The Structures of the Free-Radical Scavenger 1,1,3,3-Tetramethylisoindolin-2-Yloxyl, and of the Alkoxy Amine Derivative 5-(1,1,3,3-Tetramethylisoindolin-2-Yloxy)-1-Vinylpyrrolidin-2-One

Abstract

The structures of the title nitroxide , C₁₂H₁₆NO (1), and the alkoxy amine derivative, C₁₈H₂₄N₂O₂ (2), have been determined by single-crystal X-ray structural analyses. Crystals of (1) are monoclinic, space group Cc with a 11.585(6), b 11.697(10), c 16.753(8)Ǻ, β 94.33(6)°, Z 8; R was 0.064 for 1226 independent reflections. The -C(NO)C- group is essentially planar (sum trigonal angles 359.9, 359.9°, as is the five- membered ring. The N-O distances are 1.249(6), 1.252(8)Ǻ. Crystals of (2) are monoclinic, space group P2₁/c, a 8.295(2), b 13.567(5), c 15.294(3)Ǻ, β 98.82(2)°, Z 4; R was 0.051 for 1445 independent reflections. By contrast to (1) the geometry about the nitrogen atom is pyramidal (sum trigonal angles 328°), and the corresponding five-membered ring has an envelope conformation with a nitrogen displacement of 0.45Ǻ. The N-O distance is 1.439(4)Ǻ.

The high-resolution solid state ¹³C n.m.r . spectrum of (2) is discussed in relation to the X-ray structure.