Silicon Silanes Silica silicates and zeolites Silicones Pure
- Slides: 34
Silicon • • • Silanes Silica, silicates, and zeolites Silicones Pure silicon Computer chips
Silanes: Sin. H 2 n+2 Same structure as alkanes All unstable, pyrophoric: Si. H 4 + 2 O 2 Si. O 2 + H 2 O Generally not stable beyond Si 8 or so. No “silenes” because … _________
Why would silanes be so much less stable than alkanes? Bond Energies, k. J/mol: C-C 346 Si-Si 222 C-H 413 Si-H 328 C-O 358 Si-O 452
Silica and Silicates Silica: Si. O 2 Si = +4 O = -2 Crystalline = quartz Noncrystalline = vitreous
Silicates: Si-O anions + metal cations General Rules: 1. Si always makes 4 Si-O bonds 2. O can be terminal (Si-O) or bridging (Si-O-Si) 3. Charge comes from Si = +4, O = -2
Structure depends on O/Si ratio Si. O 4 Predict Si 2 O 7 Predict Si 3 O 9
O/Si Ratio: 4 3. 5 3
O/Si Ratio: 2. 5 2. 75 2
Silicates: General Trend As O/Si ratio decreases:
Tetrahedral structure depiction:
Aluminosilicates: Zeolites Si. O 2 base structure Substitute some Si atoms with Al
Another representation Ball and stick Tetrahedral connectivity
Sodalite Cages
Formation of Zeolites from Sodalite Cages
Different arrangements lead to different pore spaces.
Charge and counter ions Pure Si. O 2, 0% Al replacement 10% Al replacement
Affinity for water Pure Si. O 2, 0% Al replacement 10% Al replacement
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
Solution Catalyze reaction inside a zeolite pore that only accommodates the para isomer.
Silicones
Synthesis of Silicone Precursors
General Reaction
Polydimethylsiloxane is the most common and available silicone.
Silicone Structure/Properties/Reactant Relationships
Silicone Structure/Properties/Reactant Relationships
- Kais308
- Sheet silicates
- Silicones and phosphazenes notes
- Silicones uses
- Silicone inorganic polymer
- Silicones and phosphazenes
- Silica
- 1926 silica
- 1926 silica
- Mining company profile
- Colloidal silica gun mix
- What is silica
- Characteristics igneous rocks
- How does silica affect lava
- Silica fume slurry
- Osha silica standard 1910
- Silica dust abatement
- Silica sand transport
- Silica solubility
- Silica health hazards
- Fumed silica
- Silica dust exposure
- Silica in foundation
- Wacker silicones
- Silicone logo
- Forward biased germanium diode
- Oxygen and silicon
- Silicon(iv) chloride dot and cross diagram
- Ecalyptol
- What is made up of silicon and aluminium
- Silicon unit cell
- Silicon at room temperature
- Quantum number of silicon
- Silicon drift detector explained
- Zeanne artinya