Reaction Mechanism of the Elimination of Peroxyl Radical by TEMPO†

doi:10.7503/cjcu20180244

Abstract

Abstract:

Density functional theory(DFT), Møller-Plesset(MP) and frontier molecular orbital methods were employed to investigate the fundamental reaction mechanism of the elimination of peroxyl radical by 2,2,6,6-tetramethylpiperidin-1-oxyl(TEMPO) with and without weak acid environment. The results showed that the calculated result from M06-2x method is in more agreement with the relative experimental results than that from B3LYP method, suggesting that the former is more suitable for the present system. With weak acid environment, the protonated TEMPO undergoes proton coupled electron transfer and electron transfer to eliminate peroxyl radical and get the regeneration. Without acid environment, the elimination of peroxyl radical by TEMPO consists of four steps, the formation of alkoxyamine, β-hydrogen atom transfer, the decomposition of carbon radical, and the regeneration of TEMPO. After the energy calculations, the activation free energy of the elimination of peroxyl radical by TEMPO with weak acid environment is calculated to be 35.6 kJ/mol, much lower than 96.8 kJ/mol without weak acid environment, showing that weak acid environment is more favorable for the reaction and this phenomenon has also been reasonably explained.

Key words: 2,2,6,6-Tetramethylpiperidin-1-oxyl(TEMPO), Peroxyl radical, Antioxidation

CLC Number:

TrendMD:

CHEN Junchao,YAO Yuan,ZHANG Hui. Reaction Mechanism of the Elimination of Peroxyl Radical by TEMPO^†[J]. Chem. J. Chinese Universities, 2018, 39(9): 1961.

Figures/Tables 7

Fig.1 Simplified Denisov cycle(X is H or alkyl chain)

Fig.2 Mechanisms for TEMPO regeneration with (A) and without(B) acid

Fig.3 Optimized geometries of the stationary points involved in acid-catalyzed TEMPO regeneration a. B3LYP; b. M06-2x. Bond lengths are in nm.

Fig.4 Highest occupied molecular orbitals for TS1a optimized at B3LYP(A) and M06-2x(B) methods and the singly occupied molecular orbital of TS1b at M06-2x(C) method

Fig.5 Free energy profile for acid-catalyzed TEMPO regeneration a. B3LYP; b. M06-2x.

Fig.6 Optimized geometries of the stationary points for TEMPO regeneration involved in Denisov cycle

Fig.7 Free energy profile for TEMPO regeneration involved in Denisov cycle

References 31

[1]	Ingold K. U., Pratt D. A., Chem. Rev., 2014, 114(18), 9022—9046
[2]	Burton G. W., Ingold K. U., Acc. Chem. Res., 1986, 19(7), 194—201
[3]	Foti M. C., J. Pharm. Pharmacol., 2007, 59(12), 1673—1685
[4]	Brownlie I. T., Ingold K. U., Can. J. Chem., 1967, 45(20), 2427—2432
[5]	Bolsman T. A. B. M., Blok A. P., Frijns J. H. G., Recueil des Travaux Chimiques des Pays-Bas, 1978, 97(12), 310—312
[6]	Gijsman P., Photostabilisation of Polymer Materials, In Photochemistry and Photophysics of Polymer Materials, John Wiley & Sons, Inc., Hoboken, 2010, 627—679
[7]	Allen N. S., Chem. Soc. Rev., 1986, 15(3), 373—404
[8]	Brede O., Beckert D., Windolph C., Gottinger H. A., J. Phys. Chem. A, 1998, 102(9), 1457—1464
[9]	Pospíšil J., Aromatic and Heterocyclic Amines in Polymer Stabilization, In Adv. Polym. Sci., Springer, Berlin, 1995, 87—189
[10]	Geuskens G., Nedelkos G., Polym. Degrad. Stabil., 1987, 19(4), 365—378
[11]	Sedláar J., Petru̇j J., Pác J., Navrátil M., Polymer, 1980, 21(1), 5—7
[12]	Wiles D. M., Tovborg Jensen J. P., Carlsson D. J., Pure and App. Chem., 1983, 55(10), 1651—1659
[13]	Gugumus F., Polym. Degrad. Stabil., 1991, 34(1—3), 205—241
[14]	Gryn'ova G., Ingold K. U., Coote M. L., J. Am. Chem. Soc., 2012, 134(31), 12979—12988
[15]	Rossi I., Venturini A., Zedda A., J. Am. Chem. Soc., 1999, 121(34), 7914—7917
[16]	Stipa P., J. Chem. Soc., Perkin Trans., 2001, 2(9), 1793—1797
[17]	Goldstein S., Samuni A., J. Phys. Chem. A, 2007, 111(6), 1066—1072
[18]	Klemchuk P. P., Gande M. E., Cordola E., Polym. Degrad. Stabil., 1990, 27(1), 65—74
[19]	Barton D. H. R., Le Gloahec V. N., Smit. J., Tetrahedron Lett., 1998, 39(41), 7483—7486
[20]	Hodgson J. L., Coote M. L., Macromol., 2010, 43(10), 4573—4583
[21]	Haidasz E. A., Meng D., Amorati R., Baschieri A., Ingold K. U., Valgimigli L., Pratt D. A., J. Am. Chem. Soc., 2016, 138(16), 5290—5298
[22]	Frisch M. J., Trucks G. W., Schlegel H. B., Scuseria G. E., Robb M. A., Cheeseman J. R., Scalmani G., Barone V., Mennucci B., Petersson G. A., Nakatsuji H., Caricato M., Li X., Hratchian H. P., Izmaylov A. F., Bloino J., Zheng G., Sonnenberg J. L., Hada M., Ehara M., Toyota K., Fukuda R., Hasegawa J., Ishida M., Nakajima T., Honda Y., Kitao O., Nakai H., Vreven T., Montgomery J. J. A., Peralta J. E., Ogliaro F., Bearpark M., Heyd J. J., Brothers E., Kudin K. N., Staroverov V. N., Kobayashi R., Normand J., Raghavachari K., Rendell A., Burant J. C., Iyengar S. S., Tomasi J., Cossi M., Rega N., Millam J. M., Klene M., Knox J. E., Cross J. B., Bakken V., Adamo C., Jaramillo J., Gomperts R., Stratmann R. E., Yazyev O., Austin A. J., Cammi R., Pomelli C., Ochterski J. W., Martin R. L., Morokuma K., Zakrzewski V. G., Voth G. A., Salvador P., Dannenberg J. J., Dapprich S., Daniels A. D., Farkas Ö., Foresman J. B., Ortiz J. V., Cioslowski J., Fox D. J., Gaussian 09, Revision C.01, Gaussian Inc., Wallingford CT, 2009
[23]	Mayer J. M., Hrovat D. A., Thomas J. L., Borden W. T., J. Am. Chem. Soc., 2002, 124(37), 11142—11147
[24]	Migliore A., Polizzi N. F., Therien M. J., Beratan D. N., Chem. Rev., 2014, 114, 3381—3465
[25]	Li J., Zhou S., Zhang J., Schlangen M., Usharani D., Shaik S., Schwarz H., J. Am. Chem. Soc., 2016, 138, (35) 11368—11377
[26]	Guo X. K., Zhang L. B., Wei D., Niu J. L., Chem. Sci., 2015, 6(12), 7059—7071
[27]	Qiao Y., Chen X., Wei D., Chang J., Scientific Rep., 2016, 6, 38200
[28]	Wang Y., Wu B., Zhang H., Wei D., Tang M., Phys. Chem. Chem.Phys., 2016, 18(29), 19933—19943
[29]	Cheng X. L., Li Y. J., Zhao Y. Y., Liu Y. J., Chem. J. Chinese Universities, 2018, 39(3), 521—529
	(程学礼, 李衍军, 赵燕云, 刘永军. 高等学校化学学报, 2018, 39(3), 521—529)
[30]	Valgimigli L., Amorati R., Petrucci S., Pedulli G. F., Hu D., Hanthorn J. J., Pratt D. A., Angew. Chem. Int. Ed., 2009, 48(44), 8348—8351
[31]	Sobek J., Martschke R., Fischer H., J. Am. Chem. Soc., 2001, 123(12), 2849—2857