Questions tagged [nucleophilic-substitution]

For questions having their focus on SN1, SN2, SNi, SN1', SN2', or SN2th (nucleophilic acyl substitution).

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SN2 and E2 Reactions with Primary, Secondary, and Tertiary Alkyl Halides

I was wondering if there are any substitution products present when a strong base/weak nucleophile (such as tert-butoxide) reacts with a primary or secondary alkyl halide. I know that the E2 products ...
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Why doesn't an acid-base reaction occur in basic amide hydrolysis instead of nucleophilic acyl substitution?

In the reaction of Grignard reagent with a primary and secondary amide, nucleophilic acyl substiution doesn't happen. The reason given is that R- is a strong base as well as strong nucleophile, an ...
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1 answer
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What determines whether a mechanism is nucleo/electrophillic addition/substitution?

So I recognise what an electrophile and a nucleophile is, but not all mechanisms (that I know of at least) have one species substituting or adding. For example, propanone added to NaBH$_4$ has an ...
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Comparing reactivity of 3-bromocyclohexa-1,4-diene and 5-bromocyclohexa-1,3-diene towards SN1 reaction

Compare reactivity of 3-bromocyclohexa-1,4-diene (P) and 5-bromocyclohexa-1,3-diene (Q) towards $\mathrm{S_N1}$ reaction. My teacher claims that the reactivity of P is more than that of Q. He ...
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Why don't secondary alcohols react with HBr/HI via SN2?

In polar protic solvents, $\ce{Br-}$ and $\ce{I-}$ are considered to be very good nucleophiles. Now, here the solvent is alcohol which is polar protic. So, why don't secondary alcohols react with $\ce{...
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How do I determine if a nucleophile attacks the electrophilic atom directly or indirectly?

How do I determine if a nucleophile attacks the electrophilic atom directly or indirectly? For instance a nucleophile could attack the carbon in a molecule with a carbonyl directly, but in another ...
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Rearrangement vs. Ring Strain in Cyclobutanecarboxaldehyde Nucleophilic Reaction

Predict the major product of the following reaction: Note: Product A is incorrectly marked as secondary halide, it should have been primary halide This question appeared in an national level ...
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How to explain mesylate structural homologues (e.g., "esylate") being weaker leaving groups than mesylate itself?

I came across a piece of scientific literature (https://patents.google.com/patent/US20080045602A1/en) that would seem to imply leaving groups formed by reacting hydroxy groups with, e.g., ...
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2 votes
2 answers
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Reactivity of 1-bromo-4-tert-butylcyclohexane isomers with methanol

(1s,4s)-1-bromo-4-tert-butylcyclohexane (1) and (1r,4r)-1-bromo-4-tert-butylcyclohexane (2) are heated (E2) with $\ce{NaOCH3}/\ce{CH3OH}.$ Which isomer will react faster? What will change when $\ce{...
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How do mechanisms of acidic cleavage of ethers differ for anhydrous, concentrated, and aqueous HI?

I have seen the usage of anhydrous, concentrated, and aqueous HI for the acidic cleavage of ethers. What is the difference in the mechanisms and which will follow either of SN1/SN2 mechanism? Once the ...
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Difference between SN' and elimination reactions

My professor has recently taught us about SN' reaction example in which 3-bromo-3-methyl-but-1-ene was reacted with with KCN to yield 4-methyl-pent-3-ene-nitrile as the major product.When I asked him ...
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Why doesn't tetrachloromethane react with aqueous sodium hydroxide under reflux?

$\ce{CCl4}$ does not react with hydroxide nucleophile whereas $\ce{CH3Cl}$ does. I had initially thought that it was due to symmetrical geometry of $\ce{CCl4}$ and so the dipoles cancel out and the ...
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Does the character of a leaving group affect SN1/SN2 and E1/E2 differently?

This is coming from a fairly unusual question on an old test. If we consider this reaction: Will the ratio of (2+3):1 be greater if I is the leaving group? As far as I knew, the an increase in the ...
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1 answer
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Racemization on nucleophilic substitution by OH- ion [closed]

Here's the question I'm stumped by - According to the answer key, i) is the answer but why can't it be iv)? There is a chiral carbon in compound c) CH3(C2H5)CHCH2Br , so why won't the product (2-...
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On what basis is the rate of Sn1 reaction dependent

Does the rate of reaction depend on the stability of the 1st carbocation formed just after the leaving group leaves or the rearranged carbocation's stability? for eg Here if i compare the stability ...
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How can we say that one reaction is faster than another if two conflicting factors are at play in both of them

While learning about the preparation of alkyl halides from alcohols by reacting them with hydrohalic acids, it was mentioned that the order of reactivity of different alcohols is Tertiary > ...
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Why do active methylene compounds give Sn2 reactions?

I dont understand why they are strong nucleophiles when the negative charge is resonance stabilised. Also it is bulky, is there any chance of elimination?
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Would TFA be a strong enough acid to perform an SN1 reaction on alcohols?

The pKa of sulfuric acid, which is usually used to do this reaction is -3, but would TFA be sufficient even though it has a pKa of 0.5?
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Reaction of primary amine with mixed acid anhydride

Is this reaction $\ce{S_N2}$ (because attack of nucleophile and removal of leaving group are not taking place in a single step)? Which part of anhydride should form the substituted amide? If it is an ...
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4 votes
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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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Formation of α,β-unsaturated ketone from tertiary propargyl halide

My attempt: I went ahead with an $\mathrm{S_N1}$ type reaction followed by the attack of $\ce{OH-}$ on the 3 degree carbocation formed. This does not match with the answer given (see image below), in ...
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Finding the order of decreasing rate of solvolysis of the following molecules with aqueous ethanol [closed]

In this question, I need to find the order of decreasing rate of solvolysis of the above molecules with aqueous ethanol. I think this can be done by finding the species that can form the most stable ...
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Should we consider reactant as the product of a no reaction?

If a reaction doesn't take place, should we call the reactant as the product? What is the convention? Let me illustrate the question with an example from JEE Advanced 2021, paper 1: The reaction of Q ...
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Reaction of aqueous KOH and alcoholic KOH with alkyl halide [duplicate]

CONTEXT: Here's reaction of alkyl halide with aqueous $\ce{KOH}$ and here's the reaction for dehydrohalogenation by alcoholic $\ce{KOH}$ Question Initially $\ce{KOH}$ is aqueous. On reacting with ...
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-4 votes
1 answer
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CH3I + NaCl in acetone gives [closed]

How will methyl iodide react with $\ce{NaCl}$ in acetone? According to me $S_N2$ reaction will take place where iodine will be replaced by chlorine and we will get $\ce{CH3Cl}$. Can anyone suggest why ...
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-1 votes
1 answer
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SN1 mechanism on 3,5-dimethylbenzyl bromide [closed]

I wanted to see how to make the product on the right so my thought was to have an SN1 reaction to remove water and have the bromine ion attack making the product on the right hand side. Is this ...
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4 votes
1 answer
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nBuLi and tBuLi can take part in halogen metal exchange OR deprotonate. Is there any way to predict which it favours?

I have included a synarchive pathway: https://synarchive.com/syn/144 where BuLi favours deprotonation over halogen metal exchange
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What is the mechanism when 1-chloro-4-nitrobenzene reacts with NaOH?

The reaction mechanism in my textbook when 1-chloro-4-nitrobenzene reacts with NaOH is given as follows, When chlorobenzene reacts with NaOH the product formed is phenol with benzyne as the reaction ...
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How to convert benzyl alcohol to 2-phenylethanoic acid?

How can we convert benzyl alcohol to 2-phenylethanoic acid? This is what I have tried. Can someone tell me whether this is correct because I am not sure about the second reaction. In my textbook it ...
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8 votes
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Can NaH open the epoxide ring to form alcohol? If so, how?

I was looking at the organic chemistry 8th Ed textbook by Paula Yurknais Brucie. On page 509, I found this: I think about it for a while and I am doubting that it is wrong. I believe the hydride ion ...
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7 votes
1 answer
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Why doesn't NGP happen in the bromination of fumaric acid?

In this question from JEE $2015$, a surprising neighbouring group participation occurs, and the product turns out to be $(3)$. A link for the mechanism can be found here. However, why doesn't the same ...
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4 votes
1 answer
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Acid catalyzed bromine substitution in an alcoholic ester. What is the major product and why?

This was in a paper I gave. I want to know the mechanism by which both of these products will be formed and why is the 1st one the major product. My thinking is that the -OH group will be converted ...
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6 votes
1 answer
610 views

Reaction of phenol with phosphorus tribromide

I know that aliphatic alcohols react with reagents like $\ce{PBr3},$ $\ce{PBr5},$ $\ce{SOCl2}$ etc. to give alkyl halides as a product. But what will happen if we put aromatic alcohols like phenols ...
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2 answers
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If rate of SN1 is more does that automatically mean rate of SN2 is less, and vice versa?

If I have a list of compounds and I compare their SN1 reactivity, for SN2 reactivity, is it correct to use the same list but order inverted? Are there any exceptions?
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Reaction mechanism of formation of salicylic acid with Phenol and carbon tetrachloride in basic medium?

With classic Reimer-Tiemann reaction a variation is also given in my lecture notes which use carbon tetrachloride instead of chloroform. But to me, it seems like it would be just a substitution ...
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1 vote
1 answer
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Double bond or carbanion for nucleophillic attack [closed]

I came across this question: According to me the Hydride ion should take hydrogen from left (unsubstituted carbon) because carbanion will be more stable there and this carbanion will then act as a ...
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3 votes
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Advantages of p-toluenesulfonic acid over sulfuric acid in the formation of acetals

I am currently working on an undergraduate experiment to form a cyclic acetal. We were asked to use p-toluenesulfonic acid as a catalyst rather than sulfuric acid. This seems to be common practice ...
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3 votes
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Does amide ion prefers to act as a base than a nucleophile?

In this question, I think that amide ion, being a good nucleophile should attack on the terminal carbon through $\mathrm{S_N2}$ mechanism to form compound (c), but the answer given is (b), and the ...
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5 votes
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Which is better leaving group out of iodide and water?

In hydrolysis reaction of an tertiary alkyl halide , $\ce{H_2O}$ will replace the $\ce{I-}$ through $\ce{S_N1}$ mechanism and then $\ce{H+}$ will be removed from $\ce{H_2O}$ in order to form an ...
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-1 votes
1 answer
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When does bimolecular nucleophilic substitution reaction take place in phenyl group containing compounds?

We were studying SN Mechanism, and our professor gave us a question to identify the SN, mechanisms which would happen in the given compound. They were $\ce{CH3Cl}$, $\ce{PhCH2Cl}$, $\ce{Ph2CHCl}$, $\...
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4 votes
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Mechanism of Wiliamson Synthesis

I was studying about Williamson's Synthesis, and my textbook had the following statement: Williamson's Synthesis is a nucleophilic substitution reaction and proceeds via $\ce{S_N2}$ mechanism. Then ...
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In benzyne intermiediate of anisole why -I effect of OCH3 is considered not +M effect of it?

Here they considered -I effect of $\ce{OCH3}$ so carboanion is stable at orthroposition; But $\ce{OCH3}$ also shows $\text{+M}$ effect if $\text{+M}$ is shown carboanion will be stable at meta ...
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Confusion regarding nucleophilicity [duplicate]

My teacher told me that to compare nucleophilicity, check the size of the attacking atom. Bigger the attacking atom more the nucleophilicity. But while reading Solomon, I found out that the order of ...
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4 votes
1 answer
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Is the SN1 reactions stereospecific or stereoselective? [duplicate]

In the SN1 reaction, the product show retention and inversion. Since one of them is major unless it forms a racemic mixture, does it mean that the SN1 reaction is stereospecific?
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6 votes
1 answer
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Why is nitrate anion substituted but bromide anion is not in Von Richter reaction?

In Von Richter reaction which is a nucleophilic aromatic substitution. As according to this source, there is only a 37% yield of the product.I want to know what are the competing side reactions which ...
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Does ammonolysis of primary and secondary alkyl halides proceed through SN2 mechanism?

We know that the first the ammonia acting as nucleophile attack the alkyl halide forming the substituted ammonium salt, but my question is why cannot it proceed through a typical $S_\text N2$ type, ...
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9 votes
1 answer
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Why does this ring contraction take place in the following nucleophilic substitution? [closed]

While attempting this problem I thought that P1 would simply be Bromine getting substituted by OH through nucleophilic substitution. P2 would give a product formed through ring expansion as a 4 ...
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1 vote
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Determining the leaving group for substituted benzene in Aromatic nucleophilic substitution

I could figure out that After the substitution of one of the halogens, with the $\ce{-OCH3}$ group(Electron donating group), the ring would be deactivated towards nucleophilic substitution hence the ...
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4 votes
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Why is chlorosulfite a good leaving group?

I came across the following website article[1]: I understand the mechanism and also get the fact that this is nothing but an experimental result but why does the $\ce{ClSOO-}$ group departs ...
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7 votes
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Analysing reaction with chair conformation of substituted cyclohexane

Why doesn't Iodine liberate in the following reaction? (A) Inadequate ring size (B) Two Bromines are in equatorial positions (C) Steric hindrance of t-butyl group towards attacking $\ce{I-}$ ...
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