Illustrated Glossary of Organic Chemistry

Equivalent: (1) In NMR spectroscopy, nuclei that have the same magnetic environment, and because of this, the same chemical shift. Nuclei that are not equivalent are frequently called nonequivalent.

The 1H-NMR spectrum of propyl ether. The six methyl group protons Ha are equivalent (triplet at 0.90 ppm), the four methylene group protons Hb are equivalent (sextet at 1.49 ppm), and the four methylene group protons Hc are equivalent (triplet at 3.37 ppm). Note that the two sets of methylene protons (Hb and Hc) are nonequivalent.

(2) In chemical stoichiometry, the amount of one substance required to completely consume one mole of another functional group or substance.

In this catalytic hydrogenation of 2-butyne (an alkyne), the first equivalent of H2 reduces the alkyne to Z-2-butene. The second equivalent of H2 reduces the alkene to butane (an alkane).