name this molecule!

Factual Questions
1

The molecular formula for ETHANE is:

 H   H
 |   |

H-C - C-H
| |
H H (single carbon bond)

For ETHENE (ehtylene), its:

H     H
 \   /
  C=C         (double carbon bond)
 /   \
H     H

For ETHYNE (acetylene), its:

  _

H-C=C-H (triple carbon bond)
What is the name of:
_
C=C
- (Quadruple carbon bond?)

Does this molecule actually exist?
-

2

Sorry if ASCII dosen’t translate to well.

3

No such luck. Quadruple bonds don’t exist. First semester organic student in me wants to say it would be a really, really short, and you would get strain between the carbon atoms. Plus, such an electron-rich area would be really nucleophilic, that is it would be reduced in no time.

4

You can’t have two carbon quadrupally bonded to one another. Quadruple bonds aren’t all that common and they are almost exclusively seen between transition metals (IIRC). Basically you need atomic d orbitals available to make them. s and p cannot hybridize to allow a fourth bond between the same atoms.

5

::Former Chemistry Teacher enters the room::

Simply to add to Dr. Lao’s correct explanation, recall that sp[sup]3[/sup] hybridization results in a tetrahedral formation (like methane). Imagine two tetrahedrals. You can orient them so that one point on one tetrahedral touches one point on the other. You can also orient them so that two points touch two points (edges in contact) and so that three touch three (faces in contact). When in this orientation, the remaining orbitals, which you wish to have make the 4th bond, are facing away from each other. This is not particularly a problem of energy or bond strain, but a problem of spatial proximity. There is not Euclidean way that these two remaining orbitals can overlap.