3 years ago

Formation of (HCOO–)(H2SO4) Anion Clusters: Violation of Gas-Phase Acidity Predictions

Formation of (HCOO–)(H2SO4) Anion Clusters: Violation of Gas-Phase Acidity Predictions
Xue-Bin Wang, Marat Valiev, Gao-Lei Hou
Sulfuric acid is commonly known to be a strong acid and, by all counts, should readily donate its proton to formate, which has much higher proton affinity. This conventional wisdom is challenged in this work, where temperature-dependent negative ion photoelectron spectroscopy and theoretical studies demonstrate the existence of the (HCOO)(H2SO4) pair at an energy slightly below the conventional (HCOOH)(HSO4) structure. Analysis of quantum-mechanical calculations indicates that a large proton affinity difference (∼36 kcal/mol), favoring proton transfer to formate, is offset by the gain in intermolecular interaction energy between HCOO and H2SO4 through the electron delocalization and formation of two strong hydrogen bonds. However, this stabilization comes with a severe entropic penalty, requiring the two species in the precise alignment. As a result, the population of (HCOO)(H2SO4) drops significantly at higher temperatures, rendering (HCOOH)(HSO4) to be the dominant species. This phenomenon is consistent with the photoelectron data, which shows depletion in the spectra assigned to (HCOO)(H2SO4), and has also been verified by ab initio molecular dynamics (AIMD) simulations.

Publisher URL: http://dx.doi.org/10.1021/jacs.7b05964

DOI: 10.1021/jacs.7b05964

You might also like
Discover & Discuss Important Research

Keeping up-to-date with research can feel impossible, with papers being published faster than you'll ever be able to read them. That's where Researcher comes in: we're simplifying discovery and making important discussions happen. With over 19,000 sources, including peer-reviewed journals, preprints, blogs, universities, podcasts and Live events across 10 research areas, you'll never miss what's important to you. It's like social media, but better. Oh, and we should mention - it's free.

  • Download from Google Play
  • Download from App Store
  • Download from AppInChina

Researcher displays publicly available abstracts and doesn’t host any full article content. If the content is open access, we will direct clicks from the abstracts to the publisher website and display the PDF copy on our platform. Clicks to view the full text will be directed to the publisher website, where only users with subscriptions or access through their institution are able to view the full article.