Novel, Green, Simple and Uncatalyzed Route for High Yield Preparation of Benzaldehyde Glycol Acetal

CHEM. RES. CHINESE UNIVERSITIES 2011, 27(5), 799- -802Novel, Green, Simple and Uncatalyzed Route for High YieldPreparation of Benzaldehyde Glycol AcetalTANG Jia, SONG Ji-yuan, WANG Ge', YANG Mu and GUO Wan-chunSchool of Material Science and Engineering, Universily of Science and Technology Bejing,Beijing 100083, P. R. ChinaAbstract A simple approach for the condensation of benzaldehyde with ethylene glycol was adopted without em-ploying any catalyst. The study reveals that factors including temperature, molar ratio of reactants, and the water re-moval significantly influence the conversion ratio of benzaldehyde. The results indicate that the use of optimal reac-tion conditions such as temperature and water removing exhibits more pronounced effects on the conversion ratio ofbenzaldehyde compared with the use of catalysts. In a word, a green and simple method for the condensation of al-dehyde and menthandiol has been devised and investigated.Keywords Condensation; Benzaldehyde; Ethylene glycolArticle ID 1005-9040(201 1)-05-799-041 Introductionof acetal. Moreover, sulfamic acid(H2NSO;H)4), iodine'1s,iodine in ionic liquidl6, choline chloride xZnCl2(x=1- -3)I7,Fruit flavored benzaldehyde glycol acetal has been widely[TMPSA]HSO4l8), novel PEG ionic liquid!l9| and mesoporousemployed as steroids, pharmaceuticals and fragrancesl-7.Al-SBA-15[20 are used to catalyze the condensation reactionGenerally, the benzaldehyde glycol acetal is synthesized by thewith corresponding yields of 43%, 40%, 83%, 52%, 77%, 92%catalytic condensation of benzaldehyde with ethylene glycol,and 65%, respectively. In order to accelerate the formation ofproducing water as the only by-product. This method com-acetal and ketal, microwave iradiation21] has been used tomonly involves the protection of carbonyl functional group.offer a yield of about 51%.Owing to the practical uility of this compound, many catalystsThe maximum catalytic yield of 99% has been acquired byhave been investigated during the last three decades.the titanium cation exchanged montmoilonte22)1 as catalyst.Generall, benzaldchyde glycol acetal is prepared by theThe authorsl221 have ascribed the high yield to the acidity of thecondensation of benzaldehyde with ethylene glycol(Scheme 1),catalyst and its expansion of interlayer space. However, thebut the reaction has been reported in a low yield, so inorganiclimitations are the use of high catalyst loading as well asacidsl- -川 are utilized as catalysts to accelerate this condensa-the use of a noxious solvent such as toluene in high concentra-tion reaction. However, the most of these catalysts induce thetion.reduction in yield along with the production of a large numberIt can be summarized from the above discussion that by allof by-products. Therefore, persistent efforts have been put tokinds of catalysts such as inorganic acids, ion- exchange resinsfind new effective reaction conditions and catalysts that mayand Lewis acids, the yield of benzaldehyde glycol acetal lies inimprove the yield of benzaldehyde glycol acetal. Srivastavaa range of 40%- -83%. Apart from the issue of low output yield,et al.t121 have employed bismuth nitrate as a catalyst to thecondensation of benzaldehyde with ethylene glycol and ac-molar ratio and water-removing on the conversion of benzal-quired a yield of about 60%. They have atributed the low yielddchyde have been performed yet. In the present work, we haveto the dificulty in the precise control of the acidity of the sys-conducted a systematic study of these factors. Interestingly, wetem. Later [Hmim]BF413] is used as catalyst to offer 60% con-have found that the conversion ratio can be enhanced signif-version of aldehyde. The authorsl have suggested that thecantly by changing the temperature and the molar ratio of reac-electron-withdrawing substituent is conducive to the generationtants under water-removing, solvent-free conditions evenwithout any catalyst.CH)H ! Catalyst+ H2O2 ExperimentalScheme 1 llustration of the condensation of benzal2.1 Generaldehyde with ethylene glycolEthylene glycol and cyclohexane(A.R.) were purchased中国煤化工*Corresponding author. E-mail: gewang@mater.ustb.edu.cnReceived October 4, 2010; accepted November 4, 2010.MHCNMH GSupported by the National Natural Science Foundation of China(No.51073023) and the Co-building Special Profect of Bei-jing Municipal Education Comission(China).800CHEM. RES. CHINESE UNIVERSITIESVol.27from Bejing Chemical Rcagent Co., Lud, China. Benzalde-intervals to determine the conversion ratio of benzaldehyde.hyde(A.R.) was supplied by Tianjn Bodi Chemical Co.. Ltd,The results are depicted in Fig1.China. Benzaldchyde was used after distillation, and its puritywas confirmed by NMR.7.5 tFTIR spectra of pure liquid benzaldehyde glycol acetal45.were recorded with an infrared spectrophotomcter(Nicolet6700). 'H NMR spectra were taken on a Bruker Avance 40042.5 tMHz using pure liquid sample. Pure liquid benzaldehyde glycolacetal was obtained with column chromatography to separatethe reaction mixtures. GC-MS analysis was performed on a37.5 L01.0203.04.0 5.0 6.0GC7890A-MS5975 for the sample diluted with ethanol.Duration time/hFig1 Conversion rates of benzaldehyde at different2.2 Typical Procedurereaction temperatures and timeBenzaldehyde of 8 mL(0.08 mol) and ethylene glycol ofrPC:a. 80:b. 100.0. 120:d 140.6.6 mL(0.12 mol) were added into a round-bottom flaskFig1 exhibits a comparasion of conversion under fourequipped with a water separator. Cyclohexane(8 mL) was useddifferent temperatures. It is evident that the temperatures of 100as water entraining agent. The reaction system(Scheme 2) wasand 80 °C present a better equilibrium conversion. As the tem-stirred magetically and an oil bath \perature rises beyond 100。C, the conversion rate of benzalde-temperature. At fixed intervals, the reaction system was sam-hyde decreases owing to the increment in the hydrolyzation ofpled to analyze with GC to obtain the conversion ratio of ben-benzaldehyde glycol acetal2)I. Al the temperature of aboutzaldehyde. All the reactions were carried out by changing tem-100。C, the conversion extends continuously with time andperature, molar ratio of the reactants or water removal whileacquires equilibrium in about 3 h with a total conversion ofother conditions were kept unchanged.about 46%. The conversion at the other 3 temperatures exhibitssimilar profiles. Hence, it is concluded that by keeping theother reaction conditions fixed, a change in temperature slightlyOH ! No catalyst2 Solen-re.+ H2O (Walcrn,enhances the yield of benzaldehyde.OH3.2 Influence of Molar Ratios of Ethylene GlycolScheme 2 Condensation of benzaldehyde with ethy-lene glycol in the reaction systemto BenzaldehydeThe spectra data for benzaldehyde glycol acetal: 'H NMR,With the temperature of the reaction system fixed at8: 4.0(m, 4H, OCH2CH20O), 5.7(s, 1H, CH), 7.26- -7.40(m, 5H,100。C, the influence of the change in the molar ratio of reac-Ar--H); FTIR, v/cm-': 2886.63, 1457.89, 1394.51, 1219.88tants on the yicld of reaction has been studied. The amount of1092.48, 1068.84, 1027, 698.32, 757.25.benzaldehyde was fixed at 8 mL(0.08 mol), while the amountof the ethylene glycol was varied according to the mole ratio of3 Results and Discussionreactants. The results are plotted in Fig.2.The factors afecting the reaction are mainly the reactiontemperature and the molar ratio of reactants. As water is theonly by-product of this reversible reaction, hence, water-50 F士removal is an important step that influences the conversion40 tratio of benzaldehyde. Therefore, all these three influencingfactors have been systematically investigated in order 10 op-timize the decisive factors.02.03.04.05.06.0.Duration timc/h3.1 Influence of Temperaturemolar ratios and time at 100。C .In order to examine the influence of temperature, the reac-n(Ethylene gyol);:(benzaldchyde):; a.1.1:1:b. 1.5:1, c.2:1,d.3:1.tion at various temperatures, without water removal, has beenIt is evident that the conversion of benzaldchyde increasescarried out. Benzaldehyde and ethylene glycol were added to awith an increase in the molar ratio of ethylene glycol to ben-flask equipped with a condenser. The top of the flask waszaldehyde(Fig.2). As the molar ratio is increased from 1.5:1 tosealed with a glass plug to prevent water from evaporating out3.0:1, the yield of benzaldehyde rises from about 45% to 54%.of the reaction system. The molar ratio of ethylene glycol toHowever, an increase in the molar ratio also increases thebenzaldehyde was kept at 1.5:1. This molar ratio was typicallyamount of ethylene elycol in the products, which renders theused for the conversion of benzaldehyde. The reaction systempost-processing中国煤化工was stired with a magnetic bar and kept a constant temperatureby an oil bath. The reaction has been performed at four typical3.3 InflueneMHCNMHGtemperatures. The reaction mixture was sampled at fixedIt can be seen in Scheme I that the condensation ofNo.STANG Jia et al.801benzaldehyde with ethylene glycol results in by-product water,q0Hwhich deteriorates the conversion yield of benzaldehyde.HTherefore, the efect of water-removal on the conversion ofbenzaldehyde has been investigated.云The molar ratio of ethylene glycol to benzaldehydeOHOHadopted were respectively 1.5:I, 2:1, and 3:1 and 8 mL of cyc-lohexane was added to the reaction system as a watercaryingagent. The flask has been equipped with water separator. Al-though 100。C is appropriate for the reaction to be carried outScheme 3 Reaction mechanism of condensation ofin the closed system, however, it is too low to flush water out.benzaldehyde with ethylene glycolTherefore, the temperature was maintained at 135 °C by con-During heating- C= =0 becomes unstable tostant temperature oil bath. The results are plotted in Fig.3.form C==0 , which is vulnerable to be attacked by ethylene100glycol(nucleophile) and the H* is transferred to 0 toyield - OH, consequently results in the generation of hemia-8:etal. Subsequently, a dehydration reaction between- -OH anda|ethylene ketal occurs to synthesize benzaldehyde glycol acetal.60个However, the resultant product is not stable. In order to avoid40the reversible reaction, it is necessary to remove water timely.5.5.5 4.5The activation energy(E) of this condensation reactionDuration time/hwas determined to verify its feasibility by employing heatingFig.3 Conversion rates of benzaldehyde undereven without any catalyst. Owing to the instability of hemia-water-removal condition at 135 °Ccetal, an instant conversion from the dchydrated product ton(Ethylene glycol);:n(benzaldehyde): a.1.1:;b. 1.5:1;c. 2:1;d. 3:1.acetal takes place. Therefore, it is impossible to detect theThe comparasion of Fig.3 with Fig.2 revcals that the con-semi-acetal contents. Hence, the apparent E, of the whole reac-version rate of benzaldehyde can be increased significantlytion was calculated. For this purpose, 0.1 mol of ethylene gly-under the water-removing condition. A higher conversion ofcol, 0.1 mol of benzaldehyde, and a certain amount of acetoni-about 92% in a reaction time of3 h can be acquired. The con-trile are mixed to acquire about 100 mL solution in a single-densation of benzaldehyde with ethylene glycol is a reversiblemouth round bottom flask. A water-cooled condenser was usedreaction. Therefore, as water is drawn off by cyclohexane, thefor keeping refluxing, and the solution was stirred magnetically.hydrolyzation of benzaldehyde glycol acetal is restrained,The reaction was performed at 90 and 120 °C, respectively. Thehence resulting in a high yicld of benzaldehyde glycol acetal.results are shown in Fig.4.The reaction has also been carried out at 100 and 120 °C, re~spectively. These temperatures are much higher than 68.95 °C5F(zeotropic point of cyclohexane and water)24, however, the2tevaporation rate is too slow to flood water out of the system intime.The reaction has also been done at 140 。C as other condi-tions mantained, but the conversion is more or less than 90%.Therefore, the temperature of 135 °C is adopted at whichby-product water can be flushed out from the reaction systemeasily.It is clearly seen from Fig.3 that with rise in the molar r8-Time/htio of ethylene glycol to benzaldehyde from 1.1:1 to 2.0:1, the .Fig.4 Product conceotration at different reactionconversion rate of benzaldehyde increases gradually. However,temperatures and timeas the molar ratio is beyond 2.0:1, the conversion rate deteri-●90C;●120 c.orates significantly. Actually higher molar ratio results in aIn Fig.4, the relationship between product concentationhigher amount of ethylene glycol. At higher concentrations,ethylene glycol is miscible with water, and becomesand time is linear, which indicates that the reaction is a zeroorder reaction. At 90。C, the corresponding factor of R'(COD)non-conducive to the removal of water. In other words, theoptimal reactants molar ratio is 2.0:1, which yields the highestand the rate constant are 0.975 and 0.296 molL-'hr', respec-tively. At 120。C, the corresponding parameters are 0.988 andconversion of benzaldehyde.Hence, it is revealed from the above discussion that in or~1.332 molL~ 'hr', respectively.According to the Arrhenius equation, the apparent E cander to acquire the highest conversion rate, the reaction shouldbe calculated which is estimated to be 59.51 kJ/mol. This resultbe carried out at a molar ratio of 2.0:1 of reactants underalso supports that中国煤化Itthrough hea-135 9C with cyclohexane as water rermoval agent.The reaction mechanism of condensation of benzaldehydeting without catalCNMHGjound that cye-lohexanone mayproduce cyclo-with ethylene glycol is ilustrated in Scheme 3.hexanone ethylene ketal under solvent-free and catalyst-free802 .CHEM. RES. CHINESE UNIVERSITIESVol.27conditions. The detailed research is ongoing at our group to6] Narasaka K., lnoue M, Yamada T, Sugimori J, Ilwasawa N, Chem.demonstrate a facile method for condensation reaction.Lett, 1987, 12, 2409[7] Clode D. M.. Chem. Rev. 1979, 79, 4914 Conclusions[8] Sulzbacher M.. Berymann E, Praiser E. R.,J. Am. Chem. Soc. 1948,70, 2827The investigations about the effects of temperature, the[9] RallsJ. W, Dodson R M. Reigel B. J,J. m Chem. Soc, 1949,71,molar ratio of reactants, and water-removing on the conversionratio of benzaldehyde have been performed systematically. The[10] Ogata Y. Kawasaki A, Patai s.. Zabicky J. The Chemisory ofresults indicate that temperature and the molar ratio of reactantsCarboryl Group, Wiley, New York, 1970exhibit a considerable impact on the conversion of benzalde-11] LiD.. Shi F, Peng J, Gou s, Deng Y,J. Org. Chem, 2004, 69,hyde, however, water removal step is the most critical one inorder to accomplish a higher yield. This study has also deter-[12] Srivastava N., Dasgupta s. K., Banik B. K, Tetrahedron Let, 2003,mined the optimal reaction conditions for the condensation of44, 1191benzaldehyde with ethylene glycol. An apparent E。 of 59.51[13] Wu H. H, Yang F, Cui P, TangJ, He M. Y, Tetrahedron Lel, 2004,k/mol was also calculated, which verified the feasibility of45, 4963reaction theoretically. In a word, compared with other proce-[14] Wang B.. Gu Y. Song G, Yang T, Yang L, Suo J,J. Mol. Catal. A: .dures reported in the literature, there are no solvent and noChem, 2005, 233, 121catalyst in the reaction system only equipped with a water se-[15] Banik B. K., Chapa M, Marquez J.. Magda C, Tetrahedron Lelr,parator to carry water out timely, so it is a green, simple procc-2005, 46, 2341dure.[16] Ren Y. M., Cai C. Tetrahedron Lel. 2008. 49, 7110[17] Duan z. Y, Gu Y. L. Deng Y. Q, Catal. Comun. 2006 7,651Acknowledgements[18] Fang D.,. Kai G, Shi Q, Liu z, Caral. Commun, 2007, 8, 1463We are grateful to Dr. GUO Yu-peng at Jilin Universityfor[19] zhi H. 2, LuoJ. Ma W, Lu c. x, Chem. J. Chinese Univeritie,helpful discussion2008, 2910), 2007[20] Srivastava P. Srivastava R., Catal. Commun, 2008, 9, 645References[21] Perio B., Dozias M. J, Jacquault P, Hamein J Tetrahedrorn Lett,1997, 38, 7867[1] Climent M. J, Velty A.. Corma.. 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