Structural studies of N-2-(6-picolyl)-N′-tolylthioureas


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Abstract

Reaction of 2-amino-6-picoline with 2-, 3-, and 4-tolyl isothiocyanates produces the three N-2-(6-picolyl)-N′-tolylthioureas, 6PicTu2T, 6PicTu3T, and 6PicTu4T. 6PicTu2T is mono-clinic, space group P21/n with a = 8.1700(3) Å, b = 25.5840(6) Å, c = 12.6840(5) Å, β = 98.8750(16)°, and V = 2619.5(2) Å3 with Z = 8, for dcalc = 1.305 g/cm3. 6PicTu3T is monoclinic, space group C2/c with a = 23.879(3) Å, b = 6.744(3) Å, c = 17.116(10) Å, β = 99.26(4)°, and V = 2720(3) Å3 with Z = 8, for dcalc = 1.257 g/cm3. 6PicTu4T is triclinic, space group P−1 with a = 8.829(6) Å, b = 8.8950(15) Å, c = 10.495(3) Å, α = 68.63(3)°, β = 72.19(4)°, γ = 63.06(4)°, and V = 681.2(5) Å3 with Z = 2, for dcalc = 1.255 g/cm3. Intermolecular hydrogen bonding involving the thione sulfur and the NH hydrogen and the planarity of the thiourea are affected by the position of substitution on the aryl ring. 1H NMR studies in CDCl3 show the NH′ hydrogen resonance considerably downfield from other signals in the spectrum of each thiourea. The enthalpies of fusion of the present thioureas reflect the extent of intermolecular hydrogen bonding and are compared to other heterocyclic thioureas.

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