Question

(a) What is a functional group? (b) What functional group characterizes an alcohol? (c) Write a structural formula for 1-pentanol, the alcohol derived from pentane by making a substitution on one of the carbon atoms.

Short answer

(a) A functional group is an atom or group of atoms within a molecule responsible for the molecule's characteristic chemical reactions. (b) The functional group characterizing an alcohol is the hydroxyl group (-OH). (c) The structural formula for 1-pentanol is \(CH_3(CH_2)_4OH\).

Step-by-step solution

Define functional groups

A functional group is an atom or a group of atoms within a molecule that is responsible for the molecule's characteristic chemical reactions. Functional groups determine the chemical properties of a compound and are used to classify organic molecules with similar reactivities.

Identify the functional group of an alcohol

The functional group that characterizes an alcohol is the hydroxyl group (-OH). The hydroxyl group consists of an oxygen atom bonded to a hydrogen atom, and it's responsible for the chemical properties exhibited by alcohols.

Write the structural formula for 1-pentanol

To write the structural formula for 1-pentanol, we first need to know the structure of its parent compound, pentane, which consists of five carbon atoms bound together in a chain. Pentane's complete structural formula is \(CH_3CH_2CH_2CH_2CH_3\). To form 1-pentanol, we need to replace one hydrogen atom of the first carbon atom with a hydroxyl group (-OH). Hence, the structural formula for 1-pentanol will be \(CH_3CH_2CH_2CH_2CH_2OH\), or more commonly represented as \(CH_3(CH_2)_4OH\).

Key concepts

Alcohol

Alcohols are a class of organic compounds that play a vital role in chemistry and daily life. Their defining characteristic is the presence of the hydroxyl group (−OH), which sets them apart from other organic molecules. The presence of this group affects the compound's properties, such as its ability to form hydrogen bonds, which influence boiling and melting points.

Alcohols can vary significantly in structure, but they all share some universal features due to the hydroxyl group:

• They tend to be polar, meaning they can dissolve in water to some extent.
• They participate in various chemical reactions, often acting as intermediates.
• They have a generally pleasant smell, though this can vary with molecular size.

Not only common in beverages, alcohols are integral in various industrial applications, from manufacturing to healthcare.

Hydroxyl Group

The hydroxyl group is a specific functional group with the formula −OH, comprising an oxygen atom bonded to a hydrogen atom. It is key to the alcohol family of organic compounds.

This group is polar due to the electronegativity difference between oxygen and hydrogen. As a result, hydroxyl groups can form hydrogen bonds with water or other molecules, greatly affecting solubility and reactivity.

• In chemical reactions, hydroxyl groups can act as nucleophiles, which means they can donate electron pairs to form new bonds.
• They increase a molecule's ability to engage in hydrogen bonding, affecting physical properties like viscosity and surface tension.
• They're crucial in both biological and synthetic chemistry, found in everything from DNA to pharmaceuticals.

The versatility and reactivity of the hydroxyl group make it an intriguing subject of study for chemists and biologists alike.

1-Pentanol

1-Pentanol is an alcohol derived from pentane, a simple hydrocarbon chain with five carbon atoms. By transforming one end of this chain, replacing a hydrogen atom with a hydroxyl group (−OH), we create 1-pentanol.

The structure of pentane is linear: \(CH_3CH_2CH_2CH_2CH_3\). By replacing one hydrogen with a hydroxyl group, the resulting structure becomes:\(CH_3(CH_2)_4OH\).
This structural change influences its properties and uses:

• Like other alcohols, 1-pentanol is polar due to the hydroxyl group, allowing for better solubility in water than its hydrocarbon counterpart.
• It finds use as a precursor in the synthesis of pharmaceuticals and other compounds.
• Its aroma is often used in flavorings and fragrances due to its pleasant scent.

Understanding 1-pentanol's structure and characteristics is fundamental for those studying organic chemistry and its practical applications.