Questions tagged [carbene]
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14
questions
3
votes
1answer
60 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 ...
3
votes
2answers
139 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 ...
4
votes
1answer
699 views
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 ...
0
votes
1answer
1k 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?
2
votes
0answers
65 views
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 ...
2
votes
1answer
135 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 ...
4
votes
1answer
405 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 ...
6
votes
1answer
3k views
-4
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1answer
303 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
10
votes
2answers
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}...
9
votes
2answers
936 views
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 ...
9
votes
2answers
2k 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. ...
3
votes
1answer
371 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 ...
7
votes
1answer
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 ...
