ACS Organic Chemistry Practice Test 2026 - Free Organic Chemistry Practice Questions and Study Guide

A tert-butyl group has a central quaternary carbon attached to three methyl groups, giving nine equivalent hydrogens that are not split by any neighboring protons. Because there are no adjacent hydrogens to couple with, all nine protons appear as a single signal—a singlet. These alkyl protons on sp3 carbons are typically found upfield in the 0.9 to 1.5 ppm region, with the exact position depending on the surrounding substituents. The other regions correspond to different types of protons (near carbonyls around 2.0–2.5 ppm or aromatic protons around 7–8 ppm), not the tert-butyl environment. Therefore, the tert-butyl group shows up as a singlet around 0.9–1.5 ppm.