carbon with double bond chiral?

[OnlyDrilling]

Can a carbon with a double bond be chiral? I thought in order to be chiral a carbon has to have 4 different compounds coming off it. SO how can a double bonded carbon for be chiral if its only has 3 things coming off it??/???

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[adizzle87]

No, it can't be chiral because chirality (stereochemistry) only applies to carbons that are attached to 4 different substituent group (4 sp3 bonds).

 

[Parle G]

Carbon with double bonds are never chiral. In order, for it to be chiral, it has to have four different substituents, and also it cannot be identical to its mirror image.

 

[haagendazs]

in the Destroyer, they said a carbon with 2 double bonds is chiral if both groups are different, for example CH3-CH2=C=CH3 ... i forgot what these were called. allenes? or something like that. it was because the two double bonds are perpendicular to each other, not parallel, so it has a nonsuperimposble mirror image, which is the definition of chiral

 

[eilrahcmi]

in the Destroyer, they said a carbon with 2 double bonds is chiral if both groups are different, for example CH3-CH2=C=CH3 ... i forgot what these were called. allenes? or something like that. it was because the two double bonds are perpendicular to each other, not parallel, so it has a nonsuperimposble mirror image, which is the definition of chiral

this is correct

 

[haagendazs]

oh sorry i made a mistake in my example. the two groups bonded to the two carbons directly double bonded to the "chiral" carbon have to be different, eg CH3-CBr=C=CHCl

in here, the =C= is the chiral carbon. note the two carbons directly bonded to it (both bracketed in next sentence). it's -CH3-[C]Br- with a CH3 and Br group, both have to be different; and -[C]HCl- with a H and Cl group. Both of these have to be different, and different from the other two as well. These 4 groups (CH3, Br, H, Cl) represent the 4 different groups on a typical chiral carbon that we all know.

 

[eilrahcmi]

this is now correct lol

we were going over this stuff in my organic lecture today i just couldn't think of any examples

 

[OnlyDrilling]

hey thank all you guys so much! i got it...thankssss

 

[adoc2b]

NextStep says the left most carbon (double bonded to the Oxygen) IS NOT CHIRAL because it's NOT TETRAHEDRAL. But I thought double/triple bonded carbons with the exception of one, couldn't be chiral.

 

[aj30]

NextStep says the left most carbon (double bonded to the Oxygen) IS NOT CHIRAL because it's NOT TETRAHEDRAL. But I thought double/triple bonded carbons with the exception of one, couldn't be chiral.

The reason double bonds aren't chiral is because they are not tetrahedral and therefore have planes of symmetry (with the exception of alkenes which sometimes don't).