Questions tagged [nucleophilic-substitution]

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

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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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23 views

Why do I need H20/H+ for nucleophilic attach by grignard reagent? [closed]

In solving the below reaction, I am confused as to why H2O/H+ is needed when using a grignard reagent as a nucleophile..... Wouldn't the MgBr dissociate from the Alkane when dropped in a solvent and ...
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35 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
41 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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Why does alkyl iodide for fastest nucleophilic substitution as C-I bond is least polar. Also why does protonated alcohol too undergoes substitution

I was taught that the alkyl iodide undergo the fastest nucleophilic substitution because the C-I bond is the weakest and as iodide is a very large sized atom and also its fifth shell electrons don't ...
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1answer
47 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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18 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
36 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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23 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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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
33 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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31 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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32 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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44 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
80 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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48 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
56 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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53 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
16 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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28 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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37 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 ...
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1answer
59 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
179 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
69 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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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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1answer
22 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 ...
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54 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 ...
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2answers
83 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 ...
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185 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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56 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 ...
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154 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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35 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 ...
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43 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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33 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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32 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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27 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 ...
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1answer
90 views

Confusion about the Sn1 and Sn2 Mechanism

My book says, and I understand, that the Sn1 mechanism is much faster for tertiary alkyl halides than primary. And the opposite for Sn2. This all makes sense. What I don't get is the conclusion it ...
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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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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 ...
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19 views

Oxirane and ring opening

I have a problem given as :- I thought of a sn1 type mechanism in acidic medium and a sn2 pathway in basic medium . Am I correct or not . Please also check the mechanism according to which I formed ...
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1answer
78 views

Bromination of but-3-en-1-ol in basic medium and Baldwin's rules

After formation of the bromocarbocation the alkoxide anion attacks the bromocarbocation which leads to ring formation and can proceed through two pathways 5 endo tet cyclization is disfavored but 4 ...
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Nucleophilic addition - Propanal vs Benzaldehyde

According to my school textbook, carbon atom of the carbonyl group benzaldehyde is less electrophilic than that of propanal because polarity of the carbonyl group is reduced in benzaldehyde due to ...
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1answer
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SN2 reactions with primary alcohols [closed]

A problem I was recently working on poses the following scenario: A student realizes that protonation of an alcohol makes the -OH into a better leaving group. Therefore, he suggested the following ...
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1answer
205 views

Order of reactivity of hydrogen halides

Solomon and Fryhle $11^{th}$ edition says : Order of reactivity of HX in the acid catalyzed conversion of alcohols to alkyl halides follows the order : HI>HBr>HCl We can account for this by saying ...
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1answer
51 views

Reaction of cyclobutylmethanol with HX

I am interested in the reaction of cyclobutylmethanol with HX where these are the only reagents. My question is whether the reaction proceeds via SN1 or SN2. My reference text insists that primary ...
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1answer
59 views

What is the expected number of rings obtained in the following ring formation process?

Refluxing, say, one mole of 1,5-dibromo-pentane with excess ammonia in ethanol can result in the formation of rings. (e.g. $1\lambda^2$-piperidine) However, it is also possible for the 1,5-dibromo-...
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1answer
39 views

Reagents in Krapcho's decarboxylation

Krapcho's decarboxylation is a reaction involving esters with a electron-withdrawing group $\beta$ to the carbonyl group and halide ions. It is typically conducted with $\ce {LiCl}$ and $\ce {DMSO}$ ...
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1answer
121 views

Nucleophillic addition vs SN2

The following question came in Paper 2 of JEE Advanced 2014- Here we have $\ce{CH3-}$ as the nucleophile. There are 2 possible attacks: SN2 type attack on the chlorine group. Nucleophilic addition ...
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313 views

Reactivity of primary and tertiary alkyl halides

From USNCO 2004, Q58: The reaction between which pair of reactants occurs the fastest for $[\ce{OH-}] = \pu{0.010 M}$? (A) $\ce{CH3CH2CH2CH2Cl + OH-}$ (B) $\ce{(CH3)3CCl + OH-}$ (C) $...