chiral center? stereocenter?

[gomawum]

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ochem 52

allene with different substituents (adjacent double bond) can be chiral?
I mean I know that term 'chiral' is molecule with 4 different substituents
and stereocenter is the molecule that can have stereoisomers
(def. from the book)
so double bond with E/Z system has stereocenter but not chiral

but the solution in this problem said that the double bond can be chiral
and I got really confused...


and relate to 59

chiral center is optically active for sure
but is stereocenter like E/Z system(like above compound) also optically active?

 

[PreDent2009]

How could a carbon with a double bond attached to it be chiral. It is sp2, indicating that it only has 3 substituents attached to it. Also, double bonds are not optically active.

ochem 52

allene with different substituents (adjacent double bond) can be chiral?
I mean I know that term 'chiral' is molecule with 4 different substituents
and stereocenter is the molecule that can have stereoisomers
(def. from the book)
so double bond with E/Z system has stereocenter but not chiral

but the solution in this problem said that the double bond can be chiral
and I got really confused...


and relate to 59

chiral center is optically active for sure
but is stereocenter like E/Z system(like above compound) also optically active?

 

[gomawum]

yes, but it says this type of allene -> (H -)&(CH3-)C=C=(-CH3)&(-CH2CH3))
is chrial and is optically active.

so I was wondering how the heck it can be chiral and optically active

 

[Orgodox]

What you have to realize is that things can be deceiving in 2-D With allenes the two double bonds are not in the same plane. For example lets look at 1,3-Dimethylallene (pic bellow) the orbitals are in planes perpendicular to each other.(You can see it ont he picture, one the left picture the one side has a methyl coming out at us and a H pointing away from us and the other side is in the plane of the screen) If we take the mirror image of this molecule we see that it is not superimposable on the original and a pair of enantiomers is the result!