Strange Orgo Question

[drgreen]

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Can a chiral allene be assigned R or S?

 

[futuredent22]

I'm pretty sure an allene cannot be chiral. You need an sp3 carbon in order to have a stereocenter

 

[Maygyver]

Can a chiral allene be assigned R or S?

I believe, as the previous post said, that in order for a molecule to be chiral it needs to have 3 different substituents so an alkene can not be chiral. However, alkenes can be assigned as cis or trans based on the relative location of the highest priority substituents.

 

[TeamGuo]

what's the strange part?

 

[predent270808]

check L.G Wade text book page 190 allene which has 2 distinct groip at ends is chiral. I guess we can not use R or S in this case.

 

[dleodyddlek]

i don't quite understand it even after reading what wiki has to say but you might be able to figure out from this. http://en.wikipedia.org/wiki/Allene
it clearly says allen can be chiral when different substituents exist but what the hell.. i don't really get it

 

[harrygt]

Allenes CAN be chiral. Not sure about assigning R or S. I'm sure this is too much for DAT. Don't worry about it.

 

[drgreen]

you're probably right, too much detail, but apparently R and S can be assigned. unclear how, i guess it doesn't matter.

 

[mintz123]

Allene can be chiral or achiral depending on the different substituents on the terminal carbon, but in this case, I dont think one can assign a R or S on this particular compound (only on sp3 carbons).

R/S are arrangement of atoms at the chirality center and this is usually done through "the steering wheel" projection, the Fischer Projection, and the Newman Projection; all of em being in tetrahedral conformation.

hopefully someone can verify this info. 😎

 

[Maygyver]

I stand by my post still 😉 I know that when you count for possible sterogenic centers you do use the double bond as a possible one, but I dont think it can be R or S.

 

[drgreen]

I stand by my post still 😉 I know that when you count for possible sterogenic centers you do use the double bond as a possible one, but I dont think it can be R or S.

R AND S CAN BE ASSIGNED FOR ALLENES. the stereogenic center is the set of double bonds, the 3 carbons.
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1325211

 

[Maygyver]

Oo. I just found this link that's really helpful in explaining it: http://www.cem.msu.edu/~reusch/VirtualText/special1.htm