Microwave Spectrum, Conformation and Intramolecular Hydrogen Bonding of 2,2,2-Trifluoroethanethiol (CF₃CH₂SH)

Abstract

The microwave spectrum of 2,2,2-trifluoroethanethiol, CF3CH2SH, and of one deuterated species, CF3CH2SD, has been investigated in the 7-80 GHz spectral interval. The microwave spectra of the ground and three vibrationally excited states belonging to three different normal modes of one conformer were assigned for the parent species, and the vibrational frequencies of these fundamentals were determined by relative intensity measurements. Only the ground vibrational state was assigned for the deuterated species. The identified form has a synclinal arrangement for the H-S-C-C chain of atoms and the corresponding dihedral angle is 68(5) degrees from synperiplanar (0 degrees). A weak intramolecular hydrogen bond formed between the thiol (SH) group and one of the fluorine atoms is stabilizing this conformer. There is no evidence in the microwave spectrum for the H-S-C-C antiperiplanar form. The hydrogen atom of the thiol group should have the ability to tunnel between two equivalent synclinal potential wells, but no splittings of spectral lines due to tunneling were observed. The microwave work was augmented by quantum chemical calculations at the B3LYP/aug-cc-pVTZ and MP2/aug-cc-pVTZ levels of theory.

Synthesis, Microwave Spectrum, and Conformational Equilibrium of Propa-1,2-dienethiol (H2C═C═CHSH)

“…The present study also represents an extension of our recent investigations of the conformational properties of thiols such as 3-butyne-1-thiol (HSCH 2 CH 2 CtCH), 13 (Z)-3-mercapto-2propenenitrile (HSCHdCHCN), 14 cyclopropanethiol (C 3 H 5 -SH), 15 and 2,2,2-trifluoroethanethiol CF 3 CH 2 SH, 16 using MW spectroscopy augmented with quantum chemical calculations.…”

Rotational Spectrum, Conformational Composition, Intramolecular Hydrogen Bonding, and Quantum Chemical Calculations of Mercaptoacetonitrile (HSCH2C≡N), a Compound of Potential Astrochemical Interest

“…Microwave (MW) spectroscopy has shown that the thiol group can form intramolecular hydrogen (H) bonds acting as a weak proton donor with a wide variety of acceptors. Examples include 2,2,2-trifluoroethanethiol (CF 3 CH 2 SH), trifluorothioacetic acid (CF 3 COSH), 1,2-ethanedithiol (HSCH 2 CH 2 SH), thiiranemethanethiol (C 2 H 3 SCH 2 SH), aminoethanethiol (H 2 NCH 2 CH 2 SH), − methylthioglycolate (HSCH 2 COCH 3 ), propa-1,2-dienethiol (H 2 CCCHSH), 2-furanmethanethiol (C 4 H 3 OCH 2 SH), cyclopropanemethanethiol (C 3 H 5 CH 2 SH), propargyl mercaptan (HSCH 2 CCH), − 2-propenethiol (H 2 CCHCH 2 SH), 3-mercaptopropionitrile (HSCH 2 CH 2 CN), 3-butene-1-thiol (HSCH 2 CH 2 CHCH 2 ), , 3-butyne-1-thiol (HSCH 2 CH 2 CCH), and ( Z )-3-mercapto-2-propenenitrile (HSCHCHCN) . The present investigation of mercaptoacetonitrile (HSCH 2 CN) is an extension of our longstanding interest in internal H bonding in general and in thiols in particular …”

Microwave and Quantum Chemical Study of the Hydrazino Group as Proton Donor in Intramolecular Hydrogen Bonding of (2-Fluoroethyl)hydrazine (FCH2CH2NHNH2)

“…Much of our work has focused on weak proton donor groups. Recently, we reported gas-phase studies of alcohols, − carboxylic acids, thiols, − thiolcarboxylic acids, selenols, − amines, − amides, , and phosphines, − where the said groups are proton donors in internal H bonds with acceptors such as the fluorine atom, ,,, the chlorine atom, ,,, π-electrons of triple bonds, − ,,,, π-electrons of double bonds, ,,,, and Walsh pseudo-π electrons. ,, References of many of our earlier works are found in the cited literature as well as in reviews. − …”