Crystal structure and C—Cl bond properties of 2,6-dichloroacetanilide, 2,6-Cl2C6H3NHCOCH3, phase I and phase II. An X-ray and 35Cl nuclear quadrupole resonance single-crystal study
Abstract
The crystal structures of 2,6-dichloroacetanilide, 2,6-Cl2C6H3NHCOCH3, in the low-temperature phase II and high-temperature phase I have been determined at 295 K. [Phase II: C52h(P21/c); Z= 4; ρcalc= 1.475 Mg m–3; a= 783.4(2) pm, b= 1531.9(4) pm, c= 897.5(2) pm, β= 121.45(1)°; RW= 0.041. Phase I: D42(P212121); Z= 4; ρcalc= 1.416 Mg m–3; a= 1726.8(4) pm, b= 1167.4(3) pm, c= 474.9(2) pm; RW= 0.055.] The molecular geometry is very little influenced by the difference in packing between phase I and phase II. ν(35Cl)=f(T) was determined for both phases from 77 K up to the melting point/transition point. Single-crystal Zeeman split 35Cl n.q.r. investigations at T= 295 K revealed for (35Cl(2))II: e2ϕzzQh–1= 70.435(4)MHz; η= 0.1214(15); for (35Cl(6))II: e2ϕzzQh–1= 70.244(4)MHz; η= 0.1031(15); for (35Cl(2))I: e2ϕzzQh–1= 69.674(4)MHz; η= 0.1293(15); for (35Cl(6))I: e2ϕzzQh–1= 68.890(4)MHz; η= 0.1307(15). The principal axes ϕ(j)zz nearly coincide with the bond directions C(j)—Cl(j) in both phases. There is a small widening of the angle [ϕzz(35Cl(2)), ϕzz(35Cl(6))] in comparison with the value of the angle (C(2)—Cl(2), C(6)—Cl(6)) of the crystal structure. The influence of the —NHCOCH3 group on η and on the orientation of the axes ϕxx and ϕyy is discussed for both phases and is compared with the results reported for 2,3,6-Cl3C6H2OCOCH3.