Acetal Metathesis: Mechanistic InsightThis research was supported by the National Science Foundation (CHE-0848236 and CHE-1607263) and the University of Florida.
Received: 31 January 2019
Accepted after revision: 25 April 2019
13 May 2019 (eFirst)
Published as part of the Cluster Metathesis beyond Olefins
The origins and recent applications of acetal metathesis are discussed in the context of synthesizing polyacetals via acetal metathesis polymerization (AMP). A kinetic study of the acid-catalyzed acetal metathesis reaction suggests the rate = k[H+][acetal]2, with MeOCH2OMe and EtOCH2OEt interchanging to yield MeOCH2OEt, achieving the statistical 1:2:1 equilibrium distribution in 4 hours at 80 °C and in 1 hour at 90 °C. Upon heating 1,10-decanediol and diethoxymethane, polydecylene acetal is formed with sequential distillation of ethanol, followed by diethoxymethane. A full mechanism for this polymerization is proposed, which begins with a transacetalization sequence to convert the diol into a bisacetal, followed by acetal metathesis to yield a high-molecular-weight polymer.
Key wordsacetal - metathesis - transacetalization - polyacetal - acid catalysis - kinetic study - nucleophilicity
References and Notes
- 1 Currently at: Intel Corporation, Ronler Acres Campus, 2501 NE Century Blvd., Hillsboro, OR 97124, USA.
- 2 Handbook of Olefin Metathesis, 2nd ed. Grubbs RH, Wenzel AG. Wiley-VCH; Weinheim: 2015
- 3 Google: https://www.google.com (accessed Jan 14, 2019).
- 4 IUPAC Gold Book, metathesis. https://goldbook.iupac.org/ html/M/M03878.html (accessed April 25, 2019).
- 5 Miller SA, Pemba AG. US Patent 9217058, 2015
- 6 Pemba AG, Flores JA, Miller SA. Green Chem. 2013; 15: 325
- 7a Chikkali S, Stempfle F, Mecking S. Macromol. Rapid Commun. 2012; 33: 1126
- 7b Rajput BS, Chander U, Arole K, Stempfle F, Menon S, Mecking S, Chikkali SH. Macromol. Chem. Phys. 2016; 217: 1396
- 7c Hufendiek A, Lingier S, Du Prez FE. Polym. Chem. 2019; 10: 9
- 7d Nguyen HT. H, Qi P, Rostagno M, Feteha A, Miller SA. J. Mater. Chem. A 2018; 6: 9298
- 8 Sahmetlioglu E, Nguyen HT. H, Nsengiyumva O, Göktürk E, Miller SA. ACS Macro Lett. 2016; 5: 466
- 9 Vanderhenst R, Miller SA. Green Mater. 2013; 1: 64
- 10 Garcia JJ, Miller SA. Polym. Chem. 2014; 5: 955
- 11 Miller SA. ACS Macro Lett. 2013; 2: 550
- 12a Coleman CG. Dissertation 1991
- 12b McInnes JM, Mountford P. Chem. Commun. 1998; 1669
- 12c Lee YH, Morandi B. Nat. Chem. 2018; 10: 1016
- 13a Hill JW, Carothers WH. J. Am. Chem. Soc. 1932; 54: 1569
- 13b Hill JW, Carothers WH. J. Am. Chem. Soc. 1933; 55: 5031
- 14 Hill JW, Carothers WH. J. Am. Chem. Soc. 1935; 57: 925
- 15a Bielawski CW, Grubbs RH. Prog. Polym. Sci. 2007; 32: 1
- 15b Trnka TM, Grubbs RH. Acc. Chem. Res. 2001; 34: 18
- 15c Grubbs RH. Tetrahedron 2004; 60: 7117
- 15d Schrock RR. Chim. Oggi 2009; 27: 2
- 16 Opper KL, Wagener KB. J. Polym. Sci., Part A: Polym. Chem. 2011; 49: 821
- 17a Gazizova LB, Imashev UB, Musavirov RS, Kantor EA, Zlotskii SS, Kuz’michev AA, Rakhmankulov DL. J. Org. Chem. USSR (Engl. Transl.) 1981; 17: 226
- 17b Schaper U.-A. Synthesis 1981; 794
- 18 Protocol for 1H NMR Analysis of Acetal Metathesis between MeOCH2OMe and EtOCH2OEtAn equimolar stock solution was prepared containing 0.5000 mol (38.05 g) of MeOCH2OMe and 0.5000 mol (52.08 g) of EtOCH2OEt. Then, 0.20 mL of this stock solution was added to a J. Young NMR tube, followed by 0.8 mL of toluene-d 8, and 1.9 mg (0.011 mmol) of p-TSA (0.5 mol%). The sample was equilibrated at 80 °C (or 90 °C) for 10 minutes before acquiring 1H NMR spectra every 5 minutes for 345 (or 360) minutes. The acetal proton peaks at 4.49 ppm (EtOCH 2OEt), 4.56 ppm (MeOCH 2OEt), and 4.63 ppm (MeOCH 2OMe) were automatically integrated for each spectrum.
- 19 Additional details for the distillate collection and analysis are found in the Supporting Information.
- 20 Čorić I, Vellalath S, List B. J. Am. Chem. Soc. 2010; 132: 8536
- 21 McIntyre D, Long FA. J. Am. Chem. Soc. 1954; 76: 3240
- 22 The pK a values of protonated dimethoxymethane and protonated diethoxyethane have been indirectly measured to be –4.87 and –4.43, respectively. See: Kankaanperä A. Acta. Chem. Scand. 1969; 23: 1723
- 23 Wolford RK. J. Phys. Chem. 1964; 68: 3392
- 24 Trioxane is commonly proposed to be a nucleophile during its polymerization. See: Weissermel K, Fischer E, Gutweiler K, Hermann HD, Cherdron H. Angew. Chem., Int. Ed. Engl. 1967; 6: 526
- 25 Jaramillo P, Pérez P, Contreras R, Tiznado W, Fuentealba P. J. Phys. Chem. A 2006; 110: 8181
- 26 Moore JW, Pearson RG. Kinetics and Mechanism: A Study of Homogeneous Chemical Reactions, 3rd ed. John Wiley & Sons; New York: 1981: 16
- 27 Jones CM, Lewis WC. M. J. Chem. Soc., Trans. 1920; 117: 1120
- 28 Protocol for the Bisacetal SynthesisA 1 liter round-bottom flask was charged with 17.43 g (0.100 mol, 1 equiv) of 1,10-decanediol, 208.30 g (2.00 mol, 20 equiv) of diethoxymethane, 0.190 g (1 mol%) of para-toluenesulfonic acid, and 100 mL of toluene. Ethanol was exhaustively removed via distillation over 24 h, followed by refluxing for 48 h. Workup, as described in the Supporting Information, afforded the bisacetal as a colorless oil in 72% yield (21.03 g).