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Conformational Isomerism - Nomenclature Related to single and double bond rotations

Learning Objective: To study the various terminologies for single-bond and double-bond-containing molecular conformations. 

Skill Level - Intermediate

 

Prerequisites: 

 

Chapter: Stereochemistry

Sub-topic: Conformational Isomerism

 

Author's Note: Single bonds undergo bond rotations, due to which infinite conformations are possible, whereas double and triple bonds don't rotate. However, only a few conformations are stable and known amongst the others. So, this section will cover the types of eclipsed, staggered, and bisecting conformations adopted due to single bond rotations, that is, conformations arising due to sp3-sp3 and sp3-sp2 (carbon next to a double bond) bond rotations. 

Conformational Isomerism - Nomenclature Related to Single and Double Bond Rotations

sp3-sp3 bond rotations

Eclipse and staggered are the most common single-bond conformations. 

In most 1,2- substituted ethane molecules of the type YCH2-CH2Y or YCH2-CH2X (such as n-butane CH3-CH2-CH2-CH3), there are four possibilities within staggered and eclipsed conformations. 

Two types of staggered conformations are – 

.

.

 

Two types of eclipsed conformations are – 

.

.

 

sp3-sp2 bond rotations

The common conformations made by compounds with sp3-sp2 bond rotations are eclipsing and bisecting. 

For example, CH3-CH2-CHO.

Eclipsing conformations are of two types-

.

Bisecting conformations are of two types-

.

Subscribe to learn all various conformations, types, illustrations, and nomenclature. 

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