Chapter 3: Problem 18
Differentiate between intermolecular and intramolecular hydrogen bond.
Short Answer
Expert verified
Intramolecular hydrogen bonds occur within a single molecule among two functional groups, often leading to a ring-like structure, and are generally stronger. Intermolecular hydrogen bonds occur between separate molecules, such as the bond between water molecules.
Step by step solution
01
Define Hydrogen Bond
A hydrogen bond is a special type of dipole-dipole attraction between molecules, not a covalent bond to a hydrogen atom. It results from the attractive force between a hydrogen atom covalently bonded to a very electronegative atom such as a nitrogen, fluorine, or oxygen atom and another electronegative atom.
02
Define Intramolecular Hydrogen Bond
An intramolecular hydrogen bond is an attractive force that occurs within one molecule. This happens when two functional groups of a single molecule can form hydrogen bonds with each other.
03
Define Intermolecular Hydrogen Bond
An intermolecular hydrogen bond, on the other hand, occurs between two separate molecules. This happens when the functional groups of different molecules can form hydrogen bonds with each other.
04
Contrasting Intramolecular and Intermolecular Hydrogen Bonds
Therefore, the main difference between intramolecular and intermolecular hydrogen bonds is that intramolecular hydrogen bonds exist within a single molecule while intermolecular hydrogen bonds exist between separate molecules. Intramolecular hydrogen bonds tend to be stronger than intermolecular hydrogen bonds because they involve more intimate contact between the molecules.
05
Examples of Intramolecular and Intermolecular Hydrogen Bonds
A well-known example of an intramolecular hydrogen bond is found in the molecule of salicylic acid, and an example of an intermolecular hydrogen bond can be found in water (H2O) molecules where hydrogen atom of one water molecule is attracted to the oxygen atom of another water molecule.
Unlock Step-by-Step Solutions & Ace Your Exams!
-
Full Textbook Solutions
Get detailed explanations and key concepts
-
Unlimited Al creation
Al flashcards, explanations, exams and more...
-
Ads-free access
To over 500 millions flashcards
-
Money-back guarantee
We refund you if you fail your exam.
Over 30 million students worldwide already upgrade their learning with Vaia!
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Intermolecular Hydrogen Bond
Hydrogen bonds are a fascinating aspect of chemistry that significantly influence the properties of molecules. An intermolecular hydrogen bond is a type of attractive force that operates between hydrogen atoms of one molecule and electronegative atoms, such as oxygen or nitrogen, of another molecule. This attraction is primarily due to the polar nature of the molecules involved.
Consider water molecules, each consisting of one oxygen and two hydrogen atoms. The oxygen atom is more electronegative, meaning it pulls electrons towards itself more strongly than hydrogen, creating a dipole with a partial negative charge on the oxygen and a partial positive charge on the hydrogens. When water molecules come close to each other, the partial positive hydrogen of one water molecule is attracted to the partial negative oxygen of a neighboring molecule, forming a bridge-like link - that is an intermolecular hydrogen bond.
These bonds are crucial as they contribute to the high boiling point and surface tension of water, among other physical properties. In DNA, they help to hold the two strands together, forming the famous double helix structure. Without intermolecular hydrogen bonds, the very fabric of life as we know it would be different.
Consider water molecules, each consisting of one oxygen and two hydrogen atoms. The oxygen atom is more electronegative, meaning it pulls electrons towards itself more strongly than hydrogen, creating a dipole with a partial negative charge on the oxygen and a partial positive charge on the hydrogens. When water molecules come close to each other, the partial positive hydrogen of one water molecule is attracted to the partial negative oxygen of a neighboring molecule, forming a bridge-like link - that is an intermolecular hydrogen bond.
These bonds are crucial as they contribute to the high boiling point and surface tension of water, among other physical properties. In DNA, they help to hold the two strands together, forming the famous double helix structure. Without intermolecular hydrogen bonds, the very fabric of life as we know it would be different.
Intramolecular Hydrogen Bond
On a smaller scale, within a singular molecular entity, an intramolecular hydrogen bond is an attractive force, but it occurs internally, linking different parts of the same molecule. These bonds often arise when a molecule contains multiple functional groups that are capable of hydrogen bonding and are positioned such that a hydrogen atom covalently attached to an electronegative atom can interact with another electronegative atom within the same molecule.
Consider the molecule of salicylic acid, an organic compound present in many skin-care products. It has a hydroxyl (OH) group and a carboxyl (COOH) group within the same molecule. The hydrogen from the hydroxyl group can form a hydrogen bond with the oxygen of the carboxyl group, resulting in an intramolecular hydrogen bond. This internal bonding can lead to the molecule adopting a specific shape or configuration, which can influence the molecule's chemical reactivity and physical properties.
Intramolecular hydrogen bonds can make a molecule more stable and are often associated with the functionality of biomolecules, including the way proteins fold and enzymes function, playing a significant role in the stabilization of their 3D structures.
Consider the molecule of salicylic acid, an organic compound present in many skin-care products. It has a hydroxyl (OH) group and a carboxyl (COOH) group within the same molecule. The hydrogen from the hydroxyl group can form a hydrogen bond with the oxygen of the carboxyl group, resulting in an intramolecular hydrogen bond. This internal bonding can lead to the molecule adopting a specific shape or configuration, which can influence the molecule's chemical reactivity and physical properties.
Intramolecular hydrogen bonds can make a molecule more stable and are often associated with the functionality of biomolecules, including the way proteins fold and enzymes function, playing a significant role in the stabilization of their 3D structures.
Dipole-Dipole Attraction
Delving into the types of attractive forces even further, dipole-dipole attraction is a significant force that occurs between polar molecules. A molecule is polar when it has an uneven distribution of electrons between different atoms, which results in a permanent dipole moment; it has a 'positive' and a 'negative' side.
For instance, the molecule of hydrogen chloride (HCl) is polar because the electrons are more attracted to the chlorine atom, leaving the hydrogen atom with a partial positive charge and chlorine with a partial negative charge. When HCl molecules are in proximity, the partial positive end of one molecule will attract the partial negative end of another molecule. This attraction is a dipole-dipole interaction and is generally weaker than hydrogen bonding but stronger than Van der Waals forces due to the permanent nature of the dipoles involved. These interactions are critical in determining the boiling and melting points of compounds and affect how they interact with other substances.
For instance, the molecule of hydrogen chloride (HCl) is polar because the electrons are more attracted to the chlorine atom, leaving the hydrogen atom with a partial positive charge and chlorine with a partial negative charge. When HCl molecules are in proximity, the partial positive end of one molecule will attract the partial negative end of another molecule. This attraction is a dipole-dipole interaction and is generally weaker than hydrogen bonding but stronger than Van der Waals forces due to the permanent nature of the dipoles involved. These interactions are critical in determining the boiling and melting points of compounds and affect how they interact with other substances.
Electronegativity
At the core of understanding hydrogen bonding and dipole-dipole interactions lies the concept of electronegativity, which is a measure of an atom's ability to attract and hold onto electrons within a chemical bond. Essentially, electronegativity determines how 'greedy' an atom is for electrons.
On the Pauling scale, fluorine (F) is the most electronegative element with a value of 3.98, which means it has a strong tendency to pull electrons towards itself when forming chemical bonds. Atoms like oxygen (O), nitrogen (N), and fluorine (F) are highly electronegative and are often involved in hydrogen bonding because they attract the electron pair from the hydrogen atom enough to create the conditions necessary for hydrogen bonds.
Understanding electronegativity is crucial because it not only influences the type of bond (ionic or covalent) that will form between two atoms but also contributes significantly to the physical and chemical properties of molecules. High electronegativity differences usually lead to polar bonds and thus to the characteristics associated with them, such as solubility in water, reactivity, and melting and boiling points.
On the Pauling scale, fluorine (F) is the most electronegative element with a value of 3.98, which means it has a strong tendency to pull electrons towards itself when forming chemical bonds. Atoms like oxygen (O), nitrogen (N), and fluorine (F) are highly electronegative and are often involved in hydrogen bonding because they attract the electron pair from the hydrogen atom enough to create the conditions necessary for hydrogen bonds.
Understanding electronegativity is crucial because it not only influences the type of bond (ionic or covalent) that will form between two atoms but also contributes significantly to the physical and chemical properties of molecules. High electronegativity differences usually lead to polar bonds and thus to the characteristics associated with them, such as solubility in water, reactivity, and melting and boiling points.
