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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Conformational isomers of trans-urocanic acid observed by rotational spectroscopy
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Conformational isomers of trans-urocanic acid observed by rotational spectroscopy

机译：通过旋转光谱观察的逆偶胆酸的构象异构体

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摘要

Rotational spectra have been measured and assigned for four conformers of trans-urocanic acid. The acid was transferred into the gas phase through laser vaporisation of a solid sample, mixed with a neon buffer gas and then cooled through supersonic expansion. Molecules and complexes in the expanding gas jet were probed through chirped-pulse, Fourier transform microwave spectroscopy between 2.0 and 18.5 GHz. Rotational constants, A(0), B-0 and C-0; centrifugal distortion constants, Delta(J) and Delta(JK); and nuclear quadrupole coupling constants of the nitrogen atoms, chi(aa)(N) and chi(bb)(N)-chi(cc)(N), were determined for the various conformers. Data were obtained for ten isotopologues of the conformer that was observed to yield the spectrum of highest intensity. Substitution (r(s)) coordinates were determined for all carbon atoms and two hydrogen atoms of this conformer. Other observed spectra were assigned to conformers on the basis of excellent agreement between calculated and experimentally-determined rotational constants, and empirical observations of the relative intensities of a- and b-type transitions. The results of DFT calculations imply high barriers to the interconversion of assigned conformers.
机译：转动谱进行了测量，并且指定用于反式尿刊酸的4个构象。该酸通过的固体样品的激光蒸发，用氖的缓冲气体混合转移到气相中，然后通过超声膨胀冷却。分子和复合物在膨胀的气体射流是通过啁啾脉冲探测，傅里叶变换2.0和18.5 GHz之间的微波光谱。转动常数，A（0），B-0和C-0;离心畸变常数，德尔塔（J）和Delta（JK）;和核四极耦合所述氮原子的常数，志（AA）（N）和卡（BB）（N）-Chi（CC）（N），用于各种构象异构体进行了测定。数据为可观察到，得到最高强度的频谱中的构象异构体的10同位素获得。替代（R（S））座标的所有碳原子，并且该构象异构体的两个氢原子来确定。其他观测频谱被分配到的构象计算和实验确定的转动常数，以及A和B型转变的相对强度的经验观察之间具有优异的协议的基础上。 DFT计算的结果意味着高壁垒分配构象的相互转换。

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