Detailed structural, electronic and vibrational properties of 2–(1H–indol–3–yl)–2–oxoacetic acid or 3–indoleglyoxylic acid (3IGA) have been analysed with the help of FT–IR, FT–Raman and FT–NMR spectra along with the support of the theoretical investigations by B3LYP method. The conformational investigations on 3IGA showed that s–trans–I conformer with intramolecular hydrogen bonding is the most stable one. The range of total electron density of the molecule 3IGA is found to be +7.383e × 10^–2 to – 7.383e × 10^–2 and the electrostatic potential of 3AI is in the range +1.167e × 10^–2 to –1.167e × 10^–2_. The energy gap ΔE = (E_LUMO–E_HOMO) of 3IGA is 4.1008 eV. The n(O20) → π*(C18–O19) is strongly stabilized by 54.01 kcal mol^–1. Significant lowering and broadening of the stretching O–H band indicates the presence of intramolecular O–H···O hydrogen bonding. The chemical shift of C2 (138.00 ppm) and C3 (112.57 ppm) is much higher in 3IGA when compared to indole 125.07 and 100.84 ppm, respectively. The atoms C3, C4, C7, C6 and N1 are favourable for the nucleophilic attack while C16, C18, C2, C9, C5 and C8 are favourable for electrophilic attack.

借助 FT-IR、FT-Raman 和 FT-NMR 分析了 2-(1H-indol-3-yl)-2-氧代乙酸或 3-吲哚乙醛酸 (3IGA) 的详细结构、电子和振动性质光谱以及 B3LYP 方法理论研究的支持。对 3IGA 的构象研究表明，具有分子内氢键的 s - trans - I构象异构体是最稳定的构象异构体。发现分子 3IGA 的总电子密度范围为 +7.383e × 10 ^–2到 – 7.383e × 10 ^–2并且 3AI 的静电势在 +1.167e × 10 ^–2到 –1.167e范围内× 10 ^–2 _。能隙 ΔE = (E _LUMO-E _HOMO ) 的 3IGA 为 4.1008 eV。n(O20) → π*(C18–O19) 被 54.01 kcal mol ^–1强稳定。拉伸O-H带的显着降低和加宽表明分子内O-H···O氢键的存在。与吲哚 125.07 和 100.84 ppm 相比，3IGA 中 C2 (138.00 ppm) 和 C3 (112.57 ppm) 的化学位移分别高得多。原子 C3、C4、C7、C6 和 N1 有利于亲核攻击，而 C16、C18、C2、C9、C5 和 C8 有利于亲电攻击。