Chapter 4, Problem 71IP

Interpretation Introduction

Interpretation:

All of the following are representations of cis-1,2-dimethylcyclohexane except one, that exception has to be identified.

Concept Introduction:

Nomenclature of organic compounds:

The naming of the organic compound is given by IUPAC (International Union for pure and applied chemistry). In the IUPAC names consist of certain rules for giving chemical names they are,

• The longer number of Carbon chain of a compound is identified this is called parent of the compound.
• In the cyclic compounds the number of carbon involving in ring formation is called parent of the compound.
• The compound have more than one parent chains means the larger number of substitutions present in the chain is consider as a parent chain.
• The names of all substituents are arranged by alphabets to starts with lowest numbering.
• In the complex substituent having compounds the substituent name is assigned by a name each of them based on numbers going away from the parent.

Conformations: Rotation about C-C single bonds allows a compound to adopt a variety of possible three-dimensional shapes.

Newman projections: The new conformations of compounds can be drawn and analyzed by Newman projections. A Newman projection visualizes different conformations of Carbon-carbon chemical bond from front to back with the front carbon represented as a black dot and the back Carbon represented as a circle.

The angle between two hydrogens of a Newman projection is called as dihedral angle or torsional angle. This dihedral angle changes as the C-C bond rotates. Two conformations with special attentions are staggered and eclipsed conformation. Staggered conformation is the lowest in energy and the eclipsed conformation is the highest in energy.

For example,

Anti-conformation: The conformation with a dihedral angle of ${180}^{\circ }$ is called anti-conformation.

The two methyl groups achieve maximum separation from each other. In other, methyl groups are closer to each other; their electron clouds are repelling each other, causing an increase in energy. This unfavorable interaction is called gauche interaction.

Drawing Axial and Equatorial substituents:

Each carbon in cyclohexane can bear two substituents. One group is said to occupy an axial position, which is parallel to a vertical axis passing through the center of the ring. the other group is said to occupy an equatorial position, which is positioned approximately along the equator of the ring.

Conversion of chair conformation into Newman projection:

Ring flipping between Newman projections:

Ring flipping is a conformational change that is accomplished only through a rotation of all C-C single bonds. On ring flipping between two chair conformation equatorial changes into axial and vice-versa.