Question

Write the structural formulas of the alcohols with the formula \(\mathrm{C}_{6} \mathrm{H}_{14} \mathrm{O}\) and indicate those that are chiral. Show only the \(\mathrm{C}\) atoms and the \(-\mathrm{OH}\) groups.

Short answer

Draw the isomers of hexanol and identify chiral centers, like in 2-hexanol and 3-hexanol.

Step-by-step solution

Understand the Molecular Formula

The given molecular formula is \( \mathrm{C}_6\mathrm{H}_{14}\mathrm{O} \). This suggests that this is an alcohol with a total of 6 carbon atoms, 14 hydrogen atoms, and one hydroxyl group (\(-\mathrm{OH}\)). Our task is to determine all the possible structural isomers.

Consider Possible Carbon Chain Arrangements

For a 6-carbon alcohol, the main carbon chain variations can include linear chains, branched chains, and various positions for the \(-\mathrm{OH}\) group. Consider all possible carbon chain structures: straight chain (hexanol), a 5-carbon chain with a methyl branch (methylpentanol), two possible 4-carbon chains with two methyl branches (dimethylbutanol), and so on.

Determine All Isomers

Draw each possible structure using the carbon chain arrangements from Step 2. Place the \(-\mathrm{OH}\) group at different positions on each carbon chain. Examples include 1-hexanol, 2-hexanol, 3-hexanol, 2-methyl-1-pentanol, and so forth.

Identify Chiral Isomers

A chiral isomer will have a carbon atom bonded to four different groups. Inspect each structure for such a carbon center. For instance, in 2-hexanol and 3-hexanol, the carbon holding the \(-\mathrm{OH}\) group is bonded to four different substituents, making it chiral.

Key concepts

Structural Isomers

In organic chemistry, structural isomers are compounds that have the same molecular formula but different arrangements of atoms. This means that even though they share the same components, their structures differ, leading to varying properties and functions. When dealing with the molecular formula \( \mathrm{C}_6\mathrm{H}_{14}\mathrm{O} \), which represents a group of alcohols, structural isomers arise from the many possible ways to arrange the carbon backbone and place the hydroxyl group.

Consider possible arrangements:

• A straight chain (e.g., hexanol)
• Branched chains (e.g., methyl derivatives like methylpentanol or dimethylbutanol)
• Position variations for the \(-\mathrm{OH}\) group

Through these variations, each unique structure comprises a distinct isomer. Finding all possible isomers involves drawing each potential arrangement and considering the position of the \(-\mathrm{OH}\) group on the carbon skeleton.

Chiral Molecules

Chirality in molecules is akin to left and right hands - they are mirror images that cannot be superimposed. A chiral molecule has at least one chiral center, which is typically a carbon atom bonded to four different atoms or groups. For alcohols with the formula \( \mathrm{C}_6\mathrm{H}_{14}\mathrm{O} \), you search for structural isomers with such a carbon atom.

Identifying chiral isomers involves looking for positions where the \(-\mathrm{OH}\) group is attached to a carbon with different neighboring atoms or groups. As in 2-hexanol and 3-hexanol, the carbon chain configuration creates a unique situation where that carbon atom is linked to four distinct groups, making it chiral. This unique arrangement results in different stereoisomers, which exhibit different properties despite having the same formula.

Molecular Formula

A molecular formula represents the total number of each type of atom in a molecule. For instance, the formula \( \mathrm{C}_6\mathrm{H}_{14}\mathrm{O} \) indicates the presence of 6 carbon atoms, 14 hydrogen atoms, and one oxygen atom in an alcohol structure. This formula doesn't specify the connectivity of the atoms, solely their presence and quantity.

The task of generating structural isomers begins at the molecular formula level by ensuring the total number of atoms remains constant across all potential structures. Each isomer of an alcohol will contain an \(-\mathrm{OH}\) group, corresponding to the lone oxygen atom. The challenge lies in altering the arrangement of these atoms to explore all possible isomeric forms while adhering strictly to the molecular formula constraints.

Hydroxyl Group

The hydroxyl group, \(-\mathrm{OH}\), is the defining feature of alcohols, contributing to their chemical properties. When attached to a carbon chain in an alcohol molecule, this group affects solubility, boiling and melting points, and polarity.

Position matters greatly. The location of the hydroxyl group on a carbon chain determines different types of alcohols. For example, moving the \(-\mathrm{OH}\) group across the length of a carbon chain creates different isomers, each with unique properties. Isomers of \( \mathrm{C}_6\mathrm{H}_{14}\mathrm{O} \) might have the \(-\mathrm{OH}\) group at various positions, leading to names like 1-hexanol and 2-methyl-1-pentanol, dictating specific structural and functional distinctions. Hence, understanding the role of the hydroxyl group is key to grasping its influence in a molecule's behavior.