Structures of Non-Polar Molecules by High Resolution FT-IR Spectroscopy

在实验物理化学的RUI项目中 化学部的程序，克雷格将使用FTIR 光谱，以获得几个小的，非极性的结构 有机分子 他将分析旋转分解的 反式异构体及其同位素种类的红外光谱 几种分子的电子能量比 它们各自的顺式异构体。 结构将进行比较 与顺式异构体的那些，并将提供数据， 与ab initio计算比较。 高分辨率 红外光谱将记录在光谱仪上， 美国国家标准与技术研究所 Walter J. Lafford博士的实验室。 %%% 有一个奇怪的现象被称为“顺式效应”， 具有较大取代基的分子（我们称之为X 和Y）在刚性平面碳-碳的任一端 双键骨架，例如HXC=CYH。 以这样 分子的同分异构结构，其中两个大的（X和 Y）基团在同一侧（在“顺式”或接近位置） 在能量上比结构更稳定 大基团在分子的对角上（在 “反式”位置）。 直觉上，人们会认为， “顺式”结构在能量上不太稳定，因为 大的群体更容易相互干扰。 这 目前的项目将获得数据，这将允许理论 与实验结构进行比较，以便 检验理论模型的有效性。 预计 一个成功的理论将有助于解释这种奇怪的“独联体”， 效应”异常。

In this RUI project in the Experimental Physical Chemistry Program of the Chemistry Division, Craig will use FTIR spectroscopy to obtain structures of several small, non-polar organic molecules. He will analyze the rotationally resolved IR spectra of the trans isomers and their isotopic species of several molecules which have higher electronic energies than their respective cis isomers. The structures will be compared with those of the cis isomers and will provide data for comparison with ab initio calculations. High resolution infrared spectra will be recorded on a spectrometer at the National Institute for Standards and Technology in the laboratory of Dr. Walter J. Lafferty. %%% There is a curious phenomenon called the "cis effect" in molecules with large substituent groups (which we will call X and Y) at either end of a rigid, planar carbon-carbon double-bonded skeleton, for example, HXC=CYH. In such molecules the isomeric structure in which the two large (X and Y) groups are on the same side (in the "cis" or near position) is energetically more stable than the structure in which the large groups are on opposite corners of the molecule (in the "trans" position). Intuitively, one would expect that the "cis" structure would be less stable energetically because the large groups can interfere with each other more readily. This current project will acquire data which will allow theoretical studies to be compared with experimental structures in order to test the validity of the theoretical models. It is expected that a successful theory will help explain this curious "cis effect" anomaly.