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Synthesis of p-hydroxy alkyl benzoates Section A. General introduction and literature survey of p-hydroxy alkyl benzoates. Section B. Synthesis of p-hydroxy alkyl benzoates. 18 Section A: General introduction and literature survey p-hydroxy alkyl benzoates: Introduction: Parabens [Fig.2.1, 2.2, 2.3 and 2.4] have been attracting great interest because of their importance in synthetic organic chemistry. Parabens have been widely used as antimicrobial preservative agents in foods, beverages, drugs and cosmetics for more than fifty years due to their broad antimicrobial spectrum, [1]. Parabens are very versatile in terms of food preservatives, differing from the other preservatives such as benzoates, propionates and sorbates; because they are not weak acid compounds but have a wide pH range. The antimicrobial activity of parabens is directly dependent on the chain length [2, 3]. In the plant world, 4-hydroxybenzoic acid and its derivatives are commonly found in various vegetable foods, such as barley, strawberries, black currants, peaches, carrots, onions, cocoabeans, vanilla; further in foods prepared from fruit plants such as grapes and fruit juices, yeast extract, wine vinegar and also in cheeses [4]. Methyl paraben found application in the synthesis of dimethyl 4, 4 - (tetraphaioyldioxy) dibenzoates as a reactant for monomer preparation [5]. Methyl and propyl p-hydroxybenzoate are used in Rhamnolipid based formulation for fire suppression and chemical and biological hazards [6] Methyl and propyl p-hydroxy 19 benzoates are used in collagen or gelatin based crumble as a preservatives [7].Polyester is a manufactured fiber in which the fiber-forming substance is any long-chain, synthetic polymer composed of at least 85% of an ester of a substituted aromatic carboxylic acid [8]. Paraben are esters of p-hydroxybenzoic acid, from which the name is derived common parabens include methylparaben[Fig.2.1], ethylparaben [Fig.2.2], propylparaben [Fig. 2.3] and butylparaben [Fig. 2.4] O OCH3 O OH OCH2CH3 O OH Fig. 2.1. Fig. 2.2. OCH2CH2CH3 O OCH2CH2CH2CH3 OH OH Fig.2.3. Fig.2.4. Phukan et al. [9] reported a synthesis of parabens using montmorillonite K10 clay as heterogeneous catalyst. Methyl, ethyl, and propyl parabens were synthesized by esterification of phydroxy benzoic acid with corresponding alcohols [Fig. 2.5]. O O OH + ROH OR Montmorillonite K10 Clay + Reflux OH OH Fig. 2.5. 20 H2O Theodor et al. [10] reported an improved method for the synthesis of 4-hydroxy methyl benzoate using p-hydroxy benzoic acid through dipotasium salt of p-hydroxy benzoic acid and esterification was carried out by dimethyl sulphate and adjusting pH of reaction mass by sulphuric acid, NaOH, and ammonia. Thereafter the crude product was purified by charcoal and sodium dithionate to give p-hydroxy methyl benzoates [Fig.2.6]. O OH O O OK OCH3 Purification 1. charcoal 2.filter Conc H2 SO4 (pH=5) Dimethyl sulphate KOH 33% NaOH(pH=6) Water,Liq NH3 OH 3.Sodium dithionate 4.H2 SO4 (pH=8.5) OH OK OCH3 O OH Fig. 2.6. John et al. [11] reported that a stream of dry oxygen was passed through a solution of 1-(4-hydroxy phenyl)–2, 2, 2-trichloro ethanol in methanol and a solution of sodium in methanol containing cupric chloride dihydrate and 1,10 phenanthroline hydrate was added and the reaction was allowed to continue for a further 2h at room temperature and the reaction mixture was then poured into dilute hydrochloric acid, extracted with ether and the combined extracts washed with water. The dried MgSO4 extracts was evaporated to dryness and the residue crystallized from aqueous ethanol to give methyl 4-hydroxy benzoate (yield 66%) [Fig. 2.7]. Cl Cl Cl HO OH O Dry O2 Sodium in methanol CuCl2.2H2O 1,10 phenanthroline Hydrate 25-30°C,Dil.HCl Fig. 2.7. 21 CH3 O HO Hosangadi et al. [12] reported treatment of variety of aromatic carboxylic acids with alcohols in the presence of thionyl chloride results in excellent yields of corresponding esters. This esterification system is compatible with a wide assortment of functional groups [Fig. 2.8]. O O OH X SOCl 2, ROH OR X Fig. 2.8. Schlater et al. [13] demostrated esterification of 4-hydroxy benzoic acid under microwave irradiation with 42 % yield [Fig. 2.9]. O O OH + H2SO4 OCH3 CH3OH MW HO HO Fig. 2.9. Desmurs et al. [14] reported esterification of p-hydroxy benzoic acid using N, N-diisopropyl ethyl amine with isopropyl bromide gives isopropyl p-hydroxy benzoate with moderate yield [Fig. 2.10]. H3C O OH O H3C + CH3 O N,N diisopropyl ethyl amine + Br H3C OH OH Fig. 2.10. 22 CH3CH2N(C3H7)2.HBr Shi Xiaobo Li Chungen [15] reported esterification of buty paraben using Dodecatungstophosphoric acid gave moderate yield [Fig. 2.11]. O OH O O Dodecatungstophosphoric acid HO OH OH Fig. 2.11. Raghaven et al. [16] reported efficient synthesis method of n-butyl parabens under microwave irradiation in the presence of an inorganic salt Zinc chloride as a catalyst. The main advantages of this methodology are better selectivity, rate enhancement and reduction of thermal degradation and higher energy consumption efficiency when compared to traditional heating. Yield is 43% [Fig. 2.12]. O O OH + CH3CH2CH2CH2OH OCH2CH2CH2CH3 ZnCl2 + MW H2O OH OH Fig. 2.12. M.Gorsd et al. [17] investigate that trifluoro methane sulphonic acid immobilized on zirconium was found to be on effective catalyst for esterification of 4-hydroxy benzoic acid with propyl alcohol gives moderate yield [Fig. 2.13]. 23 O O OH + CH3CH2CH2OH OCH2CH2CH3 trifluoromethanesulphonic acid immobilised on Zirconium oxide + H2O OH OH Fig. 2.13. Lin Qi et al. [18] reported the synthesis of n-butyl p –hydroxy benzoate with n-butanol and p-hydroxybenzoic acid as reactants and solid super acid ZrO2/SO42- as catalysts has been studied. The yield of butyl p-hydroxybenzoate was around 87% [Fig. 2.14]. O O OH + CH3CH2CH2CH2OH OCH2CH2CH2CH3 solid superacid supported ZrO2/SO 4 + 2- H2O OH OH Fig. 2.14. GAO Wen-yi et al. [19] The ethyl p-hydroxybenzoate was synthesized by esterification of p-hydroxybenzoic acid with ethanol using solid super acid S_2O~ (2-)_8/ZrO_2-Al_2O_3 as catalyst. The yield of product reaches to 79.0% [Fig. 2.15]. O O OH + HO OCH 2CH 3 Solid Superacid CH3CH 2OH - S-2O~(2 )-8 /ZrO- 2 -Al-2O-3 HO Fig. 2.15. Alireza R. Sardarian et al. [20] reported aromatic carboxylic acid esterification in the presence of triphenylphosphin dibromide or triphenylphosphinediiodide and N,N-dimethylaminopyridine in 24 dichloromethane with 81% yield [Fig. 2.16]. O O O R'OH Ph3PX3 R OH - HX R O PPh3 R = Alkyl, Aryl - Ph3PO - HX R O R' X Fig. 2.16. Jeum Jong kim et al. [21] reported esterification of carboxylic acid with alcohol using 4,5-dichloro-2-[(4-nitrophenyl) sulphonyl]pyridazine-3(2H)-one in the presence of 4-(N,N- dimethylamino)pyridine in refluxing tetrahydrofuran gave the corresponding ester in good yield. [Fig. 2.17]. Cl Cl O R C OH + R' OH O O N S N O Pyridine Fig.2.17 25 NO 2 RCOOR' Section B Synthesis of p-hydroxy alkyl benzoates Introduction Azeotropic distillation is an essential unit operation in today’s processes. Applications using azeotropic distillation are readily apparent in the chemical process industry, specialty chemicals and food industries. The main advantages of azeotropic distillation are in allowing the separation of chemicals that cannot feasibly be separated by conventional distillation, such as systems containing azeotrope or pinch points, and improving the economics of the separation by saving energy and increasing recovery. A minimum-boiling azeotrope can be formed by the introduction of an azeotrope-forming compound (entrainer) to an existing azeotropic mixture or close boiling mixture for which separation by conventional distillation is not feasible. One example is alcohol dehydration. Ethanol and water form a minimum-boiling azeotrope with ethanol as the major component and therefore ethanol cannot be completely dehydrated by conventional distillation. Benzene forms a ternary azeotrope with ethanol and water, which boils at a lower temperature and will therefore remove the water with some ethanol overhead, leaving dry ethanol as a bottoms product. Similarly esters are produced by reacting alcohols with organic acids. The reaction is reversible and therefore unless one of the products is removed, the ester yield is limited. Assuming the reaction is equilibrium-limited and not rate-limited, higher conversions can be obtained by removing one of the products. For instance, if during the reaction the water is removed, the reaction 26 will be driven by equilibrium to produce more ester product. High purity esters can be produced with azeotropic distillation to simultaneously remove water and alcohol from the esters using aromatic and aliphatic hydrocarbons as entrainers. There are distinct advantages to using azeotropic distillation, including energy savings, increased recovery and ability to separate components contained in close boiling, pinch point and azeotropic mixtures. Azeotropic distillation will undoubtedly remains a viable alternative for simplifying difficult separations found in industry [22]. Parabens have synthetically important skeleton and possess very potent pharmacological activities. Although many synthetic protocols are reported for the preparation of parabens, most of these suffer from one or more disadvantages such as harsh reaction conditions, long reaction time, unsatisfactory yield, low purity, multistep purification, hazardous catalyst, large quantity of effluent and tedious workup. Herein, we report the simple and efficient and economical method of synthesis to get highly pure compound with short reaction time and easy workup procedure for the synthesis of phydroxybenzoic acid esters by azeotropic distillation technique using toluene as azeotropic agent in presence of minimum amount of concentrated sulphuric acid with corresponding alcohol [Fig. 2.18]. O O R OH HO + H2SO4/Toluene O ROH Azeotropic distillation HO Fig. 2.18. 27 The mechanism of esterification involves the following steps 1) Protonation of carboxyl group by H + of the acid catalyst.This makes the carbonyl carbon more strongly electropositive O HO HO + OH H + HO C + OH 2) Attack By nucleophile H HO HO C + + :O OH H HO R O OH + R OH 3) Transfer of proton to one of the -OH groups H OH H H O + + HO O R O R HO OH OH 4) The -OH group leaves as water molecule gives protonated ester H + O H HO O R HO C -H 2 O OH + O R O H 5) Elimination of Proton HO C + O R -H O + O H H + + HSO 4 - H 2 SO 4 Fig. 2.19. 28 O R HO Experimental Melting point was determined in open glass capillaries and is uncorrected. 1H NMR spectra were recorded at room temperature on Brucker “AVANCE 400” MHz spectrometer in CDCl3 using TMS as an internal standard. Reaction was monitored by TLC on aluminum sheet precoated with silica gel 60F254. p -hydroxybenzoic acid and alcohols were purchased from Merck, India. Alcohols were purified by distillation before use. Wave length was determined on UV Spectrometer model Shimadzu 1601 Experimental procedure for the synthesis of p-hydroxy ethyl benzoates A 500 mL 4-necked round bottom flask fitted with overhead mechanical stirrer, a dropping funnel, a thermometer and deanstark with condenser. Flask was charged with 100 mL Toluene, 2 mL concentrated Sulphuric acid, p-hydroxybenzoic acid (50 gm, 0.362 mole) and ethanol (16.5 gm, 0.35 mole) and heated the reaction mixture at 95-98°C and continuously added ethanol (28.0 gm, 0.6 mole) through dropping funnel within 5 h then performed azeotropic distillation with continuous removal of water formed in reaction mixture. The progress of reaction was monitored by TLC. After completion of reaction, reaction mixture was cooled to 5°C. Filtered the reaction mixture and washed with water (25mL x 3) and dried in vacuo to afford the pure product. The purity of compound was checked by HPLC [23,24] .The structures of compounds were confirmed on the basis of IR, 1H NMR and mass spectra. Similarly the compounds of the series shown in the Table-2.1 were synthesized by using above procedure and characterization data is given in Table 2.2. 29 Table 2.1 Efficient synthesis of p-hydroxy alkyl benzoates Entery No. Alcohol used Temp. range (°C) Reaction Time (h) 1 Methanol 90-95 5 2 Ethanol 95-98 5 Product obtained p-hydroxy methyl benzoate p-hydroxy ethyl benzoate Yield (%) Purity (%) 94 99.96 95 99.90 95 99.90 93 99.89 90 99.97 88 99.80 p-hydroxy 3 n-Propanol 90-105 6 n-propyl benzoate p-hydroxy 4 n-Butanol 90-105 6 n-butyl benzoate 5 iso butanol 90-107 6 p-hydroxy isobutyl benzoate p-hydroxy 6 n-Pentanol 90-107 6 n-pentyl benzoate 30 Table 2.2 Characterization data of p-hydroxy alkyl benzoates Sr. Substituents M.P./ B.P. Molecular Molecular λ Max. No. ‘R’ (°C) formula weights (nm) 1 Methanol 121 – 123 C8H8O3 152 256 2 Ethanol 114 – 115 C9H10O3 166 256 3 n-Propanol 93 - 95 C10H12O3 180 256 4 n-Butanol 68 - 70 C11H14O3 194 257 5 Iso Butanol 68.5-69 C11H14O3 194 257 6 n-Pentanol 28-30 C12H16O3 208 258 Melting points of synthesized compounds were taken by open capillary method and are uncorrected. Spectral discussion [25, 26] IR-Spectra Synthesized compound were scanned for IR Spectra on Brucker FTIR (Alpha-P) using KBr. (Fig.2.20 and 2.21). Spectral results are listed in Table 2.3 and spectra are included after table. 31 Table 2.3 IR Spectral data of p-hydroxy alkyl benzoates. Sr. No. 1. Structure of Compounds O OCH υO-H cm-1 υCalkyl cm-1 υC=O cm-1 υC-H aromatic cm-1 3 3294 28503000 1682 15141432 HO 2. O OCH υC-O str. cm-1 υC-X para disub. cm-1 1165 - 850 1118 2 CH 3 3222 28503000 1672 15921449 1169 - 849 1168 HO 3. O OCH 2 CH 2 CH 3 3274 2980 1676 15181440 HO O 1163 - 849 1125 OCH2CH2CH2CH3 4. 3383 2956 1678 15101467 1165 - 852 1127 HO CH3 5. O C O CH2 CH CH3 3367 2962 OH 32 1680 1513- 116- 1479 1127 846 33 34 1H NMR Spectra [Fig.2.22, 2.23 and 2.24] Synthesized compounds were scanned for 1H NMR using CDCl3 and DMSO as a solvent on Bruker “AVANCE 400 “ MHz spectrometer using TMS as an internal standard. Spectral results are listed in Table 2.4 and spectra are included after table. Table 2.4 1H NMR – Chemical Shifts in p- hydroxy alkyl benzoates. Sr. No. Structure of Compounds O OCH Chemical Shifts in B ppm 3 3.78(s,3H,-COOCH3) Protons 6.86(d,2H,3&5 Ar-H) Protons 7.82(d,2H,2&6 Ar-H) Protons 10.33(s,1H,Phenolic –OH) Proton 1. HO O OCH 2 CH 3 1.28(t,3H,-COOCH2CH3) Protons 4.24(q,3H,-COOCH2CH3) Protons 6.85(d,2H,3&5 Ar-H) Protons 7.81(d,2H,2&6 Ar-H) Protons 10.33(s,1H,Phenolic –OH) Proton 2. HO O OCH 2 CH 2 CH 3 3. HO O OCH2CH2CH2CH3 4. HO 0.93(t,3H,-COOCH2CH2CH3) Protons 1.67(sextet,2H,-CH2CH2CH3) Protons 4.14(t,2H,-COOCH2CH2CH3) Protons 6.86(d,2H,3&5 Ar-H) Protons 7.82(d,2H,2&6 Ar-H) Protons 10.31(s,1H,Phenolic –OH) Proton 0.91(t,3H,-COOCH2CH2CH2CH3) Protons 1.39(sextet,2H,-CH2CH2CH2CH3) Protons 1.64(quint,2H,- CH2CH2CH2CH3) Protons 4.19(t,2H,-CH2CH2CH2CH3) Protons 6.85(d,2H,3&5 Ar-H) Protons 7.82(d,2H,2&6 Ar-H) Protons 10.31(s,1H,Phenolic –OH) Proton CH3 O C O CH 2 CH CH3 5. OH 0.94(d,6H,-CH-(CH3)2)Protons 1.97(m,,1H ,-CH-(CH3)2) Protons 3.98(d,2H,-CH2,-CH-(CH3)2) Protons 6.87(d,2H,3&5 Ar-H) Protons 7.82(d,2H,2&6 Ar-H) Protons 10.32(s,1H,Phenolic –OH) Proton 35 36 37 38 Mass spectrum [24, 25] Synthesized compounds were scanned for mass spectrum on Shimadzu GCMS QP 5050A make Shimadzu Corporation Japan, mode EI. Spectral results are listed in Table 2.5 and spectra are included after table [Fig.2.25, 2.26]. Table 2.5 Mass fragmentation values of p-hydroxy alkyl benzoates. Sr. No. Structure of the Compounds O OCH Molecular weight (Calcd.) M/Z Values 152 152,121,93,65,53,40. 166 166,138,121,93,65,53,40. 180 180,151,138,121,93,65,53,40 3 1. HO O OCH 2 CH 3 2. HO O OCH 2 CH 2 CH 3 3. HO O OCH 2 CH 2 CH 2 CH 3 194,165,138,121,177,93,65, 4. 194 53,40 HO CH 3 O C O CH 2 CH CH 3 5. 194 OH 39 194,177,138,121,93,65,43,41 . 40 41 Mass fragmentation pattern: The mass fragmentation patterns of some p-hydroxy alkyl benzoate are given the representative cases [Fig.2.27]. Mass fragmentation pattern of p-hydroxy butyl benzoate O-CH 2 -CH 2 -CH 2 -CH 3 O C OH e + O O-CH 2 -CH 2 O 70 ev O-CH 2 -CH 2 -CH 2 -CH 3 C C +. . O O-CH 2 -CH 2 -CH 2 -CH 3 C . - OH -CH 2 -CH 3 + OH OH m/z = 177 m/z = 165 Molecular ion m/z = 194 + O . C CH 2 -CH 3 CH -O-CH 2 -CH 2 -CH 2 -CH 3 H CH 2 + O O C + OH m/z = 121 . . - CO HO + . CH 2 O HO H m/z = 93 O C + . - CO . -CH + C 4H 5 . -CH + HO C 3H 4 m/z = 138 + m/z = 65 CH m/z = 53 m/z = 40 Fig. 2.27 42 . CH 2 CH 2 Results and discussion: The development of environment friendly technologies is a major goal of present research in chemistry. Synthetic esters are generally prepared by reaction of alcohol with organic carboxylic acid in presence of catalyst such as sulphuric acid, the reaction is known as Fischer esterification. The Fischer esterification is a reversible reaction. The equilibrium is pushed to the product side by taking excess of a reactant by continuously removing the water formed in the reaction. We achieved simple and effective method for the synthesis of p-hydroxybenzoic acid esters by azeotropic distillation technique using Toluene as azeotropic agent in presence of minimum amount of concentrated sulphuric acid with corresponding alcohol. This method helps to avoid the etherification of free hydroxyl group and polycondensation of phenol containing carboxylic acid as an impurity. The product produced by this technique gives extremely pure and further purification is not required. Esterification of p-hydroxybenzoic acid with common alcohols was carried out under similar conditions. Good to excellent yields and perfect selectivity were obtained in all cases. Azeotropic technique seems to be more effective, efficient and economical to get highly pure compound with short reaction time and easy workup procedure. Reaction and azeotropic distillation can be carried out in same reaction vessel and as water formed in the reaction, it can be removed continuously by ternary azeotropic distillation and aqueous bottom phase separates out via phase separator. Reaction will complete within 5-6 h with minimum 43 amount of alcohol. Recovered toluene can be used as such for next batch and corresponding alcohol can be used after distillation. CONCLUSION In summary, a novel method for the synthesis of p-hydroxy alkyl benzoates by azeotropic distillation technique using toluene as azeotropic agent in presence of minimum amount of concentrated sulphuric acid with corresponding alcohol was developed on high yield with extremely high purity for the first time. The main advantages of this methodology are 1) This novel method helps to avoid the etherification of free hydroxy group and polycondensation of phenol containing carboxylic acid as an impurity. 2) Extremely high purity product obtained with good yield 3) Easy synthetic procedure 4) For commercial point of view, process is economical 5) Toluene and excess alcohol can be recycled 6) Low energy consumption (7) No additional purification required. 8) One pot synthesis. 44 References 1. Soni M. G., Burdock G. A., Taylor S. L.; Greenberg N. A., Food Chem.Toxicol, 2001,39, 513. 2. Robach M. C., Food Technol. 1980, 34, 81. 3. Dziezak J. D., Food Technol, 1986, 40,104. 4. Anthony C.Dweek Natural Parabens, (site visited) on September 2010 5. Luigi Abis, Riccardo Po, Giuliana Schimperna, Edoardo Merlo. Micromol. Chem. Phys, 1994, 195,181-193. 6. KeithDeSantowww.faqs.org/patents/app/20090126948, 2008. (Site visited on September 14, 2010) 7. Richard M. Herreid, Austin, Minn., U.S.Patent, 6, 090, 915, 2000. 8. Market data compiled by the Fibers Economics Bureau, www.fibersource.com. ( site visited on September 14, 2010) 9. Prodeep Phukan, Mridulkumar Hazarika, Raghav Paraguli, Indian Journal of Chemical Tech., 2007, 14, 104-106. 10. Theodor Papenfuhs, Frankfurt am Main, U.S.Patent 4,052,438, 1977. 11. John A. Schofield, John E. Haws, US Patent 4, 492, 015, 1981. 12. Bhaskar D.Hosangadi, Rajesh S.Dave, Tetrahedron llet. 1996, 37, 6375-6378. 13. Lisa Schalater, David Ziemnik, www.heidelberg.edu/depts./ chem./fisher .html.1995. (Site visited on September 14, 2010) 14. Jean-Roger Demurs, Dozon, Serge Ratton, U.S.Patent, 5, 260, 475, 1993. 15. Shi Xiaobo Li Chungen, Natural science edition, 1998, 45 16. Raghavan, G. S., Liao X., Yaylayan V. A., Tetrahedron Lett, 2002, 43,104. 17. Blanco’s, M.; Gorsd, M.; Pizzio, L.; 3 rd IUPAC conference on green chemistry, Argentina, abstract.icg2010.ca /vdv00013, 2010. 18. Qi L,Huilong Z, Zhicheng L, Jiqing L, Journal of Fuzhou,1999. 19. Gao wean-yi, Ren Li-guo, Zhang Xiao-li, Journal of Liaoning University of petroleum and chemical Technology, 2006. 20. Alireza R.Sardarian, Maryam Zandi and Soghra Motevally. Acta Chim.Slov. 2006, 56,729-733. 21. Jeum-Jong Kim, Yong-Dae Park, Deok-Heon Kweon, YoungJin Kong, Ho-Kyun Kim, Bull. Koream Chem.Soc. 2004, 25(4),501 22. Lee F.M., Wytcherley R.W., GTC Technology Corporation Houston Taxas, USA, 1990. 23. Marvin C. Mc Master, HPLC A practical users Guide second Edition Wiley interscience, A John willey and sons, inc., Publication, 2007. 24. Ewing’s Analytical instrumentation Handbook. Third Edition, Edited by Jacks Cazes, Florida Atantic University Boca Ration, Florida USA, 2009. 25. Schbimann F., Nuclear Magnetic Resonance and Infrared Spectroscopy, 1970, 1, 41. 26. Bellamy L.J., The Infrared spectra of complex Molecule, II Ed.Methuen London, 1964. 46