Rotational Barrier and Conjugation: Theoretical Study of Resonance Stabilization of Various Substituents for the Donors NH2 and OCH3 in Substituted 1,3-Butadienes

Ali Hussain Yateem(1*)

(1) Department of Chemistry, College of Science, University of Bahrain, P.O. Box 32038, Sakheer, Kingdom of Bahrain
(*) Corresponding Author


The barrier to internal rotation around the central C2–C3 single bond of a series of (1E)-monosubstituted 1,3-butadienes and (1E,3E)-1-Y-4-X-disubstituted butadienes, with Y=NH2 or OCH3 and X=NO2, CHO, COOH, CN, CF3, Cl or F, were studied at the density functional w B97X-D/6-31G∗∗ level. The effect of substituents on π-conjugation in disubstituted 1,3-butadienes was studied by correlating the calculated internal rotational barriers with the difference in structural, atomic and molecular properties between the transition state TS and the s-trans conformers. The calculated differences in lengths of C–C, C–NH2 and C–OCH3 single bonds, N-H-N, and C-O-CH3 angles, NH2 out-of-plane angle, natural charges on amino nitrogen and methoxy oxygen, and the maximum electrostatic potential on amino hydrogens, were found to correlate strongly with the rotational barriers. The conjugative interaction was strongly stabilized in the case of strong π-electron acceptors such as NO2 or CHO and is slightly or negligibly affected with Cl and F groups. The resonance stabilization with the remaining acceptors decreases in the order COOH > CN > CF3. Acceptors X maintain their relative order of stabilization for the two donors, and NH2 is more stabilizing. Dominant resonance structures are suggested for highly and negligibly conjugated systems.


1,3-butadiene; rotational barrier; donors and acceptors; conjugation

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[1] Lipnick, R.L., and Garbisch, E.W., 1973, Conformational analysis of 1,3-butadiene, J. Am. Chem. Soc., 95 (19), 6370–6375.

[2] Squillacote, M.E., Sheridan, R.S., Chapman, O.L., and Anet, F.A.L., 1979, Planar s-cis-1,3-butadiene, J. Am. Chem. Soc., 101 (13), 3657–3659.

[3] Haugen, W., and Traetteberg, M., 1966, The molecular Structure of 1,3-butadiene and 1,3,5-trans-hexatriene, Acta Chem. Scand., 20, 1726–1728.

[4] Feller, D., and Craig, N.C., 2009, High-level ab initio energies and structures for the rotamers of 1,3-butadiene, J. Phys. Chem. A, 113 (8), 1601–1607.

[5] Guo, H., and Karplus, M., 1991, Ab initio studies of polyenes. 1. 1,3-butadiene, J. Chem. Phys., 94 (5), 3679–3699.

[6] Karpfen, A., and Parasuk, V., 2004, Accurate torsional potentials in conjugated systems: Ab initio and density functional calculations on 1,3-butadiene and monohalogenated butadienes, Mol. Phys., 102 (8), 819–826.

[7] De Mare, G.R., and Neisius, D., 1984, Ab initio study of rotational isomerism in 1,3-butadiene. Effect 21 of geometry optimization and basis set size on the barriers to the rotation and on the stable rotamers, J. Mol. Struct. THEOCHEM, 109 (1-2), 103–126.

[8] Craig, N.C., Demaison, J., Groner, P., Rudolph, H.D., and Vogt, N., 2015, Electron delocalization in polyenes: A semiexperimental equilibrium structure for (3E)-1,3,5-Hexatriene and theoretical structures for (3Z,5Z)-, (3E,5E)-, and (3E,5Z)-1,3,5,7-Octatetraene, J. Phys. Chem. A, 119 (1), 195–204.

[9] Mannfors, B., Koskinen, J.T., Pietilä, L.-O., and Ahjopalo, L., 1997, Density functional studies of conformational properties of conjugated systems containing heteroatoms, J. Mol. Struct. THEOCHEM, 393 (1-3), 39–58.

[10] Xi, H.W., Karni, M., and Apeloig, Y., 2008, Silabutadienes. Internal rotations and π-conjugation. A density functional theory study, J. Phys. Chem. A, 112 (50), 13066–13079.

[11] Xi, H.W., and Lim, K.H., 2008, Theoretical study of germabutadienic internal rotations and π-conjugation, Organometallics, 27 (22), 5748–5758.

[12] Haloui, A., and Arfaoui, Y., 2010, A DFT study of the conformational behavior of para-substituted acetophenones in vacuum and in various solvents, J. Mol. Struct. THEOCHEM, 950 (1-3), 13–19.

[13] Chieh, Y.C., Chen, P.C., and Chen, S.C., 2003, Theoretical study of the internal rotational barriers in some N-substituted nitropyrroles, J. Mol. Struct. THEOCHEM, 636 (1-3), 115–123.

[14] Radom, L., Hehre, W.J., Pople, J.A., Carlson, G.L., and Fateley, W.G., 1972, Torsional barriers in para-substituted phenols from ab initio molecular orbital theory and far infrared spectroscopy, J. Chem. Soc., Chem. Commun., 0 (6), 308–309.

[15] Chen, P.C., and Chieh, Y.C., 2002, Density functional theory study of the internal rotational barriers of some aromatic nitro compounds, J. Mol. Struct. THEOCHEM, 583 (1-3), 173–180.

[16] Tsuzuki, S., Houjou, H., Nagawa, Y., and Hiratani, K., 2000, High-level ab initio calculations of torsional potential of phenol, anisole, and o-hydroxyanisole: Effects of intramolecular hydrogen bond, J. Phys. Chem. A, 104 (6), 1332–1336.

[17] Varkey, E.C., Hutter, J., Limacher, P.A., and Lüthi, H.P., 2013, Impact of donor-acceptor functionalization on the properties of linearly π-conjugated oligomers: Establishing quantitative relationships for the substituent and substituent cooperative effect based on quantum chemical calculations, J. Org. Chem., 78 (24), 12681–12689.

[18] Ehrenson, S., Brownlee, R.T.C., and Taft, R.W., 1973, “A Generalized Treatment of Substituent Effects in the Benzene Series. A Statistical Analysis by the Dual Substituent Parameter Equation (1)” in Progress in Physical Organic Chemistry, eds., Streitwiesr, A., and Taft, R.W., John Wiley & Sons, Inc., 1–80.

[19] Hansch, C., Leo, A., and Taft, R.W., 1991, A survey of Hammett substituent constants and resonance and field parameters, Chem. Rev., 91 (2), 165–195.

[20] Exner, O., and Böhm, S., 2006, Conjugation of two functional groups through an unsaturated system, J. Phys. Org. Chem., 19 (1), 1–9.

[21] Böhm, S., and Exner, O., 2005, Quantitative evaluation of resonance interaction: Monosubstituted 1,3-butadienes, J. Mol. Struct. THEOCHEM, 722 (1-3), 125–131.

[22] Exner, O., and Böhm, S., 2004, Enthalpies of formation of monoderivatives of hydrocarbons: Interaction of polar groups with an alkyl group, J. Comput. Chem., 25 (16), 1979–1986.

[23] Pross, A., Radom, L., and Taft, R.W., 1980, Theoretical approach to substituent effects. Phenols and phenoxide ions, J. Org. Chem., 45 (5), 818–826.

[24] Chai, J.D., and Head-Gordon, M., 2008, Long-range corrected hybrid density functionals with damped atom-atom dispersion corrections, Phys. Chem. Chem. Phys., 10 (44), 6615–6620.

[25] Guo, H., and Karplus, M., 1992, Ab initio studies of methylated 1,3-butadienes, J. Mol. Struct. THEOCHEM, 260, 347–393.

[26] Wavefunction, Inc., Irvine, CA 92612, U.S.A.

[27] Gross, K.C., and Seybold, P.G., 2000, Substituent effects on the physical properties and pKa of aniline, Int. J. Quantum Chem., 80 (4-5), 1107–1115.

[28] Gross, K.C., and Seybold, P.G., 2001, Comparison of quantum chemical parameters and Hammett constants in correlating pKa values of substituted anilines, J. Org. Chem., 66 (21), 6919–6925.

[29] Ghafourian, T., and Dearden, J.C., 2004, The use of molecular electrostatic potentials as hydrogen-bonding-donor parameters for QSAR studies, Il Farmaco, 59 (6), 473–479.

[30] Riley, K.E., Tran, K.A., Lane, P., Murray, J.S., and Politzer, P., 2016, Comparative analysis of electrostatic potential maxima and minima on molecular surfaces, as determined by three methods and a variety of basis sets, J. Comput. Sci., 17 (1), 273–284.

[31] Sudlow, K.P., and Woolf, A.A., 1998, What is the geometry at trigonal nitrogen?, J. Chem. Educ., 75 (1), 108–110.

[32] Krygowski, T.M., and Steüpien, B.T., 2005, Sigma- and pi-electron delocalization: Focus on substituent effects, Chem. Rev., 105 (10), 3482–3512.

[33] Böhm, S., and Exner, O., 2007, Dipole moments and electron distribution of conjugated molecules; Para derivatives of benzene, J. Mol. Struct. THEOCHEM, 803 (1-3), 9–16.


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