Role of O–H⋯O/S conventional hydrogen bonds in considerable C_sp²–H blue-shift in the binary systems of acetaldehyde and thioacetaldehyde with substituted carboxylic and thiocarboxylic acids

Abstract

The presence of O–H⋯O/S conventional hydrogen bonds in the complex governs a significant blue shift of Csp2–H bonds.

Characteristics of nonconventional hydrogen bonds and stability of dimers of chalcogenoaldehyde derivatives: a noticeable role of oxygen compared to other chalcogens

“… 46,62 A very large C sp 2 –H blue-shift of the stretching frequency up to 104.5 cm −1 was also found in CH 3 CHO⋯FCOOH calculated at the MP2/6-311++G(3df,2pd) level. 54 Consequently, the substitution of one CH 3 CHO molecule in the dimer of CH 3 CHO by one carboxylic acid, like HCOOH or FCOOH, induces a significant increase in the magnitude of the C sp 2 –H stretching frequency blue-shift upon complexation. As seen in Table 1 , the polarity of C sp 2 –H in the F/Cl/BrCHO monomers is greater than that in the H/CH 3 /NH 2 CHO ones.…”

“… 57 It is noteworthy that a very large C sp 2 –H blue-shift of 104.5 cm −1 was reached in the complexes between CH 3 CHZ and RCZOH (R = H, CH 3 , F; Z = O, S). 54 The nonconventional C sp 2 –H⋯Se/Te and Z–H⋯Se/Te hydrogen bonds have recently been found in some systems. Indeed, O/N–H⋯Se/Te hydrogen bonds have been detected through experiments.…”

Comparison of the Molecular Properties of Euglobals Differing by the Mutual Positions of the Two R–C=O Groups (R = H and CH2CH(CH3)2): A Computational Study

“…The computed vibrational frequencies of the C-H bonds in AC-ald that act as donors in C-H•••O IHBs highlight the phenomenon called 'blueshift': for less polar H-bond donors, the bond length of the donor decreases and its stretching mode frequency increases [60][61][62]66]. Blueshifts are frequent for C-H bonds in which C has sp 2 hybridisation [67].…”