Abstract: The strength of intramolecular hydrogen bond of acyl thiourea can be monitored by the hydrogen chemical shiftδ_β-NH. We measured the physical properties of 23 N-ferrocenoyl-N'-aromatic(also alkyl,ferrocenyl) thioureas and 14 N-benzoyl-N'-aromatic thioureas including δ_β-NH,pK_bin relation with the σ-parameter of substituents on the aromatic ring. We found that there are a good relationship between the strength of the intramolecular hydrogen bondδ_β-NH and pK_bor σ-parameter of the substituents, thus the substitution effect toword the hydrogen bonding can be revealed.

Key words: N-Ferrocenoyl(benzoyl)-N'-substituted thiourea, Intramolecular hydrogen bond, Thiourea derivatives, Basic strength, Substituent effect