CHEM2311 Lecture 7: Conformational Analysis of Alkanes

These flashcards cover key vocabulary terms and concepts related to the conformational analysis of alkanes discussed in the lecture.

Conformational Analysis

The study of the energies of different conformations of a molecule.

Torsional Strain

The increased energy of a molecule due to electron-electron repulsion in an eclipsed conformation.

Steric Strain

The repulsion of bulky groups that are near each other in three-dimensional space.

Factors affecting conformer energy

Torsional strain (due to eclipsed interactions) and steric strain (due to repulsion of bulky groups).

Gauche Conformer

A conformer where bulky substituents on adjacent atoms have a 60-degree dihedral angle.

Anti Conformer

A conformer where bulky substituents on adjacent atoms have a 180-degree dihedral angle.

Eclipsed Conformation

Conformation where bonds on adjacent atoms are aligned with each other, leading to higher energy.

Staggered Conformation

Conformation where bonds on adjacent atoms are at a maximum distance from each other, leading to lower energy.

Dihedral Angle

The angle between two bonds on different atoms, important for analyzing conformations.

Newman Projection

A method used to visualize the conformation of a molecule by viewing along the bond connecting two atoms.

What is the primary function of a Newman projection?

To visualize the conformation of a molecule by viewing along a specific C-C bond, aiding in the identification of different conformers and their associated strains.

Potential Energy Diagram

A graph showing the energy levels of different conformers, indicating stability and energy barriers.

Barrier to Rotation

The energy required to convert one conformer to another, represented as the energy difference between an energy minimum (stable conformer) and an energy maximum (transition state) on a potential energy diagram.

Cycloalkanes

Alkanes that are arranged in a ring structure, with the general formula CnH2n.

Angle Strain (Ring Strain)

The destabilization in a cyclic molecule due to bond angles deviating significantly from the ideal bond angles for its hybridization (e.g., 109.5^\circ for sp^3 carbons).

Cycloalkane Stability Factors

Determined primarily by the interplay of angle strain (deviation from ideal bond angles) and torsional strain (eclipsing interactions between atoms or groups within the ring structure).

Cis/Trans Isomerism

Stereoisomerism that arises due to the different orientations of substituents around a ring or a double bond.

Cis/Trans Isomerism in Cycloalkanes

Describes the relative orientation of substituents on a ring: 'cis' for substituents on the same side, and 'trans' for substituents on opposite sides.

Constitutional Isomers

Compounds that have the same chemical formula but different connectivity of atoms.