X-Ray Crystal Structure of N-[3-(Diethylaminomethyl)-4- hydroxyphenyl]acetamide and its Hydrochloride Salt. Two Forms of an Important Precursor in the Synthesis of Anti-Tuberculosis Drugs

Abstract

N-[3-(Diethylaminomethyl)-4-hydroxyphenyl]acetamide (dmhpa) and its hydrochloride salt (dmhpaH⁺ Cl⁻) have been prepared and their X-ray crystal structures determined. The structure of dmhpa comprises an intramolecular hydrogen bond between the hydroxy group and the diethylaminomethyl nitrogen and an intermolecular association between adjacent N-acetamide groups resulting in a non-centrosymmetric interdigitated ‘V’ polymeric network. Quantitative non-linear optical measurements on a powdered sample of dmhpa revealed a second harmonic signal of two-thirds the intensity of a urea standard. In contrast, the hydrochloride salt is formed via protonation of the diethylaminomethyl nitrogen and resides in a complex hydrogen-bonded network which involves not only the free chloride ion but also one water molecule per dmhpaH⁺ Cl⁻.