Problem 83 - Chemistry: The Central Science

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.

Step-by-Step Solution

Answer

(a) A functional group is an atom or group of atoms within a molecule responsible for its characteristic chemical reactions and properties. It is the site on a molecule where most chemical reactions occur, determining the nature and reactivity of the compound. (b) The functional group that characterizes an alcohol is the hydroxyl group (-OH), bonded to a carbon atom. (c) The structural formula for 1-pentanol, derived from pentane, is \(\text{HOC-CH}_2\text{-CH}_2\text{-CH}_2\text{-CH}_{2}\text{-CH}_{3}\).

Step 1: (a) Define Functional Group

A functional group is an atom or group of atoms within a molecule that is responsible for the molecule's characteristic chemical reactions and properties. It is the site on a molecule where most chemical reactions occur and from where a compound derives its particular properties. By studying functional groups, we can understand the nature and reactivity of organic molecules.

Step 2: (b) Identify the Functional Group of Alcohols

The functional group that characterizes an alcohol molecule is the hydroxyl group (-OH). In an alcohol molecule, a hydroxyl group is bonded to a carbon atom, making the molecule an organic compound. Alcohols are classified as primary, secondary, or tertiary based on the carbon atom bonded with the hydroxyl group.

Step 3: (c) Write the Structural Formula for 1-Pentanol

To determine the structural formula of 1-pentanol, we first need to know the structure of its parent hydrocarbon, pentane. Pentane is an alkane with the chemical formula \(\text{C}_5\text{H}_{12}\) and has the following structure: \(\text{H}_3\text{C-CH}_2\text{-CH}_2\text{-CH}_2\text{-CH}_{3}\) To create the structural formula for 1-pentanol, we will replace one of the hydrogen atoms of the first carbon atom with a hydroxyl group (-OH), as follows: \(\text{HOC-CH}_2\text{-CH}_2\text{-CH}_2\text{-CH}_{2}\text{-CH}_{3}\) So, the structural formula for 1-pentanol is: \(\text{HOC-CH}_2\text{-CH}_2\text{-CH}_2\text{-CH}_{2}\text{-CH}_{3}\)