Molecular structure and conformation of diethylmethylamine determined by gas electron diffraction and vibrational spectroscopy combined with theoretical calculations

Abstract

We have investigated the molecular structure and conformation of diethylmethylamine, C(4)H 3C(2)H 2N(1)[CH 3]C(3)H 2C(5)H 3, by gas electron diffraction and vibrational spectroscopy with the aid of theoretical calculations. Diffraction data are consistent with a conformational mixture of 35(14)% tt + 27(14)% g +t + 20(17)% g −t + 18(23)% g +g + where the numbers in parentheses denote three times the standard errors (3 σ). Normal-coordinate analysis based on B3LYP/6-311+G ∗∗ calculations supports the existence of the four conformers. The dihedral angle ϕ 1(C4C2N1C3) (= − ϕ 2(C5C3N1C2)) of the tt conformer was 170(4)° whereas the ϕ 1 and ϕ 2 values of the other conformers were fixed at the B3LYP/6-311++G(2df,p) values: 72.4° and −163.3° for the g +t, −66.0° and −158.2° for the g −t, and 60.3° and 63.5° for the g +g +. Average values of the structural parameters ( r g/Å and ∠ α/°) with 3 σ are: 〈 r(N–C)〉 = 1.462(2), 〈 r(C–C)〉 = 1.523(3), 〈 r(C–H)〉 = 1.113(2), 〈∠CNC〉 = 111.6(5), 〈∠NCC〉 = 114.5(5), 〈∠NCH/∠CCH Me〉 = 110.6(5).