Investigating The Connectivity Between Atoms In Chiral Molecules

When the mirror image of the structure of a molecule cannot be superimposed on its parent structure, these two molecules with non-superimposable chemical structures are called enantiomers and the corresponding compounds fall under the category of chiral compounds. The enantiomers have opposite handedness, loosely categorized as left handed and right handed. Even though the enantiomers with non-superimposable mirror image structures have the same chemical composition, their chemical properties can be drastically different.

Human life owes much of its existence to chirality because the life-controlling proteins in the human body are made of chiral amino acids, all with one particular handedness. Because of this specificity of handedness in our human body, it is necessary to have the proper handedness for a chiral drug compound to function beneficially, when ingested. Therefore, it is of utmost importance to properly characterize, and document, the handedness of chiral compounds used for treating the human illnesses. In this characterization process, establishing the correct chemical structure of chiral molecules is the first step.


If an error occurs in this first step, all subsequent analyses would lose relevance. Continuous ongoing developments in scientific methods are providing sophisticated methods for verifying the chemical structures of chiral compounds.

Among the latest methods are Raman optical activity (ROA) and vibrational circular dichroism (VCD), which along with two other methods, electronic circular dichroism (ECD) and optical rotatory dispersion (ORD), are categorized as the branches of chiroptical spectroscopy. In this paper, we propose a new application of chiroptical spectroscopy.

ROA and VCD methods have come into existence in the early 1970s and since then blossomed into practically useful methods for establishing the handedness of chiral compounds. These methods depend on the fact a molecule with a particular handedness will interact differently with left handed and right handed light waves, also referred to as left circularly polarized (LCP) light and right circularly polarized (RCP) light waves.

ROA and VCD spectroscopies derive their usefulness from the differences in the interaction of LCP and RCP light waves with the vibrational transitions of a chiral molecule, and these differences depend on the chemical structure of that molecule.


ROA and VCD spectroscopies have recently been used to establish the absolute configurations (ACs), for the first time, of chiral molecules, isoflurane, bromochlorofluoromethane, and neopentane-d6. They were also used to confirm the known ACs of several chiral molecules. In all reported applications of chiroptical spectroscopy, the connectivities between the atoms of the studied chiral molecule were known.

If the connectivities between the atoms in a given chiral molecule are not known with certainty, then can chiroptical spectroscopic methods distinguish between the correct and incorrect atomic connectivities? To answer this question, several chiral compounds whose chemical structures have been mis-assigned in the literature, and later corrected, were subjected to chiroptical spectroscopic investigations.

Using spectral similarity overlap criteria, it was found that ROA and VCD spectroscopies, when applied carefully, can discriminate between the correct and incorrect atomic connectivities in chiral molecular structures. This observation is the basis for a new approach for identifying the incorrect chemical structures of chiral compounds.

This study, “To Avoid Chasing Incorrect Chemical Structures of Chiral Compounds: Raman Optical Activity and Vibrational Circular Dichroism Spectroscopies” was recently published (ChemPhysChem 2017, 18, 2459–2465). For more detailed information please see “Chiroptical Spectroscopy: Fundamentals and Applications”, Prasad L. Polavarapu, Taylor & Francis (2017).




The Role And Potential For Solar Thermal In Future Energy Systems 

The necessary reductions in greenhouse gas emissions to the atmosphere need to occur within the next decades. During that period, […]

Global Adaptation Governance: Why It’s Weak In Precision And Obligation

In Paris in December 2015, states established a new ‘global goal on adaptation’ at the United Nations Framework Convention on […]

Labeled Neuron Diagram

Neurons are the basic organizational units of the brain and nervous system. Neurons form the bulk of all nervous tissue […]

Energy Transfer Phenomenon Leading To Photon Up-conversion With Application To Optical Thermometry

Temperature is a fundamental property of matter and it is related to the degree of warmth of a material. Temperature […]

Record Low Voltage Losses In Efficient Cascade Organic Solar Cells

The sun is a limitless energy source, and photovoltaics is the most commonly used technology for converting solar energy into […]

Hybrid Polysaccharide Membranes For Dehydration Processes

Solvent dehydration processes have a high economic and environmental relevance in the pharmaceutical, fine-chemistry, and chemical industries. In particular, ethanol […]

The Importance Of Microbes, From Earth To Martian Soil

When you think of microbes such as bacteria and fungi, what is your first reaction? What do you think when […]

Science Trends is a popular source of science news and education around the world. We cover everything from solar power cell technology to climate change to cancer research. We help hundreds of thousands of people every month learn about the world we live in and the latest scientific breakthroughs. Want to know more?