Questions tagged [carbene]

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0 answers
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Why is carbon monoxide non-Brönsted-basic in aqueous solution when it has a lone pair on carbon?

Carbon monoxide is not protonatable in aqueous solution; a quick Google search even leads to a paper that talks about using carborane acids, i.e. extreme superacids, to protonate the molecule. However,...
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4 votes
2 answers
99 views

Acidity of thiamine - how comes hydroxide anion with pK about 15 ionizes thiamine with pK about 18?

Textbooks say removing proton from thiamine's C atom will produce a resonance stabilized carbanion which is hence bioactive. That's OK, but how comes that 1) we abstract the acidic proton with the OH ...
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3 votes
2 answers
193 views

Methylene "anti" Jahn-Teller effect

Yesterday a Reddit user posted a page from Morrison's Organic Chemistry in which it is said that singlet methylene is less stable than triplet methylene. Another user asked basically the same I'm ...
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  • 116
5 votes
1 answer
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Reimer-Tiemann reaction on indole

According to me net reaction should be at $\ce{C3}$ when Reimer-Tiemann reaction is done on indole (see image), since in the resonance structure, negative charge is on this carbon. But, the answer ...
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0 votes
2 answers
2k views

Which is more stable? CF2 (singlet) or CF2 (triplet)

Generally, we know that triplet carbene is more stable than singlet. But in my book, it is written that singlet difluorocarbene is more stable than triplet difluorocarbene. What's the reason for it?
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2 votes
0 answers
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Hydrogen Bonding by Carbenes

A hydrogen bond is formed between hydrogen attached to highly electronegative atoms (nitrogen, oxygen, and fluorine) which are small in size too and the non-bonding pair of electrons of another such ...
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  • 35
2 votes
1 answer
245 views

How is chlorocarbene synthetised?

The wikipedia page on cyclononatetraene says that the aromatic cyclononatetraenyl anion can be synthetised by a rearangement of 9-chlorobicyclo[6.1.0]nona-2,4,6-triene. My first idea on how to ...
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  • 744
5 votes
1 answer
543 views

Mechanism of Fritsch–Buttenberg–Wiechell rearrangement

The following reaction was given, which uses potassium t-butoxide. The solution to this problem was given as follows: Step 1 is the attack of strong base, t-butoxide, on the vinyl proton. Step 2 ...
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11 votes
1 answer
6k views

How does chloroform react with cyclopentadiene in base?

Is my reaction mechanism feasible?
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-4 votes
1 answer
321 views

reimer tieman reaction only one ortho product [closed]

why we cannot have two reimer tiemann substitutions on the same phenol as CHO- group is electron withdrawing it wont disturb electron concentration at its meta which is phenol's ortho- product
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  • 594
11 votes
2 answers
1k views

Reaction between a carbene and n-pentane

Does the following reaction occur when n-pentane reacts with methylene or does it form some other simpler products due to the reactivity of the carbene? $\ce{CH3-(CH2)3-CH3 + :CH2-> CH3-(CH2)4-CH3}...
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  • 819
9 votes
2 answers
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Correct way to draw a carbene

What is the correct way to draw a carbene? On most/all material I have seen, both singlet and triplet carbenes are depicted as so: With 2 "dots" representing the non-bonding electrons on either a ...
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9 votes
2 answers
3k views

Why is triplet carbene sp2-hybridised?

Triplet carbene has a carbon with 6 electrons, of which 2 are unpaired. I would expect the carbon to be $\ce{sp}$ or $\ce{sp^3}$ hybridised and the two singly occupied orbitals to be degenerate. ...
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  • 1,636
3 votes
1 answer
399 views

Origin of diastereoselectivity in Simmons–Smith cyclopropanation of allylic alcohol

In Organic Chemistry by Clayden et al., the following reaction is shown: The cyclopropane ring is formed on the same side as the alcohol group. Is this because of the interaction between Zn and the ...
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  • 7,380
7 votes
1 answer
1k views

Which singlet dihalocarbene has the strongest carbon-halogen bond?

There are three singlet carbenes - difluorocarbene, dichlorocarbene and dibromocarbene. Which has the strongest carbon halogen bond? Obviously backbonding is a point to be considered, as carbene is ...
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