100903-68-2Relevant academic research and scientific papers
Substituent and solvent effects on the proton transfer equilibrium in anils and azo derivatives of naphthol. Multinuclear NMR study and theoretical calculations
Alarcón, Sergio H.,Olivieri, Alejandro C.,Sanz, Dionisia,Claramunt, Rosa M.,Elguero, José
, p. 1 - 9 (2007/10/03)
The tautomeric equilibrium due to proton transfer is compared in a series of anils of 2-hydroxynaphthalene-1-carbaldehyde and azo derivatives of 2-naphthol. Although structurally similar, these systems suffer different substituent effects on the solution-state proton transfer properties. The comparative study was performed using 1H, 13C and 15N NMR spectroscopy in a variety of solvents. Hartree-Fock ab initio calculations involving relative stability of tautomers and full geometry optimization for the ground state are in agreement with the experimental observations.
(13)C NMR and X-ray Structure Determination of 1-(Arylazo)-2-naphthols. Intramolecular Proton Transfer between Nitrogen and Oxygen Atoms in the Solid State
Olivieri, Alejandro C.,Wilson, Roxy B.,Paul, Iain C.,Curtin, David Y.
, p. 5525 - 5532 (2007/10/02)
The tautomeric reaction involving a single proton transfer in 1-(phenylazo)-2-naphthol and its 4'-methoxy, ethoxy, and N,N-dimethylamino derivatives has been investigated with variable-temperature solution and high-resolution solid-state (13)C NMR spectroscopy.Crystal structures of the parent unsubstituted compound and the 4'-N,N-dimethylamino derivative have been determined.All of these compounds undergo a fast proton exchange on the NMR time scale between the tautomeric azo and hydrazone forms in both solution and the crystalline phase.Equilibrium compositions inthe solid materials are similar to those measured in solution.Crystals of 1-(phenylazo)-2-naphthol are monoclinic, a = 27.875 (7), b = 6.028 (2), c = 14.928 (5) Angstroem, β = 103.57 (2)0, the space group is C2/c with Z = 8, and the structure at 213 K was refined to an R factor of 0.0414 on 1082 observed reflections.Crystals of 1-(azo)-2-naphthol are monoclinic, a = 7.604 (1), b = 7.970 (3), c = 24.381 (7) Angstroem, β = 99.33 (2)0, the space group is P21/c with Z = 4, and the structure at 193 K was refined to an R factor of 0.0405 on 1522 observed reflections.
1H-N.M.R. Spectroscopic Investigations of the Azo-Hydrazon-Equilibrium in Substituted 1-Phenylazo-2-naphthols
Haessner, R.,Mustroph, H.,Borsdorf, R.
, p. 555 - 566 (2007/10/02)
In substituted 1-phenylazo-2-naphthols an equilibrium between the azoic and the quinoid hydrazone form is observed.It is possible to obtain the equilibrium constants by means of 1H-n.m.r.-spectroscopy in CDCl3.Both chemical shifts δH-3 and δH-8 in the naphthalene ring system can be used to determine independently the equilibrium constants. 1-Phenylazo-2-naphthylamine and 1-(pyrid-2-ylazo)-2-naphthole were used as reference substances for the pure azoic and hydrazone form, respectively.An appropriate correction is introduced to compare the different influence of OH- and NH2-groups, respectively, on the protons H-3 and H-8.All equilibrium constants measured show a linear correlationship with respect to Hammett-?-constants of the substituents attached to the phenyl ring.The standard reaction entropy for the conversion of the azoic form into the hydrazone form is always negative and of nearly identical magnitude.Obviously, no substituent effect to this value exists.One possibility to interprete these results is to assume that the quinoid hydrazone form shows a higher tendency to aggregation.
