Benzoic acid is reduced with Na in liquid $\mathrm{NH}{}_3$ and ethanol, and the mixture is acidified. The major product is

An electron-withdrawing group such as COOH ends up on an sp3 carbon, since protonation takes place at the ipso and para positions. The ring carbon bearing COOH becomes sp3 and the 2,5-diene results. A 1-carboxy-1,4-diene would have COOH on an sp2 carbon, which is the pattern for donor groups.