The Chirped Pulse, Fourier Transform Microwave Spectrum Of 1-chloromethyl-1-fluorosilacyclopentane


The microwave spectrum of 1-chloromethyl-1-fluorosilacyclopentane has been recorded for the first time using the chirped pulse, Fourier transform microwave technique. Quantum chemical calculations show the two lowest energy conformers as being a twist-trans and a gauche form with the gauche form previously being shown as having two separate conformations, a gauche+ (lower in energy) and gauche- (higher in energy) form. Analysis of the spectrum provided the observation of the twist-trans conformer only, with 253 and 85 transitions being assigned to the 35Cl and 37Cl isotopologues, respectively. R-branch, a- and b-type transitions were observed. The spectrum was fit to a Watson S-reduced Hamiltonian and consisted of rotational constants, quartic centrifugal distortion constants, and nuclear quadrupole coupling constants, including the determination of the off-diagonal nuclear quadrupole coupling constant, χab. Interpretation of the structure was provided using second moments and is found to have a similar ring structure to other known silacyclopentanes. Analysis of the χzz has been carried out and compared to other similar molecules. An investigation of the known quantum chemical energies of the gauche conformer reveals that the reported B3LYP energies do not align with the observed microwave results.




National Science Foundation, Grant CHE-MRI-2019072

Keywords and Phrases

1-chloromethyl-1-fluorosilacyclopentane; CP-FTMW; Quantum chemical calculations; Structure

International Standard Serial Number (ISSN)

1096-083X; 0022-2852

Document Type

Article - Journal

Document Version


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© 2023 Elsevier, All rights reserved.

Publication Date

01 May 2023