# Type of hybridisation

State the hybridisation of asterisked carbon in $\ce{CH3-CH=C^{✪}=CH2}$

I am not sure between $sp^2$ and $sp$ hybridization. Because of double bond I think it should be $sp^2$ but because of 2 $\pi$ bonds iI think $sp$.

So which one is correct?

• You are correct that a carbon with two double bonds is not $sp^2$. I'd suggest thinking about the geometry around that atom. What shape will it have to handle both double bonds? – Geoff Hutchison Oct 5 '14 at 4:24
• To add to what Geoff Hutchison wrote, an atom with similar geometry and hybridization that you have probably encountered previously is the carbon in CO2. – Jason Patterson Oct 5 '14 at 4:52
• @hey The molecule you've drawn belongs to a class of molecules called "allenes." Here are some diagrams of the molecule's structure and bonding that may be helpful. – ron Oct 5 '14 at 12:39
• The hybridization is the same as carbon dioxide. – LDC3 Oct 5 '14 at 14:25
• @GeoffHutchison Sorry it's linear. – Freddy Oct 5 '14 at 15:54

You must be clear that the hybridization is decided by the number of sigma electrons So for $\ce{CH4}$ the number of sigma electrons is 4 and so its hybridization is $sp^3$.
In your case: $\ce{CH3-CH=C^{✪}=CH2}$ the $*$ carbon is having 2 sigma and 2 pi bonds so its hybridization is $sp$.
Remember that possible hybridization for $\ce{C}$ are $sp^3$,$sp^2$ and $sp$.