Question

For the general formula \(C_{6} \mathrm{H}_{14} \mathrm{O},\) draw the structures of three isomeric alcohols that illustrate primary, secondary, and tertiary structures.

Short answer

The three isomeric alcohols with the molecular formula \(C_{6}H_{14}O\) representing primary, secondary, and tertiary structures are: 1. Primary alcohol (Hexan-1-ol): \(CH_{3}CH_{2}CH_{2}CH_{2}CH_{2}CH_{2}OH\). The hydroxyl group is attached to a carbon atom that is connected to only one other carbon atom. 2. Secondary alcohol (Hexan-2-ol): \(CH_{3}CH(OH)CH_{2}CH_{2}CH_{2}CH_{3}\). The hydroxyl group is attached to a carbon atom that is connected to two other carbon atoms. 3. Tertiary alcohol (2-methylpentan-3-ol): \(CH_{3}C(OH)(CH_{3})CH_{2}CH_{2}CH_{3}\). The hydroxyl group is attached to a carbon atom that is connected to three other carbon atoms.

Step-by-step solution

Primary Alcohol Structure

For a primary alcohol, we need the carbon atom attached to the hydroxyl group to be connected to only one other carbon atom. One possible structure is: CH3CH2CH2CH2CH2CH2OH This compound is called hexan-1-ol, and is a primary alcohol as the carbon atom attached to the hydroxyl group (in bold) is only connected to one other carbon atom.

Secondary Alcohol Structure

For a secondary alcohol, the carbon atom attached to the hydroxyl group needs to be connected to two other carbon atoms. One possible structure is: CH3CH(OH)CH2CH2CH2CH3 This compound is called hexan-2-ol, and is a secondary alcohol as the carbon atom attached to the hydroxyl group (in bold) is connected to two other carbon atoms.

Tertiary Alcohol Structure

For a tertiary alcohol, the carbon atom attached to the hydroxyl group needs to be connected to three other carbon atoms. One possible structure is: CH3C(OH)(CH3)CH2CH2CH3 This compound is called 2-methylpentan-3-ol, and is a tertiary alcohol as the carbon atom attached to the hydroxyl group (in bold) is connected to three other carbon atoms. These three structures represent primary, secondary, and tertiary alcohols with the molecular formula C6H14O.

Key concepts

Primary Alcohol Structure

Understanding the primary alcohol structure is crucial for students delving into organic chemistry. A primary alcohol has its hydroxyl (-OH) group bound to a carbon atom that is in turn only attached to one other carbon atom and two hydrogen atoms. This is the simplest form of alcohol structures.

Let's consider hexan-1-ol as an example. The hydroxyl group is attached to the first carbon in the chain, making it primary. Visually, this can be represented as CH₃CH₂CH₂CH₂CH₂CH₂OH, with the terminal carbon carrying the -OH group. In general, primary alcohols are often characterized by their mild reactivity compared to their secondary and tertiary counterparts, and by the tendency to undergo oxidation to form aldehydes.

• Primary alcohols can be recognized by their '-ol' suffix and number positioning, indicating where the hydroxyl group is attached.
• They tend to oxidize to aldehydes when reacted with suitable oxidizing agents.
• Named by identifying the longest carbon chain attached to the -OH group.

Secondary Alcohol Structure

A secondary alcohol is characterized by having its hydroxyl group attached to a carbon atom that is connected to two other carbon atoms. This structure is slightly more complex than a primary alcohol and has a distinct reactivity profile.

For instance, hexan-2-ol represents a secondary alcohol. It's shown as CH₃CH(OH)CH₂CH₂CH₂CH₃, with the hydroxyl bound to the second carbon in the chain. Secondary alcohols are more resistant to oxidation than primary ones but can still be converted to ketones. The '2-ol' indicates the position of the -OH on the second carbon.

• Secondary alcohols can be easily distinguished by their connectivity, where the -OH group is bonded to a carbon that's attached to two other carbon atoms.
• Oxidation reactions typically yield ketones if a suitable oxidizing agent is applied.
• The naming also follows the longest carbon chain rule, akin to primary alcohols.

Tertiary Alcohol Structure

Tertiary alcohols are more complex, with the hydroxyl group connected to a carbon atom bonded to three other carbon atoms. This arrangement significantly affects the reactivity, making tertiary alcohols quite resistant to oxidation.

Take 2-methylpentan-3-ol as a tertiary alcohol example. Its structure, CH₃C(OH)(CH₃)CH₂CH₂CH₃, shows the hydroxyl group on a carbon atom that's directly connected to three other carbons. Unlike primary and secondary alcohols, tertiary alcohols seldom oxidize to form carbonyl compounds under standard conditions.

• In identifying tertiary alcohols, look for the carbon connected to three other carbons, which in turn is bonded to the -OH group.
• Their oxidation is not commonly observed with normal oxidizing agents, demonstrating their stability.
• Nomenclature includes identifying the carbon that carries the -OH group regardless of it being bonded to other carbon atoms or substituents.