Question

Draw the condensed structural formula for the three isomers of pentane, \(\mathrm{C}_{5} \mathrm{H}_{12}\).

Short answer

The three isomers of pentane are n-pentane, isopentane, and neopentane.

Step-by-step solution

Understand the Problem

We are tasked to draw the condensed structural formulas for the isomers of pentane. Pentane has the molecular formula \( \mathrm{C}_5 \mathrm{H}_{12} \), and we are looking for its three structural isomers.

Identify the First Isomer

The first isomer of pentane is n-pentane, which is a straight-chain alkane with the formula \( \mathrm{CH}_3(\mathrm{CH}_2)_3\mathrm{CH}_3 \). All carbon atoms are connected in a single continuous chain with no branches.

Identify the Second Isomer

The second isomer is isopentane (or methylbutane). It has a four-carbon chain with a methyl group attached to the second carbon. The condensed structural formula is \( \mathrm{(CH_3)_2CHCH_2CH_3} \).

Identify the Third Isomer

The third isomer is neopentane (or dimethylpropane), where the structure is a central carbon atom bonded to three methyl groups and one additional carbon. Its formula is \( \mathrm{(CH_3)_4C} \).

Key concepts

Isomers

In organic chemistry, isomers are fascinating molecules that share the same molecular formula but have different structural arrangements. This means they contain the same number of atoms of each element, but their atoms are arranged in distinct ways.

Let's consider the isomers of pentane (\( \mathrm{C}_5 \mathrm{H}_{12} \)). Each isomer exhibits unique physical and chemical properties due to these structural differences.

There are three primary isomers for pentane:

• n-Pentane: This is the straight-chain form where all the carbon atoms are connected in a continuous, unbranched line.
• Isopentane (methylbutane): This features a branching on the second carbon, creating a more compact structure.
• Neopentane (dimethylpropane): This structure has a central carbon atom bonded to three methyl groups, forming a highly branched isomer.

Understanding and visualizing isomers helps chemists predict how a compound will behave in different chemical reactions or environments, highlighting the importance of these structural differences.

Structural Formulas

A structural formula is a detailed way of representing the arrangement of atoms within a molecule. While the molecular formula gives us a simple count of each type of atom in the compound, the structural formula reveals the actual connections between those atoms.

For pentane and its isomers, the structural formulas are essential tools to differentiate between the three possibilities. Each formula highlights how atoms are bonded:

• Condensed structural formula: This format reduces repetitive information by grouping atoms. For example, n-pentane's condensed formula is written as \( \mathrm{CH}_3(\mathrm{CH}_2)_3\mathrm{CH}_3 \), showing a streamlined sequence.
• The condensed formula for isopentane, \( \mathrm{(CH_3)_2CHCH_2CH_3} \), highlights the branching by grouping the twice-repeated methyl group.
• Neopentane, with the formula \( \mathrm{(CH_3)_4C} \), is condensed to show its highly branched nature.

By using structural formulas, chemists can communicate the three-dimensional arrangement of atoms in a molecule, which is crucial for understanding its reactivity and interactions.

Pentane Molecular Structure

Pentane is a simple yet intriguing alkane, which is a type of hydrocarbon comprised only of carbon and hydrogen atoms. Its molecular formula, \( \mathrm{C}_5\mathrm{H}_{12} \), indicates that it contains five carbon atoms and twelve hydrogen atoms.

The term "pentane" refers to the straight-chain isomer, also known as n-pentane. In the context of molecular structure:

• n-Pentane is the simplest form where all five carbon atoms are in a straight chain. It's the least crowded and therefore often exhibits different boiling and melting points compared to its isomers.
• Isopentane and neopentane introduce branching to this structure, creating variations in shape that impact how these molecules pack together in the solid or liquid state, affecting their physical properties.

The exploration of pentane's molecular structure demonstrates the concept of molecular isomerism, where small changes in structure lead to significant differences in chemical behavior and properties. Observing these differences in pentane's isomers leads to deeper insights into the significance of molecular architecture in organic chemistry.