Abstract
Rotation spectra of 1.2,4-thiadiazole have been studied for naturally occurring 34S-, 13C-and 15N-species of the normal and the 5-d1 form, and the 12 sets of moments of inertia have been used to determine the substitution structure in the two principal axes systems. Agreement within less than 0.0005 Å and 0.02° for distances and angles, respectively, between the two independent sets of structure parameters was obtained through the use of the rotation of axes under substitution in combination with the first and second moment conditions.
The averaged bond lengths (in Å) and angles (in degrees) are:
S(1) - N(2) : 1.6490 C(5)S(1)N(2) : 92.75
N(2) - C(3) : 1.3166 S(1)N(2)C(3) : 107.09
C(3) - N(4) : 1.3663 N(2)C(3)N(4) : 120.12
N(4) - C(5) : 1.3133 C(3)N(4)C(5) : 107.74
C(5) - S(1) : 1.7071 N(4)C(5)S(1) : 112.30
C(5) - H(5) : 1.0785 S(1)C(5)H(5) : 123.90
C(3) - H(3) : 1.078 N(2)C(3)H(3) : 119.94
The H(3) atom was assumed on the external bisector of N(2)C(3)N(4) at a distance of 1.078 Å from C(3).
Geometric features of the four thiadiazoles are compared, and the method used in the structure calculation is discussed.
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