Question

What is the relationship between the molecules 2-hexene and 3-hexene? Justify your answer.

Short answer

2-hexene and 3-hexene are isomers, as they have the same molecular formula (C6H12) but different structural formulas due to the different positions of the carbon-carbon double bond. This results in varied physical and chemical properties between the two molecules.

Step-by-step solution

Understand the molecules

2-hexene and 3-hexene are both unsaturated hydrocarbons with a double bond between two carbon atoms. The numbers 2 and 3 represent the position of the double bond in the carbon chain. The prefix 'hex' means that there are six carbon atoms in the molecule, and 'ene' means that there is a carbon-carbon double bond present.

Draw the structures

To compare 2-hexene and 3-hexene, we first draw their structures. Write down the longest carbon chain and place the double bond at the correct position. For 2-hexene, the structure is: H2C=CH-CH2-CH2-CH2-CH3 For 3-hexene, the structure is: CH3-CH2-CH=CH-CH2-CH3

Compare their characteristics

Now, we will compare their characteristics to determine the relationship between them. 1. The molecular formula for both molecules is C6H12, as they have the same number of carbons and hydrogens. 2. They both have a carbon-carbon double bond, making them unsaturated hydrocarbons. 3. The position of the double bond is different: In 2-hexene, the double bond is between the first and second carbon atoms, whereas, in 3-hexene, it is between the third and fourth carbon atoms.

Determine the relationship

Based on the similarities and differences in their characteristics, we can conclude that 2-hexene and 3-hexene are isomers. Isomers are molecules with the same molecular formula but different structural formulas. The difference in the position of the double bond leads to different physical and chemical properties. In conclusion, the relationship between 2-hexene and 3-hexene is that they are isomers, due to the same molecular formula but different structural formulas, leading to varied properties.

Key concepts

Unsaturated Hydrocarbons

Unsaturated hydrocarbons are organic compounds that contain at least one carbon-carbon double or triple bond in their structure, which means they have fewer hydrogen atoms than their saturated counterparts. These compounds are highly reactive due to the presence of these multiple bonds, making them key players in chemical reactions such as polymerization and hydrogenation.

In the case of hexene, we are dealing with an alkene, which is a type of unsaturated hydrocarbon with one or more double bonds. The presence of a double bond provides different points of reactivity, allowing for various isomers to be formed. This variation gives rise to a rich chemistry where the position of the double bond, as seen in 2-hexene and 3-hexene, significantly affects the molecule's properties and reactions.

Structural Formula

The structural formula of a molecule represents the arrangement of atoms within it. Unlike the molecular formula, which only tells us the number of each type of atom present, the structural formula gives us a visual representation, showing how those atoms are connected to one another.

For instance, when comparing 2-hexene to 3-hexene, both share the same molecular formula of C₆H₁₂, suggesting they have identical numbers of carbon and hydrogen atoms. However, when we scrutinize their structural formulas, we notice a key difference in the positioning of the double bond. This slight variance leads to the individual molecules exhibiting distinct properties, such as differences in boiling points and reactivity, despite their common molecular composition.

Molecular Formula

A molecular formula indicates the number and types of atoms present in a molecule but does not reveal any information about the arrangement of these atoms. It serves as a compact way to show what a substance is made of. For example, the molecular formula C₆H₁₂ represents a molecule that has six carbon atoms and twelve hydrogen atoms.

The molecular formula is crucial in identifying different isomers, as isomers share the same molecular formula while having different structures. The exercise comparing 2-hexene and 3-hexene perfectly exemplifies the concept of isomerism: despite possessing the same molecular formula, the atoms are arranged differently resulting in unique chemicals with distinct physical and chemical characteristics.