In case of silicone halides inductive effect dominate over back bonding hence Lewis acid character decided by inductive effect.
Hence order of Lewis acid character:
[SiF4>SiCl4> SiBr4 > SiI4]
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Saturday, February 8, 2020
How to write the mechanism of ring expansion in organic chemistry?
- How to write dehydration and ring expansion mechanism of 1-(1-cyclopentyl) methanol?
- How to write dehydration and ring expansion mechanism of Tetrahydrofurfuryl alcohol?
- How to write dehydration and ring expansion mechanism of 2-cyclopentylethanol?
- Write the Dehydration and ring expansion mechanism of following alcohol:
- Write Dehydration and ring expansion mechanism of 1-cyclobutylethanol in the presence of con H2SO4.
- Explain the ring expansion mechanism of Bicyclic 1,2-Diols which undergoes pinacol pinacolone mechanism?
- Explain Dehydration and ring expansion mechanism of 1-(1-Methylcyclopentyl)ethan-ol?
- Write the major and minor product of hydration of 1 -Methylcyclopent-1-ene in acidic medium?
- Write the major and minor product of hydrohalogenation of 2-Methylbut-1-ene in acidic medium?
- To synthesize 2, 3-dimethylbut-1-ene in the better yield dehydrohalogenation of 2, 3-dimethyl-1-bromobutane is preferred over dehydration of 2, 3-dimethylhutan-1-ol. Why ?
- Why dehydration proceeds in acid but not in base?
- Why alcohols do not undergo base induced dehydration in the same way that alkyl halides are dehydrohalogenated ?
- How can write dehydration mechanism of 1,2,3-Trihydroxymethylcyclopropane into Benzene in acidic medium?
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Friday, February 7, 2020
The tendency of polymerisation is observed as SiO4 4- > PO4 3- > SO4 2- > ClO4 - Explain.
We know that the pπ-dπ bonding is much more
significant than the pπ-pπ bonding from the standpoint of overlap integral.
In pπ-pπ bonding, the
overlapping lobes are parallel and as a result, there occurs a pure sideways
overlap. On the other hand, in pπ-dπ bonding, the lobes
of the overlapping d-orbitals are at an angle <<180° to the lobes of
the p-orbital. Thus in the pπ-dπ interaction, the
ovelap is better.
Now let us consider the O(2p)
- X(3d)
π-bonding (where, X= Si, P, S, Cl).In the tetrahedral structure
of XO4 n- the dX2-y2 and dz2 orbitals of X can participate in the said pπ-dπ bonding
interaction. On moving from left to right along a period, the effective nuclear
charge generally increases and consequently the energy of the 3d-orbitals
decreases from Si > P > S > Cl. The overlap becomes better
when the overlapping orbitals have comparable energies. Thus the π-bonding
efficiency increases from Si < P < S < CI. Now let us consider the
oxyanions in the order of increasing tendency of polymerization,
[SiO44- > PO43- >
SO42- > ClO41- ]
Here, besides the different periodic positions of
Sl, P, S and Cl, it is worth mentioning that the 1 positive oxidation state of
the central element increases as, Si(+4), P(+5), S(+6): Cl(+7). With the increase of positive oxidation state, the
energy of the 3d-orbitals gradually decreases and it favours the π- bonding
interaction. Thus the 2pπ(O) - 3dπ(X) bonding
in X - O increases
from Si to Cl. This is why, the systems where the π-bonding is not effective,
the stabilization is attained through the single bonded structure, i.e. through
the polymerization. Thus the concept of pπ-dπ can
explain the observed sequence of tendency towards polymerization
What are the SESQUI OXIDES ? give the examples.
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