The solvent effect on polar compounds containing acidic hydrogens

• Main Author: Ng, Soon
• Format: Article
• Published: Heyden & Son 1970
• Subjects: Q Science (General); QD Chemistry
• Online Access: http://eprints.um.edu.my/24696/; https://doi.org/10.1002/mrc.1270020308

The effect of aromatic and non‐aromatic solvents on the proton chemical shifts of 23 polar compounds has been determined. The protons which are activated by electron‐withdrawing groups show large highfield shifts in benzene (relative to the isotropic solvents). Based on evidence provided by infrared data, the highfield shifts of the acidic protons in benzene solution are interpreted in terms of a model involving CHπ hydrogen bonding. This model successfully interprets the data reported previously for steroidal ketones. The same model can be extended to benzene solutions of other polar compounds containing strongly electron‐deficient sites to which alkyl groups are attached. It is observed that the use of CCl4 as a reference solvent in studies of benzene induced shifts may have greater significance, since these two solvents have similar dielectric constants. Copyright © 1970 Heyden & Son Ltd.