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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16
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6answers
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Will bridged compounds the undergo SN1 reaction?

$\mathrm{S}_{\mathrm{N}}1$ reaction involves only one molecule in the rate determining step. So, the molecule which undergoes $\mathrm{S}_{\mathrm{N}}1$ reaction should be stable when it forms a ...
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3answers
894 views

Are carbocations that bad?

My professor has an anti-fetish for carbocations. In any mechanism that we draw with a carbocation, the maximum earnable credit is automatically halved. In any case, he draws all mechanisms involving ...
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What is the mechanism of the reaction between hexane-2,5-dione and nitrous acid?

I don't understand the mechanism of the first reaction; I tried different ways but I can usually find how to make the ring without the double bonds, but it's obviously not the right thing; I think ...
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Designing a theoretical synthesis of methamphetamine from phenylpropyne

I am asked to synthesize "methamphetamine." Note that there is no configuration designated for this molecule, and methamphetamine refers to a very specific configuration. In any case, here are the ...
16
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3answers
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Selective nitro reduction of poly nitro compounds

Is there any way through which I could selectively reduce one $\ce{NO2}$ group from a dinitro- or trinitro- compound to an amine. I was reading Solomons and Frhyle and it says that m-dinitrobenzene ...
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Why is pyridine used when making tosyl esters from alcohols?

Tosyl chloride is used to make a hydroxyl group into a better leaving group. However, when the reaction of tosyl chloride and an alcohol occurs, a weak base such as pyridine should be used. Why?
15
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1answer
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Why do BH3 and NaBH4 have different selectivities?

I've always known borane ($\ce{BH3}$), as a reagent for alkene hydroboration. Recently in class we talked about its use in the reduction of carboxylic acids to alcohols as well. Now obviously $\ce{...
15
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1answer
594 views

ICHO Synthesis Problem 2018

I've several doubts about this ICHO synthesis problem, which was a part of the preparatory problem package of 2018 (so yes, it's not a part of an ongoing contest) Before sharing the answer given, I'...
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2answers
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Reaction of alcohols with PCl5 and PCl3

The reaction of alcohols $\ce{ ROH }$ with $\ce{ PCl5 }$ and $\ce{ PCl3 }$ yields an alkyl halide $\ce{RCl}.$ With $\ce{ PCl5 }$, the reaction is quite simple leading to the formation of $\ce{ RCl }$ ...
15
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1answer
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By what mechanism do acids deprotect primary silyl ethers?

Standard protocols report the selective deprotection of primary silyl ethers in the presence of secondary silyl ethers under acidic conditions, as exemplary shown in scheme 1, a reaction by Hartmann ...
15
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1answer
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Acid catalysed synthesis of ethyl ethoxymethylenemalonate

One synthesis of quinolones begins with the formation of an ethyl ethoxymethylenemalonate, as seen in this Organic Syntheses paper. I've been asked if the malonate derivative would be formed if ...
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1answer
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Reduction of carboxylic acids by LiAlH4

I've read that when a carboxylic acid reacts with $\ce{LiAlH4}$ the corresponding alcohol is formed: But when I try to think of the mechanism, I get stuck here: $\ce{LiAlH4}$ produces $\ce{H-}$. ...
15
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1answer
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What is the mechanism of APTES mono-layer formation on glass substrates?

The reagent APTES is a fairly common "ink" for microcontact printing, a technique that forms covalent bonds between the silanols found on the surface of the glass and the silane in the the APTES. It's ...
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372 views

Would the carbocation intermediate undergo rearrangement?

I have my concerns regarding option (a) in this question. During the dehydration step, wouldn't the resulting carbocation intermediate formed in option (a) rearrange? That is, the ring should ...
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2answers
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Exocyclic vs. endocyclic double bonds in E1 elimination

What will be the major product of this elimination reaction? The exocyclic product has more substituent groups on the alkene which should make it more stable but I have heard that exocyclic alkenes ...
15
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1answer
506 views

Mechanism of dehydrogenation with nosylate

What is the mechanism of the attached reaction? How could nosylate do the dehydrogenate the species? The reaction is from this synthesis (46th IChO preparatory problem 26):
15
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1answer
908 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 ...
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2answers
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Are children's sparklers based on a magnesium reaction?

We were letting our kids play with sparklers on New Year's Eve, and my friend's son asked his Dad: What would happen if we threw the sparkler into the water? Would it keep burning under water. My ...
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3answers
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Difference between intermediates and transition states

Can someone please explain what exactly the difference between an intermediate and a transition state is? I understand that they are formed as part of the process in converting the reactants to ...
14
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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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3answers
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Reaction mechanism of combustion of hydrogen

After a discussion about the usefulness of hydrogen fuel for cars with a friend of mine, I wondered what the reaction mechanism for combustion of $\ce{H2}$ was. I only study (well almost) organic ...
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1answer
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Mechanism for basic hydrolysis of α-chloronitrile to ketone?

In Corey's 1969 prostaglandin synthesis,1 compound 2 is formed from compound 1 by: [...] treatment with 2.5 equiv of potassium hydroxide (added as a hot saturated aqueous solution) in dimethyl ...
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1answer
543 views

Reaction of substituted furan with methyl vinyl ketone with subsequent rearomatisation

I am supposed to provide a mechanism for the above transformation. I observed that the order of substituents on the product is same as that on furan, and since furan undergoes Diels–Alder reactions, I ...
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1answer
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How are $\sigma$ and $\sigma^\pm$ determined in Hammett plots?

The Hammett plot is commonly invoked in organic chemistry to reason about the plausibility (or implausibility) of various reaction mechanisms. The vertical axis is essentially the logarithm of an ...
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1answer
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How can a group be both a good nucleophile and a good leaving group?

I'm reading about $\:\mathrm{S_N1}$ and $\:\mathrm{S_N2}$ reaction mechanisms, and I have a few questions. My book has a couple of tables, one lists a bunch of substances grouped as good, moderate ...
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1answer
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Reaction of furan with chloroform in base

This reaction looks like the Riemer-Tiemann reaction. The only difference is the reactant. First step is the formation of carbene. Second step involves the attack of π-electrons of furan on the vacant ...
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1answer
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Why does Mg react vigorously in NaCl solution and less so in water?

When you put $\ce{Mg}$ into water a few $\ce{H2}$ bubbles appear. But when you put $\ce{Mg}$ into a $\ce{NaCl}$ solution there is a vigorous release of $\ce{H2}$, why is this and what reactions are ...
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2answers
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Reduction of glucose to hexane with hydroiodic acid

My book (NCERT India) states that n-hexane is formed when glucose is heated in the presence of hydrogen iodide. That is, the following reaction takes place: $$\ce{C6H12O6 + HI ->[{\Delta}] C6H14}$$ ...
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2answers
147 views

Mechanism of a Gold catalyzed organometallic reaction: Confusion regarding the last step

I needed to draw the reaction mechanism for this reaction: So, after consulting some literature I drew this mechanism: But, I am not sure about the last step. Does the $\ce{H+}$ just substitute the $...
14
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1answer
482 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 ...
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4answers
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Which chemical properties make a substance explosive?

I know that some chemical substances are used as explosives. Amongst the most famous nitroglycerin in dynamite and cyclonite in C-4. Which chemical properties (I suspect that physical properties have ...
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2answers
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Mechanism of formation of 2-naphthol red dye (aka Sudan 1)

As you can see in the image diazonium can attack at 2 different positions to form different products then why only the first product is correct? As there are two ortho positions available why does it ...
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HI/P reduction mechanism

I recently answered a question about Breaking Bad's initial methamphetamine production method (i.e. the reduction of (pseudo)ephedrine). The reaction is as follows: (Source) It is infamously known ...
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1answer
12k views

Difference between nickel catalyst and Raney nickel catalyst

Many times I have seen the catalyst as Raney nickel instead of nickel catalyst. Raney nickel catalyst is developed by Murray Raney, and I think Raney nickel catalyst and nickel catalyst are two ...
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2answers
426 views

Mechanism of initiation in contact explosives?

It's well known that undiluted nitroglycerin will explode when subjected to a physical shock. What is happening as a result of the physical shock that sets off the explosive reaction? In particular, ...
13
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1answer
487 views

Base catalyzed rearrangement of an alkyl substituted cyclopent-2-enone

I have been asked to provide a mechanism for the following transformation: I don't see any viable way to make this happen. All I can see that is possible is the formation of an acetal or a Michael ...
13
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1answer
2k views

Are compounds containing active methylene groups positive for the haloform test?

Are compounds containing active methylene groups (e.g. 1,3-diketones) positive for the haloform test? Support your answer with a suitable explanation. I was stuck on a certain question wherein a ...
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2answers
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What is the mechanism of the Clemmensen reduction?

I have learned that we can reduce a ketone to an alkane using the Clemmensen reduction, where we treat the ketone with amalgamated zinc in the presence of $\ce{HCl}$. My book didn't mention the ...
13
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1answer
416 views

Rearrangement of a bicyclic dienone under acidic conditions

Find the major product of the following reaction. Attempt: First step would be the formation of oxonium ion. After that, there are two possibilities. Either the upper double bond or the lower bond ...
13
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1answer
196 views

Mechanism for palladium-catalysed spirocyclisation of conjugated diene

I'm trying to work out the catalytic cycle for the following process: I gather that the palladium will be reduced from Pd(II) to Pd(0) in the process and that the 1,4-benzoquinone is a redoxidant. ...
13
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1answer
364 views

Stereoelectronic effects in carbamate carbonyl oxygen attack on halide

2-Bromoethyl (2-bromoethyl)carbamate can react through either Path A or Path B to form salt 1 or salt 2. In both instances the carbonyl oxygen functions as the nucleophile in an intramolecular ...
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1answer
264 views

Does (2-fluoroethyl)benzene undergo elimination via E1cb or E2?

I have seen in two different sources claiming that $\ce{PhCH2CH2F}$ gives styrene $\ce{PhCH=CH2}$ when treated with alcoholic $\ce{KOH}$, but one source suggests an E1cb mechanism, while the other ...
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1answer
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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...
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3answers
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Mechanism for Amino-Imidazole Ring Fission

A reaction I've tried several times in the past is the hydrogenation of nitroimidazole derivative shown below. The amino product is extremely unstable and rapidly decomposes. This instability is ...
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4answers
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What's the mechanism of the reaction of (E)-methyl 3-(furan-2-yl)acrylate in acidic methanol?

In the organic chemistry textbook by Clayden et al. they mention that the reaction of (E)-methyl 3-(furan-2-yl)acrylate in acidic methanol yields dimethyl 4-oxoheptanedioate without providing the ...
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2answers
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Is it possible, chemically, to change a dextrorotatory compound to its levorotatory counterpart?

Is it possible, chemically, to change a dextrorotatory compound to its levorotatory counterpart? E.g., is it possible to change dextrodopa to levodopa?
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3answers
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Comparing SN2 reaction rates

I've read in a book that the main factor for determining SN2 reaction rate is steric hindrance. The lesser it is, the faster the reaction. So consider this question: $\ce{KI}$ in acetone undergoes ...
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2answers
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Nitrobenzene reduction with (tin) Sn catalyst: Why is C-H bond cleavage preferred over O-H bond cleavage?

I am trying to understand this mechanism for nitrobenzene reduction with $\ce{Sn/HCl}$. I do not understand why it implies that you pull off the $\ce{C-H}$ hydrogen instead of the $\ce{O-H}$ hydrogen ...
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2answers
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Bromination of 1,3,5-cyclooctatriene followed by nucleophilic substitution by excess dimethylamine

Write the mechanism for the following reaction (bromination of 1,3,5-cyclooctatriene followed by nucleophilic substitution by excess dimethylamine): My answer so far: I have only shown one of ...
12
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1answer
11k 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?