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Ch.24 - The Chemistry of Life: Organic and Biological Chemistry
Chapter 24, Problem 43

Dichloroethylene 1C2H2Cl22 has three forms (isomers), each of which is a different substance. (a) Draw Lewis structures of the three isomers, all of which have a carbon–carbon double bond.

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Identify the molecular formula for dichloroethylene: \( \text{C}_2\text{H}_2\text{Cl}_2 \).
Recognize that the presence of a carbon-carbon double bond (C=C) is a key feature in each isomer.
Consider the possible arrangements of the chlorine (Cl) atoms around the C=C bond, keeping in mind that each carbon atom must also have a hydrogen (H) atom to satisfy the tetravalency of carbon.
Draw the first isomer, where both Cl atoms are on the same side of the C=C bond, known as the cis isomer.
Draw the second isomer, where the Cl atoms are on opposite sides of the C=C bond, known as the trans isomer, and the third isomer where both Cl atoms are attached to the same carbon atom, known as the geminal isomer.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. They use dots to represent electrons and lines to represent bonds between atoms. Understanding how to draw Lewis structures is essential for visualizing molecular geometry and predicting the behavior of molecules in chemical reactions.
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Isomers

Isomers are compounds that have the same molecular formula but different structural arrangements of atoms. This can lead to variations in physical and chemical properties. In the case of dichloroethylene, the presence of different isomers highlights the importance of molecular structure in determining the characteristics of a substance.
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Carbon-Carbon Double Bonds

A carbon-carbon double bond consists of one sigma bond and one pi bond formed between two carbon atoms. This type of bond is crucial in organic chemistry as it influences the reactivity and stability of molecules. The presence of a double bond in dichloroethylene is significant for its isomeric forms, affecting their geometry and properties.
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