Blue- and Red-Shifting C-H ×××O Hydrogen Bonds of Cyclic Ethers with Haloforms: Effect of Ring-Size and Consistency with Bent's Rule

Chemphyschem. 2024 Apr 8:e202400263. doi: 10.1002/cphc.202400263. Online ahead of print.ABSTRACTA DFT-based computational study is carried out to delve into the interplay between hyperconjugation and rehybridization effects underlying the formation of blue- or red-shifting H-bonds (HBs) in 1:1 complexes of cyclic ethers (HB acceptor) of varying ring-size with haloforms, CHF3 and CHCl3 (HB donor). The calculations reveal that with decreasing angular strain (increasing ring-size) of the cyclic ethers, the extent of blue-shift increases for 1:1 complexes with CHF3, while a reverse sequence is observed with CHCl3, eventually leading to a red-shifting HB in the oxepane:CHCl3 complex. It is noted that the trend in the shift of C-H stretching fundamental is not mirrored by the C-H bond length or interaction energies for both the systems studied, that is, the low sensitivity of the changes on the strain on the O-atom of HB acceptor (cyclic ethers) is to be emphasized.PMID:38590027 | DOI:10.1002/cphc.202400263

Source: Chemphyschem - April 9, 2024 Category: Chemistry Authors: Bijan K Paul Source Type: research