3-Chlorothiophene

3-Cl-C₄H₃S

Chlorine and Sulfur

Nuclear Quadrupole Coupling Constants

in 3-Chlorothiophene

Calculation of the chlorine nqcc's in 3-chlorothiophene was made on molecular structures obtained by B3PW91/6-31G(2d,2pd) and B3P86/6-31G(3d,3p) optimization. Comparison of the calculated and experimental nqcc's [1] in Tables 1 and 2 suggests an error in the assignment of experimental coupling constants with respect to intertial axes. This conclusion is strongly supported by an investigation of the microwave spectrum of the title molecule by Caminati et al. [2], wherein X_aa and X_bb respectively are reported as -73.2(5) and 38.2(3) MHz.

Calculated ³³S nqcc's are given in Table 3. Structure parameters are given in Table 4, atomic coordinates in Table 5, and rotational constants in Table 6.

In Tables 1 - 3, subscripts a,b,c refer to the principal axes of the inertia tensor, subscripts 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 plane of the molecule. 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 nqcc's (percent of average absolute experimental nqcc). RSD is the residual standard deviation of calibration of the model for calculation of the nqcc's.


Table 1. ³⁵Cl nqcc's in 3-Chlorothiophene-³²S (MHz). RMS* is the root mean square difference between calculated and experimental nqcc's assuming the experimental X_bb and X_cc to be reversed (see Caminati et al. [2]).

Calculation was made on
	the [a] B3PW91/6-31G(2d,2pd) r_opt structure, and
	the [b] B3P86/6-31G(3d,3p) r_opt structure.

		Calc. [a]		Calc. [b]		Expt. [1]

X_aa	-	73.26	-	72.78	-	72.62(16)
X_bb		38.24		38.08		34.59(90)
X_cc		35.02		34.70		38.03(91)
\|X_ab\|		9.58		9.63

RMS		2.76 (5.7 %)		2.79 (5.8 %)
RMS*		0.46 (0.96 %)		0.12 (0.25 %)
RSD		0.49 (1.1 %)		0.49 (1.1 %)

X_xx		39.06		38.92
X_yy		35.02		34.70
X_zz	-	74.08	-	73.62
ETA	-	0.054	-	0.057
Ø_z,a		4.87		4.93
Ø_a,CCl		5.16		5.22
Ø_z,CCl		0.28		0.30

Because B3PW91/6-31G(2d,2pd) optimization gives structures on which good agreement is obtained between calculated and experimental ³³S nqcc's in thiophene and thiazole, and because B3P86/6-31G(3d,3p) works for chlorine substituted benzenes and pyridines, as well as 2-chlorothiophene, calculation was made on a structure consisting of the B3PW91/6-31G(2d,2pd) ring with the B3P86/6-31G(3d,3p) CCl bond length. The results are given below in Table 2 for both ³⁵Cl and ³⁷Cl, and in Table 3 for ³³S.


Table 2. Chlorine nqcc's in 3-Chlorothiophene-³²S (MHz). Calculation was made on the B3PW91/6-31G(2d,2pd) ring structure with the B3P86/6-31G(3d,3p) optimized CCl bond length. RMS* is the root mean square difference between calculated and experimental nqcc's assuming the experimental X_bb and X_cc to be reversed (see Caminati et al. [2]).

			Calc.		Expt. [1]

³⁵Cl	X_aa	-	72.74	-	72.62(16)
	X_bb		38.07		34.59(90)
	X_cc		34.67		38.03(91)
	\|X_ab\|		9.56

	RMS		2.79 (5.8 %)
	RMS*		0.05 (0.11 %)
	RSD		0.49 (1.1 %)

	X_xx		38.89
	X_yy		34.67
	X_zz	-	73.56
	ETA	-	0.057
	Ø_z,a		4.90
	Ø_a,CCl		5.18
	Ø_z,CCl		0.28

³⁷Cl	X_aa	-	57.36	-	57.57(16)
	X_bb		30.03		27.46(75)
	X_cc		27.32		30.11(76)
	\|X_ab\|		7.37

	RMS		2.79 (5.7 %)
	RMS*		0.15 (0.40 %)
	RSD		0.44 (1.1 %)


Table 3. ³³S nqcc's in 3-Chlorothiophene-³⁵Cl (MHz). Calculation was made on the B3PW91/6-31G(2d,2pd) ring structure with the B3P86/6-31G(3d,3p) optimized CCl bond length.

	Calc. [a] B3LYP/6-311G(3df,3p) Model.
	Calc. [b] B3LYP/TZV+(3df,3p) Model.

		Calc. [a]		Calc. [b]	Expt.

X_aa		- 1.93		- 1.90
X_bb	-	20.30	-	20.37
X_cc		22.23		22.27
\|X_ab\|		14.67		14.73

RSD		0.39 (1.7 %)		0.35 (1.5 %)

X_xx		6.20		6.25
X_yy		22.23		22.27
X_zz	-	28.42		28.52
ETA		0.564		0.561
Ø_x,a		28.98		28.96
Ø_a,bi		27.79		27.79
Ø_x,bi*		1.19		1.17

* Angle between the x-axis and the bisector ( 'bi' ) of the CSC angle.


Table 4. 3-Chlorothiophene and Thiophene. Structure parameters (Å and degrees).

		B3P86	B3PW91	B3PW91
		X = Cl	X = Cl	X = H

	S(1)C(2)	1.7090	1.7181	1.7197
	C(2)C(3)	1.3663	1.3648	1.3660
	C(3)C(4)	1.4203	1.4222	1.4229
	C(4)C(5)	1.3646	1.3637	1.3660
	C(5)S(1)	1.7116	1.7199	1.7197
	C(2)H(2)	1.0786	1.0773	1.0787
	C(3)X(3)	1.7240	1.7331	1.0816
	C(4)H(4)	1.0815	1.0800	1.0816
	C(5)H(5)	1.0799	1.0786	1.0787
	C(5)S(1)C(2)	92.40	92.25	91.95
	S(1)C(2)C(3)	110.54	110.37	111.42
	C(2)C(3)C(4)	113.77	114.05	112.60
	C(3)C(4)C(5)	111.40	111.50	112.60
	C(4)C(5)S(1)	111.90	111.83	111.42
	S(1)C(2)H(2)	121.39	121.20	119.93
	S(1)C(5)H(5)	119.98	119.85	119.93
	C(3)C(4)H(4)	123.88	123.69	124.04
	C(4)C(3)X(3)	122.76	122.62	124.04


Table 5. 3-Chlorothiophene, normal species. Atomic coordinates. B3PW91/6-31G(2d,2pd) ring structure with the B3P86/6-31G(3d,3p) optimized CCl bond length.

			a (Å)		b (Å)

	S(1)	-	1.9310	-	0.4933
	C(2)	-	0.2982	-	1.0281
	C(3)		0.5516		0.0399
	C(4)	-	0.1038		1.3021
	C(5)	-	1.4602		1.1609
	H(2)	-	0.0546	-	2.0774
	Cl(3)		2.2685	-	0.1157
	H(4)		0.4177		2.2478
	H(5)	-	2.2130		1.9334


Table 6. 3-Chlorothiophene, normal species. Rotational Constants (MHz).

	[a] B3PW91/6-31G(2d,2pd) opt structure.
	[b] B3P86/6-31G(3d,3p) opt structure.
	[c] B3PW91/6-31G(2d,2pd) ring structure with the B3P86/6-31G(3d,3p) optimized CCl bond length.

	Calc [a]	Calc [b]	Calc [c]	Expt. [1]

A	7149.7	7184.0	7150.4	7144.19(41)
B	1503.4	1512.0	1509.9	1508.3654(31)
C	1242.2	1249.1	1246.6	1245.0304(31)

[1] Y.Niide and I.Ohkoshi, J.Mol. Spectrosc. 130,46(1988).

[2] W.Caminati, B.Velino, F.Caccinelli, R.S.Cataliotti, S.M.Murgia, G.Paliani, and S.Santucci, J.Mol.Struct. 174,285(1988): X _aa and X_bb respectively are reported as -73.2(5) and 38.2(3) MHz.

3ClThioph.html

Last Modified 15 Feb 2015