- #1
sameeralord
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Just interested how this positive charge occurs. Thank you
Why does imidazolium ring contain a positive charge?
In summary, the positive charge in a cyclic structure can occur through the movement of double bonds and resonance forms. However, in order to maintain the octet rule for carbon, it is necessary to have 4 bonds to one of the Nitrogens. Additionally, in a substituted imidazole molecule, only one of the R1 or R3 groups can be quaternized while the other must be equal to 'nothing' or an alkyl group. Both R1 and R3 cannot be quaternized.
Just interested how this positive charge occurs. Thank you
- #2
ChrisW
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- 0
Draw the cyclic structure, then draw in double bonds where necessary to keep the octet rule for carbon. Should end up with 4 bonds to one of the Nitrogens, which gives a + charge. Now if you draw the resonance forms you'll see that the double bonds (and + charge) can bounce around throughout the ring system, so it's easier to just draw the whole ring system as positively charged.
- #3
chemisttree
Science Advisor
Homework Helper
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Actually, your diagram needs a bit of revision (or definition). In the example you provide, R1 and R3 cannot be equal to H. If this were the case, you would have a substituted imidazole molecule. Deprotonation would yield (R1 or R3 = nothing) a substituted imidazolium species whereas alkylation (or quaternization) of one of those species would yield one as well. Keep in mind that R1 and R3 cannot both be quaternized, only one (in your example). Therefore, either R1 or R3 must be equal to H (they can both be equal to H as well) but they both can't be an alkyl group.
Edit: Bolded item is wrong. It should read, "either R1 or R3 must be equal to 'nothing' and either one or the other may be equal to an alkyl. Both may also be equal to 'nothing' ".
Edit: Bolded item is wrong. It should read, "either R1 or R3 must be equal to 'nothing' and either one or the other may be equal to an alkyl. Both may also be equal to 'nothing' ".
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1. Why does the imidazolium ring contain a positive charge?
The imidazolium ring contains a positive charge because of the presence of a nitrogen atom that is sp2 hybridized. This nitrogen atom has a lone pair of electrons that is available for bonding, resulting in a positively charged ring.
2. What is the significance of the positive charge in the imidazolium ring?
The positive charge in the imidazolium ring makes it a strong acid, which is useful in various chemical reactions. It also allows for the formation of ionic liquids, which have unique properties and applications in various fields.
3. Can the positive charge in the imidazolium ring be removed?
Yes, the positive charge in the imidazolium ring can be removed by reacting it with a base, such as an amine, to form a neutral imidazole ring. This reaction is reversible, and the positive charge can also be restored by reacting the imidazole ring with an acid.
4. How does the positive charge affect the structure of the imidazolium ring?
The positive charge in the imidazolium ring results in a more polar and reactive structure compared to the neutral imidazole ring. This can affect the physical and chemical properties of the molecule, such as solubility and reactivity.
5. Are there other molecules besides imidazolium that contain a positive charge in a ring structure?
Yes, there are other molecules that contain a positive charge in a ring structure, such as pyridinium, phosphonium, and sulfonium. These molecules also have unique properties and applications in various fields, similar to imidazolium.
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