4-Methylthiazole						PDF
	Nitrogen and Sulfur
	Nuclear Quadrupole Coupling Constants
		in 4-Methylthiazole
	Assuming Cs symmetry for 4-methylthiazole, one methyl CH bond lies in the plane of the thiazole ring.  Calculation of the nitrogen and sulfur nqcc's was made here on B3PW91/6-31G(2d,2pd) optimized molecular structures corresponding to each of two possible orientations of the methyl group, the in-plane CH bond being either trans or cis with respect to the nitrogen atom.  These calculated nitrogen nqcc's are compared in Tables 1 and 2 with the experimental nqcc's of Jäger and Mäder [1]. Calculated sulfur nqcc's are given in Tables 3 and 4. Calculated nitrogen nqcc's in the 33S isotopomer are given in Table 5.  Structure parameters are compared in Table 6.  Atomic coordinates for the lower energy trans conformer are given in Table 7.
	As for the molecular energy, Etrans < Ecis by 0.85 kcal/mol calculated at the B3PW91/6-31G(2d,2pd) level of theory, 1.0 kcal/mol at B3PW91/ 6-311+G(df,pd), 0.88 kcal/mol at B3LYP/6-311G(3df,3p), and 0.96 kcal/mol at B3LYP/TZV+(3df,3p).
	In Tables 1 and 5, 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 = (Xxx - Xyy)/Xzz.  RSD is the residual standard deviation of calibration of the model for calculation of the nqcc's.
	Table 1.  Nitrogen nqcc's in 4-Methylthiazole-32S in the trans conformer (MHz).  Calculation was made on the B3PW91/6-31G(2d,2pd) ropt structure.     Calc. Expt. [1]     14N Xaa - 0.319 - 0.3097(60) Xbb - 2.229 - 2.2288(66) Xcc 2.548 2.5385(66) |Xab| 2.713     RMS 0.008 (0.45 %) RSD 0.030 (1.3 %)   Xxx 1.603 1.608 * Xyy 2.548 2.5385 Xzz - 4.151 - 4.147 ETA 0.228 0.224 Øz,a 54.70 54.74 Øa,bi 56.15 56.15 Øz,bi**   1.45   1.41
	* Calculated here from the experimental diagonal nqcc's and the calculated |Xab|.
	** Angle between the z-axis and the bisector ( 'bi' ) of the CNC angle.
	Table 2.  Nitrogen nqcc's in 4-Methylthiazole-32S in the cis conformer (MHz).  Calculation was made on the B3PW91/6-31G(2d,2pd) ropt structure.     Calc. Expt. [1]     14N Xaa - 0.347 - 0.3097(60) Xbb - 2.230 - 2.2288(66) Xcc 2.577 2.5385(66) |Xab| 2.722     RMS 0.031 (1.8 %) RSD 0.030 (1.3 %)   Xxx 1.591 1.617 * Xyy 2.577 2.5385 Xzz - 4.168 - 4.155 ETA 0.236 0.222 Øz,a 54.54 54.71 Øa,bi 56.28 56.28 Øz,bi**   1.74   1.57
	* Calculated here from the experimental diagonal nqcc's and the calculated |Xab|.
	** Angle between the z-axis and the bisector ( 'bi' ) of the CNC angle.
	Table 3.  33S nqcc's in 4-Methylthiazole in the trans conformer (MHz).  Calculation was made on the B3PW91/6-31G(2d,2pd) ropt structure. Calc. [a] B3LYP/6-311G(3df,3p) Model. Calc. [b] B3LYP/TZV+(3df,3p) Model.     Calc. [a] Calc. [b] Expt.     Xaa   1.99   2.07 Xbb - 21.50 - 21.64 Xcc 19.51 19.58 |Xab| 11.69 11.71   RSD 0.39 (1.7 %) 0.35 (1.5 %)   Xxx   6.82   6.88 Xyy 19.51 19.58 Xzz - 26.33 - 26.45 ETA 0.482 0.480 Øx,a 22.44 22.32 Øa,bi 20.86 20.86 Øx,bi*   1.58   1.46
	* Angle between the x-axis and the bisector ( 'bi' ) of the CSC angle.
	Table 4.  33S nqcc's in 4-Methylthiazole in the cis conformer (MHz).  Calculation was made on the B3PW91/6-31G(2d,2pd) ropt structure. Calc. [a] B3LYP/6-311G(3df,3p) Model. Calc. [b] B3LYP/TZV+(3df,3p) Model.     Calc. [a] Calc. [b] Expt.     Xaa   2.35   2.44 Xbb - 21.15 - 21.27 Xcc 18.80 18.84 |Xab| 11.87 11.91   RSD 0.39 (1.7 %) 0.35 (1.5 %)   Xxx   7.31   7.38 Xyy 18.80 18.84 Xzz - 26.10 - 26.22 ETA 0.440 0.437 Øx,a 22.64 22.56 Øa,bi 20.99 20.99 Øx,bi*   1.65   1.57
	* Angle between the x-axis and the bisector ( 'bi' ) of the CSC angle.
	Table 5.  14N nqcc's in 4-Methylthiazole-33S in the cis and trans conformer (MHz).  Calculation was made on the B3PW91/6-31G(2d,2pd) ropt structure.     Calc/cis Calc/trans Expt.     Xaa - 0.343 - 0.371 Xbb - 2.205 - 2.206 Xcc 2.548 2.577 |Xab| 2.722 2.730   RSD 0.030 (1.3 %) 0.030 (1.3 %)
	Table 6.   4-Methylthiazole.  Structure parameters, ropt (Å and degrees).    trans   cis S(1)C(2) 1.7316 1.7291 C(2)N(3) 1.2964 1.2981 N(3)C(4) 1.3765 1.3752 C(4)C(5) 1.3665 1.3684 C(5)S(1) 1.7195 1.7169 C(2)H(2) 1.0815 1.0813 C(5)H(5) 1.0783 1.0785 C(4)C(6) 1.4949 1.4995 C(6)H(7) 1.0896 1.0885 C(6)H(8,9) 1.0923 1.0922 C(5)S(1)C(2)   88.70   88.84 S(1)C(2)N(3) 115.22 115.08 C(2)N(3)C(4) 110.94 111.06 N(3)C(4)C(5) 114.77 114.61 C(4)C(5)S(1) 110.37 110.39 S(1)C(2)H(2) 120.49 120.64 C(4)C(5)H(5) 128.57 128.66 N(3)C(4)C(6) 119.18 119.35 C(4)C(6)H(7) 111.40 109.31 C(4)C(6)H(8,9) 110.49 111.54
	Table 7.  4-Methylthiazole.  Atomic coordinates, ropt.  32S isotopomer, trans conformer.   a (Å)   b (Å)   b (Å) S(1) - 1.5073 0.3948 0 C(2) - 0.7882 - 1.1805 0 N(3) 0.5080 - 1.1959 0 C(4) 1.0152 0.0837 0 C(5) 0.0727 1.0731 0 H(2) - 1.4082 - 2.0667 0 H(5) 0.2194 2.1414 0 C(6) 2.4971 0.2805 0 H(7) 2.7577 1.3385 0 H(8,9) 2.9452 - 0.1891 ± 0.8786
	[1] W.Jäger and H.Mäder, Z.Naturforsch. 42a,1405(1987).
	Thiazole			4-Fluorothiazole			5-Fluorothiazole
	2-Fluorothiazole			2-Methylthiazole			5-Methylthiazole
	1,2,4-Thiadiazole			1,2,5-Thiadiazole			1,3,4-Thiadiazole
	Pyrazole			Imidazole			Oxazole
	Table of Contents
	Molecules/Nitrogen
	Molecules/Sulfur
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						Last Modified 3 Oct 2004