Jump to main content
Jump to site search

Issue 40, 2019
Previous Article Next Article

An experimental and computational IR and hybrid DFT-D3 study of the conformations of l-lactic and acrylic acid: new insight into the dehydration mechanism of lactic acid to acrylic acid

Author affiliations

Abstract

We have studied using hybrid Density Functional Theory (DFT) with an aug-cc-pVTZ basis set and D3 dispersion corrections the intra-molecular hydrogen bond of L-lactic acid and L-lactic-acid analogs with the hydroxyl group on the alpha carbon atom substituted by α-XH (where X = S, Se, Te) as well as the conformations of acrylic acid. The results show that there are three types of intramolecular hydrogen bonds that can form only when α-OH is present, whereas other less electronegative functional groups such as –SH, –SeH and –TeH do not exhibit the formation of an intramolecular H-bond. We show that the intra-molecular H-bond formed between the alpha-OH hydrogen and the COOH carbonyl oxygen would enhance the rate of nucleophilic substitution of alpha-OH at the K+ sites in the previously suggested dehydration mechanism of L-lactic to acrylic acids. We find that a temperature range between 190 and 210 °C would be optimum to maximise the rate of nucleophilic substitution of the alpha-OH group at the potassium sites during the dehydration mechanism of L-lactic acid to acrylic acid. Additionally, our hybrid-DFT simulation of the infrared spectrum of the various conformers shows that the lowest energy conformer can be identified by a single vibrational band at 3734 cm−1 whereas for the other conformers, this vibrational band is split with Δν that ranges between 6 cm−1 and 176 cm−1. We also find that the various conformers of acrylic acid can be identified by a double peak for the C[double bond, length as m-dash]O and O–H vibrations, which have Δν′ and Δν′′ values of 24 and 42 cm−1, respectively. This computational study is useful for spectroscopic experimental efforts that try to identify the various conformers of L-lactic acid and acrylic acid and to gain mechanistic insight into the dehydration mechanism over K substituted NaY zeolites.

Graphical abstract: An experimental and computational IR and hybrid DFT-D3 study of the conformations of l-lactic and acrylic acid: new insight into the dehydration mechanism of lactic acid to acrylic acid

Back to tab navigation

Publication details

The article was received on 25 May 2019, accepted on 11 Sep 2019 and first published on 12 Sep 2019


Article type: Paper
DOI: 10.1039/C9CP02968K
Phys. Chem. Chem. Phys., 2019,21, 22331-22343

  •   Request permissions

    An experimental and computational IR and hybrid DFT-D3 study of the conformations of L-lactic and acrylic acid: new insight into the dehydration mechanism of lactic acid to acrylic acid

    C. D. Zeinalipour-Yazdi and C. R. A. Catlow, Phys. Chem. Chem. Phys., 2019, 21, 22331
    DOI: 10.1039/C9CP02968K

Search articles by author

Spotlight

Advertisements