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 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-by-step solution

(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.

(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.

(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: ${\text{HOC-CH}}_2{\text{-CH}}_2{\text{-CH}}_2{\text{-CH}}_2{\text{-CH}}_3$