactions
  • Ion-Induced Dipole - Introduction, Strength and Occurrence
  • Factors Affecting the Strength of Ion-Induced Dipole Interactions
  • Ion-Induced Dipole Interactions in Polar Molecules
  • Vander Waals Forces -Introduction
  • Examples of Vander Waals' forces
  • Vander Waals Debye (Polar-Nonpolar) Interactions
  • Factors affecting the Strength of Debye Forces
  • Vander Waals Keesom Force - Introduction, Occurrence and Strength
  • Vander Waals London Force - Introduction, Occurrence, And Importance
  • Factors Affecting the Strength of London Dispersion Forces- Atomic size and Shape
  • Introduction, Occurrence and Donor, Acceptors of Hydrogen Bond
  • Hydrogen bond Strength, Significance and Types
  • Factors Affecting Hydrogen Bond Strength
  • Impact of Hydrogen bonding on Physical Properties- Melting and boiling point, Solubility, and State
  • Calculation of the Number of Hydrogen Bonds and Hydrogen bond Detection

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Physical Properties

  • Physical Properties- Introduction, Role of Intermolecular Forces
  • Physical State Change-Melting Point
  • Role of Symmetry, Role of Carbon numbers, Role of Geometry
  • Physical State Change-Boiling Point
  • Intermolecular Forces and their Effect on the Boiling Point, Role of Molecular Weight (Size), Molecular Shape, Polarity
  • Boiling Point of Special Compounds- Amino acids, Carbohydrates, Fluoro compounds
  • Solubility in Water
  • Density
  • Preliminary Qualitative Analysis of some Organic Compounds | Intensive Physical Property Measurements

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Fundamentals of Organic Reactions

  • Types of Arrows Used in Chemistry
  • Curved Arrows in Organic Chemistry- with Examples
  • Electrophiles - Introduction, Identification and Reaction
  • Formation and Classification of Electrophiles- Neutral and Charged
  • Difference between Electrophiles and Lewis Acids
  • Nucleophiles - Identification and Role in a Reaction
  • Types of Nucleophiles- Lone Pair
  • Types of Nucleophiles- Pie Bond
  • Types of Nucleophiles- Sigma Bond
  • Periodic Trend and Order in Nucleophilicity
  • Introduction to Reactions Involving Nucleophiles
  • Nucleophile Reactions- Aliphatic Displacement type - SN1, SN2
  • Nucleophile Reactions- Acyl Displacement type
  • Nucleophile reactions- Aromatic Displacement type- Electrophilic, Nucleophilic
  • Addition Reactions- Electrophilic, Nucleophilic, and Acyl
  • Ambident Nucleophiles- Introduction and Formation
  • Ambident Nucleophile - Nature of the Substrate
  • Ambident Nucleophile- Influence of the Positive Counter Ions
  • Ambident Nucleophile- Effect of Solvent
  • Lone Pair - Introduction and Formation
  • Physical Properties Affected by the Lone Pair- Shape and Bond Angle
  • Physical Properties Affected by the Lone Pair- Hydrogen Bonding
  • Physical Properties Affected by the Lone Pair- Polarity and Dipole Moment
  • Chemical property affected by the Lone pair- Nucleophilicity
  • Leaving Group - Introduction and Nature
  • Good and Bad Leaving Group
  • Factors Determining Stability of the Leaving Groups- Electronegativity, Size, Resonance Stability
  • Using pKa as a Measure of Leaving Group Ability
  • Leaving Groups in Displacement Reactions
  • Leaving Groups in Elimination Reactions

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Reactive Intermediates

  • Carbocation - Introduction, Nature, and Types
  • Formation of Carbocation
  • Stability of Carbocations- Inductive, Resonance, and Hyperconjugation
  • Other Structural Features Increasing Carbocation Stability
  • Structural Feature Decreasing Carbocation Stability
  • Fate of the Carbocation
  • General Carbocation Formation Reactions
  • Carbanion - Introduction, Nature, and Types
  • Formation of Carbanions
  • Carbanion Stabilization
  • Ease of Formation of Carbanion -Acidic proton
  • Fate of the Carbanion
  • Free Radical - Introduction and Types of Carbon-Centred Radicals
  • Structure of Carbon-Centred Free Radical
  • Formation of Radicals
  • Stability of the Carbon-Centred Radicals
  • Other Structural Feature Increasing Free Radical Stability
  • Comparing Free Radical Stability using Dissociation energies (D-H)
  • Fate of Free Radicals
  • Common Reactions Involving Carbon-Free Radicals

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Stereoisomerism - Conformation and Configurational Isomerism

  • Conformations in Organic Chemistry - An Introduction
  • How are Conformational Isomers Depicted
  • Open Chain and Closed Chain Conformations
  • Nomenclature related to sp3-sp3 and sp3-sp2 bond rotations
  • Conformational Analysis
  • Factors affecting the stability of conformers - Stabilizing Interactions |Hyperconjugation
  • Factors affecting the stability of conformers - Stabilizing Interactions | Intramolecular Hydrogen Bonding
  • Factors affecting the stability of conformers - Stabilizing Interactions | Dipole Minimizations
  • Factors affecting the stability of conformers - Destabilizing Interactions | Steric strain
  • Factors affecting the stability of conformers - Destabilizing Interactions | Torsional strain
  • Factors affecting the stability of conformers - Destabilizing Interactions | Angle strain
  • Importance of Conformational Analysis
  • Conformation in Compounds with Lone Pairs
  • Role of Solvents in Conformations
  • An Example of Conformation Dependent Reaction and Product Selectivity
  • Geometrical Isomerism - Introduction
  • Impact of cis-trans isomerism on physical properties
  • Impact of cis-trans isomerism on chemical reactions
  • Scope of Geometrical Isomerism in Biological Systems and Industrial Applications
  • E/Z Nomenclature in Substituted Alkenes
     

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