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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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376 views

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 ...
15
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0answers
325 views

How does the cyclopropyl group influence conjugation and aromaticity?

While answering the question Why isn't cyclobutane planar?, I recollected that cyclopropane and its derivatives behave like double-bond compounds, e.g. a cyclopropyl group can potentially be ...
13
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688 views

Neighbouring group participation with and without retention of configuration in nucleophilic substitution of 2,6-dichloro-9-thiabicyclo[3.3.1]nonane

Treatment of the dichloride A under the conditions indicated gives B with retention of configuration, while treatment of dichloride C gives D with inversion of configuration. I am having ...
11
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0answers
95 views

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 ...
10
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0answers
122 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 ...
10
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0answers
165 views

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 ...
10
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0answers
126 views

Possibility of π–π stacking in non-aromatic systems

Is it possible to have π–π stacking for non-conjugated double bond systems? For example, can the carbonyl groups of two urea molecules participate in π–π stacking? Although urea prefers to stay in ...
10
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0answers
151 views

Obtaining activity coefficients of conjugate acids of some common carboxylic acid molecules

Recently, I have been wondering about justifying the notion on how some common acids (e.g. carboxylic acids) are themselves weaker bases than water to the point that we don't usually consider them to ...
10
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0answers
114 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 ...
10
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0answers
18k views

Reaction of phenol with Zinc dust

I have seen this reaction many times: $\text {Phenol}+\text{Zn}\ce {->}\text{Benzene}+\text{ZnO} $ But what is the mechanism?! Tried a lot but couldn't cook up one... Thanks for any help...
9
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0answers
48 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 $\ce{P=O}$ ...
9
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0answers
136 views

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 ...
9
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0answers
131 views

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. ...
9
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0answers
91 views

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 ...
9
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0answers
1k views

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 ...
9
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0answers
151 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 ...
9
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0answers
776 views

Nucleophilicity/basicity in protic and aprotic solvents

In polar aprotic solvent, why is $\ce{F-}$ a stronger nucleophile than $\ce{I-}$? What I think: If I talk about their basicity, $\ce{F-}$ would be more basic due to instability from its high electron ...
9
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0answers
164 views

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 ...
9
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0answers
366 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 ...
8
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0answers
547 views

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 ...
8
votes
0answers
247 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 & ...
8
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0answers
1k views

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 ...
8
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0answers
192 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:...
8
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0answers
131 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 ...
8
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0answers
243 views

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 ...
7
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0answers
69 views

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?
7
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0answers
69 views

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 ...
7
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0answers
253 views

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: $\lambda_{max}=114+5M+n(48-1.7n)-16.5\ R_{endo} - 10\ R_{exo}$ ...
7
votes
0answers
1k views

Product of Friedel-Crafts cyclisation of (3-methylpent-4-en-1-yl)benzene

My proposed mechanism and final product is: But the book says the answer is: I know that a 6 membered ring is more stable than a 5 membered ring so I made the product with the 6 membered ring (...
7
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0answers
366 views

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 ...
7
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0answers
127 views

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?
6
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0answers
126 views

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 ...
6
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0answers
75 views

The effect of the groups at para position on SN2 reactivity

Compare the SN2 reactivity order for: The benzyl group stabilises the transition state of SN2 reaction using the π system of the benzene ring for conjugation with the p- orbital of the ...
6
votes
0answers
345 views

SN1 reactivity order for chloromethyl methyl ether and trityl chloride

Compare the reactivity order towards SN1 reaction for: (2-chloropropan-2-yl)cyclopropane $\ce{CH3OCH2Cl}$ $\ce{Ph3CCl}$ Owing to the exceptional stability of cyclopropyl ethyl ...
6
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0answers
72 views

Compare rate of hydrohalogenation between 1,2-diphenylethene and 1-phenylpropene

Consider the compounds, (I) - 1,2-diphenylethene and (II) - 1-phenylpropene. Compare their rate of hydrohalogenation (HX addition) I feel that the answer should be (II) > (I), but to my surprise it's ...
6
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0answers
210 views

Why does acetonitrile have a larger dipole moment and boiling point than acetaldehyde?

Experimentally, acetonitrile has a larger dipole moment than acetaldehyde, but I've never understood why. I always thought that the charge separation between carbon/oxygen is larger than that of ...
6
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0answers
513 views

Is hydronium an electrophile, nucleophile, both or neither?

Is hydronium an electrophile or a nucleophile? I expected $\ce{H3O+}$ to be a nucleophile due to the presence of electrons in the $\ce{2p}$ orbitals of $\ce{O}$. But the answer key of the test states ...
6
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0answers
46 views

How can organocuprates generated with catalytic Cu(I) be competitive in 1,4-addition to an enone?

Organocoppper 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 $\alpha,\beta$-...
6
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0answers
407 views

Why does phenol react on oxygen in the Gattermann–Koch reaction?

When discussing the Gattermann–Koch reaction on phenol substrates, it has been said that O-acylation is a problematic competing reaction as in a phenol, there's high electron density on the O atom [...
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0answers
445 views

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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0answers
44 views

Using Ethylene Glycol as anti-freeze in a biodigester gas storage system

I am busy building a bio-digester to produce biogas for cooking / water heating in a cold climate. I am using the 3 IBC tank solution. Tank 1 is the digester itself. Tank 2 is the gas storage unit. ...
6
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0answers
58 views

Colour of polytetrafluorethylene

Why are teflon coated dishes black or dark grey in colour when teflon as such is white (and the underlying aluminum is not black either)?
6
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0answers
62 views

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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0answers
352 views

Treatment of ketones with excess Tebbe reagent

The reaction in black below was presented in a set of lecture notes as an example of the use of the Tebbe reagent, however it's not immediately obvious (to me, at least) that the product should be the ...
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0answers
162 views

Reaction of fumaric acid and performic acid

Performic acid ($\ce{CH2O3}$) has strong oxidizing properties. So when it reacts with fumaric acid, is this the product (2,3-dihydroxybutanedioic acid) that I should expect?
6
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0answers
333 views

Do both NH2 groups in semicarbazide have the same properties?

Would it be correct to consider both the hydrazine and amide $\ce{-NH2}$ groups in semicarbazide (hydrazinecarboxamide) as derivatives of ammonia? I thought about this possibility while writing the ...
6
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0answers
582 views

Mixing naphthalene, formaldehyde and sulfuric acid (Marquis reagent + naphthalene)

Excuse me if this a dumb question but it has haunted me for years. Back in my old school days I mixed naphthalene, formaldehyde and sulfuric acid in a mad attempt to make $\mbox{2-Methoxynaphthalene}$...
6
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0answers
380 views

How big is the gauche interaction of methyl with phenyl in a disubstituted cyclohexane?

I'd like to compare the equatorial 1-methyl-2-phenylcyclohexane conformation of with axial conformation of 1-chloro-3-methylcyclohexane conformation. In which molecule there is less steric repulsion? ...
6
votes
0answers
252 views

Lemieux-Johnson oxidation on cycles

Consider 5-cyano-2,2-dimethylpentyl 4-methylbenzene-1-sulfonate: What would it yield by a Lemieux-Johonson oxydation ($\ce{OsO4}$, $\ce{NaIO4}$)? My first guess would have been that $\ce{OsO4}$ was ...
6
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0answers
61 views

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?