2-Chloropropene

CH₃ClC=CH₂

Chlorine

Nuclear Quadrupole Coupling Constants

in 2-Chloropropene

Calculation of the chlorine nqcc tensors in 2-chloropropene was made on a r_opt and ~r_e molecular structures, where r_opt is given by MP2/aug-cc-pVTZ(G03) optimization (assuming C_s symmetry) and ~r_e is r_opt but with empirically corrected CCl, C-C, and C=C bond lengths. Calculated nqcc's are compared with the experimental results of Fliege and Dreizler [1] in Tables 1 and 2. (Earlier measurements of the nqcc's were made by Good et al. [2] and by Unland et al. [3].) Structure parameters are given in Table 3, rotational constants in Table 4.

In Tables 1 and 2, 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, these are perpendicular to the molecular symmetry plane. Ø (degrees) is the angle between its subscripted parameters. ETA = (X_xx - X_yy)/X_zz.

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 B1LYP/TZV(3df,2p) model for calculation of the chlorine nqcc's.


Table 1. ³⁵Cl nqcc's in 2-Chloropropene (MHz). Calculation was made on r_opt and ~r_e molecular strcutures.

		Calc r_opt		Calc ~r_e		Expt. [1]

X_aa	-	68.39	-	68.19	-	68.072
X_bb		37.83		37.74		37.097
X_cc		30.56		30.45		30.975
\|X_ab\|		9.60		9.72

RMS		0.52 (1.2 %)		0.49 (1.1 %)
RSD		0.49 (1.1 %)		0.49 (1.1 %)

X_xx		38.69		38.63
X_yy		30.56		30.45
X_zz	-	69.25	-	69.08
ETA	-	0.117	-	0.118
Ø_z,a		5.12		5.20
Ø_a,CCl		4.95		5.05
Ø_z,CCl		0.18		0.15


Table 2. ³⁷Cl nqcc's in 2-Chloropropene (MHz). Calculation was made on r_opt and ~r_e molecular strcutures.

		Calc r_opt		Calc ~r_e		Expt. [1]

X_aa	-	53.93		53.78	-	53.763
X_bb		29.85		29.78		29.370
X_cc		24.08		24.00		24.394
\|X_ab\|		7.37		7.48

RMS		0.34 (0.96 %)		0.33 (0.92 %)
RSD		0.44 (1.1 %)		0.44 (1.1 %)

X_xx		30.50		30.44
X_yy		24.08		24.00
X_zz	-	54.58	-	54.44
ETA	-	0.117	-	0.118
Ø_z,a		5.00		5.07
Ø_a,CCl		4.82		4.92
Ø_z,CCl		0.18		0.15


Table 3. 2-Chloropropene. Heavy atom structure parameters, r_opt and ~r_e (Å and degrees). Complete strcutres are given here in Z-matrix format.

		r_opt	~r_e

	ClC(2)	1.7446	1.7413
	C(2)=C(4)	1.3329	1.3291
	C(2)C(3)	1.4903	1.4896
	ClC(2)C(3)	113.85	113.85
	ClC(2)C(4)	119.71	119.71


Table 4. 2-Chloropropene. Rotational Constants (MHz). ³⁵Cl species.

		r_opt	~r_e	Expt. [1]

	A	9 318.5	9 345.6	9 271.706(79)
	B	4 994.7	5 011.3	4 983.816(45)
	C	3 318.4	3 329.1	3 304.414(45)

[1] E.Fliege and H.Dreizler, Z.Naturforsch. 38a,1231(1983).

[2] W.Good, R.J.Conan Jr., A.Bauder, and Hs.H.Günthard, J.Mol.Spectrosc. 41,381(1972).

[3] M.L.Unland, V.Weiss, and W.H.Flygare, J.Chem.Phys. 42,2138(1965).

"Identification of Trace 2-Chloropropene with a New Chirped Pulse Microwave Spectrometer" Z.Kisiel and J.Kosarzewski, Acta Phys. Pol. A. 131,311(2019). Global fit, Table 2: X _aa = -68.1308(59), X_bb = 37.1638(67), X_cc = 30.967067(67) MHz.