Annals of West University of Timisoara Series of Chemistry 22 (2) (2013) 57-66 THE SYNTHESIS OF SALICYLALDEHYDE VARYING DIFFERENT PARAMETERS Roxana Crişan, Dorina Modra West University of Timişoara, Faculty of Chemistry, Biology, Geography, Department of Biology-Chemistry, Pestalozzi Street, 16, Timişoara, 300115, Romania Received: 21 October 2013 Modified: 30 October 2013 Accepted: 8 November 2013 SUMMARY We tried to find the optimum conditions for salicylaldehyde synthesis. The influence of ratio of reactants, the solvent used, the time of synthesis, reaction temperature, steam entrainment method of the product from the reaction mixture were studied. Crude salicylaldehyde is processed, and purified by distillation, and then is physico-chemical characterized. Keywords: salicylaldehyde, 2-hydroxybenzaldehyde, ortho-hydroxybenzaldehyde INTRODUCTION Salicylaldehyde is called 2-hydroxybenzaldehyde and ortho-hydroxybenzaldehyde and is an organic compound with the formula C7H6O2. Part of the class hydroxy aromatic aldehydes, aromatic nucleus contains two functional groups: a hydroxyl and aldehyde one. This colorless liquid has a bitter almond odor at higher concentrations The natural oils found in Spiraea [Filipendula (Spiraea) ulmaria (Rosaceae)]. Sweet-smelling flowers containing salicylaldehyde and methyl salicylate, glycosides form. Was also identified as a component of the characteristic flavor of buckwheat. [1] Salicilaldehyde is used as an important intermediate in the chemical industry, in medicine. It is used in perfume, fragrances, dyes, pharmaceuticals, etc.[2] Salicylaldehyde and its derivatives can be used as preservatives in cosmetic products, [3] fragrances, essential oils in various biological applications. [4] antibacterial Her work is powerful enough to allow its use in very low concentrations. Also get in formulation of perfumes and fragrances. 57 C RIŞ AN R., M ODRA D. Salicylic aldehyde is an important intermediate in the manufacture of herbicides and pesticides. [5] Also, salicylaldehyde and its derivatives are used for various reactions for the production of polymers and fibers. Largest quantity is used in the manufacture of coumarin. Coumarin is a chemical used in soaps, flavors, fragrances and extensively in electroplating, as a leveling agent. [6] Salicylaldehyde and its derivatives are used in electroplating formulations. [6] Salicylic aldehyde is a precursor to aspirin [7]. Compounds derived from salicylaldehyde are also used in large quantities in various applications. Thus, salicylaldoxime branched alkyl chain are used as extraction agent in the separation and concentration operations in copper recovery. [8-10] Schiff bases may be used in the formation of ligands that are used as polymerization catalysts in a variety of industrial applications. Salicylaldehyde is an essential precursor for a variety of chelating agents, some of which are very important Transition metal complexes with Schiff ligand were very much studied in recent years because they are widely applied in many fields: biochemistry, analytical, etc. The ligands and metal complexes of Co(II), Ni(II), Cu(II), Zn(II) Cd(II), shows the antibacterial and antifungal activities. [11, 12] Salicylaldehyde with other aliphatic aldehydes (2-methylbutyraldehyde, hexanal, 3-metilbutraldehida, etc.) are used as additives in the cigarette. The main processes for manufacturing hydroxybenzaldehyde is based on the use of phenol as a raw material. One method consists in preparing the salicylaldehyde phenol and chloroform by heating with sodium hydroxide or potassium hydroxide in a Reimer-Tiemann reaction. In most cases, the yield of aldehyde is low and the reaction has the disadvantage that it uses excess chloroform and is expensive to recover and recycling it. [13] When the reaction is carried out in mixtures of organic solvents, salicylaldehyde is obtained in higher yields and, in addition, the amount of p-hydroxybenzaldehyde as an undesired product is drastically reduced. There are many methods for the synthesis of salicylaldehyde. [14] The current research and development trends in the synthesis of salicylaldehyde include formylation reactions of phenol in the presence of Sn ions, Mg, Li, etc. [15-17] Salicylaldehyde was synthesized by the reaction between formaldehyde and phenol in the presence of a complex of magnesium methoxide in an anhydrous medium. [6] An alternative method of synthesis involves the condensation of phenol with formaldehyde yielding hydroxybenzyl alcohol, which is oxidized to salicylaldehyde. [18, 19] Salicylaldehyde was obtained by electrolytic reduction of salicylic acid. 58 THE SYNTHESIS OF SALICYLALDEHYDE VARYING DIFFERENT PARAMETERS Salicylaldehyde was obtained with a purity of 96%, with a yield of 74%. [20] Must be found new efficient catalysts to improve the yield in salicilaldehyde, to obtain simple and efficient method for separating of products, to reduce costs. In this study, we synthesized salicylaldehyde from phenol and chloroform in the presence of sodium hydroxide and a mixture of solvents to determine the optimal conditions according to the variation of reaction parameters, conditions that lead to higher yields. MATERIALS AND METHODS For the synthesis, reagents that we used were: phenol (99%) (Sigma-Aldrich), chloroform (99%) (Sigma-Aldrich), sodium hydroxide (99.8%) (Merck), methanol (99.8%) (Sigma-Aldrich) and toluene (99%) (Sigma-Aldrich). The other substances and materials used are of analytical grade and used without special treatment. Refractive index is measured by Abbe refractometer. FT-IR spectra was determined with a Perkin Elmer FT-IR Spectrum 100. The chromatographic analysis was performed on a high performance liquid chromatograph (HPLC) (JASCO), detector model PDA MD-1510; separation and quantitation were made on Kromasil column, 250 mm × 4 mm (i.d) (5 μm particle size). The injection volume was 7.0 μL, with a flow rate of 1.0 ml/min and the run time was 10 minutes.The solvents and reagents used were toluenul (Sigma-Aldrich Chemical, Steinheim, Germany) and acetone (Merck, Germany). Phenol is heated with chloroform and NaOH. It works in the presence of a mixture of solvents. The reaction temperature of the mixture will be maintained for a period of time sufficient to ensure the largest possible conversion of reagents. Salicylaldehyde is then separated from the reaction mixture by adding water to the reaction mixture. Solvents are distilled off, and then acidified and salicylaldehyde was removed by steam entrainment. RESULTS DISCUSSION To determine the optimum conditions of synthesis the variation of various reaction parameters was studied, such as: the ratio of reactants, the solvent used, the time of synthesis, reaction temperature, steam entrainment method of the product from the reaction mixture. Influence of solvent Because some synthesis is performed in the presence of mixtures of solvents, we tried to find mixtures that will produce good returns. 59 C RIŞ AN R., M ODRA D. In the summaries have used three different solvent mixtures. Option I contains a mixture of methanol: toluene ratio of 1:1. Variant II contains a mixture of ethanol: toluene ratio of 1:1, and variant III a mixture of isopropanol: toluene ratio of 1:1. The amount of solvent used is 20% compared to the amount of phenol and chloroform used in the reaction It works with a molar ratio of phenol:chloroform 1:2, the reaction time used is 90 minutes. In the reaction sodium hydroxide is used in a proportion of 10% relative to the amount of phenol. The synthesis time is 1.5 hours. The results obtained are shown in Table I: Table I. Experimental data obtained Nr. crt. Solvent Yield [ % ] 1 H2O 54.5 2 Option I 60.2 3 Option II 50.9 4 Option III 49.1 Figure 1 playback performance variation depending on the mixture of solvents used. Figure 1. The variation of the yield depending on the reaction solvents It is observed from the experimental data that the best yield is obtained by working with Option I of solvent (methanol: toluene 1:1), the value is 60.2%. The other variants of solvents used gives yields around 50%. Temperature in the last two variants of the solvent was about 80-90º C and 65-68º C in Option I. In the synthesis were solvent is not used, the reaction temperature was 60-65º C. Following these synthesis, we agreed to find the best working conditions for obtaining high yields in anhydride salicylic version that uses a solvent mixture of ethanol: toluene. 60 THE SYNTHESIS OF SALICYLALDEHYDE VARYING DIFFERENT PARAMETERS The influence of the molar ratio of the reactants To determine the influence of the molar ratio of the reactants on the yield of the reaction, we have used different molar ratios of phenol: chloroform 1:1, 1:1.5, 1:2, 1:3. Temperature was 65-67º C. Synthesis time was 1 hour and 30 minutes, and sodium hydroxide was used in 10% of the quantity of phenol. It works in the presence of a solvent mixture of methanol: toluene, ratio 1:1. The amount of solvent used is 20% compared to the amount of phenol and chloroform used in the reaction. The results obtained are shown in Table II: Table II. Experimental data in the synthesis of salicylaldehyde Nr. crt. Molar ratio Yield [%] phenol:chloroform 1 1:1 20.6 2 1:1.5 54.1 3 1:2 60.2 4 1:3 63.5 In Figure 2 is represented on graph the variation of yield by different molar ratios of phenol: chloroform, used in synthesis. Figure 2 : Variation of yield on different molar ratios of phenol: chloroform From the graphical representation is found that the yield of salicylaldehyde increases with increasing molar ratio of reactants phenol: chloroform. It is also apparent that the increase in yield a molar ratio of phenol:chloroform 1:2 at a ratio of 1:3 is rather less than about 3%, it is better to work with lower molar ratio. This allows us to not use an excessive quantities of chloroform, which then must be recovered and purified Influence of synthesis time It works at different values of the reaction time to determine the best value for 61 C RIŞ AN R., M ODRA D.