2-Chloroethanethiol

CH₂Cl-CH₂SH

Chlorine

Nuclear Quadrupole Coupling Constants

in 2-Chloroethanethiol

For each conformer of 2-chloroethanethiol shown below, calculation of the chlorine nqcc tensors was made on a molecular structure given by MP2/6-311+G(3df,3pd) optimization with empirically corrected approximate equilibrium C-Cl and C-C bond lengths. These calculated nqcc's are given in Tables 1 and 2. Structure parameters are given in Z-Matrix format in Table 3, rotational constants and dipole moments in Table 4, quartic centrifugal distortion constants in Table 5.

"trans"

"gauche"

At the

MP2/6-311+G(3df,3pd)

level of theory,

E_trans < E_gauche

by 0.58 kJ/mol

ClCCS Dihedral = 178.40^o

ClCCS Dihedral = 68.44^o

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. ETA = (X_xx - X_yy)/X_zz. Ø_z,CCl (degrees) is the angle the z-principal axis makes with the CCl bond axis.

RSD is the calibration residual standard deviation of the B1LYP/TZV(3df,2p) model for calculation of the chlorine efg's/nqcc's.


Table 1. Chlorine nqcc's in trans-2-Chloroethanethiol (MHz). Calculation was made on a molecular structure given by MP2/6-311+G(3df,3pd) optimization with approximate r_e C-Cl and C-C bond lengths.

			Calc.	Expt.

³⁵Cl	X_aa	-	57.33
	X_bb		20.96
	X_cc		36.37
	X_ab		35.65
	X_ac		- 1.95
	X_bc		0.86

	RSD		0.49 (1.1 %)

	X_xx		36.42
	X_yy		34.75
	X_zz	-	71.17
	ETA	-	0.0233
	Ø_z,CCl		0.45

³⁷Cl	X_aa	-	45.22
	X_bb		16.56
	X_cc		28.66
	X_ab		20.05
	X_ac		- 1.54
	X_bc		0.67

	RSD		0.44 (1.1 %)


Table 2. Chlorine nqcc's in gauche-2-Chloroethanethiol (MHz). Calculation was made on a molecular structure given by MP2/6-311+G(3df,3pd) optimization with approximate r_e C-Cl and C-C bond lengths.

			Calc.	Expt.

³⁵Cl	X_aa		- 0.66
	X_bb	-	28.55
	X_cc		29.21
	X_ab	-	47.78
	X_ac		14.83
	X_bc		21.84

	RSD		0.49 (1.1 %)

	X_xx		36.94
	X_yy		34.36
	X_zz	-	71.30
	ETA		0.0361
	Ø_z,CCl		0.78

³⁷Cl	X_aa		- 1.12
	X_bb	-	21.96
	X_cc		23.09
	X_ab	-	37.85
	X_ac		11.75
	X_bc		17.03

	RSD		0.44 (1.1 %)


Table 3. 2-Chloroethanethiol. MP2/6-311+G(3df,3pd) Optimized structure parameters (Å and degrees). Approximate r_e bond lenths are given in parentheses.

"trans"				"gauche"
		Cl C,1,R1 C,2,R2,1,A1 O,3,R3,2,A2,1,D1,0 H,4,R4,3,A3,2,D2,0 H,3,R5,2,A4,1,D3,0 H,3,R6,2,A5,1,D4,0 H,2,R7,1,A6,3,D5,0 H,2,R8,1,A7,3,D6,0

	B1=1.78172087 (1.7863) B2=1.51287936 (1.5112) B3=1.80954553 B4=1.33419339 B5=1.08706265 B6=1.08843323 B7=1.08655279 B8=1.08561415 A1=110.24755838 A2=111.36798465 A3=96.33396022 A4=110.89259953 A5=110.06266044 A6=107.20225694 A7=107.70188592 D1=-178.39790404 D2=-68.99131048 D3=58.10979796 D4=-61.40874417 D5=121.18911894 D6=-121.27621696		R1=1.77863452 (1.7832) R2=1.513748 (1.5120) R3=1.80616081 R4=1.33427585 R5=1.08814911 R6=1.09069757 R7=1.08621353 R8=1.0875114 A1=111.37621722 A2=114.15475316 A3=95.81491858 A4=110.34118438 A5=108.36947644 A6=107.23531904 A7=106.54706384 D1=68.43946188 D2=-61.18808371 D3=-56.63577808 D4=-174.77538871 D5=121.76066422 D6=-120.53250035


Table 4. 2-Chloroethanethiol-³⁵Cl. Rotational constants (MHz) and dipole moments (D). Calc = MP2/6-311+G(3df,3pd) with approximate r_e C-Cl and C-C bond lengths.

		__________"trans"__________		________"gauche"________
		Calc	Expt	Calc	Expt.

	A	27119.8		9690.6
	B	1510.5		2288.7
	C	1468.9		1969.8

	\|µ_a\|	0.68		0.14
	\|µ_b\|	0.40		1.84
	\|µ_c\|	0.62		0.10


Table 4. 2-Chloroethanethiol-³⁵Cl. Quartic centrifugal distortion constants (kHz). Calc = B3LYP/cc-pVTZ

		"trans"			"gauche"
		Calc	Expt		Calc	Expt.

Delta_J		0.144			1.34
Delta_JK	-	1.47		-	11.6
Delta_K		85.0			48.5
delta_J		0.00563			0.316
delta_J		0.106			3.33

D_J		0.144			1.32
D_JK	-	1.47		-	11.4
D_K		85.0			48.4
D_1	-	0.00563		-	0.316
D_2	-	0.00002		-	0.0159

R.N.Nandi, M.F.Boland, and M.D.Harmony, J.Mol.Spectrosc. 92,419(1982): B + C = 2955.17(2) MHz for the ³⁵Cl species, and 2879.73(2) for the ³⁷Cl species.

CH₃Cl

CH₃-CH₂Cl

CH₂Cl-CH₂OH

Table of Contents

Molecules/Chlorine

CH2ClCH2SH.html

Last Modified 9 Jan 2014