Spectrochemical Insights into Aromatic Hydrocarbons in 1,2-Disubstituted Naphthalenes: Investigations Using 1D and 2D NMR Spectroscopy and X-Ray Crystallography Analysis

Naphthalene and its derivatives are often determined as markers of environmental pollution, although they are also recognized as crucial building blocks in many beneficial compounds. In the course of this study, a range of 1,2-disubstituted naphthalenes bearing nitro, amine, sulfonate, chlorine, and hydroxyl substituents were synthesized and characterized using several spectroscopic techniques, including FT-IR,¹H NMR,¹³C NMR, DEPT-90, DEPT-135, DEPTq, elemental analysis, and high-resolution mass (HRMs). The NMR analysis of the aromatic hydrocarbon moiety in these compounds emphasized the impact of substituent variations on the appearance of ¹H and ¹³C NMR signals. To resolve the issue of overlapping one-dimensional (1D) ¹H NMR signals and determine the connectivity of hydrogen and carbon atoms from the aromatic naphtayl ring, we employed a “two-dimensional” experiment, using homonuclear correlation spectroscopy (2D ¹H-¹H COSY) and heteronuclear single quantum correlation (2D ¹H - ¹³C HSQC) and heteronuclear multiple‐bond correlation spectroscopy (2D ¹H - ¹³C HMBC). This work also investigated the correlation between ¹H NMR signals and thin-layer chromatography (TLC) data. X-ray crystallography data validates that the presence of a specific group, not aligned coplanarly with the naphthyl ring, exerts a spatial influence on the manifestation of ¹H NMR signals, alongside other electronic effects. This study will offer NMR data, providing insights into the potential applications and analyses of naphthalene derivatives across various theoretical and practical domains.