2,2′-(Ethane-1,2-diyl)bis(4-chlorophenol)

Abstract

The X-ray structure of the title compound, obtained as a byproduct in a natural product synthesis, has been determined and shows an unusual pattern featuring chains of molecules with both intra- and intermolecular hydrogen bonding of the OH groups.

Low-Temperature Infrared Spectra and Ultraviolet-Induced Rotamerization of 5-Chlorosalicylaldehyde

“…Another fact to highlight is the appearance of the carbonyl stretching Fermi doublet characteristic of conformer I in the spectra of both the crystal and amorphous states, which doubtlessly proves that the intramolecular H-bond is kept in both cases. In the crystalline state, this has been verified experimentally in the previously reported single-crystal X-ray diffraction studies, 16,17 as it was already mentioned above.…”

“…Supporting this conclusion is the observation that the spectrum of the glassy state resembles very much that of conformer I (see Figure 6), as well as the fact that this situation happens in the crystal structure of 5CSA. 16,17 A straightforward assignment of the spectrum of the amorphous 5CSA could be given (Table 5) due to the general similarity of the spectra of this condensed phase and that observed for the matrix-isolated compound for the vibrations that are not localized in the hydroxyl and carbonyl moieties, since those are directly involved in the intermolecular interactions.…”

“…Finally, it can be noticed that, while the CCl stretching band experiences the general broadening in the amorphous compound, interestingly, its frequency is the same as observed for the matrix-isolated molecules of 5CSA (909 cm −1 in both cases), which indicates the relative insensitivity of this vibration to the intermolecular environment. Nevertheless, the frequency of this mode decreases slightly (to 906 cm −1 ) in the neat crystalline phase, much probably due to the intermolecular contact between the chlorine atoms and the para CH bond (d H•••Cl = 3.141 Å) 16 in the crystal (see Figure S2, in the Supporting Information), which is close to the sum of the van der Waals radii of Cl and H atoms (1.75 + 1.2 = 2.95 Å). This close contact in the crystal can be expected to pull electrons out of the C−Cl bond, thus reducing the corresponding CCl stretching force constant and, consequently, the associated vibrational frequency, as observed.…”

“…The crystalline structure of 5CSA is known, 16,17 the crystals being monoclinic, space group P2 1 (n°= 4), with a = 3.8818(5) Å, b = 5.6515 (7) Å, c = 15.204(2) Å, β = 93.176(1)°, at room temperature, and two molecules per unit cell (Z = 2). 17 In the crystals, the molecules adopt a conformation where the hydroxyl group is intramolecularly hydrogen bonded to the aldehyde oxygen atom and are arranged in two alternate arrays that make an angle of ca.…”

“…60°b etween them; they are further interconnected by intermolecular O−H ••• O hydrogen bonds, forming zig-zag chains. 16,17 To the best of our knowledge, no other structural, vibrational, or photochemical studies (either experimental or theoretical) have been reported on 5CSA hitherto.…”