Negative ion photoelectron spectra of ortho (o-), meta (m-), and para (p-) deprotonated benzonitrile (o-, m-, p-C 6 H 4 (CN) − ) isomers as well as the associated thermochemical values corresponding to deprotonation at o-, m-, and p-positions in C 6 H 5 (CN) are presented. Quantum mechanical results based on the density functional theory (DFT) utilizing the aug-cc-pVQZ basis set indicate that the o-, m-, p-C 6 H 4 (CN) • radicals have electron affinity values (EAs) of 1.901, 1.778, and 1.789 eV, respectively. The computed Franck−Condon (FC) factors give rise to o-, m-, and p-C 6 H 4 (CN) − negative ion spectra with FC active ring distortion vibrational modes with harmonic vibrational frequencies of ∼450, 760, and 1000 cm −1 as the dominant vibrational progressions. Deprotonation at the o-, m-, and ppositions in C 6 H 5 (CN) results in calculated gas-phase acidity values (Δ acid H 298K o ) of 383.9, 385.7, and 385.3 kcal mol −1 , respectively. The calculated Δ acid H 298K o is in close agreement with the previously reported high-pressure mass spectrometry experimental value of 383.4.0 ± 4.4 kcal mol −1 . The computed Δ acid H 298K o and EAs are utilized to estimate the bond dissociation energy (DH 298 (H-C 6 H 4 CN)) associated with the formation o-, m-, and p-C 6 H 4 (CN) • using the negative ion thermochemical cycle: DH 298 (C 6 H 5 CN) = Δ acid H 298K o (H-C 6 H 4 (CN) + EA (C 6 H 5 CN) • − IP(H). The respective values of DH 298 (H-C 6 H 4 CN) corresponding to the formation of ortho, meta, and para C 6 H 4 (CN) radicals are 114.15, 113.11, and 113.51 kcal mol −1 .