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Questions tagged [nucleophilic-substitution]

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

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51 views

Organic Chemistry - Effect of methyl substituent in Aromatic Substitution via Benzyne

The following reaction has been taken from my study material. This shows that the benzene ring is undergoing a nucleophilic aromatic substitution via benzyne mechanism (presence of a strong base like $...
3
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1answer
124 views

Mechanism for the reaction between trisilylamine and hydrogen chloride

In Concise Inorganic Chemistry by J. D. Lee (adapted by Sudarsan Guha), in the chapter "Chemical Bonding", under the topic "Back Bonding with Nitrogen as a donor atom" the following reaction is given: ...
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2answers
35 views

Alkene reaction with acid via SN1 reaction

I want to ask a question about alkenes and their reactivity with acids. From high school studies, I recall that if you had an acid $\ce{H3O+}$ i.e. $H^+$ that it would react with an alkene as shown ...
4
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0answers
25 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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0answers
25 views

Nucleophilic Substitution Reaction of Alcohol

What is the final product? According to me, it's option (3). But given answer in the booklet is (2). Given primary alcohol undergoes SN2 reaction to produce isopentyl bromide and the latter again ...
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79 views

Which is faster- SN1 or SN2?

We were studying about nucleophilic substitution reactions. My professor said that in general SN1 reactions are faster than SN2 reactions. I am unable to understand that how can we generalise the rate ...
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1answer
65 views

Why does the reaction between 2‐methylbut‐3‐en‐2‐ol and hydrogen bromide show allylic shift?

In the following reaction shouldn't the minor product be the major one as the carbocation formed before attachment of bromine is 3°? Also, can someone tell me why the product includes only ...
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0answers
41 views

Confused about inversions in $S_N2$ Reaction

I just learned that in $S_N2$ reaction there is an inversion of configuration. I thought that it is a change of $R$ to $S$ and vice-versa. But that is wrong as mentioned in this answer. While I was ...
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35 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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2answers
101 views

Acidic cleavage of ether with a 2° alkyl group

I know that an ether with a 3° alkyl group and a 1° alkyl group is cleaved by $\mathrm{S_N1}$ mechanism to give a tertiary alkyl halide and a 1° alcohol. And an ether with a two 1° alkyl groups is ...
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23 views

Explanation of SN2 Mechanism using MOT

SN2 is usually explained by MOT, where we state that the incoming nucleophile starts donating the electron density into the σ∗ orbital and the carbon-leaving group bond weakens and finally breaks and ...
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67 views

Why can't carboxylic acid + NaH + tert-butyl bromide react to create an ester?

So, the picture I showed above asks for which reagents can form the ester product. I was wondering why D can't form it? I was thinking that first, the $\ce{NaH}$ would react with the carboxylic acid ...
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16 views

Why does the hydride ion in LAH act as a nucleophile rather than a base in the reduction of carbonyl compounds? [duplicate]

Why does the $\ce{H-}$ ion in $\ce{LiAlH4}$ act as a nucleophile rather than a base in the reduction of carbonyl compounds ?? Because $\ce{H-}$ being a small ion would act as a better base than a ...
2
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0answers
42 views

Why doesn't Grignard reagent attack alkyl halides [duplicate]

When we add magnesium to alkyl halide, Grignard reagent is formed. $$\ce{R-X + Mg -> RMgX } $$ It is highly nucleophilic in nature. Now at this time the electrophilic alkyl halide is also present ...
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1answer
64 views

Adding cyanide vs nitrite for nucleophilic substitution and why does it change when we use silver salts for it

On adding $\ce{NaCN}$ to $\ce{RX}$, we get $$\ce{NaCN + RX -> RCN + NaX}$$ And not $\ce{RNC}$. Clayden gives the explanation as follows: Although linear cyanide (which is isoelectronic with $\...
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1answer
53 views

What is the major product of the reaction between 4-chlorobut-1-ene?

When acetic acid looses hydrogen, an acetate ion is formed which attacks 4-chlorobut-1-ene, forming methyl butenoate. How does the cyclic structure form? Does the lone pair of oxygen attack the butene ...
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0answers
44 views

Formation of isocyanide on reaction with silver cyanide whereas sodium cyanide forms a regular cyanide

Organic halide react with silver cyanide and an isocyanide is formed, whereas on reaction of sodium cyanide, normal cyanide is found. What is the reason behind the difference in the products?? In a ...
2
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1answer
49 views

Rearrangement considerations in feasibility of SN1 in given reactants

I have been asked to compare the feasibility of Unimolecular Nucleophilic Substitution ($\mathrm{S_N1}$) in the following question. I have received instruction that the reaction will be feasible only ...
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24 views

Iodide via SN1 in anhydrous medium

In anhydrous medium fluoride ion is the strongest nucleophile whereas iodide is the weakest. I was wondering if in anhydrous conditions, SN1 reaction with an iodide could take place. I have been ...
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20 views

Rate of reaction of halogens in a substitution reaction

When a substitution reaction takes place in a substrate having halogen, Why is it that iodine reacts the fastest and fluoride is the slowest ? For sure the iodine has a weaker bond but it is also ...
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1answer
43 views

Addition of aqueous KOH to 3-bromobut-1-ene

On addition of aq $\ce{KOH}$ to 3-bromobut-1-ene, substitution reaction should take place via $S_N1$ mechanism but in this an allylic carbocation forms which could rearrange. In that case which ...
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0answers
32 views

Addition v/s elimination with double bond and OH together

If a compound has both an hydroxyl group and a double bond and we add $\ce{HBr}$ to it, (a) substitution reaction to the hydroxyl group can take place, or (b) an addition reaction of a ...
-1
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1answer
41 views

Methyl iodide in water

Iodide being a good leaving group and water being quite a weak $\ce{Nu-}$, does $\ce{CH3I}$ undergo $\mathrm{S_N1}$ reaction? I was taught that whenever a protic solvent which can ionize the halide ...
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0answers
54 views

Reactivity of Grignard reagent

I had the following question at an exam: What is the fastest reacting compound towards nucleophilic addition with Grignard reagent? (a) Acyl chloride (b) Aldehyde (c) Ester It is ...
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2answers
112 views

Williamson Ether and Carboxylic Acids

What would happen if you tried a Williamson Ether Synthesis on something that has both an alcohol and a carboxylic acid? Would both -OH groups be functionalized, where the alcohol would become an ...
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0answers
29 views

How to rationalise the difference in reactivity between alcoholic and aqueous KOH with alkyl bromides? [duplicate]

Why is it that when we use alcoholic $\ce{KOH}$ with say $\ce{R-Br}$, E2 elimination occurs, whereas with aqueous $\ce{KOH}$, SN reaction takes place, as both have the same nucleophile, ie $\ce{OH^-}$?...
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1answer
71 views

Nucleophilic Substitution

when I add $\ce{RCl + H2O -> ROH + HCl}$ but it's also true in reverse $\ce{ROH + HCl -> RCl +H2O}$ however this is not in case of $\ce{FeSO4 +Zn -> Zn + FeSO4}$ $\ce{ZnSO4 + Fe -> no ...
2
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1answer
64 views

Why aren't there 2 products formed?

The question is asking for the major organic product. This seems like an $S_N1$ reaction to me as there is a weak base in $\ce{CH3OH}$ and heat. If it is, shouldn't there be 2 products. One with the $\...
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0answers
79 views

Why does SN1 not occur as a minor product when a strong nucleophile/strong base attacks a tertiary substrate?

The following is part of a table that appears in my Organic Chem Text (Klein) Nucleophile Only (e.g. Strong Nucleophile/ Weak base) $1^\circ - \text{ SN2}\\ 2^\circ - \text{ SN1 + SN2}\\ 3^\circ - \...
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1answer
25 views

When will acid-base reactions occur before substitution reaction

For example, given the reaction below: The substrate is secondary, the solvent is aprotic and it is to react with a strong bulky base. From this, I assumed that the reaction would be $\ce{E2}$. ...
1
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0answers
103 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 ...
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0answers
49 views

Does a non-chiral substrate (2-bromo-2-methylpropane) also form two products via an SN1 mechanism?

If I have an alkyl halide, in which its tertiary carbon is non-chiral (for example 2-bromobutane), which reacts via an SN1 mechanism does it also produce 2 products? I am asking because I know that ...
4
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1answer
110 views

Why do we use LiCl as a source of chloride ions as nucleophile but not other alkali metal chlorides? [closed]

$\ce{LiCl}$ has higher covalent character than other alkali-metal chlorides, so in polar solutions like ethanol, its ioniztion will be less, and so less chloride ions will be available for ...
4
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1answer
762 views

Why do polar aprotic solvents favour SN2 over E2?

I was reading about Substitution and Elimination Reactions and I came across the following on MasterOrganicChemistry: Polar protic solvents tend to favor elimination (E2) over substitution (SN2). ...
4
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1answer
102 views

Stereochemical outcomes in opening of vinyl epoxides

Explain the outcomes of the following reactions. In each case the major product is shown. Firstly, I don't understand why the chloride always attacks on the right hand side of the epoxide. Also,...
3
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0answers
39 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 ...
0
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1answer
26 views

Do the mechanism (SN1 or SN2 ) which reaction follow depends more upon intermediate stability than on substrate and nucleophilic?

For eg : would the reaction of 3-methylbut-2-en-1-ol with HBr follow SN1 mechanism due to stability of your intermediate carbocation stability or SN2 due to the compound being primary alcohol and ...
0
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0answers
56 views

Why doesn't solvent form the major product in SN1 reactions?

If in a reaction SN1 pathway is followed then after the formation of carbocation the reagent or the solvent molecule can attack to form the product. As the number of solvent molecules are ...
2
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2answers
238 views

Why is it aqueous and ethanolic conditions for nucleophillc substitution of cyanide ion with benzyl chloride?

I was doing an exam question where benzyl chloride was undergoing a nucleophilic substitution with cyanide ion to form benzyl cyanide. Please can someone enlighten me as I have never seen both ...
0
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0answers
334 views

Reaction of ketones with sodium amide

Find the product of the reaction of dimethyl ketone i.e. $\ce{CH3C(O)CH3}$ with $\ce{NaNH2}.$ Should I do nucleophilic addition and form the product in the picture?
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1answer
90 views

Why doesn't open-chain glucose react with water readily in aqueous solution?

Though the exact number given varies from 0.02% to 3%, it's well agreed that glucose spends a very small percentage of its time in aqueous solution as a linear aldehyde. Glucose's overwhelming ...
10
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1answer
207 views

Is isobutyl chloride or ethyl chloride more reactive in an SN1 reaction?

Compare the rate of $\mathrm{S_N1}$ reaction in the following compounds: We see that both compounds form primary carbocations. However, there is more hyperconjugation in the second compound as ...
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0answers
39 views

Which of these chlorides is more reactive? [duplicate]

We do learn that for $\mathrm{S_N1}$ reaction the rates are tertiary > secondary > primary > methyl. The reasons mentioned are usually inductive and hyper-conjugative effect. But which of the ...
4
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1answer
58 views

Can the nitrogen of an amide displace a primary chloride in a S_N_2 reaction in the presence of a strong base?

I was looking at the following reaction and am confused. It appears that $\ce{N}$ is attacking the $\ce{C-Cl}$ and $\ce{Cl}$ is leaving in a $\mathrm{S_N2}$ reaction. I know that $\ce{Cl}$ is a good ...
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0answers
37 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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0answers
73 views

In nucleophilic acyl substitution, why will the Nu never displace the leaving group (e.g., Cl) directly by an SN2 mechanism?

In my class notes, it says: "The Nu will NEVER displace the leaving group directly in an SN2 reaction." We have previously been taught that SN2 reaction only occur at tetrahedral carbons, so I can ...
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0answers
33 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 ...
2
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1answer
123 views

Confusion about the SN1 and SN2 Mechanism

My book says, and I understand, that the $\mathrm{S_N1}$ mechanism is much faster for tertiary alkyl halides than primary. And the opposite for $\mathrm{S_N2}.$ This all makes sense. What I don't get ...
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0answers
188 views

Why don't acyl chlorides give positive test with 2,4-DNPH?

In this post, Ron discusses the reasons why carboxylic acid derivatives such as amides, acids and esters do not give a positive result with 2,4-dinitrophenylhydrazine. He mentions that it is largely ...
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0answers
158 views

How many moles of methyl iodide will be consumed by one mole of crixivan?

My take on this question : a total of 5 moles of $\ce{CH3I}$ should be consumed. The oxygen atoms in the $\ce{2 OH}$ groups each have a lone pair of electrons. They should displace $\ce{I-}$ from ...