Polymers Flashcards
Synthesis of silicones
Me2SiCl2 and water
Driving force behind the synthesis of silicones
The Si-Cl bond is polar and easily hydrolysed and the Si-O bond is strong
How to get cross-linkage between silicones
Use a more chlorine containing reagent
What determines the stability of a silicone
the R groups in the starting material
Explain the flexibility of silicones
The oxygens in the backbone have no substituents. The energy to bend bonds is also low, this gives them more flexibility
What is a phosphazene
P-N cyclic species. Two Cl on the P
Bonding characteristics of P-N bonds
Typically drawn with some degree of double bond character. Really a single bond with a formal charge.
Electronic structure of nitrogen in phosphazenes
each N has two lone pairs, one sits outside of it in an sp2 orbital and the other in a p orbital perpendicular to the ring
pi system in phosphazenes
the sigma* orbital of the P-Cl is non-bonding but overlaps with the p lone pair on N
S4N4 bonding picture
cyclic, non-planar species. Each atom has one lone pair, uses two electrons to form sigma bonds. Each S has two electrons in a p orbital and N has one. 12 total pi electrons
Properties of {SN}x
metallic conductor due to the pi framework and a superconductor at v low temperatures
Interest in ammonia borane
Its isoelectronic with ethane but is a white solid due to the slight polarity and hence increased electrostatic interactions. Interest is in using it as a hydrogen storage material for fuel cells
What is borazene and how is it formed
six membered ring with alternating N-B bonds. N are methyl substituted. Formed from the heating of ammonia borane
Difference between borazene and typical organic aromatic systems
Susceptible to nucleophilic vs electrophilic attack (accessible LUMO). If heated further, it forms a graphite like structure
Product of catalytic heating of ammonia borane
Polymer as supposed to borazene
