Chemistry World was pleased to sponsor a poster prize at ISACS18 (Challenges in Organic Materials and Supramolecular Chemistry), held in Bangalore, India, last month. PhD student Emmanuel Etim from the Indian Institute of Science, India, was the winner with his poster titled: Interstellar hydrogen bonding

Emmanuel Etim

Emmanuel explains his work:

‘We are interested in understanding the chemistry of interstellar molecules – ie molecules that exist in the space between the stars – because of their importance in astrochemistry, astrophysics, astrobiology, astronomy and related fie

Over 200 of these molecules have been detected in different astronomical sources largely via their rotational spectra. Isomerism is a conspicuous feature of these molecules with over 40% of the known molecules (excluding the diatomics and other special species like the C3, C5, which cannot form isomers) observed in more than one isomeric form.

But why are some isomers observed and others are not has been a question for decades. In addressing this question, we investigated 130 molecules from 31 isomeric groups and we found a unique relationship, which accounts for the detection of some isomers and the non-detection of others. According to the Energy, Stability and Abundance (ESA) relationship, interstellar abundances of related species are directly proportional to their stabilities. However, we observed some deviations from the ESA relationship in a few isomeric groups: Where the most stable isomers are not observed and where the most stable isomers are not the most abundant. What could be responsible for these deviations?

How are these molecules formed? Reactions that occur on the surfaces of interstellar dust particles have been invoked in the formation of molecular hydrogen; as well as for the synthesis of larger interstellar molecules. Water molecules constitute about 70% of the interstellar dust grains (interstellar ice). These water molecules serve as the platform for hydrogen bonding. This interstellar hydrogen bonding causes a greater portion of these molecules to be attached to the surface of the dust grains. This reduces the overall abundances of the molecules in the gas phase.

Our high level quantum chemical calculations for the hydrogen bond interaction between the interstellar molecules (known and possible) and water, shows a direct correlation between the binding energies of these complexes and the abundances of the interstellar molecules. This accounts for the observed deviations from the ESA relationship.

From both ESA relationship and interstellar hydrogen bonding, we predicted ketenes as potential candidates for astronomical observation. In line with this, ketenyl radical has just been observed in space.

Finally, the weakly bound complexes that are formed in the interstellar medium (ISM), are they detectable? The conditions in the terrestrial laboratories where weakly bound complexes are observed are similar to the conditions in ISM and the high binding energies of the complexes imply that these complexes are detectable in ISM.’

Congratulations to Emmanuel on his great poster.


Submit a poster abstract for ISACS19 (Challenges in organic chemistry), to be held in Irvine, US, in March 2016, here:

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ISACS18 poster prize winner: Emmanuel Etim, 10.0 out of 10 based on 4 ratings
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