Chemistry

Chemistry

Problem

The acetate ion, CH3_3COO −^{\,-}, is represented by two resonance structures in which one C–O bond is double and the other is single. Considering the resonance hybrid, what is the total number of σ\sigma bonds and π\pi bonds present in a single acetate ion? a) 6  σ bonds,  1  π bond6 \;\sigma\text{ bonds},\;1\; \pi\text{ bond} b) 6  σ bonds,  2  π bonds6 \;\sigma\text{ bonds},\;2\; \pi\text{ bonds} c) 6  σ bonds,  0  π bonds6 \;\sigma\text{ bonds},\;0\; \pi\text{ bonds} d) 5  σ bonds,  1  π bond5 \;\sigma\text{ bonds},\;1\; \pi\text{ bond}
Intuitive explanation

Resonance structures don't represent two separate molecules—they're different ways of drawing the same ion. The actual structure is a hybrid that averages the electron distribution between the two forms. In the acetate ion, each C–O bond is neither fully single nor fully double, but rather a blend of both resonance forms. Count all the σ\sigma bonds (single and double bonds each contribute one) and all the π\pi bonds (only double bonds contribute one) by treating the hybrid as a single, averaged structure rather than flipping between two extremes.

Intuitive explanation

Resonance structures don't represent two separate molecules—they're different ways of drawing the same ion. The actual structure is a hybrid that averages the electron distribution between the two forms. In the acetate ion, each C–O bond is neither fully single nor fully double, but rather a blend of both resonance forms. Count all the σ\sigma bonds (single and double bonds each contribute one) and all the π\pi bonds (only double bonds contribute one) by treating the hybrid as a single, averaged structure rather than flipping between two extremes.

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