Association and solubility of chlorophenols in CCl4: MIR/NIR spectroscopic and DFT study.
Spectrochim Acta A Mol Biomol Spectrosc
; 274: 121077, 2022 Jun 05.
Article
in En
| MEDLINE
| ID: mdl-35248856
ABSTRACT
This work provides new information on the effect of position and number of substituents on association and solubility of chlorophenols in CCl4. Using MIR and NIR spectroscopy we examined solutions of 12 chlorophenols at several concentrations. In addition, we calculated (DFT) theoretical spectra and structures of monomers and associates of chlorophenols from dimer to tetramer. The number of substituents at positions 2 and 6 allows to divide studied chlorophenols into three Groups I (3; 4; 3,4; 3,5), II (2; 2,3; 2,4; 2,5; 2,4,5), and III (2,6; 2,4,6; 2,3,4,5,6). An equilibrium between intermolecular OHâ
â
â
OH and intramolecular OHâ
â
â
Cl hydrogen bonding depends on position and number of substituents. The extent of association decreases in going from Group I to Group III due to growing steric hindrance near the OH group and the resonance effect from Cl. In chlorophenols of Group I, Cl at positions 3 or 5 weakens the OHâ
â
â
OH intermolecular hydrogen bonding, while for Group II it strengthens the OHâ
â
â
â
Cl intramolecular bonding. In contrast, Cl at position 4 has minor effect on association. In the case of Group I, increasing concentration shifts the equilibrium towards solute-solute interactions, whereas for Groups II and III dominate the species with intramolecular OHâ
â
â
Cl bonding. The theoretical calculations predict that for monosubstituted chlorophenols of Group I the most stable are non-planar cyclic tetramers, while for disubstituted ones, the non-planar cyclic tetramers and linear trimers have similar binding energies. Chlorophenols of Group II prefer the cyclic non-planar trimers, whereas those of Group III form the planar dimers with an antiparallel orientation of the OH groups. Our study reveals that chlorophenols creating the cyclic associates are better soluble in CCl4 as compared with those forming the linear ones. Hence, one can conclude that in an inert or weakly interacting solvents the solubility is closely related to the structure of the solute associates.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Chlorophenols
Type of study:
Prognostic_studies
/
Risk_factors_studies
Language:
En
Journal:
Spectrochim Acta A Mol Biomol Spectrosc
Journal subject:
BIOLOGIA MOLECULAR
Year:
2022
Document type:
Article
Affiliation country:
Polonia