Question

Given the following condensed formulas, write the molecular formulas for the following molecules. (a) dimethylamine \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{NH}\) (b) propyl alcohol \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{2} \mathrm{OH}\)

Short answer

Answer: (a) The molecular formula for dimethylamine is CH₃CH₃NH. (b) The molecular formula for propyl alcohol is CH₃CH₂CH₂OH.

Step-by-step solution

(a) Write the molecular formula for dimethylamine

Dimethylamine is represented by the condensed formula \((\mathrm{CH}_{3})_{2}\mathrm{NH}\). In order to obtain the molecular formula, follow these steps: 1. Write down the two methyl groups \((\mathrm{CH}_{3})_{2}\) as \(\mathrm{CH}_{3}\mathrm{CH}_{3}\). 2. Add the amine group (\(\mathrm{NH}\)) to the end of the molecular formula: \(\mathrm{CH}_{3}\mathrm{CH}_{3}\mathrm{NH}\). Thus, the molecular formula for dimethylamine is \(\mathrm{CH}_{3}\mathrm{CH}_{3}\mathrm{NH}\).

(b) Write the molecular formula for propyl alcohol

Propyl alcohol is represented by the condensed formula \(\mathrm{CH}_{3}(\mathrm{CH}_{2})_{2}\mathrm{OH}\). To obtain the molecular formula, follow these steps: 1. Write down the methyl group at the beginning of the molecular formula: \(\mathrm{CH}_{3}\). 2. Add the two methylene groups \((\mathrm{CH}_{2})_{2}\) to the end of the step 1 chemical representation: \(\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{CH}_{2}\). 3. Finally, add the hydroxyl group (\(\mathrm{OH}\)) to the end of the molecular formula: \(\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{OH}\). Thus, the molecular formula for propyl alcohol is \(\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{CH}_{2}\mathrm{OH}\).