Podcast
Questions and Answers
Which of the following compounds is classified as 'cis'?
Which of the following compounds is classified as 'cis'?
Trans-1-bromo-3-chlorocyclobutane has substituents on the same side of the cyclobutane ring.
Trans-1-bromo-3-chlorocyclobutane has substituents on the same side of the cyclobutane ring.
False
What geometrical configuration is indicated when substituents point toward opposite faces?
What geometrical configuration is indicated when substituents point toward opposite faces?
trans
The compound _______ features an equatorial bromo substituent.
The compound _______ features an equatorial bromo substituent.
Signup and view all the answers
Match the compound with its configuration:
Match the compound with its configuration:
Signup and view all the answers
What is the primary reason for geometrical isomerism in alkenes?
What is the primary reason for geometrical isomerism in alkenes?
Signup and view all the answers
Cyclic compounds can have geometrical isomers due to restricted rotation.
Cyclic compounds can have geometrical isomers due to restricted rotation.
Signup and view all the answers
What are the designations used in the E/Z nomenclature system?
What are the designations used in the E/Z nomenclature system?
Signup and view all the answers
Cis-dichloroethene and trans-dichloroethene are examples of __________ isomers.
Cis-dichloroethene and trans-dichloroethene are examples of __________ isomers.
Signup and view all the answers
Match the following terms with their definitions:
Match the following terms with their definitions:
Signup and view all the answers
Which condition does NOT lead to geometrical isomerism?
Which condition does NOT lead to geometrical isomerism?
Signup and view all the answers
The priority of groups in the E/Z nomenclature is determined using the Cahn-Ingold-Prelog rules.
The priority of groups in the E/Z nomenclature is determined using the Cahn-Ingold-Prelog rules.
Signup and view all the answers
What is an example of a cycloalkane?
What is an example of a cycloalkane?
Signup and view all the answers
Which type of isomerism is characterized by isomers that can be interconverted exclusively by rotations about single bonds?
Which type of isomerism is characterized by isomers that can be interconverted exclusively by rotations about single bonds?
Signup and view all the answers
The staggered conformation is the least stable conformation of butane.
The staggered conformation is the least stable conformation of butane.
Signup and view all the answers
What is the dihedral angle in molecular structure?
What is the dihedral angle in molecular structure?
Signup and view all the answers
The _____ conformation of ethylene glycol is more stable due to intramolecular hydrogen bonding.
The _____ conformation of ethylene glycol is more stable due to intramolecular hydrogen bonding.
Signup and view all the answers
Match the type of conformation with its description:
Match the type of conformation with its description:
Signup and view all the answers
Which conformation has a dihedral angle of 0 degrees?
Which conformation has a dihedral angle of 0 degrees?
Signup and view all the answers
Conformational isomers are typically called rotamers.
Conformational isomers are typically called rotamers.
Signup and view all the answers
What is the most stable conformation of butane?
What is the most stable conformation of butane?
Signup and view all the answers
Study Notes
2- Geometrical Isomerism
- Stereoisomers (diastereomers) have the same molecular formula but differ in spatial arrangement.
- This difference arises due to either restricted rotation around double bonds (in alkenes) or restricted rotation in cyclic structures (in cycloalkanes).
- Open-chain alkanes rotate freely about single bonds.
- Alkenes and cycloalkanes exhibit restricted rotation.
- Cis- and trans- isomers have different physical and chemical properties.
Example of Geometrical Isomers
- Cis-dichloroethene and trans-dichloroethene are examples of geometrical isomers.
- The difference lies in the arrangement of chlorine atoms around the double bond.
Z/E Nomenclature
- Used to name geometrical isomers with different groups on a double bond.
- Z (Zusammen): Higher priority groups are on the same side of the double bond.
- E (Entgegen): Higher priority groups are on opposite sides of the double bond.
- Cahn-Ingold-Prelog rules determine priority.
Examples of Z/E isomers
- Specific examples of molecules with Z/E configurations were given with priority rules.
Geometrical Isomers in Cyclic Compounds
- Cycloalkanes are cyclic alkanes with restricted rotation around carbon-carbon bonds.
- Cis- and trans- descriptors indicate relative positions of substituents on the ring relative to the ring plane.
- Cis: substituents are on the same side of the ring
- Trans: substituents are on opposite sides of the ring
Examples of Cis/Trans isomers in cyclic compounds
- Specific examples of cyclic compounds with cis and trans isomers were shown.
No Geometrical Isomers
- If one carbon of a double bond has two identical substituents, there are no geometrical isomers.
3 - Conformational Isomerism (Rotamers)
- Conformational isomerism is a form of stereoisomerism where isomers interconvert solely via rotation about single bonds.
- These isomers are also known as conformers or rotamers.
Types of Conformational Isomers in Ethane
- Eclipsed: C-H bonds are directly aligned.
- Staggered: C-H bonds are maximally separated.
What is a Dihedral/Torsional Angle
- The angle between C-H bonds on adjacent carbons in a Newman projection.
- In an eclipsed conformation, the dihedral angle is 0°.
- In a staggered conformation, the dihedral angle is 60°.
- Skew conformations have intermediate dihedral angles.
Conformations of Butane
- The different conformations of butane (e.g., anti, gauche, eclipsed) were shown.
- Staggered conformations (e.g., anti) are generally more stable than eclipsed conformations due to reduced steric hindrance.
Most Stable Conformers
- The most stable conformers maximize the distance between bulky groups.
- Intramolecular forces like hydrogen bonding can increase the stability of certain conformations in specific molecules.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Test your understanding of geometrical isomerism, including stereoisomers, restricted rotations, and Z/E nomenclature. This quiz covers the distinctions between cis- and trans- isomers and their properties. Challenge yourself with examples and rules governing molecular arrangements.
