Questions tagged [organic-chemistry]

Use this tag for questions relating to organic molecules and their properties (structure of organic molecules, spectroscopic properties, reaction mechanisms, stereochemistry etc). DO NOT use this tag as the only tag in your question, as this tag by itself cannot appropriately classify your question. Always use this tag in addition to other more specific tags.

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Ambimodal transition states in some organic reaction pathways

In many computational studies, mechanisms appear to have so-called ambimodal transition states, i.e. a transition state which can lead to multiple products, in conflict to the common undergraduate ...
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Why is the endo product the major product in a Diels-Alder reaction?

I understand that the endo product is, at least in all cases in my textbook, the major product in a Diels-Alder reaction. However, I don't understand why this is the case. The explanation in my ...
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Why does a Diels–Alder reaction not occur here?

I have recently come across this organic chemistry problem. I thought it would undergo simple Diels–Alder reaction But it didn't turn out to be. The product to me looks like a nucleophilic attack ...
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156 views

Products formed on cleavage of epoxides using HI

There seems to be multiple forms of HI used to cleave epoxides: conc. HI, anhydrous HI, cold HI, hot HI, cold conc. HI, hot conc. HI, etc. So, does concentration of HI and temperature have any ...
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680 views

Explanation of the strength of phosphorus-oxygen bond

When discussing the Wittig reaction, Clayden's Organic Chemistry cites the strength of the $\ce{P=O}$ formed in triphenylphosphine oxide as a driver of the reaction through enthalpy: The $\ce{P=O}$ ...
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Tetrahedrane Properties and Analogs

I took a look into some tetrahedrane (C4H4) analogs, platonic hydrocarbon, basically very strained tetrahedral geometry at every carbon. I was wondering what will be the predicted delta H of ...
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128 views

Color of methoxy substituted phenyl rings when heated in the presence of acid

Anyone who's familiar with organic synthesis will probably have came across the DMB and PMB protecting groups. When TLC-ing compounds containing these protecting groups using common stains like ...
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555 views

Nucleophilicity with respect to the solvent

I am currently studying nucleophilicity of molecules and am getting a set of conflicting information, so I wanted to clarify nucleophilicity trends with respect to solvent. Master Organic Chemistry ...
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1answer
134 views

Electrophilic aromatic substitution of napthalene

It is known that the $\alpha$-position (or 1-position) for napthalene is the preferable position for substitution to occur at. However, I am getting two different explanations as to why this is the ...
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Does the alpha effect apply to third row elements?

Alkylperoxy anions are stronger nucleophiles than alkoxides (the so-called alpha effect), but would an alkyldisulfide anion be a better nucleophile than an alkylthiolate anion?
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Aza-enolates: why no reaction at N

My understanding is that aza-enolates have an advantage over enamines in enolate-type alkylations because the reaction at N is less likely. As a result, unactivated electrophiles can be used (i.e. ...
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Some materials emit more photoelectrons than others - why?

Again, I'm a physicist turning to chemists (so bear with me). So I've been measuring some materials by changing the wavelength of the incident light on the material and I have a detecting tip like in ...
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Synthesis of Anthracene: Mechanism

Recently, I happened to find a problem that involved the synthesis of anthracene from bromobenzene in the presence of tert-butyl lithium, using THF as the solvent, and at room temperature. I am ...
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Triplet oxygen ene reaction with enols

It is observed that whereas singlet oxygen is required for an ene reaction with an alkene to give an allyic hydroperoxide, triplet oxygen will react similarly with an enol to give an alpha-hydroperoxy ...
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158 views

Does a cationic 1,3-triphosphinane react with a methyl cation?

The question is: Reaction of $\ce{Et2P(CH2)3PEt2}\text{ with }\ce{PCl3}$ ($1:1$) in the presence of $\ce{SnCl2}$ gives a ring system A, which exhibits two phosporus NMR resonances, a doublet and a ...
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What is the difference between Fukui FMO approach and Woodward-Hoffmann rules?

If I understand correctly Frontier MO-theory is based on the perturbation theory of reactivity and the Woodward-Hoffmann rules consider conservation of orbital symmetry. Does FMO use symmetry ...
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639 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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417 views

Free Web-Based Orbital Solver to look into the Walsh orbitals of a perturbed cyclopropane

There exists a free online orbital calculator. When I draw cyclopropane it plots three molecular orbitals, but unfortunately it doesn't use the Walsh orbitals. Are there any free online tools which ...
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134 views

Justifying the tremendous -I effect of -[NMe₃]⁺ by molecular orbital theory

The $\ce{-[NMe3]+}$ group is ranked almost at the first position in the -I effect series, which is often given at the very beginning of the teaching of general organic chemistry. I know this can be ...
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How is the aromaticity in graphene different from the aromaticity in benzene?

The web page Aromaticity in Graphene and other 2-D Systems begins: I. Graphene While the σ-bonding in graphene is assumed to be a rigid honeycomb framework built out of two-center two-...
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What is the mechanism for this reaction?

The closest reaction I can find is Lossen rearrangement but in that hydroxyamic acid is first converted to its derivative but how will that be possible here? Moreover, even if I make an amine in this ...
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327 views

Why are two three-membered rings preferred to a single five-membered ring in the reaction of a dihalide with alcoholic KOH?

The given answer is 1,1-dicyclopropylmethanone: Step 1 is abstraction of acidic H by the strong base. Then, there's surely going to be anchimeric assistance. But there can be two places where the ...
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Protonating/basic site and Brønsted basicity orders of beta, gamma, and delta lactams

Consider the three cyclic amides: $\beta$-lactam $\gamma$-lactam $\delta$-lactam My question What is the basic site (site of protonation) for these three lactams? And what should be their Brønsted ...
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Birch reduction of anisole

Hepworth, Waring and Waring (2002) mentions that: In general, electron-withdrawing substituents make the arene more susceptible to reduction, while the opposite applies for electron-donating ...
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300 views

Why are lithium (Z)-enolates more stereoselective than (E)-enolates in aldol reactions?

In aldol reactions, it is apparently a general rule of thumb that (Z)-enolates give higher stereoselectivity (for the syn aldol product) than (E)-enolates do for the anti product. Quoting Carey & ...
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Why can't I dry/concentrate ethanol using calcium chloride … or can I?

My (very unreliable) school textbook tells me: Lower alcohols form a solid derivative with certain metal salts. and, It is for this reason that ethanol cannot be dried/concentrated using ...
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1answer
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Role of methanol in NaBH4 reduction

In reduction of carbonyls (aldehyde and ketones) to alcohols using NaBH4/Methanol, alkoxides are formed with the Boron which usually gets protonated on addition of water/acid. My question is what is ...
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260 views

Sulfonyl azides: diazo or azide transfer?

Sulfonyl azides, $\ce{RSO2N3}$, are capable of acting as sources of electrophilic azide ("$\ce{N+3}$"), but are also capable of effecting diazo transfer, as shown in the scheme below, taken from ref 1:...
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147 views

Where is bifurcation situated on cyclohexane isomerisation PES?

I am wondering what does PES for cyclohexane isomerisation looks like. I have two possibilities in mind but each has some kind of vagueness. 1) Starting from boat conformation minimum, followed by ...
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Mechanism for an Étard reaction (chromium complex)

In the following reaction, a chromium complex is formed during the Étard reaction: I have the following questions: How is this complex formed? How does its hydrolysis take place? (What's the ...
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Stereoselectivity of 1,3-dipolar cycloadditions

How do the 1,3-dipolar cycloadditions follow the endo rule as in the reaction below, where the anti diastereoisomer is formed predominantly?
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Grubbs, Wittig & hydroboration reactions and Woodward-Hoffmann rules

Several organic mechanisms I know involve [2+2] cycloadditions and retro-[2+2] cycloadditions, namely: The Wittig reaction Hydroboration of an alkene Olefin metathesis (using Grubbs' catalyst) How ...
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What is the hybridization state of the carbon atoms in [10]annulene?

I know that one of the more stable structures of [10]annulene or cyclodecapentaene is planar boat-shaped. But that means the hybridization state of the carbons must have changed to suit the geometry. ...
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The Action of Nitrogen Iodide on Methyl Ketones

I recently encountered two old publications on action of nitrogen iodide on various compounds (Ref.1 and Ref.2). Between them, Ref.1 described the idoform formation by methyl ketones upon treatment of ...
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Is the 9H-fluoren-9-ylium cation aromatic?

In this cation, there are two individual benzene rings which are aromatic. But in the entire π system, there are 12 π-electrons which should make it antiromatic. Which is correct?
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Selectivity in aldol condensation of 7-oxo(6,6-²H₂)octanal

I am supposed to find the product of the following reaction: I know that six-membered rings are more stable than five-membered rings, but the C-D bonds are stronger, so it confuses me where will the ...
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How can I solve this synthesis?

I have this task to do: My solution: Is that possible? Can you please help me with the steps 2 and 3? This is what I did, but my teacher told me I should make the diketone (compound no. 5) from ...
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Green colour resulting from the formation of pi complex

Peter Sykes mentions in Guidebook to Mechanism in Organic Chemistry (6th ed.) on p.132 that there would significant differences in physical properties of the resultant mixture when we: React ...
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How can organocuprates generated with catalytic Cu(I) be competitive in 1,4-addition to an enone?

Organocopper compounds (e.g. $\ce{LiCuR_2}$) are often prepared from an organolithium or Grignard reagent when a soften nucleophile is needed, such as for a conjugate addition to an $\alpha,\beta$-...
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Finding the wavelength of maximum absorption of Tartrazine using Fieser-Kuhn

How would you use Fieser-Kuhn rules to calculate the wavelength of maximum absorption for tartrazine? Fieser-Kuhn rules states that: $\lambda_{max}=114+5M+n(48-1.7n)-16.5\ R_{endo} - 10\ R_{exo}$ ...
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Effect of Zn dust reduction of phenolic -OH group on other groups

We use distillation with zinc dust to remove -OH group from phenol. $$\ce{Ph-OH + Zn \rightarrow Ph-H + ZnO }$$ What I want to know is that whether this reaction has any effect on other groups ...
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Why does magnesium prefer to insert into C–Br bonds over C–Cl bonds?

In the formation of a Grignard reagent from a compound possessing both bromine and chlorine, magnesium preferentially inserts into the C–Br bond over the C–Cl bond. For example, the formation of a ...
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Which of the five conformers of propyl propanoate is most stable?

I've worked out five different conformations of propyl propanoate: I think the bisected conformations (E) should be the most stable one. Are my rationals and suggestions in my scheme correct?
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567 views

Nucleophilic aromatic substitution on pyrimidines: C2 vs C4 selectivity

[There are many similar questions on Chemistry.SE (e.g. 1, 2) and a quick search will reveal all of them, but nothing on this in particular.] The reaction of 2,4-halopyrimidines with nucleophiles ...
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Can you use a photon's torque to change a molecule?

Can you use the torque of a photon to change bond angles, etc.? 11-Cis-Retinal to the all trans version, in the eye, is a good illustration [1]. Note: This phenomenon can be observed by closing ...
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Is there a reliable chemical theory that predicts pKa based on structure?

Obviously, there are general stability arguments that can be made to estimate relative pKas, such as evaluating the stability of the conjugate base of an acid, or thinking about how polarized the bond ...
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1answer
71 views

Can I make a mirror on PET plastic using Tollen's reaction?

I want to make a very shiny surface, like a mirror. I tried to use chrome paint but it's barely shiny. It's more like gray even though I bought one of the most expensive crom looking paint. I know ...
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Mechanism for Friedel-Crafts Acylation in Synthesis of Sertraline

In the first step of the synthesis of Sertraline, aluminium chloride catalyst was used in a Friedel-Craft's reaction to give the following product. My question is how does the exact mechanism work? 1-...
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Role of pH in azo C-coupling reaction, continued

In the question, "What is the role of pH in azo coupling reaction of diazonium with phenol and aniline?" asked by @DhrubaBanerjee and answered by @Klaus-DieterWarzecha, I find several ends untied. I ...
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Bredt's rule applied to fused bicyclic systems

Ultimate question: Is Bredt's rule equally valid for fused bicyclic system (no bridgehead alkenes without a ring 8 carbons or more), but for other reasons (historical?) it is only defined as applying ...