1,1-Dichloroethane

Cl₂HC-CH₃

Chlorine

Nuclear Quadrupole Coupling Constants

in 1,1-Dichloroethane

Calculation of the chlorine nqcc's in 1,1-dichloroethane was made on the substitution molecular structure of Sugie et al. [1], and on a structure given by MP2/aug-cc-pVTZ(G03) optimization with empirical correction for the C-C and CCl bond lengths (~ r_e). These are compared with the experimental nqcc's of de Luis et al. [2] in Tables 1 - 3. Structure parameters are given in Table 4.

In Tables 1 - 3, subscripts a,b,c refer to the principal axes of the inertia tensor; x,y,z to the principal axes of the nqcc tensor. Ø_z,CCl (degrees) is the angle between the principal z-axis of the nqcc tensor and the CCl bond axis. ETA = (X_xx - X_yy)/X_zz.

RMS is the root mean square difference between calculated and experimental diagonal nqcc's. RSD is the calibration residual standard deviation of the B1LYP/TZV(3df,2p) model for calculation of the chlorine nqcc's.


Table 1. Chlorine nqcc's in ³⁵Cl₂HC-CH₃(MHz). Calculation was made on the r_s structure of Sugie et al. [1], and on the ~ r_estructure.

³⁵Cl		Calc/ ~ r_e		Calc/ r_s		Expt. [2]

X_aa	-	39.62	-	40.01	-	39.0405(22)
X_bb		11.06		11.25		10.6742(30)
X_cc		28.56		28.76		28.3663(30)
X_ab*	+/-	44.22	+/-	44.42	+/-	44.22(36)
X_ac*	+/-	25.22	+/-	25.32	+/-	24.08(74)
X_bc*	-	16.13	-	16.04	-	16.27(29)

RMS		0.42 (1.6 %)		0.69 (2.6 %)
RSD		0.49 (1.1 %)		0.49 (1.1 %)

X_xx		35.70		35.96		34.79(93)
X_yy		38.28		38.40		38.41(57)
X_zz	-	73.98	-	74.36	-	73.19(71)
ETA		0.035		0.033		0.049(21)
Ø_z,CCl		1.08		1.11

* The algebraic signs of the off-diagonal nqcc's depend on the orientation of the molecule with respect to positive/negative sense of the a,b,c axes. Here, X_bc is negative, while for one Cl, X_ab and X_ac are both positive, and for the other, both negative. The product X_abX_acX_bc is negative, independent of positive/negative sense of a,b,c axes. This note applies also to Tables 2 and 3.


Table 2. Chlorine nqcc's in ³⁵Cl³⁷ClHC-CH₃(MHz). Calculation was made on the r_s structure of Sugie et al. [1], and on the ~ r_estructure.

³⁵Cl		Calc/ ~ r_e		Calc/ r_s		Expt. [2]

X_aa	-	38.10	-	38.47	-	37.4807(67)
X_bb		9.57		9.74		8.854(10)
X_cc		28.53		28.73		28.626(10)
X_ab*	+/-	45.04	+/-	45.25	+/-	43.95(68)
X_ac*	+/-	24.99	+/-	25.08	+/-	23.30(89)
X_bc*	-	16.58	-	16.50	-	16.26(65)

RMS		0.55 (2.2 %)		0.77 (3.1 %)
RSD		0.49 (1.1 %)		0.49 (1.1 %)

³⁷Cl

X_aa	-	32.41	-	32.72	-	31.9600(73)
X_bb		9.83		9.99		9.540(22)
X_cc		22.58		22.73		22.419(22)
X_ab	-/+	34.21	-/+	34.35	-/+	34.81(70)
X_ac	-/+	19.99	-/+	20.07	-/+	19.95(88)
X_bc	-	12.34	-	12.27	-	12.46(68)

RMS		0.32 (1.5 %)		0.54 (2.5 %)
RSD		0.44 (1.1 %)		0.44 (1.1 %)

* See the footnote with Table 1.


Table 3. ³⁷Cl nqcc's in ³⁷Cl₂HC-CH₃(MHz). Calculation was made on the r_s structure of Sugie et al. [1], and on the ~ r_estructure.

³⁷Cl		Calc/ ~ r_e		Calc/ r_s		Expt. [2]

X_aa	-	31.23	-	31.53	-	30.7594(19)
X_bb		8.67		8.82		8.3663(29)
X_cc		22.55		22.70		22.3931(29)
X_ab*	+/-	34.89	+/-	35.04	+/-	33.78(45)
X_ac*	+/-	19.82	+/-	19.90	+/-	18.59(77)
X_bc*	-	12.69	-	12.62	-	12.83(22)

RMS		0.38 (1.6 %)		0.54 (2.7 %)
RSD		0.44 (1.1 %)		0.44 (1.1 %)

X_xx		28.13		28.34		26.50(72)
X_yy		30.17		30.26		30.15(60)
X_zz	-	58.30	-	58.61	-	56.65(77)
ETA		0.035		0.033		0.064(25)
Ø_z,CCl		1.08		1.11

* See the footnote with Table 1.


Table 4. 1,1-Dichloroethane. Structure parameters, ~ r_eand r_s [1] (Å and degrees). Complete structures, including dihedral angles, are given here in Z-matrix format.

	CCl	1.7766	1.775(1)
	CC	1.5058	1.517(3)
	CCCl	110.51	110.78(16)
	ClCCl	110.11	110.45(12)
	CH(6)	1.0846	1.085(2)
	CH(5)	1.0877	1.100(5)
	CH(3,4)	1.0887	1.098(27)
	CCH(6)	112.88	109.16(38)
	CCH(5)	109.85	109.16(38)
	CCH(3,4)	109.47	109.0(29)