Questions tagged [nucleophilic-substitution]

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

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14 views

How does the nucleophilicity of a leaving group affect SN1/SN2 reactions?

I was reading about SN1 and SN2 reactions and I was wondering how nucleophilicity of the leaving group contributed to the reaction? For example, if I react iodoalkane with a strong nucleophile (but ...
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23 views

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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1answer
63 views

why are E2 and SN2 reactions not competing reactions?

I am quite confused about the competition of $\mathrm{E2}$ and $\mathrm{S_N2}$ reactions. My lecturers say $\mathrm{E2}$ and $\mathrm{S_N2}$ reactions are not competing reactions but most websites say ...
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31 views

Mechanism of reduction of alkyl halides into alkanes by sodium borohydride with ethanol as solvent

From what I have studied, primary halides do not undergo this reaction whereas secondary and tertiary halides get converted into alkanes via this reaction. Since primary haldies do not show this ...
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1answer
36 views

Which mechanism should a reaction between the cyclopentylmethanol and the HBr should follow?

I just thought that the reaction should follow $\mathrm{S_{N}2}$ mechanism this is because the alkyl halide is primary but the book says that the reaction will follow $\mathrm{S_{N}1}$ mechanism ...
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1answer
39 views

Why is t-butyl chloride favored over t-butanol at 0°C? [closed]

To make t-butyl chloride from t-butanol, you need to bubble HCl gas into a 0°C ether solution of t-butanol. To make t-butanol from t-butyl chloride, you can dissolve t-butyl chloride into water (not ...
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1answer
61 views

Why O and N promote SN1 but C=O inhibit SN1 although both are electron-withdrawing?

Source: Jonathan Clayden, Nick Greeves, Stuart Warren, Organic Chemistry 2th Edition, 339. The general idea I got so far, is that, carbocation will be more stable if the + charge at central C is ...
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64 views

Reaction of alc. KOH with alkyl halide

The following question was given in FIITJEE study material: At first, I thought it should be elimination. But, soon I realized that there is no heating, plus a primary alkyl halide is used. So, "...
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38 views

Reaction of alpha-naphthol with benzyl iodide [duplicate]

In preparation for Olympiad, I faced this question: $\alpha$ naphthoxide ion (analogue to phenoxide ion) is reacted with benzyl iodide in two different mediums: $(i)$ DMSO (dimethyl sulfoxide) ...
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36 views

Reactivity of carbonyl derivatives with a nucleophile [duplicate]

As observed, the reactivity of carbonyl derivatives with a nucleophile goes like: Acid halide > acid anhydride > acid > amide > ketone > aldehyde. So is nucleophile a code word to nucleophilic ...
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1answer
120 views

Reimer-Tiemann reaction on indole

According to me net reaction should be at $\ce{C3}$ when Reimer-Tiemann reaction is done on indole (see image), since in the resonance structure, negative charge is on this carbon. But, the answer ...
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1answer
62 views

Are the reaction rates of these equations equal? [closed]

$$\ce{CH3CH2CH2Br + OH- -> CH3CH2CH2OH + Br-}$$ $$\mathrm{rate} = k[\ce{CH3CH2CH2Br}][\ce{OH-}]$$ If I change the $\ce{Br}$ with any element from halogens (without changing concentration, volume, ...
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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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1answer
58 views

Can NaCN or HCN be used as sources of cyanide ion in substitutions? [duplicate]

When cyanide ions act as nucleophiles in substitution reactions, why is KCN the reagent of choice? Would some other source of cyanide such as NaCN or HCN work equally well in the reaction, since they ...
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1answer
106 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 $...
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1answer
149 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
130 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 ...
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39 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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64 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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815 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
99 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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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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48 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
249 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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45 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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131 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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23 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 ...
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50 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
110 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
97 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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60 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 ...
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1answer
63 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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25 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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27 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
53 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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33 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 ...
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1answer
44 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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67 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
143 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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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
102 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 ...
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1answer
77 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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110 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
35 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 $\ce{E2}$. ...
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227 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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70 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 ...
5
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1answer
194 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 ...
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1answer
1k 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). ...
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1answer
147 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,...
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40 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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