Which of the following substituents are correctly classified as secondary () alkyl groups? — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

In sec-butyl (1-methylpropyl) and isopropyl (1-methylethyl), the carbon with the free valency is attached to two other carbons, making them $2^\circ$ alkyl groups. Isobutyl is $1^\circ$ and tert-butyl is $3^\circ$.