Calculations on the structure of 3,4,5-trifluorobenzoic acid were made using the Gaussian 16 program. The potential energy surfaces were scanned along CCCO and OCOH dihedral angles at the B3LYP/6-311G level to analyze its conformational landscape. Two conformations were identified and reoptimized at the B3LYP/aug-cc-pVTZ level. The result indicates that 3,4,5-trifluorobenzoic acid prefers a planar structure in its global minimum conformation. The pure rotational spectra of 3,4,5-trifluorobenzoic acid were measured in the frequency range of 6 – 12.5 GHz using a chirped pulse Fourier transform microwave (CP-FTMW) spectrometer. The spectra of the parent, seven ¹³C, and one deuterium singly substituted isotopologues were analyzed and fitted to measurement accuracy for a semi-rigid asymmetric top molecule. The rotational constants and centrifugal distortion constants were accurately determined. The rotational constants for the parent isotopologue are A = 1535.31408(32) MHz, B = 650.31751(16) MHz, and C = 456.98499(12) MHz. The effective structure of its ground vibrational state was determined from the spectra of the mono-substituted isotopologues. The agreement between the calculated and experimental spectroscopic constants is excellent.

使用Gaussian 16程序计算3,4,5-三氟苯甲酸的结构。在 B3LYP/6-311G 水平上沿 C C C O 和 O C O H 二面角扫描势能表面，以分析其构象景观。在 B3LYP/aug-cc-pVTZ 水平上鉴定并重新优化了两种构象。结果表明，3,4,5-三氟苯甲酸在其整体最小构象中更喜欢平面结构。使用啁啾脉冲傅里叶变换微波 (CP-FTMW) 光谱仪在 6 – 12.5 GHz 频率范围内测量 3,4,5-三氟苯甲酸的纯旋转光谱。亲本的光谱，七¹³C和一种氘单取代同位素体进行了分析，并适合半刚性不对称顶部分子的测量精度。准确测定了旋转常数和离心畸变常数。母体同位素体的旋转常数为A  = 1535.31408(32) MHz、B  = 650.31751(16) MHz 和C  = 456.98499(12) MHz。从单取代同位素体的光谱确定了其基振动态的有效结构。计算的光谱常数和实验的光谱常数之间的一致性非常好。