Precise dipole moments and quadrupole coupling constants of the cis and trans conformers of 3-aminophenol: determination of the absolute conformation.
The rotational constants and the nitrogen nuclear quadrupole coupling constants of cis-3-aminophenol and trans-3-aminophenol are determined using Fourier-transform microwave spectroscopy. We examine several J = 2 <-- 1 and 1 <-- 0 hyperfine-resolved rotational transitions for both conformers. The transitions are fit to a rigid rotor Hamiltonian including nuclear quadrupole coupling to account for the 14N nuclear spin. For cis-3-aminophenol we obtain rotational constants of A = 3734.930 MHz, B = 1823.2095 MHz, and C = 1226.493 MHz, for trans-3-aminophenol of A = 3730.1676 MHz, B = 1828.25774 MHz, and C = 1228.1948 MHz. The dipole moments are precisely determined using Stark effect measurements for several hyperfine transitions to micro(a) = 1.7718 D, micro(b) = 1.517 D for cis-3-aminophenol and micro(a) = 0.5563 D, micro(h) = 0.5375 D for trans-3-aminophenol. Whereas the rotational constants and quadrupole coupling constants do not allow to determinate the absolute configuration of the two conformers, this assignment is straightforward based on the dipole moments. High-level ab initio calculations (B3LYP/6-31G* to MP2/aug-cc-pVTZ) are performed providing error estimates of rotational constants and dipole moments obtained for large molecules by these theoretical methods.
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany.
Frank
F
Filsinger
Kirstin
K
Wohlfart
Melanie
M
Schnell
Jens-Uwe
JU
Grabow
Jochen
J
Küpper
D000627:Aminophenols / Q000737:chemistry*; D007536:Isomerism; D008958:Models, Molecular; D008968:Molecular Conformation
D000627:Aminophenols