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organic chemistry - orbital hydridization shape question

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"The three sp² orbitals lie in a plane with 120° angles with p-orbital perpendicular to this plane."

I have been asked what this shape is known as...

"This is the reason double bonds are shorter than single bonds because p-orbital overlap is optimal"

I have also been asked what about the shape that this causes?

Can anyone give any insight into this?

Reply 1

charco

Study Forum Helper

Original post by hurricaneee

•

"The three sp² orbitals lie in a plane with 120° angles with p-orbital perpendicular to this plane."

I have been asked what this shape is known as...

"This is the reason double bonds are shorter than single bonds because p-orbital overlap is optimal"

I have also been asked what about the shape that this causes?

Can anyone give any insight into this?

The shape adopted by the sp2 orbitals is trigonal planar.

Your second question makes no sense ...

Reply 2

ChemistryBud

Original post by hurricaneee

•

"The three sp² orbitals lie in a plane with 120° angles with p-orbital perpendicular to this plane."

I have been asked what this shape is known as...

"This is the reason double bonds are shorter than single bonds because p-orbital overlap is optimal"

I have also been asked what about the shape that this causes?

Can anyone give any insight into this?

Hmm I don't see anything wrong whith the second quote/question. In a double bond each atom is sp2 hybridized with one electron in an unhybridized p orbital (perpendicular to the trigonal plane). For effecive overlap and formation of a pi bond the atoms are brought closer together. Whilst this results in increased repulsion between the non-bonding molecular orbitals of each atom, it is generally outweighed thermodynamically by the increase in bonding strength.

(edited 9 years ago)

Reply 3

hurricaneee

Cheers for that mate!

I wrote this when talking about ethylene,

" The p-orbitals have to remain parallel for optimal overlap and for this reason rotation around the central bond is not possible. This is the reason double bonds are shorter than single bonds because p-orbital overlap is optimal[KO1]

She has asked, "what about the shape that this causes?"

Reply 4

hurricaneee

Original post by ChemistryBud

Just seen this reply, thankyouy very much!

Reply 5

charco

Study Forum Helper

Original post by ChemistryBud

Hmm I don't see anything wrong whith the second quote/question.

You don't see anything wrong with this...

"This is the reason double bonds are shorter than single bonds because p-orbital overlap is optimal"

I have also been asked what about the shape that this causes?

... how can double bonds being shorter cause a specific 'shape'?

Reply 6

ChemistryBud

Original post by charco

You don't see anything wrong with this...

... how can double bonds being shorter cause a specific 'shape'?

alright the quote made sense, the question not so much :smile:

Reply 7

ChemistryBud

Original post by hurricaneee

She has asked, "what about the shape that this causes?"

Ok, just to clarify there is nothing wrong with this answer. The second half (highlighted in bold) could be worded slightly better to avoid misinterpretation but only small changes are required. For example:

As the p-orbitals are parallel to the sigma bond, for effective overlap and the formation of a pi bond the atoms have to be closer in space. As a result, double bonds are shorter in length than sigma bonds. Whilst this creates repulsion between the non-bonding molecular orbitals, it is compensated for thermodynamically by the increase in bond strength.

Edit: im not convinced that this is even related to the question (as charco pointed out, the bond length is more a property of sp2 hybridization than it is a consequence). I believe that you had the question answered with:

"The p-orbitals have to remain parallel for optimal overlap and for this reason rotation around the central bond is not possible"

Hope this helps.

(edited 9 years ago)