CH2(CN)2
		Nitrogen and Deuterium
	Nuclear Quadrupole Coupling Constants
		in Dicyanomethane
	Dicyanomethane has been the subject of a number of microwave investigations [1-8]. Randell et al. [6] measured the nitrogen nqcc's in the mixed species, and determined the ground state average structure.  Cox et al. [7] measured the nqcc's in the normal species.  An equilibrium structure was determined by Demaison et al. [8].
	Calculation was made here of the nitrogen and deuterium nqcc's on both the average and equilibrium molecular structures.  These nitrogen nqcc's are compared with the experimental nqcc's in the mixed species in Table 1, and in the normal species in Table 2.  Calculated deuterium nqcc's are shown in Table 3.  In Table 4, the structures are compared.
	In Tables 1 - 3, RMS is the root mean square difference between calculated and experimental diagonal nqcc's (percentage of the average of the magnitudes of the experimental nqcc's).  RSD is the calibration residual standard deviation for the B3PW91/6-311+G(df,pd) model for calculation of the nitrogen nqcc's.
	Subscripts a,b,c refer to the principal axes of the inertia tensor; x,y,z to the principal axes of the nqcc tensor.  The nqcc y-axis is chosen coincident with the inertia c-axis.  Ø (degrees) is the angle between its subscripted parameters.  ETA = (Xxx - Xyy)/Xzz.
	Table 1. Nitrogen nqcc's in CH2(C14N)(C15N) (MHz).  Calculation was made on the rz and re structures.     Calc. rz Calc. re Expt. [6]     Xaa - 2.365 - 2.352 - 2.364(9) Xbb 0.340 0.291 0.313(6) Xcc 2.024 2.061 2.051(6) |Xab| 3.019 3.074   RMS 0.022 (1.4 %) 0.016 (1.0 %) RSD 0.030 (1.3 %) 0.030 (1.3 %)   Xxx 2.315 2.327 * Xyy 2.061 2.051(6) Xzz - 4.376 - 4.378 ETA - 0.058 - 0.063 Øz,a 33.37 33.23 Øa,CN 33.34 33.34 Øz,CN   0.03   0.11
	* Calculated here from the experimental diagonal nqcc's and the calculated off-diagonal nqcc.
	Table 2. Nitrogen nqcc's in CH2(CN)2 (MHz).  Calculation was made on the rz and re structures.     Calc. rz Calc. re Expt. [7]     Xaa - 2.412 - 2.400 - 2.368(28) Xbb 0.387 0.339 0.318(20) Xcc 2.024 2.061 2.050(20) |Xab| ± 2.998 ± 3.052   RMS 0.050 (3.1 %) 0.023 (1.4 %) RSD 0.030 (1.3 %) 0.030 (1.3 %)   Xxx 2.315 2.309 * Xyy 2.061 2.050(20) Xzz - 4.376 - 4.359 ETA - 0.058 - 0.059 Øz,a 32.92 33.12 Øa,CN 32.89 32.89 Øz,CN   0.03   0.23
	* Calculated here from the experimental diagonal nqcc's and the calculated off-diagonal nqcc.
	Table 3. Deuterium nqcc's in CD2(CN)2 (kHz).  Calculation was made on the equilibrium structure.     Calc. Expt.     2H Xaa - 85.4 Xbb     2.6 Xcc   82.8 Xbc ± 129.9   Xxx - 93.2 Xyy - 85.4 Xzz 178.6 ETA - 0.044 Øz,b 53.58 Øb,CH 53.91 Øz,CH   0.33
	Table 4. Molecular structure parameters (Å and degrees). rz [6] re [8] CC 1.4593 1.464 CN 1.1602 1.155 CH 1.1090 1.091 CCC 112.50 111.98 HCH 106.94 107.82 CCN 178.60 178.88 CN tilts outward.
	[1] N.Muller and D.E.Pritchard, J.Am.Chem.Soc. 80,3483(1958).
	[2] E.Hirota and Y.Morino, Bull.Chem.Soc.Jpn. 33,158(1960); 33,705(1960).
	[3] E.Hirota, J.Mol.Spectrosc. 7,242(1961).
	[4] R.L.Cook, R.T.Walden, and G.E.Jones, J.Mol.Spectrosc. 53,370(1974).
	[5] J.Burie, D.Boucher, J.Demaison, and A.Dubrille, J.Phys. (Paris) 43,1319(1982).
	[6] J.Randell, A.P.Cox, I.Merke, and H.Dreizler, Chem.Soc. Faraday Trans. 86,1981(1990).  Table 6.
	[7] A.P.Cox, Y.Kawashima, E.Fliege, and H.Dreizler, Z.Naturforsch. 40a,361(1985).
	[8] J.Demaison, G.Wlodarczak, H.Rück, K.H.Wiedenmann, and H.D.Rudolph, J.Mol.Struct. 376,399(1996).
	"Rotational spectroscopy of malononitrile and its corresponding monoisocyanide isomer, isocyanoacetonitrile" R.A.Motiyenko, I.A.Armieieva, L.Margulès, E.A.Alekseev, and J.-C.Guillemin, A&A, 623,A162(2019).  Malononitile: X aa = -2.377(15) MHz and Xbb - Xcc = -1.731(17) MHz.
	CH3CN		O=C(CN)2		H2C=C(CN)2		S(CN)2
	CD2F2		CD2Cl2		CD2Br2		CH3D
	Table of Contents
	Molecules/Nitrogen
	Molecules/Deuterium
	Summary/Methyls  Deuterium nqcc's in the substituted methanes.
						CH2CN2.html
						Last Modified 11 May 2019