CONFORMATIONAL ANALYSIS OF 1-ALKENE SECONDARY OZONIDES BY MEANS OF MATRIX ISOLATION FTIR SPECTROSCOPY

Author Institution: Dept. of General Physics and Spectroscopy, Faculty of Physics, Vilnius University, Sauletekio av. 9 bl. 3, LT-01222, Vilnius, LithuaniaAn ability of ozone to break double C=C bond in olefins is known for more than five decades. Understanding of those reactions is very important in atmospheric chemistry. During different steps of the reaction the primary ozonide (POZ), carbonyl oxide (COX) and the secondary ozonide (SOZ) are formed. Fate of the reaction depends on many parameters such as type of radical, conformation of alkene, temperature of the reaction and environmental effects. Despite of numerous studies of the reaction by different spectroscopic techniques the precise mechanism of the reaction is still unknown. It is experimentally observed that the SOZ is more stable than POZ. Stability of the SOZ depends on the size and configuration of the radical. Unfortunately, it is not much known about the spatial structures of the SOZ es. The aim of this study is to define the geometrical structures and stability of the different conformers of the 1-butene and 1-heptene secondary ozonides by combined analysis of the matrix isolation FTIR spectral data with the results of Density Functional Theory (DFT) calculations

Strong Isotope Effect in the Vibrational Response of the Hydration Shells of Hydrophobic Ions

We have studied the properties of water molecules at the surface of salt solutions containing hydrophobic anions like triflate (CF₃SO₃^–), ethanesulfonate (C₂H₅SO₃^–), and butanesulfonate (C₄H₉SO₃^–) using vibrational sum-frequency generation (VSFG) spectroscopy. The VSFG spectra reveal a surprisingly strong isotope effect in the intra- and intermolecular mixing of the water molecules contained in the hydration shells of the hydrophobic anions. The O–H stretch vibrations of H₂O molecules in the hydration shell are strongly mixed, whereas the O–D stretch vibrations of hydrating D₂O molecules are decoupled. This isotope effect is not observed for other ions like perchlorate (ClO₄^–), and can be explained from the structure of the hydration shells of the hydrophobic ions

Observation of ice-like water layers at an aqueous protein surface

\u3cp\u3eWe study the properties of water at the surface of an antifreeze protein with femtosecond surface sum frequency generation spectroscopy. We find clear evidence for the presence of ice-like water layers at the ice-binding site of the protein in aqueous solution at temperatures above the freezing point. Decreasing the temperature to the biological working temperature of the protein (0°C to -2°C) increases the amount of ice-like water, while a single point mutation in the ice-binding site is observed to completely disrupt the ice-like character and to eliminate antifreeze activity. Our observations indicate that not the protein itself but ordered ice-like water layers are responsible for the recognition and binding to ice.\u3c/p\u3