Questions tagged [nucleophilic-substitution]

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

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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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1answer
1k views

Can an SN1 reaction occur in compounds with the leaving group attached to a primary carbon, which can later rearrange?

Can SN1 reactions occur in compounds where the carbocation, even though is is initially $1^\circ$, can rearrange to form a more stable carbocation? Examples cases:
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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 ...
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83 views

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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146 views

Why isn't PBr3 used to halogenate tertiary alcohols?

I've been looking into activation of alcohols for nucleophilic substitution, and I've come across a series of reactions that differentiate between primary, secondary and tertiary alcohols. I've seen ...
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675 views

Why do t-butyl bromide and silver(I) nitrite form the nitroalkane, not the nitrite ester?

We know that reaction of $\ce{AgNO2}$ with alkyl halides is SN1 type reaction and follows HSAB principle. So in the reaction of $\ce{(CH3)3C Br}$ we would expect $\ce{AgBr}$ to form and also a ...
4
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1answer
87 views

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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67 views

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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92 views

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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44 views

When does reaction of alcohol with alumina give ethers and when an alkene?

This problem given in my book confused me a little bit: when an excess of ethyl alcohol vapour is passed over heated alumina ($250^\circ$C), the main product is? I read that this reaction gives an ...
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76 views

How are σ+ values in Hammett Plots calculated?

First of all, I know a similar question has already been asked & answered about σ values in general, however, I am not 100 % sure this answer is correct for the following situation. So for the σ ...
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128 views

Favourability of leaving groups in nucleophilic aromatic substitution

It is known that the order of leaving group favourability of the halide ions changes when we go from nucleophilic substitution, in the form of $ \ce {S_N1}$ and $\ce {S_N2}$ reactions, to nucleophilic ...
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75 views

Activation of alcohols by forming sulphonate ester

In activation of alcohol by tosyl chloride, why does the chloride ion not displace the poor leaving group? I think that's because chlorine is a poorer base than that thing which will be formed. But ...
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640 views

Textbook suggests secondary alkyl halides do not undergo SN1 reaction

The 8th edition of Organic Chemistry by Paula Bruice suggests that secondary alkyl halides do not undergo SN2 reactions. However, many other sources state the opposite. So, what is the correct answer? ...
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295 views

Substitution of a cyclic diether by a halogen

I’m in an organic synthesis class and I have to draw a mechanism for the reaction in the picture. At first I thought it was just forming a free radical but I haven’t been able to find any way to do ...
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905 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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1answer
84 views

Is the Beckmann Rearrangement technically an "SN2" reaction at an "sp2" center?

Below is the mechanism from this link of the Beckmann Rearrangement. In the alkyl migration step, the alkyl group migrates simultaneously as the $\ce{H2O}$ leaving group is expelled. This seems as ...
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779 views

Determining the stereochemistry of the product(s) when an alkyl shift in a carbocation generates a chiral carbon

Consider this carbocation: We know that this carbocation would immediately rearrange - by a methyl shift - to form the more stable carbocation. Now, notice that the migration will produce a chiral ...
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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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63 views

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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135 views

Comparing nucleophilicity of oxygen and nitrogen in acetylation of 4-aminophenol

Here, the answer has $\ce{N}$ acting as a nucleophile making the answer (C). I thought that $\ce{O}$ would be more nucleophilic, considering the fact that $\ce{O}$ has two lone pairs, one in ...
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407 views

How does C−Br bond obtain energy through solvation?

I came across a question related to SN1 mechanism. In an example of SN1 reaction, i.e. hydrolysis of tert-butyl bromide to form tert-butyl alcohol, the following was given in NCERT Chemistry: Textbook ...
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29 views

Why can SN2 reactions occur when the reagents are a primary substrate and a weak nucleophile/base?

The reagents are ethyl bromide and water. In this Khan Academy video at 5:20, the narrator says because ethyl bromide is a primary substrate, the reaction is neither SN1 or E1. This makes sense ...
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Formation of intimate ion pair by halogenoalkanes

I was recently doing this organic chemistry question that tested on the concept of the formation of the intimate ion pair in the nucleophilic substitution reaction at an $\ce {sp^3}$ carbon: $\ce {...
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45 views

Halogen bonding in organic reactions

Recently, a group of researchers from the Nanyang Technological University in Singapore have investigated the novel $\ce {S_N2X}$ mechanism which involves a "frontside attack" on the substrate, rather ...
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2k views

What are the partial charges in an SN2 transition state?

What are the partial charges of on the atoms in a SN2 reaction? The nucleophile is normally negatively charged and has a lone pair of electrons. This would make you think the transition state would ...
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50 views

Substitution reaction rate for tertiary halide substrate with adjacent carbonyl

In the book "Organic Chemistry" by Clayden et al. p 343 it is stated that this substrate reacts very slowly through both the SN1 and SN2 pathways. It is shown side by side with neopentyl chloride as ...
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Nucleophilic Substitution rate comparison 1-bromobutane and 2-bromo-2-methylpropane with NaOH

I want to ask a question about the hydrolysis of haloalkanes to form alcohols. I have been presented with a flowchart diagram of possible reactions of haloalkanes below: Now, I have been presented ...
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103 views

Nucleophilic substitution in aromatic compounds

Predict the major product in following reaction: In my view this reaction will proceed via benzyne intermediate and $\ce{NH2-}$ will act as a base and substitute one of the chlorine. After benzyne ...
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46 views

What constitutes something being designated as big, bulky in terms of SN2 vs E2

When deciding between $\mathrm{S_N2}$ and $\mathrm{E2}$ for primary and secondary alkyl halides, is there a particular method or molecular size or any other threshold, which allows us to designate ...
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Can the directionality of an SN2 reaction depend on solvent polarity?

Because of the effects of solvation, halide ions have differing nucleophilicity in protic solvents vs aprotic solvents, iodide being the best nucleophile in protic solvents and fluoride being best in ...
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166 views

What hinders SN2 more: geminal alkyl group or alkyl group on the aromatic ring?

Which among these two (1-chloro-1-phenyl-ethane and 2-(chloromethyl)-1,3-dimethylbenzene) is more reactive towards SN2? I strongly believe that it should be Y because of lesser hindrance on the ...
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Products of the reaction between cyclohexanone and N-bromosuccinimide

Problem Treating cyclohexanone with N-bromosuccinimide in the presence of carbon tetrachloride gives A. A on treatment with aqueous KOH gives B. Deduce the structures of A and B. Solution Questions ...
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Does KCN prefer SN2 or nucleophilic addition?

If we have a 1° halide that also contains a carbonyl group (like 5‐chloropentan‐2‐one), and we add 1 mole of KCN in DMSO to it, what will happen? Will the SN2 product by substitution of chlorine or ...
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79 views

Alternate pathway of Gabriel synthesis to prepare secondary amine

Can modifying the Gabriel synthesis, which is generally restricted to synthesis of primary amines, be used to synthesise secondary amines? I have attached my idea regarding the synthesis (the final ...
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46 views

Nucleophilic substitution of trifluoroiodomethane

Will $\ce{CF3I}$ show nucleophilic substitution? In other words, is the following reaction feasible? $$\ce{CF3I + NaOH -> CF3OH + NaI}$$ I know that $\ce{I-}$ is a pretty good leaving group. Also ...
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180 views

Reaction of Alkyl Halide with Ag2S / Na2S

What does alkyl halides give on reaction with $\ce{Ag2S / Na2S}$? In my book, it is given as $\ce{R-S-R}$ but I am not quite sure as alkyl halide react with moist $\ce{Ag2O}$ to gives $\ce{R-OH}$ and ...
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When is a compound sterically hindered?

In a nucleophilic substitution reaction , which one of the following undergoes complete inversion of configuration ? (A) $\ce{C_6H_5CCH_3C_6H_5Br}$ (B) $\ce{C_6H_5CHCH_3Br}$ (C) $\ce{C_6H_5CHC_6H_5Br}$...
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288 views

Charge distributions in the transition state of the SN2 reaction

I understand that a similar question has been posed here. However, the scope of my question is framed differently. I will present analysis of two different sources of information and I would like to ...
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Multiple leaving groups and SN2/E2

In the first stage of the reaction i am confused in which place will the SN2 happen (we have aprotic polar solvent and 4 leaving groups). In my opinion SN2 will happen either to the carbon with F- ...
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Reactivity of carbonyl adjacent to cyclopropyl group

We know that cyclopropyl, because of $\ce{sp^{\sim 5}}$, hybrid orbitals behaves much like a double bond. It even takes part in conjugation to stabilise positive charge on carbons adjacent to it. I ...
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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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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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Possible mechanism by which a methyl glycinate hydrochloride salt in toluene (insoluble) reacts with an acid chloride through the nitrogen atom?

I'm trying to work out a possible mechanism for the reaction of a methyl glycinate hydrochloride salt in toluene (it is insoluble) with an acid chloride, reacting through the N-terminus. As the amine ...
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32 views

Use of TsN3, toluene at high temperature

My reasoning: My understanding is in first step the alcohol’s O- does an Sn2 attack on the OTs containing carbon. In the second step I am confused where does the reaction happen in the triple bond or ...
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76 views

Order of reactivity of alkyl halides in Sn1 reactions

Problem:: Predict the order of reactivity of the following compounds in SN1 reactions . i) $\ce{PhCH2Br}$ ii) $\ce{Ph2CHBr}$ iii) $\ce{PhMeCHBr}$ iv) $\ce{Ph2MeCBr}$ Answer:: SN1:iv>ii>iii>i ...
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Nucleophilic Aromatic substitution in 3-Bromoanisole

I came across an example in my textbook where $\ce{3-Bromoanisole}$ is reacted with $\ce{NaNH2}$ in liq. $\ce{NH3}$. My understanding is that the reaction would proceed by a Benzyne intermediate, with ...
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749 views

Why is the nucleophilic substitution of OH- with 1-bromopentane slower than with 2-bromo-2-methylbutane?

Which statement about the reaction of a hydroxide ion with the organic reagent is correct? A. 1-bromopentane predominantly follows an $\mathrm{S_N1}$ mechanism. B. 2-bromo-2-methylbutane predominantly ...
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52 views

Why is this reaction not feasible?

The reaction is:$$NH_3+CH_3OCH_3 \rightarrow CH_3NH_2+CH_3OH$$ The mechanism here would be $S_N2$ and since $NH_3$ is a stronger base so it should be a better nucleophile. Why then is this reaction ...
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91 views

Distinguishing between a nucleophilic substitution and an electrophilic substitution

Why don't we consider all nucleophilic substitution reactions as electrophilic reactions and vice versa? For example, look at this reaction I found in my textbook. (See picture) This is an ...