Questions tagged [reaction-mechanism]

The detailed (and as complete as possible) description of plausible or observable pathways leading from reactants to products of a chemical process. This tag should be applied to questions about these processes. It may be applied to hypothetical and/or proposed mechanisms.

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1answer
185 views

How to explain the selectivity between methanol and methanethiol in an SN1 reaction with an halogenated hydrocarbon?

Consider the SN1 reaction shown below: Would different products be formed if $\ce{CH3SH}$ was an additional reagent? Superimpose both energy diagrams on top of each other. For ...
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1answer
623 views

SN1, SN2 or acid-base reaction

I am asked to give the type of reaction (SN1, SN2 or acid-base reaction) for the following reactions. I know that both $\ce{MeOH}$ and $\ce{EtOH}$ polar protic solvents, so because the first is an SN2 ...
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0answers
481 views

Comparison of the rate of SN1 and SN2 reaction

It is known that $\mathrm{S_N1}$ (Substitution Nucleophilic Unimolecular) follows the order of rate of reaction: Tertiary ($3^\circ$) > Secondary ($2^\circ$) > Primary ($1^\circ$) For $\mathrm{...
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Hoffmann's rearrangement

In Hoffmann's rearrangement of acid amide...the OH from the basic medium attacked the H ..now my question is...isn't the carbonyl carbon more acidic as it's surrounded by 2 electronegative elements?
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1answer
231 views

How can weaker nucleophiles kick out stronger ones in the reaction of chloroalkanes with sodium iodide in acetone?

I have the following SN2 reaction, in an acetone: 1,4-dichlorohexane (1 mol) reacting with NaI (1 mol) to form 4-chloro-1-iodohexane and NaCl. However, chloride ions are stronger nucleophiles than ...
2
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1answer
948 views

Oxidation of cycloalkenes

Non-cyclic alkenes can be oxidized to carboxylic acids in presence of hot alkaline $\ce{KMnO4}$ and quenched with dilute $\ce{H2SO4}$ to form carboxylic acids. I suddenly got a thought. Can ...
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2answers
361 views

mechanism of mechanically triggered explosion [duplicate]

There are several well known explosives which can be mechanically triggered. I am curious about the mechanism of such a reaction, though. I guess one can give an easy answer when the explosive is ...
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3answers
16k views

C + O2 is equal to C + O, how is that possible

C + O = CO2 . This is because carbon has valency of 4 while oxygen has valency of 2. When they react the valencies are criss crossed which means we will get C2O4 but this is simplified to CO2. But ...
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1answer
9k views

Mechanism for decarboxylation

Propose a mechanism for the following transformation. I gather that this mechanism might be similar to decarboxylation of keto acids: However, I am unsure of how to begin.
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1answer
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Clarifications about the mechanism of the Wittig reaction [closed]

Ok so this is the proposed mechanism for the Wittig Reaction as stated by my textbook, LG Wade. I have some doubts regarding this mechanism: 1) Why is only triphenyl phosphine used here? Why not ...
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4answers
8k views

Will this beta-branched secondary alkyl halide undergo SN1 or SN2?

What is the correct mechanism here? Would SN1 occur here? I chose SN2 because we have a secondary alkyl halide with a weak base $\ce{CN-}$. However, the solution says SN1 is major. Can you explain ...
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1answer
7k views

Why would sulfuric acid turn gray/black?

About 2 years ago I purchased 2 liters of 98% concentrated sulfuric acid. It's in a standard poly bottle with leakproof lids, and originally was clear. Recently I noticed the acids have turned a dark ...
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1answer
535 views

What are the key chemical characteristics that determine the octane rating of fuel?

The octane rating of petrol (gasoline) is a measure of the how much compression a fuel air mixture can have before detonating (which in petrol engines is a bad thing as you want the mix to combust ...
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1answer
10k views

Mechanism for chloromethylation of benzene with formaldehyde and HCl

What is the mechanism of the above reaction? I have thought of one possibility: Would this work? How exactly is the chlorine installed on the alkyl chain?
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3answers
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Does Wurtz reaction follow an ionic mechanism or a free radical mechanism?

In a Wurtz reaction, is the intermediate formed a carbanion or a free radical. And if can assume both mechanisms to be true, how can we decide the reactivity of a tertiary halide?
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1answer
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How does HF dissolve glass?

By what mechanism does HF proceed in dissolving glass? Why is it the only acid that has this capability? Is it because of the small size and high electronegativity of fluorine?
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4answers
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What is the reaction between Magnesium chloride and Sodium bicarbonate?

For some reason it has been very difficult to find the right answer for this question as there's so much conflicting information to be found online. Some mention a reaction where carbonic acid is made,...
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1answer
139 views

Significance of Proton Tunneling

It has been repeatedly emphasized that proton transfers "involving" three or four membered ring transition states are not favorable and should not be drawn as the primary mechanism for any reaction. ...
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2answers
2k views

How does SO2Cl2 react with alcohols?

Is the mechanism similar to the reaction of $\ce{SOCl2}$ with alcohols? If not, then how is it different? We have been taught about the latter at school but my friend quizzed me about $\ce{SO2Cl2}$. ...
7
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1answer
368 views

Mechanism for bromoetherification of olefinic alcohol

Propose a mechanism for the following reaction showing the relevant stereochemistry of intermediates and the final product. I am confused as to what is going on here. I guess there's some sort ...
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2answers
6k views

Why does the reduction of a Weinreb amide give an aldehyde instead of an amine?

The reduction of a regular amide with $\ce{LiAlH4}$ yields an amine. However, with a Weinreb amide, the product is an aldehyde. How can this be justified? I can't find the mechanism for the Weinreb ...
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2answers
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What is an example of a very low temperature endothermic reaction?

Shakashiri describes the reaction of solid Ammonium Thiocyanate and solid Barium Hydroxide Octahydrate resulting in an endothermic reaction leading to subzero temperatures. I've performed this ...
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1answer
901 views

Mechanism for conversion of ketone to dichloride with phosphorus pentachloride

I would like to know the mechanism of this reaction leading to the formation of a geminal dichloride. I am unable to predict how the $\ce{C=O}$ breaks and how the 2 $\ce{Cl}$ atoms replace the oxygen ...
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1answer
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Nitrosation of benzene

How does benzene react with $\ce{NaNO2/HCl}$? Will $\ce{PhNO}$ be obtained? I read that pyridine can be produced under special conditions, but what will happen in some less exotic conditions?
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2answers
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Why is a strong base needed for an E2 reaction and not a an E1 reaction?

For E2 reactions, why is a strong base like $\ce{NaOH}$ or $\ce{RONa}$ needed? Whereas for E1, even a weak base like $\ce{H2O}$ could be used. Wikipedia states: E2 typically uses a strong base, ...
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1answer
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Mechanism of synthesis of allene

I would like to know the mechanism of this reaction. In my first attempt to the question, I had replaced the two $\ce{Br}$s by $\ce{CH3}$s by $\ce{S_N2}$ of the organometallic compound but the answer ...
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2answers
954 views

Claisen Condensation to Ketone

Can someone explain (and preferably draw) the intermediates of this reaction? I understand that it is a Claisen Reaction, and likely a condensation due to the heat, but I am not sure why there isn't ...
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1answer
431 views

Benzene from cyclopropane-1,2,3-triyltrimethanol in acidic medium

What is the mechanism of this reaction? After performing $\ce{E1}$ thrice I was expecting 1,2,3-trimethylidenecyclopropane to be formed instead. I know it's highly strained but I couldn't adopt any ...
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3answers
418 views

Making three membered ring using different reactants

I am struggling with the above question. It will be the conjugate base of trichloromethane that is involved. The same is true of the carboxylate. However, I have no idea about the reaction mechanisms. ...
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1answer
214 views

Facial selectivity of iodonium formation in an iodolactonisation

I am trying to understand the stereochemistry of iodolactonisation of this cyclohexene. I can't work out if the iodonium ion would form on top or the bottom. There is $\ce{CH2COO-}$ and $\ce{Me}$ ...
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1answer
6k views

Selectivity in aldol condensation between pivaldehyde and acetone

In a crossed aldol condensation (condensation between aldehyde and a ketone), the primary products are such, that the carbonyl group of the ketone remains intact, and the $\alpha$-hydrogen of ketone ...
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1answer
2k views

Cleavage of Ethers

Very confused by this video I stumbled across describing the cleavage of ethers with strong acids: From what I can gather, the cleavage of ethers is run in aqueous strong acids such as HI or HBr. ...
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1answer
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Elimination from Vinylic Halides

Vinylic halides do not show nucleophilic substitution at all, because of their stability due to resonance. But elimination to form alkynes is possible. No nucleophile at all can displace the halide ...
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1answer
379 views

Regioselectivity in Claisen condensation and aldol reaction

I'm having a hard time determining regio-selectivity in those two reactions. At the image above I've drawn one example for each on of them. My question is how do we choose where the deprotonation ...
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1answer
3k views

Are all esterification reactions reversible? What is their general mechanism?

For example the reaction of ethanoic acid with ethanol is reversible, however is this true for all esters? I'm not quite whether it is as easy for a reversible reaction to occur both ways. Is there a ...
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2answers
982 views

A few questions about the conditions of the Diels Alder Reactions

I'm attempting to extract the diels alder reaction into a generic reaction and am trying to gain a better understanding of it. Can a conjugated diene react with another conjugated diene via the diels ...
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2answers
579 views

Is the compound CH2(OH)(ONa) possible?

I was just pondering about the reaction mechanism of Cannizzaro reaction. $\ce{H2C^{+}-O- + OH- -> H2C(OH)O-}$ $\ce{HCHO + H2C(OH)O- -> H3CO- + HCOOH}$ $\ce{H3CO- + HCOOH -> HCOO- + H3COH}$...
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1answer
5k views

What are the roles of pyridine and DCM in the acylation of an alcohol?

What role does pyridine and $\ce{CH2Cl2}$ play in this reaction? (Prior to this step, the corresponding carboxylic acid was converted to the acyl chloride using DMF, oxalyl chloride, and DCM.) This ...
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1answer
211 views

Are there natural conditions that could enable the formation of noble gas compounds?

Noble gases were considered to be inert until compounds that include them, such as xenon trioxide (as an example) were found. My question is, what natural conditions allow the formation of noble gas ...
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1answer
413 views

Is there a relation between the ionization energy and the electron affinity?

I am aware of the definition and equation of IE and EA. I was wondering if there is a direct relation between this two quantities with the energy of the neutral specie.
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2answers
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Why does the rate-determining step determine the overall rate of reaction?

I can appreciate that the rate determining step affects the rate of reaction. What I take issue with however is the exact wording given in the definition of the RDS. From here: The rate ...
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0answers
934 views

Does the addition of chlorine to carbon-carbon double bonds proceed through a halonium ion?

I need some serious help with the mechanism of ionic addition, both my textbook and my teacher are at odds with internet videos (khan academy) which both seem to be at odds with quote, "recent ...
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1answer
1k views

What is trans-addition?

A question from JEE-Advanced(2017) : Bromination of both Z-but-2ene and E-but-2-ene involve syn and anti addition. So, there would be 4 products as suggested in the question. But, I don't ...
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1answer
2k views

Reactions in the presence of sunlight

Some reactions in my textbook specify the need for the presence of sunlight, eg-photolytic decomposition of silver bromide and substitution reaction of methane with chlorine. What is going on in ...
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1answer
379 views

Which of these reduction reagents would me most appropriate to yield this product?

I am very confused, I think using reduction would be a good start, but LiAl would go straight to an OH.
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2answers
2k views

Why does carbocation stability increase in the order 1°, 2°, 3°?

I'm reading about $\:\mathrm{S_N1}$ and $\:\mathrm{S_N2}$ reaction mechanisms. 1° carbocations are unstable to the point of not having been observed in solution, ever. 2° are more stable, and 3° ...
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1answer
1k views

Why must the leaving group in E1cb be poor?

Typically the leaving group for E1cb is poor (like -OH or -OR) but why must this be the case? The substrate appears in the rate equation so surely a good leaving group would be beneficial?
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1answer
2k views

Dehydrobromination of 3-bromo-3-cyclopentylhexane and number of possible alkene products

I faced a question like this: The total number of alkene products possible from the dehydrobromination of 3-bromo-3-cyclopentylhexane is: The answer is given 5. But I only found 3. 3-...
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1answer
655 views

Can grignard reagent contain secondary amino group?

Is there any reason why this grignard reagent wouldn't work? My best guess is that perhaps the nitrogen could act as a second nucleophilic "head", thereby not giving a good yield on the intended ...
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1answer
286 views

Allylic Radicals Bromination Mechanism

For (a) (iii), how do you get the second product listed in the answers manual? I just can't visualize it. What about (c) (i), why are there three resonance structures? If a hydrogen is taken away ...