Symmetry Lab › Td › Tetramethylsilane (TMS)
Si(CH₃)₄ Tetramethylsilane (TMS)
Central Si with four methyls · point group Td · order 24
- Point group
- Td — The full symmetry of a regular tetrahedron: four C3 axes, three C2 axes (each also an S4 axis) and six dihedral mirror planes. There is no centre of inversion.
- Order
- 24
- Operations
- E, 8C₃, 3C₂, 6S₄, 6σd
- Shape
- Central Si with four methyls
- Atoms
- 17 (Si, C × 4, H × 12)
Symmetry elements of Si(CH₃)₄
- C₃ (1) — along one Si–C bond
- C₃ (2) — along one Si–C bond
- C₃ (3) — along one Si–C bond
- C₃ (4) — along one Si–C bond
- C₂ (x) — bisects two C–Si–C angles
- C₂ (y) — bisects two C–Si–C angles
- C₂ (z) — bisects two C–Si–C angles
- S₄ (x) — rotate 90°, then reflect
- S₄ (y) — rotate 90°, then reflect
- S₄ (z) — rotate 90°, then reflect
- σd (1) — contains two methyl carbons
- σd (2) — contains two methyl carbons
- σd (3) — contains two methyl carbons
- σd (4) — contains two methyl carbons
- σd (5) — contains two methyl carbons
- σd (6) — contains two methyl carbons
Structure
- Si–C 1.87 Å, C–H 1.09 Å
- All angles 109.5°
- The NMR reference: twelve equivalent H, four equivalent C
