ADVERTISEMENT

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.

ADVERTISEMENT

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).

ADVERTISEMENT

Speak Your Mind!

READ THIS NEXT

Wild Rice Populations: A Key Resource For Global Food Security

Published by Robert J. Henry Queensland Alliance for Agriculture and Food Innovation, University of Queensland These findings are described in […]

Land Cover Changes In Central European Mountains: A Case Study of Šumava

Central European mountains are covered predominantly by forests. Norway spruce is the most frequently-occurring species and the most affected one. […]

Combinations Of Tests For A Better Prediction Of Carcinogens

Cancer is one of the leading cause of mortality globally with an estimated 17.5 million cases reported worldwide in 2015. With […]

How To Gain Insight Into Biochar Sorbing Behavior Using Rare Earth Elements 

Biochar is a carbon-rich product that comes from biomass pyrolysis. Biochar has sparked a wide interest due to its great […]

Can The Subthreshold Volatile Phenol Chemistry Of A Potentially Smoke-Tainted Wine Explain Its Aroma? We Tested Twelve Commercial Red Wines To Find Out

Wine aroma is arguably the most important intrinsic factor used to judge wine quality. The perception of wine aroma is […]

Measuring Parked Vehicles’ Effect On Noise Pollution

Many types of research indicate that exposure to noise pollution can induce negative effects on human health: cardiovascular diseases, sleep […]

Skidding Nanoparticles For Modular And Scalable Biocomputing

The cellular membrane is a biological circuit board where multiple nanostructures (e.g. proteins) process dynamic information of the extracellular environment […]