Synthesis and Characterization of Schiff Bases Derived from 1-Naphthylamine Hydrochloride, Syria: Homs

The three Schiff bases namely NPNA (L 1 ): N-[(E)-Pheny lmethylene]Naphthalene-1-Amine, newly NNNA (L 2 ): N-[(E)-1-Naphthylmethylene]Naphthalene-1-Amine and NFNA (L 3 ): N-[(E)-2-Furylmethylene] Naphthalene-1-Amine have been synthesized in equimolar reaction of 1-Naphthylamine hydrochloride with or naphthalene-1-carbaldehyde or 2-furfuraldehyde in the presence of acetic acid glacial. The characterization of Schiff bases was done by 1 HNMR, UV–VIS, IR, spectral studies and analytical data.


Introduction
Schiff bases are named in the owner of Hugo Schiff (1834Schiff ( -1915 [1][2]. Their formula is {HR-C=N-R} R=aryl group and Hugo Schiff prove it in (1864) [1].They are formed by condensation of aldehyde compounds with primary amine compounds in alcoholic medium in the presence of acetic acid as catalyst to make PH ranges between(4.5-5) [3]. Schiff base is called imine, azomethine, aldimine and anil. Schiff base derived from aromatic aldehyde and aromatic amine is more stable because the having effective conjugation and readily synthesized. Schiff bases used as antibacterial [4], antifungi [5], anti-inflammatory [6], analgesic [6], anticancer [7] and corrosion Inhibition [8]. In industry section they are used as antioxidant agents [9], and as primary compound to synthesis new compounds [10]. The goal of the study presented here is to synthesize from condensation of 1-Naphthyl amine hydrochloride with benzaldehyde or naphthalene-1-carbaldehyde or 2-furfuraldehyde.
Ultraviolet-Visible spectra were recorded using a Optizen UV 3220 Spectro-photometer in the range of 200-800 nm and DMF is used as a solvent. Elemental analyses (C, N,H) were analyzed on FEI Quanta 200 Scanning Electron Microscopes. Decomposing point of the compounds were recorded using Electro Thermal Melting Point Apparatus (10-370 °C). Differential Thermal Analyzer (DTA) were recorded for only NFNA using Shimadzu.

2.2.
General procedure for the synthesis of the ligands NPNA , NNNA and NFNA solution of (3mmol, 0.03gr) of Benzaldehyde or (3mmol, 0.47gr) of naphthalene-1-carbaldehyde or (3mmol, 0.29gr) of 2-furfuraldehyde in (6ml) absolute ethanol added dropwise to a solution of (3mmol,0.55gr) of 1-Naphthylamine hydrochloride in (6ml) absolute ethanol in round bottom flask (50ml), then(1ml) of acetic acid glacial was added to this solution. The mixture was refluxed 23h for NPNA and 21h for NNNA in an oil bath at (77-79°C).The reaction was monitored through TLC. After completion of the reaction (TLC analysis) the flask was cooled on crush ice to afford a solid product. The precipitates obtained were filtered, washed with acetonitrile and ethanol. Then they recrystallization from (CH2Cl2:EtOH) in ratio (1:2). Then they driedunder vacuum.

Results and discussion
The Schiff base NPNA (scheme1) was prepared by condensation in ethanol of 1-Naphthyl amine hydrochloride and benzaldehyde. The same method was used for the preparation of the ligand NNNA and NFNA. (scheme1) The structure of Schiff bases thus formed was established by IR, 1 HNMR, UV and CHN analysis. The synthesized Schiff bases were soluble in DMF, DMSO. The composition of the ligands was consistent with their NMR, IR, and CHN data. The results of the elemental analyses of the ligands, which are recorded in Table 1, are in good agreement with those required by the proposed formulae.

IR spectra
The characteristic bands of IR spectra of ligands L 1 , L 2 and L 3 are reported in Table 2. Peak corresponding to ν(C=O) stretching vibrations was absent in IR spectra of L 1 and, instead, a new band assigned to azomethine ν(HC=N) linkage appeared at 1636 cm -1 confirming the formation of Schiff base [3]. Similarly, the peak at 1633 cm -1 in L 2 corresponds to ν(HC=N) linkage [3], and similarly, the peak at 1637 cm -1 in L 3 corresponds to ν(HC=N) linkage [3]. A medium intensity band due to ν(C-O-C) stretching vibration of furan appeared at 1200 cm -1 in the ligands L 3 [3]. Table 1 Physical measurements and analytical data of the ligands L 1 , L 2 , L 3 .

Electronic spectra
The electronic spectra of the ligands and their complexes were recorded in DMF medium at room temperature. All the spectra of the ligands show band in range (301,308, 330nm) are attributable to the transition (→π*) of the azomethine corresponding of the ligands (L 1 ,L 2 ,L 3 ) respectively [12,11,5].

Thermal analysis
The DTA curve of the ligand L 3 (Fig 4) shows an endothermic band at 84.87°C which represent the loss of lattice water [13].