Question

Draw the structures of (a) pentan-l-ol; (b) heptan- \(3-01\); (c) 2 -methylpentan-2-ol; (d) propane- 1,2,3 -triol.

Short answer

Draw each structure by sketching straight carbon chains and positioning the OH groups and additional side chains based on the specific position numbers indicated (like 1, 2, 3, etc.).

Step-by-step solution

Understanding Pentan-1-ol

Pentan-1-ol is an alcohol with the molecular formula C\(_5\)H\(_{11}\)OH. It consists of a 5-carbon chain (pentane), with an -OH group attached to the first carbon (1-ol).

Drawing Pentan-1-ol

Start by drawing a linear chain of 5 carbon atoms. Attach an -OH (hydroxyl) group to the first carbon. Fill in with hydrogen atoms so each carbon has four bonds: CH\(_3\)-CH\(_2\)-CH\(_2\)-CH\(_2\)-CH\(_2\)OH.

Understanding Heptan-3-ol

Heptan-3-ol is an alcohol with the molecular formula C\(_7\)H\(_{15}\)OH. It has a 7-carbon chain (heptane), with the -OH group on the third carbon atom (3-ol).

Drawing Heptan-3-ol

First, draw a linear chain of 7 carbon atoms. Attach an -OH group to the third carbon. Add hydrogen atoms to ensure each carbon forms four bonds: CH\(_3\)-CH\(_2\)-CH(OH)-CH\(_2\)-CH\(_2\)-CH\(_2\)-CH\(_3\).

Understanding 2-Methylpentan-2-ol

2-Methylpentan-2-ol features a five-carbon chain with a methyl group on the second carbon and an -OH group also on the second carbon.

Drawing 2-Methylpentan-2-ol

Draw a 5-carbon chain. Attach a CH\(_3\) (methyl) group and an OH group to the second carbon. Ensure every carbon has four bonds: CH\(_3\) | CH\(_3\)-C(OH)(CH\(_3\))-CH\(_2\)-CH\(_2\)-CH\(_3\).

Understanding Propane-1,2,3-triol

Propane-1,2,3-triol, commonly known as glycerol, consists of a 3-carbon chain with an -OH group attached to each carbon.

Drawing Propane-1,2,3-triol

Draw a 3-carbon chain. Attach an -OH group to each of the three carbon atoms. Complete the structure using hydrogen atoms:CH\(_2\)(OH)-CH(OH)-CH\(_2\)(OH).

Key concepts

Alcohol Structure

Alcohols are organic compounds that feature one or more hydroxyl groups (-OH) attached to a carbon atom. The arrangement of the carbon atoms forms the backbone or "skeleton" of the molecule. Understanding the structure of alcohols is crucial because it determines the compound's properties and reactivity. Each alcohol is named using the IUPAC system, reflecting its structure.

• The base name indicates the length of the carbon chain. For example, "pentan" in pentan-1-ol implies a five-carbon chain.
• The suffix "-ol" denotes the presence of the hydroxyl group, typical of alcohols.
• If there are additional groups such as a methyl group, it's positioned as a prefix with its location along the carbon chain, such as in 2-methylpentan-2-ol.

To draw these structures, one must start by laying out the carbon chain, placing any branching groups accordingly, and attaching the hydroxyl group to the specified carbon atom.

Molecular Formula

The molecular formula of an alcohol provides vital information about the number and types of atoms present in a molecule. The basic formula for an alcohol can be represented as C extsubscript{n}H extsubscript{2n+1}OH, where "n" stands for the number of carbon atoms.

• For example, pentan-1-ol has a molecular formula of C extsubscript{5}H extsubscript{12}O, which means it contains five carbon atoms, eleven hydrogen atoms, and one oxygen atom (in the hydroxyl group).
• Molecular formulas are essential in predicting the behavior of alcohol, as they indicate which carbon the hydroxyl group attaches to.

By analyzing the molecular formula, it's possible to deduce not just the length of the carbon chain but also any branching functionalities, such as the case in 2-methylpentan-2-ol.

Hydroxyl Group

A hydroxyl group is a significant functional component in many organic molecules. It's composed of one oxygen atom and one hydrogen atom, covalently bonded to each other, represented as -OH. The presence of a hydroxyl group is what makes an organic molecule an alcohol.

• The hydroxyl group is typically electronegative, which allows it to engage in hydrogen bonding. This property contributes to the solubility of alcohols in water and affects their boiling points.
• The position of the hydroxyl group within the carbon chain can significantly influence the compound's chemical behavior and name classification. For instance, in heptan-3-ol, the hydroxyl group is located on the third carbon atom, influencing the molecule's reactivity.

Understanding the placement and characteristics of the hydroxyl group is key to predicting and explaining the physical and chemical properties of alcohols such as glycerol (propane-1,2,3-triol), which features multiple hydroxyl groups and thus exhibits strong hydrogen bonding.