C5H10N2O
		Nitrogen
	Nuclear Quadrupole Coupling Constants
	in 1,3-Dimethyl-2-Imidazolidione
	Molecular conformation and 14N nuclear quadrupole coupling constants in 1,3-dimethyl-2-imidazolidione were determined by Vigorito, et al. [1].
	Calculation of the 14N nuclear quadrupole coupling constants was made here on an MP2/6-311++G(d,p) opimized molecular structure reported in Ref. [1], and on another derived here by MP2/6-311+G(3d,3p) optimization.
	Calculated and experimental nqcc's are compared in Table 1.  Structure parameters in z-matrix format are given in Table 2, rotational constants in Table 3.
	In Table 1, subscripts a,b,c refer to the principal axes of the inertia tensor; x,y,z to the principal axes of the nqcc tensor.  ETA = (Xxx - Xyy)/Xzz.  Ø (degrees) is angle between z- and c- axes.  RMS is the root mean square difference between calculated and experimental diagonal nqcc's.  RSD is the calibration residual standard deviation of the B3PW91/6-311+G(df,pd) model for calculation of the nitrogen efg's/nqcc's.
	Table 1. 14N nqcc's in 1,3-Dimethyl-2-imidazolidione (MHz).  Calculation was made on the ropt(1) = MP2/6-311++G(d,p) and ropt(2) = MP2/6-311+G(3d,3p) structures.     Calc /ropt(1) Calc /ropt(2) Expt [1]     Xaa 2.300 2.288 2.14(14) Xbb 2.438 2.446 2.56(10) Xcc - 4.738 - 4.734 - 4.70(10) Xab +/- 0.135 +/- 0.134 Xac 0.136 0.138 Xbc -/+ 0.456 -/+ 0.416   RMS 0.118 (3.8 %) 0.110 (3.5 %) RSD 0.030 (1.3 %) 0.030 (1.3 %)   Xxx 2.234 2.226 Xyy 2.536 2.535 Xzz - 4.770 - 4.761 ETA 0.0632 0.0650 Øz,c 3.8 3.5
	Table 2.  1,3-Dimethyl-2-imidazolidione:  Structure parameters,  ropt(1) and ropt(2) (Å and degrees).   O  C,1,B1  N,2,B2,1,A1  N,2,B3,1,A2,3,D1,0  C,3,B4,2,A3,1,D2,0  C,4,B5,2,A4,1,D3,0  H,5,B6,3,A5,2,D4,0  H,6,B7,4,A6,2,D5,0  H,5,B8,3,A7,2,D6,0  H,6,B9,4,A8,2,D7,0  C,3,B10,2,A9,1,D8,0  C,4,B11,2,A10,1,D9,0  H,11,B12,3,A11,2,D10,0  H,12,B13,4,A12,2,D11,0  H,11,B14,3,A13,2,D12,0  H,12,B15,4,A14,2,D13,0  H,11,B16,3,A15,2,D14,0  H,12,B17,4,A16,2,D15,0       ropt(1)       ropt(2)  B1=1.22080009  B2=1.39310133  B3=1.39310133  B4=1.45411835  B5=1.45411835  B6=1.10207972  B7=1.10207972  B8=1.09302508  B9=1.09302508  B10=1.45028672  B11=1.45028672  B12=1.09004367  B13=1.09004367  B14=1.10003545  B15=1.10003545  B16=1.09264532  B17=1.09264532  A1=126.28804500  A2=126.28804500  A3=109.12987381  A4=109.12987381  A5=111.03788705  A6=111.03788705  A7=111.52798073  A8=111.52798073  A9=118.68964962  A10=118.68964962  A11=108.26615601  A12=108.26615601  A13=111.48819480  A14=111.48819480  A15=109.57240039  A16=109.57240039  D1=-180.  D2=168.17481779  D3=168.17481779  D4=-88.57827681  D5=-88.57827681  D6=149.17358123  D7=149.17358123  D8=26.03101788  D9=26.03101788  D10=-38.20348554  D11=-38.20348554  D12=81.62214705  D13=81.62214705  D14=-157.48274650  D15=-157.48274650  B1=1.22104035  B2=1.38946743  B3=1.38946743  B4=1.45232915  B5=1.45232915  B6=1.09655484  B7=1.09655484  B8=1.0880191  B9=1.0880191  B10=1.44734849  B11=1.44734849  B12=1.08602678  B13=1.08602678  B14=1.09477797  B15=1.09477797  B16=1.08804203  B17=1.08804203  A1=126.26806375  A2=126.26806375  A3=109.29419808  A4=109.29419808  A5=110.89423864  A6=110.89423864  A7=111.55455766  A8=111.55455766  A9=118.74744738  A10=118.74744738  A11=108.20479406  A12=108.20479406  A13=111.38826932  A14=111.38826932  A15=109.82420364  A16=109.82420364  D1=180.  D2=168.43761728  D3=168.43761728  D4=-89.47787724  D5=-89.47787724  D6=148.53156374  D7=148.53156374  D8=26.13643993  D9=26.13643993  D10=-35.32512903  D11=-35.32512903  D12=84.45312914  D13=84.45312914  D14=-154.68170399  D15=-154.68170399
	Table 3.  1,3-Dimethyl-2-imidazolidione: Rotational Constants (MHz).   Calc /ropt(1) Calc /ropt(2)   Expt [1]    A     3356.    3364. 3358.889(1)  B     2029.    2037. 2024.311(1)  C     1321.    1325. 1317.033(2)
	[1] A.Vigorito, L.Paoloni, C.Calabrese, L.Evangelisti, L.B.Favero, S.Melandri, and A.Maris, J.Mol.Spectrosc. 342,38(2017).
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