Questions tagged [heterocyclic-compounds]

For questions concerning compounds possessing rings with two or more different types of atoms.

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Mechanism of Grignard reaction with 2-(thiiran-2-yl)oxirane

What will be the final major product? The answer is 2-(methoxymethyl)-3-(substituted methyl)thiirane: I think $\ce{R}$ of $\ce{RMgX}$ attacks thiirane ring because negative charge on sulfur is more ...
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4 votes
1 answer
82 views

Is 2-pyrone an aromatic compound?

I was told by my professor that α-pyrone is not an aromatic compound, but I count two π-electrons as well as one of the lone pairs on oxygen giving six total which would be one of Hückel's $4n + 2$ ...
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Purpose of "1H" in naming of substituted heterocyclic compouns [duplicate]

I had a curious thought about the following molecule's name: For such a simple molecule it seemed awfully complicated. From what I gathered, the "[c][1,2]oxaborinin-1-ol" stems from the ...
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1 vote
1 answer
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Do azaindoles primarily exist in anionic form at physiological pH and act as bases?

I am reading an article where they describe azaindoles (bicyclic pyridine/pyrrole rings) as being basic with $\mathrm{p}K_\mathrm{a} \approx 4.6.$ I suppose at physiological $\mathrm{pH}$ and after ...
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1 vote
1 answer
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Comparing stability of 1,3-dioxolan-2-ide and 1,3-dithiolan-2-ide carbanions

I'd like to compare stability of 1,3-dioxolan-2-ide and 1,3-dithiolan-2-ide carbanions: I think there is no mesomeric or hyperconjugation effect and we should consider inductive effect. Oxygen is ...
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2 votes
1 answer
406 views

Complete mechanism of benzotriazole synthesis from o-phenylenediamine

Does my suggested mechanism for benzotriazole synthesis look correct? Are the arrows for the cyclization in the right place? Chemdoodle (which I drew this with) makes the curly arrows look a bit weird....
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3 votes
1 answer
109 views

Why is selenophene aromatic?

According to Wikipedia, The selenophene molecule is flat and aromatic. Being aromatic, it undergoes electrophilic substitution reactions at the 2- or 2,5-positions. These reactions are slower than ...
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3 votes
2 answers
138 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 ...
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2 votes
0 answers
38 views

Naftiridine hydrogenation

I was reading an article about the synthesis of 1,2,3,4 tetrahydronaphtyridine and I found this image. I don't understand why the major product of hydrogenation is the less substituted and not the ...
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4 votes
1 answer
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Regioselectivity in the opening of 3-membered heterocycles

(a) Consider the following reactions : For these two reactions, the nucleophile attacks the less substituted carbon as it is less sterically hindered. (b) Now consider the following reactions : For ...
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3 votes
1 answer
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What molecule is pictured on the cover of Dead Sara's album "Ain't It Tragic?"

An album released today by Dead Sara, titled Ain't It Tragic, has a chemical structure on the album cover. Here's a close-up of that structure: As the structure is partially obscured, it's difficult ...
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12 votes
2 answers
295 views

What is the reaction mechanism between acetophenone and ethyl phenylpropiolate to form a 2-pyrone?

I am looking for the mechanism of the following reaction (I believe it is a type of Michael reaction), which is in the textbook "Advanced Organic Chemistry Part B: Reaction and Synthesis" by ...
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12 votes
1 answer
595 views

Does folic acid contain a benzyl or a phenyl group?

I'm studying for my MCAT currently and I stumbled upon this question. It gives the structure of a folic acid molecule and asks what functional groups can be found within the molecule. I understand ...
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4 votes
3 answers
292 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 ...
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Comparing nucleophilic strengths of tetrahydropyran and (2R,6R)-2,6 dimethyltetrahydropyran

Compare the nucleophilic strengths of the following two compounds: According to me it should be the second one, that is, (2R,6R)-2,6-dimethyltetrahydropyran because the methyl groups would exert +I ...
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Which atoms in indole possess the greatest amount of electron density?

Presumably the amine acts as an electron donor, but that would suggest extra electron density of the adjacent carbons, making them more shield, which isn't seen in the results in the image below. ...
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-3 votes
1 answer
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What is the double bond equivalence of the following compound?

What is the double bond equivalence of the given compound? The given answer is 14 (8 pi electrons and 6 rings = 14 DBE). But why isn't the lone pair on nitrogen considered?? The lone pair on nitrogen ...
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1 vote
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What is the product of reaction between 2‐cyclobutyl‐2‐isopropyl‐1,3‐dioxane and hydrogen with Raney nickel?

I have 2‐cyclobutyl‐2‐isopropyl‐1,3‐dioxane (alcohol protection) and I have to react it with $\ce{H2}$ and Raney nickel, but I don't know what the product would be. I have seen a similar reaction ...
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0 answers
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Examples to show how useful or not useful of dimerization, trimerization, tetramerization and their likes in synthesizing alkenes and other compounds?

this answer shows that dimerization is a synthetic method On wikipedia, 1-octene is showed to made from numerous dimerizations or a tetramerization. When I read that piperazine $\ce{C4H10N2}$ is made ...
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1 answer
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How does NaOH modify pyranodioxins?

I am given the molecule in black which is treated with $\ce{NaOH}$. The product is in blue. Could someone explain the mechanism? All I have so far is that the $\ce{-OH}$ group on the bottom right ...
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3 votes
1 answer
203 views

Make pyridine from furfural

Furfural $(\ce{C5H4O2})$ has been used as a feedstock for synthesis. Furfurylamine $(\ce{C5H7NO})$ is made from furfural. Given that industrial manufacturing ammonia is matured, how about combining ...
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3 votes
1 answer
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How to carry out cyclization of 1‐(2‐methylbutyl)‐2‐nitrocyclohexane?

How the cyclization can take place as there is no other functional group than $\ce{NO2}?$ One way that I can think of is photochemical bromination which occurs selectively at tertiary center which ...
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8 votes
1 answer
141 views

What's special about the purine scaffold?

Purine is a remarkable substance, given Nature has chosen it as the scaffold for two nucleobases from DNA/RNA: adenine (A) and guanine (G). Its structure also appears in several other substances of ...
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Why is Tyrian purple called 6,6′-dibromoindigo?

If the two bromines are attached at opposite ends of the molecule, why are they both labelled with a 6? Also, why is 6,6′-dibromoindigo not called 1,1′-dibromoindigo if carbons in a ring are numbered ...
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4 votes
1 answer
143 views

Proton NMR splitting in 2-substituted furan

I have recently run proton NMR on 1-(furan-2-yl)ethan-1-ol I synthesised in the lab. My 400 MHz spectrum consists of the following peaks: 7.36 ppm (dd, J = 1.9, 0.9 Hz, 1H) 6.31 ppm (dd, J = 3.3, 1....
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3 votes
1 answer
521 views

Fischer indole synthesis: significance of choice of acid catalyst

Lately, as a matter of interest, I have been studying sigmatropic rearrangements. I came across the Fischer indole synthesis, whose Wikipedia article states: The Fischer indole synthesis is a ...
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5 votes
0 answers
82 views

Type of chirality in polycyclic compounds

Ignoring whether or not this molecule could exist, is there a name for this type of chirality? This molecule's mirror image cannot be superimposed on itself but there are no chiral centres. Even ...
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-1 votes
1 answer
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Pyridine: Protic or Aprotic

I know pyridine is a polar aprotic solvent (owing to a permanent dipole generated), but if acidified it forms pyridinium cation. So, does it then function as polar protic solvent?
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1 vote
1 answer
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Why is aniline more basic than pyrrole?

In a question asking to compare the basicity of pyrrole and aniline, the explanation given for aniline being more basic than pyrrole was as follows: Basicity depends on the availability of lone pair ...
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0 votes
1 answer
130 views

Why does magnesium bromide transfers from a carbon atom to nitrogen in piperidine?

In this reaction, why does $\ce{MgBr}$ goes to the $\ce{>NH}$ group and form a bond with nitrogen by removing $\ce{-H}$. Also where does the negative charge go?
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4 votes
2 answers
100 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
1 answer
200 views

Pyridine synthesis by tin(II) chloride reduction of 5-nitronorbornene

What is the reaction mechanism here? I guess the $\ce{SnCl2}$ reduces $\ce{NO2}$ to $\ce{NH2}$ but then what happens?
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6 votes
1 answer
3k views

Regioselectivity in Electrophilic Aromatic Substitution of Pyrrole and Indole

If we look into the structures of Pyrrole and Indole, they are very similar. Only Indole has one extra Benzene ring attached to it, i.e. if we attach one Benzene ring to Pyrrole, what we'll have is ...
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4 votes
1 answer
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Stubborn CuAAC reaction as derivatization for ESI-MS

Problem description I have a substance that is extremely non-polar and therefore does not ionize in the ESI source, which makes it impossible to quantify small amounts. The substance contains only two ...
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-1 votes
1 answer
772 views

Friedel-Crafts acylation of furan [closed]

Can furan undergo Friedel–Crafts acylation with benzoyl chloride? Some people say it will have no reaction. Is it true? If so, why cannot it undergo Friedel–Crafts acylation like other ketones?
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1 vote
0 answers
78 views

Can Diels-Alder reaction occur using reagents of Robinson annulation?

Robinson annulation seemed somewhat like the Diels-Alder reaction to me, if all ketonic groups were to be represented as enol then cyclohexanone would be like diene and the Michael acceptor as a ...
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3 votes
0 answers
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Metalation of thiophene

So lately I've been studying the concerted metalation-deprotonation of thiophene and I came to the conclusion that the alpha positions of thiophene are the most reactive, which is why one of those ...
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2 votes
0 answers
306 views

Reaction of diamines with carboxylic acids to form imidazole

I've recently came across this reaction and my guess is that firstly an amide forms that later reacts with the second amine group. Is this a general reaction? Does it matter if the compounds used are ...
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3 votes
1 answer
2k views

Comparing basic strength order of amines

In the above question I was asked to compare the basic strength order. So I did it like this: The Nitrogen in I and II will not participate in resonance so the only effect it could produce is ...
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2 votes
1 answer
325 views

Name of "the" benzodiazepine

Wikipedia has a thorough article on the benzodiazepines. Of course, it is written primarly from the pharmacological point of view; but there is also the "Chemistry" section, which includes the IUPAC ...
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1 vote
1 answer
265 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?
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1 vote
0 answers
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Favoured position in nitration of pyrrole [duplicate]

I try to figure out the preferred position of nitration (determine whether compound A or B is the major product) by looking at the resonance structures of the intermediate cation. The solution then ...
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16 votes
2 answers
435 views

What is the IUPAC preferred name of this tetracyclic natural product?

On page 819 of Vollhardt, Organic Chemistry 7th Ed., the following "subunit of the antibacterial platensimycin" appears. I have attempted to apply von Baeyer and skeletal replacement ('a') ...
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0 votes
1 answer
86 views

What is wrong in this reaction? [closed]

What is wrong in this reaction? I cannot find anything wrong, please help. Any hints would be appreciated.
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9 votes
3 answers
2k views

Why are carbons of Inositol chiral centers?

I was asked to draw all possible stereoisomers of inositol (1,2,3,4,5,6-cyclohexanehexol). To obtain the answer I had to assume that all six carbons of the molecule are asymmetric, which (bearing in ...
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5 votes
1 answer
997 views

What is the mechanism of azulene synthesis?

In the Organic Syntheses preparation of azulene (http://www.orgsyn.org/demo.aspx?prep=CV7P0015) there are two reactions. First is a clevage of the C-N bond in pyridine and the second one is the ...
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7 votes
0 answers
107 views

Exceptionally weak basicity of pyridine [duplicate]

It is often explained that the relatively lower basicity of pyridine, relative to most amines, is due to the fact that the $\ce {N}$ lone pair resides in an $\ce {sp^2}$ hybridised orbital, instead of ...
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1 vote
2 answers
126 views

How do dibromopyrazolones undergo base-promoted decomposition?

I was not sure but seeing the base as NaOH I used the fact that it will take most acidic hydrogen that is N-H and electron pair will come over it and it will resonate from two sides. I could make upto ...
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14 votes
1 answer
409 views

Are nucleophilic aromatic substitutions stepwise or concerted?

Recently, there has been a lot of discussion about nucleophilic aromatic substitution (SNAr) reactions apparently being concerted instead of stepwise (e.g. Krämer, K. Textbook aromatic substitution ...
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3 votes
0 answers
445 views

Reaction between Salicylaldehyde and 2-Benzoylpyridine

In a paper by Sheng et al (10.1016/j.dyepig.2018.07.036) the authors synthesize the compound MZC as shown in the scheme below. I'm looking for information about what the reaction mechanism is that ...
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