1. Silicon Silanes Silica, silicates, and zeolites Silicones Pure silicon Computer chips

3. Silanes: Si n H 2n+2 Same structure as alkanes All unstable, pyrophoric: SiH 4 + 2 O 2  SiO 2 + H 2 O Generally not stable beyond Si 8 or so. No “silenes” because … __________________

4. Why would silanes be so much less stable than alkanes? Bond Energies, kJ/mol: C-C346C-H413C-O358 Si-Si222Si-H328Si-O452

5. Silica and Silicates Silica: SiO 2 Si = +4 O = -2 Crystalline = quartz Noncrystalline = vitreous

6. Silicates: Si-O anions + metal cations General Rules: 1.Si always makes 4 Si-O bonds 2.Can be terminal (Si-O) or bridging (Si-O-Si) 3.Charge comes from Si = +4, O = -2

7. Structure depends on O/Si ratio SiO 4 Predict Si 2 O 7 Predict Si 3 O 9

8. O/Si Ratio: 4 3.5 3

9. O/Si Ratio: 2.5 2.75 2

10. Silicates: General Trend As O/Si ratio decreases:

11. Tetrahedral structure depiction:

17. Aluminosilicates: Zeolites SiO 2 base structure Substitute some Si atoms with Al

18. Another representation Ball and stick Tetrahedral connectivity

19. Sodalite Cages

20. Formation of Zeolites from Sodalite Cages

21. Different arrangements lead to different pore spaces.

22. Pure SiO 2, 0% Al replacement10% Al replacement Charge and counter ions

23. Pure SiO 2, 0% Al replacement 10% Al replacement Affinity for water

24. Zeolites and Catalysis Purpose of a catalyst: increase rate, selectivity Desired: react para isomer to form terephthalic acid Problem: under reaction conditions, three isomers can interchange So, might end up with wrong isomers of C 6 C 4 (CO 2 H) 2

25. Solution Catalyze reaction inside a zeolite pore that only accommodates the para isomer.

26. Silicones

27. General Reaction

30. Synthesis of Silicone Precursors

31. Polydimethylsiloxane is the most common and available silicone.

32. Silicone Structure/Properties/Reactant Relationships

33. Pure Si and Computer Chips