The Conformational Analysis Of 2-halocyclooctanones

The establishment of the most stable structures of eight membered rings is a challenging task to the field of conformational analysis. In this work, a series of 2-halocyclooctanones were synthesized (including fluorine, chlorine, bromine and iodine derivatives) and submitted to conformational studies using a combination of theoretical calculation and infrared spectroscopy. For each compound, four conformations were identified as the most important ones. These conformations are derived from the chair-boat conformation of cyclooctanone. The pseudo-equatorial (with respect to the halogen) conformer is preferred in vacuum and in low polarity solvents for chlorine, bromine and iodine derivatives. For 2-fluorocyclooctanone, the preferred conformation in vacuum is pseudo-axial. In acetonitrile, the pseudo-axial conformer becomes the most stable for the chlorine derivative. According to NBO calculations, the conformational preference is not dictated by electron delocalization, but by classical electrostatic repulsions.137176184Eliel, E.L., Wilen, S.H., Mander, L.N., (1994) Stereochemistry of Organic Compounds, , Wiley New YorkBasso, E.A., Kaiser, C., Rittner, R., Lambert, J.B., (1993) J. Org. Chem., 58, p. 7865Basso, E.A., Abiko, L.A., Gauze, G.F., Pontes, R.M., (2011) J. Org. Chem., 76, p. 145Wiberg, K.B., Hammer, J.D., Castejon, H., Bailey, W.F., Deleon, E.L., Jarret, R.M., (1999) J. Org. Chem., 64, p. 2085Rozada, T.C., Gauze, G.F., Favaro, D.C., Rittner, R., Basso, E.A., (2012) Spectrochim. Acta A, 94, p. 277Allinger, N.L., Chen, K., Rahman, M., Pathiaseri, A., (1991) J. Am. Chem. Soc., 113, p. 4505Langley, C.H., Lii, J., Allinger, N.L., (2001) J. Comput. Chem., 22, p. 1451Anet, F.A., (1974) Top. Curr. Chem., 45, p. 178Anet, F.A., (1988) Conform. Anal. Med. Heteroc., p. 35. , R.S. Glass, VHC New YorkAnet, F.A.L., St. Jacques, M., Henrichs, P.M., Cheng, A.K., Krane, J., Wong, L., (1974) Tetrahedron, 30, p. 1629Weigert, F.J., Roberts, J.D., (1970) J. Am. Chem. Soc., 92, p. 1347Rounds, T.C., Strauss, H.L., (1978) J. Chem. Phys., 69, p. 268Stavber, S., Zupan, M., (1996) Tetrahedron Lett., 37, p. 3591Lautens, M., Bouchain, G., (2002) Org. Synth., 79, p. 251Tanemura, K., Suzuki, T., Nishida, Y., Satsumabayashi, K., Horagushi, T., (2004) Chem. Commun., p. 470Harpp, D.N., Bao, L.Q., Black, C.J., Gleason, J.G., Smith, R.A., (1975) J. Org. Chem., 40, p. 3420Frisch, M.J., Trucks, G.W., Schlegel, H.B., Scuseria, G.E., Robb, M.A., Cheeseman, J.R., Montgomery, J.A., Jr., Pople, J.A., (2004) Gaussian 03, , Revision E.01, Gaussian Inc, Wallingford CTBecke, A.D., (1993) J. Chem. Phys., 98, p. 5648Dunning, T.H., (1989) J. Chem. Phys., 90, p. 1007Hay, P.J., Wadt, W.R., (1985) J. Chem. Phys., 82, p. 270Cammi, R., Mennucci, B., Tomasi, J., (2000) J. Phys. Chem. A, 104, p. 5631Head-Gordon, M., Pople, J.A., Frisch, M.J., (1988) Chem. Phys. Lett., 153, p. 503Krishnan, R., Binkley, J.S., Seeger, R., Pople, J.A., (1980) J. Chem. Phys., 72, p. 650Cancès, E., Mennucci, B., Tomasi, J., (1997) J. Chem. Phys., 107, p. 3032Glendening, E.D., Badenhoop, J.K., Reed, A.E., Carpenter, J.E., Bohmann, J.A., Morales, C.M., Weinhold, F., (2001) NBO 5.G, , Theoretical Chemistry Institute, University of Wisconsin, Madison, WIFarrugia, L.J., (1997) J. Appl. Cryst., 30, p. 565Pan, Y., Stothers, J.B., (1967) Can. J. Chem., 45, p. 2943Zhao, Y., Truhlar, D.G., (2008) Acc. Chem. Res., 41, p. 157Weinhold, F., Landis, C., (2005) Valency and Bonding: A Natural Bond Orbital Donor-Acceptor Perspective, , Cambridge University Press Cambridg