Question

There are two different substances with the formula \(\mathrm{C}_{3} \mathrm{H}_{6}\). Draw both, and tell how they differ.

Short answer

Propene and cyclopropane differ in structure: one is linear with a double bond, the other is a ring.

Step-by-step solution

Identify the Formula

The formula \(\mathrm{C}_{3}\mathrm{H}_{6}\) indicates a molecule that can either form a ring or have a double bond, as it follows the general formula for alkenes (\(\mathrm{C}_n\mathrm{H}_{2n}\)) and cycloalkanes (\(\mathrm{C}_n\mathrm{H}_{2n}\)).

Draw Propene (Alkene)

Propene is an alkene with a double bond between two carbon atoms. The structure is:- \(\mathrm{CH}_2=\mathrm{CH}-\mathrm{CH}_3\).This molecule features a double bond between the first and second carbon atoms.

Draw Cyclopropane (Cycloalkane)

Cyclopropane forms a ring with the carbon atoms. The structure is: - A triangle-shaped ring made of three carbon atoms, each bonded to two hydrogen atoms. This molecule forms a closed ring of carbon atoms.

Compare Structures

Propene has a linear structure with a double bond, while cyclopropane is a ring structure with only single bonds. This structural difference leads to different chemical properties and reactivity.

Key concepts

Alkenes

Alkenes are hydrocarbons that contain at least one carbon-carbon double bond. This double bond is a key feature that influences the chemical properties of alkenes.
One of the simplest examples of an alkene is propene, which has the molecular formula \(\text{C}_3\text{H}_6\). Here, propene features a double bond between the first and second carbon atoms. Its structural representation is \(\text{CH}_2=\text{CH}-\text{CH}_3\), where the equals sign represents the double bond.This double bond not only affects the geometry of the molecule but also its reactivity.
Alkenes are typically more reactive than alkanes. This reactivity is due to the presence of the double bond which can open and participate in various chemical reactions, such as addition reactions. Some important points to remember about alkenes:

• They have the general formula \(\text{C}_n\text{H}_{2n}\).
• The presence of the double bond makes them unsaturated hydrocarbons.
• They are known for undergoing reactions that alkanes cannot because of the double bond.

Cycloalkanes

Cycloalkanes are a type of hydrocarbon that form a closed ring of carbon atoms, and they do not have any double bonds. Instead, the carbons are joined by single bonds only. A key feature of cycloalkanes is that they adhere to the same general formula as alkenes, \(\text{C}_n\text{H}_{2n}\), despite not possessing any double bonds.
Cyclopropane is one of the most straightforward examples of a cycloalkane. The structure of cyclopropane: three carbons arranged in a triangle, each bonded to two hydrogens. This results in a ring that provides a distinct shape to the molecule.

• Cyclopropane is a triangle-shaped structure which influences its chemical properties and stability.
• It features only single bonds between atoms and is often considered less reactive than alkenes due to the absence of a double bond.

The closed-ring structure of cycloalkanes leads to distinctive chemical behavior compared to acyclical alkanes and alkenes.

Structural Isomers

Structural isomers are molecules that have the same molecular formula but differ in the connectivity of the atoms within the molecule. This results in entirely different physical and chemical properties.
When considering \(\text{C}_3\text{H}_6\), propene and cyclopropane serve as prime examples of structural isomers.

• Propene has a linear structure with a key double bond between two of its carbon atoms.
• Cyclopropane, on the other hand, possesses a ring structure of carbon atoms, each connected by a single bond.

The concept of structural isomerism underscores the diversity of organic chemistry. Even with the same set of atoms, different arrangements provide distinct properties and reactivities. Understanding how structural isomers differ can offer insights into why certain chemicals behave the way they do.