Ring strain一問

Billyionaire

2013-01-04 2:55 am

Some substances(e.g. cyclopropane) have ring strains because the atoms in it are forced to be closer together and leads to the overlapping of atomic orbitals. But why this overlapping of atomic orbitals make them unstable?

In a C=C double bond, the atoms in itt can't rotate because rotation reduce the efficiency of orbital overlapping. Why this time overlapping of orbitals make them more stable?

更新1:

thx,maybe i think it wrongly! also i want to asj why Si and O can't form double bond while P and S can do so with O? both Si,P and S are using their 3p orbital and hence weak interaction with 2p of O, and can't form pi bond right?

更新2:

but why is Si=O interaction not effective but P=O and S=O are effective?

回答 (1)

老爺子

2013-01-04 9:26 pm

✔ 最佳答案

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2013-01-05 23:44:53 補充：
Why Si and O can't form double bond while P and S can do so with O?

The size of Si atom is greater than those of P and S, and thus the side overlapping of p orbitals for Si atom and O atom is less effective, and the π bond formed betwen Si and O atoms is weaker.

2013-01-05 23:49:15 補充：
However, it was found that O=Si=O molecules are formed when SiO2 solid is decomposed at a high temperature.

2013-01-05 23:50:32 補充：
both Si,P and S are using their 3p orbital and hence weak interaction with 2p of O, and can't form pi bond right?

The weak π bond is due to the low effectively of side overlapping, but not due to what type of orbital is used.

2013-01-05 23:51:34 補充：
The weak π bond is due to the side overlapping of orbitals is not effective, but is not due to what type of orbital is used.

2013-01-14 22:46:19 補充：
In comparing with P=O and S=O bonds, Si=O bond is weaker may be due to the fact that Si has greater size and weaker nuclear charge than P and S.

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