(S)-(+)-N-Benzyl-idene-1-(1-naphth-yl)ethyl-amine

Area of Science:

• Organic Chemistry
• Crystallography
• Computational Chemistry

Background:

• Chiral aldimines are important synthetic intermediates.
• Understanding their conformational preferences is key to controlling reactivity and properties.
• Previous computational studies provide a basis for comparison.

Purpose of the Study:

• To investigate the crystal structure of a specific chiral aldimine.
• To compare experimental findings with theoretical density functional theory (DFT) calculations.
• To elucidate the conformational landscape of the molecule.

Main Methods:

• Single-crystal X-ray diffraction was used to determine the molecular structure.
• Density Functional Theory (DFT) calculations, specifically DFT-B3LYP/6-31 G(d), were employed.
• Analysis of dihedral and torsion angles was performed.

Main Results:

• The X-ray structure revealed a dihedral angle of 23.0(2)° between the phenyl and azomethine planes.
• The experimental C=N-C(*)-C(naphthyl) torsion angle of -118.0(2)° deviates from the calculated global energy minimum (0°).
• The observed conformation aligns with the second lowest energy minimum predicted by DFT, approximately 8.5 kJ mol⁻¹ above the global minimum.

Conclusions:

• The determined crystal structure represents a kinetically accessible, yet not the most thermodynamically stable, conformer.
• The findings suggest that the chiral aldimine exists in a conformation close to a secondary energy minimum.
• The possibility of other polymorphs arising from different conformers is anticipated.