2013. 54, 2 – UDC 541.6:547.12:543.422 SPECTRAL ANALYSIS OF ACETYLCHOLINE HALIDES BY DENSITY FUNCTIONAL THEORY CALCULATIONS M. Karakaya, F. Ucun Department of Physics, Faculty of Arts and Sciences, Sьleyman Demirel University, Isparta Turkey E-mail: mkarakayafizik@hotmail.com Received October, 29, 2011 Revised — April, 8, 2012 The optimized molecular structures, vibrational frequencies and 1H and 13C NMR chemical shifts of acetylcholine halides (F, Cl and Br) have been investigated using density functional theory (B3LYP) method with 6-311G(d) basis set. <...> The comparison of their experimental and calculated IR, R and NMR spectra of the compounds has indicated that the spectra of three optimized minimum energy conformers can simultaneously exist in one experimental spectrum. <...> Thus, it was concluded that the compounds simultaneously exist in three conformations in the ground state. <...> The calculated optimized geometric parameters (bond lengths and bond angles), vibrational frequencies and NMR chemical shifts for the minimum energy conformers were seen to be in a good agreement with the corresponding experimental data. <...> All the assignments of the theoretical frequencies were performed by potential energy distributions using VEDA 4 program. <...> INTRODUCTION Acetylcholine [CH3COOCH2CH2N+(CH3)3] plays a central role in neurotransmission. <...> These studies have showed that low energy conformations appear corresponding to the orientation of the acetoxy group with respect to the rest of the molecule. <...> The ab initio data of acetylcholine have indicated that the most stable conformation is the trans-gauche arrangement of the two essential torsion angles (1; C—C—O—C and 2; N—C—C— O) [ 6, 7 ]. <...> Theoretical study of acetylcholine bromide has denoted that the experimental gauche-gauche conformation corresponds only to a local energy minimum about 2 kcalmol–1 above the global one associated with a different gauche-gauche conformation [ 12 ]. © Karakaya M., Ucun F., 2013 . 258 – 268 . 2013. . 54, 2 259 As seen from the above discussion the ground state conformation of acetylcholine is labile and influenced by its environment. <...> In this study we wish to report the vibrational and NMR analysis of acetylcholine halides to obtain the minimum energy conformations in the ground state by means of density functional theory <...>