Questions tagged [tautomer]

Tautomers are constitutional isomers of (usually organic) compounds that readily interconvert into each other. This tag is also suitable for tautomerization, the isomerization by which tautomers are interconverted. It may synonymously specified for questions about tautomerism.

Filter by
Sorted by
Tagged with
0 votes
0 answers
31 views

Why does polar solvents favor Ketonization and non-polar solvents favor Enolization? [duplicate]

I was just studying isomerism, when I came across this statement for keto-enol tautomerism: A polar solvent favors ketonization, while a non-polar solvent favors enolization. And I just can't get my ...
Nishant's user avatar
  • 11
13 votes
3 answers
2k views

Why Is Hydrogen in HSO3- Connected to Oxygen Instead of Sulfur?

One of the questions in my homework was to draw $\ce{HSO3-}$, which I thought to be pretty easy. Sulfur is the least electronegative (except hydrogen but it can't be the central atom), hence it is the ...
Lyborick's user avatar
  • 155
2 votes
0 answers
93 views

Stability of different tautomers of vitamin C

Above all four tautomers represent Vitamin C (Ascorbic acid) So here are some basic rules that I learnt. 1.Usually keto form is more stable due to bond enthalpy considerations 2.Enol form is stable if ...
Mithun M R's user avatar
-2 votes
2 answers
94 views

Racemization at stereogenic centre [closed]

I am getting a bit confused about why the configuration at the optical centre changes from d to l after enolization? Any stereogenic centre next to a carbonyl group will be destroyed by enolization. ...
Cara's user avatar
  • 15
3 votes
1 answer
2k views

Acid hydrolysis of Birch-reduced Anisole

The following is a question from Advanced problems in organic chemistry by MS Chouhan: Product $A$ is rather straightforward: and on acidic hydrolysis, the following reaction takes place: Here the ...
Lost Anisole's user avatar
3 votes
2 answers
560 views

2-Pyridone tautomer ratio

The following excerpts from different textbooks about keto–enol tautomerism in pyridones seem to be contradictory. Could someone explain which one is right? MARCH’S ADVANCED ORGANIC CHEMISTRY pg-103 ...
Math-Wiz's user avatar
4 votes
0 answers
55 views

Do ketdione molecules have diol tautomers?

In my chemistry textbook there's a keto-enol tautomerism example: But will it also be in equilibrium with pent-1,3-dien-2,4-diol in a reaction like this or will it just be a functional isomer?
Frisk17's user avatar
  • 69
0 votes
0 answers
340 views

Number of enol forms of acetylacetone

Here is what I tried: These are the two enolic forms that I could make. So according to me, the total number of distinct enol forms of acetylacetone is $2$. But the answer is 3, what am I missing?
Soumil Gupta's user avatar
4 votes
0 answers
519 views

Tautomerism between cyclohex-2-en-1-one and cyclohex-3-en-1-one

I think cyclohex-2-en-1-one and cyclohex-3-en-1-one should undergo tautomerism as shown below: I'm calling it tautomerism because of it's similarity with the tautomerism mechanism in basic medium. I ...
Box Box Box Box's user avatar
4 votes
3 answers
304 views

Finding the major contributing tautomer of 1-(propan-2-yl)-1,2,3,5-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one [closed]

I am having a problem generating the correct tautomer for 1-(propan-2-yl)-1,2,3,5-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one. I am told by my collaborator that the one I am generating is wrong. I am ...
srinivasan ranga's user avatar
0 votes
0 answers
30 views

Keto-Enol tautomerism acidity of α Hydrogen vs stability of double bond [duplicate]

If I consider a ketone that has an ethyl group and a methyl group attached to it. The α-Hydrogen of the methyl group would be more acidic than that of the ethyl group due to -I effect of the adjacent ...
Ashish's user avatar
  • 1,409
3 votes
2 answers
712 views

Keto-enol tautomerism in a bicyclo compound

Question Which one is more stable- the keto or enol form. The compound given is this: Solution The enol form would violate Bredt's Rule and would therefore be unstable. Hence the keto form is more ...
lazearoundallday's user avatar
2 votes
1 answer
149 views

Determining the most stable enolic form of 1-phenylbutane-1,3-dione?

Question Which form of 1-phenylbutane-1,3-dione is more stable? Answer 3-hydroxy-1-phenylbut-2-en-1-one My question I've been told that between the above two, 3-hydroxy-1-phenylbut-2-en-1-one is ...
Have a Good day's user avatar
1 vote
0 answers
93 views

Comparing the boiling points of common organic molecules

The order I was provided with is(comparing molecules of similar molecular mass from each); alkanes< ethers< esters< aldehydes< ketones<< alcohols<< carboxylic acids<< ...
harry's user avatar
  • 1,134
5 votes
1 answer
867 views

On the stabler tautomer in amide-imidic acid tautomerism

In the section on acid-catalysed hydrolysis of nitriles, this webpage has the following line of reasoning; ...the more stable amide tautomer predominates the (following) equilibrium. (credit) How ...
harry's user avatar
  • 1,134
10 votes
1 answer
570 views

Why is quinone mono oxime more stable than 4-nitrosophenol?

When we do nitrosation of phenols, we get para-nitrosophenol as the major product, which tautomerises to quinone mono oxime. This article states that it largely exists in the quinonoid form. My ...
V.G's user avatar
  • 1,251
5 votes
1 answer
109 views

Is tautomerism in ketimines possible?

In a reaction between an aliphatic primary amine and a ketone, I could expect a ketimine as a product or intermediate. My question regards tautomerization of this intermediate: has tautomerization ...
Anger Density's user avatar
0 votes
0 answers
447 views

Which enol form is more stable?

I came across an example today while I was studying tautomerism. It is an example of tautomerism exhibited by acetylactone/1,3-diketone; given under the keto-enol systems under 1-3 migration/triad ...
Desai's user avatar
  • 471
1 vote
0 answers
151 views

Find the major products when these cyclohexenone bromides react with caustic potash in alcoholic medium:

Question: Also find the order of the rates of the given reactions. Answer: The answer of this question is given as option 'D' ie. all products are identical, however I am getting the answer as ...
Shriom707's user avatar
  • 197
-1 votes
1 answer
90 views

Is a tautomer's stability compared with refernce to its initial compund [closed]

Considering the following example while comparing the enolic content in the product, am I supposed to compare its stability with reference to its initial state or am I supposed to compare it between ...
Saniya's user avatar
  • 63
4 votes
1 answer
94 views

Tautomerism in 3,5‐dimethyl‐4H‐pyrazole

How would tautomerism take place in 3,5‐dimethyl‐4H‐pyrazole? I am aware of nitro–aci nitro and keto–enol, but I haven't seen such a compound before. I recognize that a hydrazone formation was done ...
Shaurya Goyal's user avatar
0 votes
1 answer
236 views

Phenol vs 4-hydroxypyridine - Enol Content [duplicate]

Which has a higher enol content; phenol or 4-hydroxypyridine? The solution to this question in my book says that phenol has a higher enol content due to aromaticity. But 4-hydroxypyridine is also ...
gauri agrawal's user avatar
0 votes
0 answers
208 views

Which has a higher enol content between 4-Pyridone and Cyclohexa-2,5-dien-1-one?

I am new to organic chemistry but here is what I feel. 4-Pyridone will have a lower enol content as in its keto form it has higher resonance stabilisation due to the involvement of lone pairs on ...
Vishnu P's user avatar
-1 votes
1 answer
1k views

Why doesn't keto enol tautomerism take place in acid derivatives?

Why does keto enol tautomerism take place only in ketones and aldehydes? Why doesn't it take place in carboxylic acids, esters, amides, anhydrides and acid chlorides?
trinitrotoluene's user avatar
4 votes
2 answers
639 views

Tautomer of acrolein

Are $\ce{CH2=CH-CH=O}$ and $\ce{CH2=C=CH-O-H}$ tautomers? There is only a shift of a hydrogen atom and a pi bond. So why are these two not tautomers?
gauri agrawal's user avatar
-1 votes
1 answer
331 views

Why Nitroso tautomer is more stable than its oxime counterpart? [closed]

As I was looking for the answer of the question I found that it is explained using the Electronegativity difference concept. That's correct but I am unable to prove the same through the bond energy ...
Anshu Apoorva's user avatar
2 votes
3 answers
1k views

Which compound will have the most stable enol form?

Which compound will have the most stable enol form, Phloroglucinol or 4-Pyridone? My Thoughts: Both in their enol form are aromatic. I am not sure how do I compare their stabilities. The answer ...
Tony's user avatar
  • 292
13 votes
4 answers
2k views

Stability of 4-pyridone vs 4-pyridinol

In kryptomerism assignment, there was a question to compare more stable tautomeric form between 4-pyridone (1) and 4-pyridinol (2): Answer: 4-pyridone. My friend gave two plausible reasons: $\ce{C=...
Zenix's user avatar
  • 1,350
0 votes
1 answer
906 views

Role of tautomerism and its difference from hyperconjugation [closed]

I would like to know the role of tautomerism, if any, in increasing stability of an organic compound. Moreover, how is it different from that of hyperconjugation? I know that hyperconjugation ...
userHappyHogan's user avatar
1 vote
0 answers
624 views

Do alpha hydroxy ketones give iodoform test

So, we know that alpha hydroxy ketones give tollens test as the tautomerise into their enol form and the then have an equilibrium between the 2 keto forms. So going ahead with the same logic. Do ...
Dushtesh_'s user avatar
1 vote
1 answer
388 views

Why does coumarin predominantly exist in keto form?

By applying the logic that phenol exists in enol form rather than keto form as it attains aromatic character, why is it not the case in coumarin?
Abhigyan's user avatar
  • 160
2 votes
2 answers
389 views

How are there three possible tautomers of 2,2,4-trimethylheptane-3,5-dione? [closed]

The answer for the above question is three. But I am able to draw four structures: Where am I getting it wrong?
Garima Singh's user avatar
3 votes
2 answers
12k views

Which has the highest enol content?

Which of the following compound has highest enol content? The answer is an option (c) and I think the reason behind it is that there are two phenyl groups attached to it, hence there will be a good ...
Garima Singh's user avatar
-1 votes
1 answer
575 views

Enol content tautomers

I have figured out that 4 one will have the highest enol content of all, and the 1 structure would come after 4 in enol content, i.e 4 > 1. Then I got confused between the 2nd and the 3rd structures. ...
Neelansh's user avatar
3 votes
2 answers
398 views

Will (3R,4S,5R)-1,3,4,5,6-pentahydroxyhexan-2-one tautomerise in nitric acid?

The following question was sent to me .The question is " Which of the following is A ?" The given answer was a,b,c Background If both ends of an aldose chain are oxidized to carboxylic ...
Chakravarthy Kalyan's user avatar
2 votes
0 answers
181 views

Chirality with tautomers

This molecule has 6 peaks in its proton NMR. I think this is due to the following tautomerisation: However, I am unsure as to whether this molecule would be chiral, as it can freely interconvert ...
J. Deans's user avatar
  • 175
3 votes
1 answer
543 views

What will be the major enol form of methyl acetoacetate?

I presume the best enol form would have a double bond between the two $\ce{C=O}$ so they're conjugated, but I'm not sure how the resonance would play out.
Ryan's user avatar
  • 31
3 votes
1 answer
874 views

Equilibrium Constants For Phenol Tautomers

I encountered the following equilibrium constant values for the keto-enol interconversions of phenol in Organic Chemistry (Solomons, Fryhle, Snyder, 3rd Edition): I wonder what could explain the ...
Kartik's user avatar
  • 166
0 votes
1 answer
746 views

Tautomerism in alkenes

Why doesn't but-2-ene exhibit tautomerism like alkenols? By transfer of 1 hydrogen from terminal CH₃ to the middle carbon and forming a double bond between the two?
user226375's user avatar
0 votes
0 answers
226 views

Acid catalyzed enolization and alpha hydrogen

In acidic catalyzed enolization of butan-2-one: We have 2 alpha hydrogens available. From the mechanism of acid catalyzed enolization there is a certain carbocation character at the carbonyl carbon ...
Akshat Joshi's user avatar
2 votes
0 answers
3k views

Number of enolizable hydrogens in 2-methylcyclohex-2-en-1-one [duplicate]

The number of enolizable hydrogen atoms according to me is four, but the answer given for the question says it has seven enolizable hydrogens. Where are the rest of them?
Chloritone_360's user avatar
-1 votes
2 answers
2k views

What is the predominant enol tautomer of 1-phenylbutane-1,3-dione?

In 1-phenylbutane-1,3-dione (1), which enol tautomer will be predominant? Both carbonyl groups possess α-hydrogens, so can undergo keto-enol tautomerism. In particular, the carbonyl group on the ...
user avatar
3 votes
2 answers
818 views

Compound having the highest enol content will be?

The answer written in book is 3 but no solution is given. After referring to some other question I think that hydrogen bonding can take place in compounds like 3 but am not sure about it. Am I right ...
Shresth Jain's user avatar
13 votes
1 answer
1k views

Stability of keto-enol vs. conjugation

I am trying to figure out which tautomer of creatinine: is more stable. We see that the enol tautomer is more highly conjugated: the $\pi$ electrons from the alcohol to the double bond to the $\pi$ ...
Shakthi Visagan's user avatar
5 votes
2 answers
4k views

What is the most stable structure amongst the keto-enol tautomers of pentane-2,4-dione?

I was assigned the following question and I cannot decide which is the correct answer. Which is the most stable structure? (a) pentane-2,4-dione (b) 4-hydroxypent-4-en-2-one (c) (Z)-4-...
MeAndMyLucidLife's user avatar
3 votes
3 answers
2k views

Why enol content of ethyl acetoacetate is more in toluene than water?

Ethyl Acetoacetate has enol content of 0.4% in water and 19.8% in toluene. What is the reason behind this? Does this anything have to do with the intramolecular hydrogen bonding in the enol form?
Abhijith S Raj's user avatar
5 votes
2 answers
557 views

Structure of the compound C9H7O2Cl?

A compound having formula $\ce{C9H7O2Cl}$ (O = oxygen) exists predominantly in enol form (A) and also in keto form (B). On oxidation with $\ce{KMnO4}$ it gives m-chlorobenzoic acid as one of the ...
Anirudh's user avatar
  • 305
4 votes
1 answer
542 views

What anions does the loss of a proton from HOCN and HNCO produce? Are they same or different?

What anions does the loss of a proton from $\ce{HOCN}$ and $\ce{HNCO}$ produce? Are they same or different? Once, I had asked my teacher if $\ce{HCN}$ and $\ce{ HNC }$ are different or same compunds, ...
Iceberry's user avatar
  • 1,218
3 votes
1 answer
497 views

Deuteration of enone - mechanism?

What happens when the above compound is mixed with D2O (deuterated water)? As a result of tautomerism, I'd expect the 4H atoms, one alpha to carbonyl carbon, and three at gamma position; to be ...
stoic-santiago's user avatar
5 votes
1 answer
3k views

In the bicarbonate ion, why can the hydrogen not bond to the carbon?

I've been studying electrophiles and nucleophiles recently, including how the carbonate ion ($\ce{CO3^2-}$) is stabilised through resonance. While drawing the model for bicarbonate, however, I ...
Gustav Christensson's user avatar