Organic Compounds: Structural Representation

What is an Organic Compound?

The covalently bonded carbon-containing compounds called organic compounds are substantial for life on earth.

The specific branch of science that deals with organic compounds are called organic chemistry. Organic chemistry encompasses every characteristic feature of an organic compound, its properties, and behaviour under different conditions. Here we will discuss the structural representation of organic molecules.

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Structural Representation of Organic Compounds:

Though an organic compound has only one chemical formula, structurally it can be depicted in numerous ways. The three ways by which a compound can be represented are;
1. Complete Structural Formula
2. Condensed Structural Formula
3. Bond line Structural Formula

Complete Structural Formula:

The Lewis dot structure is considered the complete structural formula. In Lewis’s structure, the covalent bonds in the compound are denoted by a dash (―). This helps to emphasize the number of bonds formed by the atoms present in the molecule. Every single bond, a double bond, and a triple bond are represented by one dash, double dash, and triple dash respectively. It illustrates every single bond formed between every atom in the compound, thus called the complete structural formula.

For example, the complete structural formula for ethane, ethene and ethyne is shown as below:

Organic Compounds Structural Representation 01

Condensed Structural Formula:

In condensed structural formulas, the bonds to each carbon are omitted, but each distinct structural unit (group) is written with subscript numbers designating multiple substituents, including the hydrogens.

Organic Compounds Structural Representation 02

Bond Line Structural Formula:

A bond line structural formula is another way of structural representation of organic compounds.  Here, every bond is represented as a line in a zigzag manner. If not specified, every terminal is assumed to be a methyl (-CH3) group.

Organic Compounds Structural Representation 03

Organic Compounds Structural Representation 04

3-D Representation of Organic Compounds:

The organic compounds which were represented using structural formulas in the previous section are three-dimensional compounds. In order to draw the 3-D structure of an organic compound, we can use wedge-dash representation.

In wedge-dash representation, the bond that protrudes out of the plane of paper towards the viewer is denoted by a solid wedge while that projects away from the viewer or into the plane of the paper is denoted by a dashed wedge and the bond in the plane of the paper is represented by a line. For example, the wedge-dash representation for methane molecule is shown as below:

Organic Compounds Structural Representation 05

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