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Questions tagged [allenes]

Use for question regarding the structure and properties of compounds containing a sequence of two cumulated double bonds.

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Synthesis of alkynes by double dehydrohalogenation; don't allenes also form?

So I was randomly looking at some really random exercises and I stumbled across synthesis of propyne from given compounds. There was $\ce{CH3CHBrCH2Br}$ as my substrate and I had to propose a way of ...
Roxtron's user avatar
  • 105
2 votes
2 answers

Does a chiral allene have stereogenic centres?

This a picture of what my professor taught in class. According the the definition of a stereogenic centre, allene should have two of them. So I don't understand what I am interpreting wrong.
Shikhar's user avatar
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3 votes
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Can allenes be used as motors or generators?

I was thinking about an allene, fucoxanthin: Potentially, we can draw a resonance structure in which up to eight of the carbon-carbon double bonds have moved one position to the left, a carbocation ...
Mike Serfas's user avatar
5 votes
1 answer

Does 1,3-dichloroallene possess a C2 symmetry axis?

Is there an $C_2$ axis of symmetry in $\ce{Cl-CH=C=CH-Cl}$? A $C_2$ axis of symmetry means that I should be able to rotate the molecule about an axis by $180^\circ$. But I would need a composition ...
gauri agrawal's user avatar
8 votes
1 answer

Mechanism of synthesis of allene

I would like to know the mechanism of this reaction. In my first attempt to the question, I had replaced the two $\ce{Br}$s by $\ce{CH3}$s by $\ce{S_N2}$ of the organometallic compound but the answer ...
Archer's user avatar
  • 5,501
7 votes
2 answers

Do allenes form rings?

I was wondering whether allenes can form rings; geometrically speaking, this seems like it would be energetically unfavorable due to their 180 degree linear geometry.
John Smith's user avatar
3 votes
2 answers

How to calculate the number of geometrical isomers in allenes?

Can someone explain how to calculate the number of geometrical isomers in allenes like $\ce{CH3-(CH=CH)4-CH3}$ or $\ce{CH3-(CH=CH)5-CH3}$
user avatar
2 votes
2 answers

What is the hybridization of the central carbon in buta‐1,2‐diene?

State the hybridisation of asterisked carbon in $\ce{CH3-CH=\overset{\ast}{C}=CH2}.$ I am not sure between $\mathrm{sp^2}$ and $\mathrm{sp}$ hybridization. Because of the presence of double bonds I ...
Freddy's user avatar
  • 5,127
4 votes
1 answer

Stability of Allenes and Alkynes,

In Allenes, the $\ce{C=C=C}$ structure makes sure that the $p$-orbital of central carbon overlaps with 2 other carbons and the $p$-orbital of central carbon spreads out over the 3 carbons. In ...
user4114's user avatar
  • 959
23 votes
3 answers

Why are allenes chiral?

How is 1-bromo-3-chloropropa-1,2-diene ($\ce{BrHC=C=CHCl}$) chiral? It doesn't have any carbon that is connected to four different groups.
Rajath Radhakrishnan's user avatar