Keto-enol tautomerism, conformations, and structure of 1-[N-(4-chlorophenyl)]aminomethylidene2(1H)naphthalenone

Abstract

1-[N-(4-chlorophenyl)]aminomethylidene-2(1H)naphthalenone (C17H12NOCl) (1) was synthesized and the crystal structure was determined. Compound I crystallizes in the monoclinic space group P2(1)/n with a = 4.761(3) Angstrom, b = 20.347(1) Angstrom, c = 13.773(2) Angstrom, beta = 92.89(3)degrees, V = 1332.4(3) Angstrom(3), Z = 4, D-c = 1.404 g cm(-3), mu(Mo Kalpha) = 0.28 mm(-1), and R = 0.036 for 2680 reflections [I > 2sigma(I)]. Molecule I is not planar, and the dihedral angle between the naphthaldeyde plane A [Cl-C11, 01] and the 4-chloroaniline plane B [C12-C17, C11, N1] is 20.1(3)degrees. An intramolecular hydrogen bond occurs between the hydroxyl oxygen and imine nitrogen atoms [2.528(3) Angstrom]. IR, H-1 NMR, and UV measurements and AM1 semiempirical quantum mechanical calculations support the keto form found in the X-ray structure.