Lu Kang

Interplay of Phenol and Isopropyl Isomerism in Propofol from Broadband Chirped-Pulse Microwave Spectroscopy

The conformational equilibrium of the general anesthetic propofol (2,6-diisopropylphenol) has been studied in a supersonic expansion using broadband chirped-pulse microwave spectroscopy. Three conformers originated by the combined internal rotation of the hydroxyl and the two isopropyl groups have been detected in the jet-cooled rotational spectrum. The most stable conformer exhibits tunneling splittings associated with the internal rotation of the hydroxyl group, from which we determined the torsional potential and barrier heights (905-940 cm(-1)). The carbon backbone structure was derived from the spectral assignments of all 12 (13)C monosubtituted isotopologues in natural abundance and confirmed a plane-symmetric gauche orientation of the two isopropyl groups (Gg) for this conformer. In the other two detected conformers (EG and GE) one of the isopropyl groups is eclipsed with respect to the ring plane while the other is gauche, differing in a ∼180° rotation of the hydroxyl group. Supporting ab initio calculations provided information on the potential energy surface and molecular properties of the title compound.

Fluorination Effects on the Shapes of Complexes of Water with Ethers: A Rotational Study of Trifluoroanisole–Water

The rotational spectra of five isotopologues of the 1:1 complex trifluoroanisole-water have been investigated with pulsed jet Fourier transform microwave spectroscopy. The triple fluorination of the methyl group greatly affects the features of the rotational spectrum of the complex with water, with respect to those of the related complex anisole-water. The shape, the internal dynamics, and the isotopic effects turned out to be quite different from those of the anisole-water adduct ( Giuliano , B. M. ; Caminati , W. Angew. Chem., Int. Ed. 2005 , 44 , 603 - 606 ). However, as in anisole-water, water has the double role as a proton donor and proton acceptor, and it is linked to trifluoroanisole through two, O-H···O and C-H···O hydrogen bonds.

Water-vapor measurement via cavity ring down spectroscopy in the visible

Using cavity ring down spectroscopy, we recorded high resolution spectra of water overtones in the visible region. While the system is simple, experimental results have shown that the detection sensitivity is better than 2 X 10-8 cm-1. We have also studied the effects of cavity mirror reflectivity and cavity length on the detection sensitivity. The observed spectrum agrees well with the standard reference spectrum. Thus, this highly sensitive, quantitative, and widely applicable absorption spectroscopy technique proves to be capable of water vapor measurement, especially in Chemical Oxygen Iodine Laser.