Questions tagged [nucleophilic-substitution]
For questions having their focus on SN1, SN2, SNi, SN1', SN2', or SN2th (nucleophilic acyl substitution).
2
votes
2answers
41 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) $...
8
votes
1answer
55 views
Alcohol or Carbonyl - Which is more reactive towards PCl5?
We're aware that ketones and alcohols both react with phosphorus pentachloride, to produce geminal dichlorides and alkyl chlorides respectively.
What happens in the compound shown below, when ...
-1
votes
0answers
19 views
Nucleophilic attack on carbonyl vs. SN2 - who wins?
If a nucleophile is to attack the above compound, how do I determine wheather it kick the chlorine atom out via an SN2, or will it attack the electron deficient carbonyl?
Does it depend on the ...
2
votes
1answer
72 views
Order of reactivity of nucleophilic addition at carbonyl group with Grignard reagent
I thought the order would be $1 > 3 > 2$ as 1 is aldehyde and 2, 3 are ketones. As generally aldehydes are more reactive, I placed it first. I chose 3 over 2 as two alkyl groups would make ...
-1
votes
1answer
48 views
Why can't you form an anhydride from an ester via nucleophilic attack?
The reaction referred to is the nucleophilic acyl substitution reaction, where the nucleophile is a carboxylate ion and the electrophile is the ester. I am having a difficult time visualizing why this ...
2
votes
0answers
22 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 ...
1
vote
0answers
14 views
Effect of solvent polarity on SN1 reactions of different charge types
On the topic of the ionisation mechanism (i.e. $\mathrm{S_N1}$), Carey & Sundberg (2007) discuss the effect of polarity of solvent on the rate of $\mathrm{S_N1}$ reactions of different charge ...
6
votes
1answer
43 views
Dependence of rates of neighbouring group participation on length of alkyl chain
On the topic on neigbouring group participation, it is mentioned in Carey & Sundberg (2007)[1] that the effectiveness of the participation is dependent on on the ease with which the molecular ...
4
votes
2answers
61 views
Regioselectivity in iodolactonisation of γ,δ-unsaturated carboxylic acid
In the last step of the iodolactonisation of 3,3-dimethylpent-4-enoic acid,[1,2] why does the carboxylate attack the iodonium to form a 5-membered ring, when a more stable 6-membered ring is possible? ...
0
votes
0answers
57 views
Benzene diazonium chloride and ethanol
Benzene diazonium chloride is reduced to benzene by ethanol which itself gets oxidised to ethanal.
Most reactions of diazonium salts are due to nucleophilic substitution on the carbon attached to ...
0
votes
1answer
38 views
Why does using NaI as a nucleophile and acetone as solvent lead to an SN2 reaction mechanism instead of SN1? Is I- not considered a weak nucleophile?
In a reaction with a secondary leaving group, why does using NaI with acetone as a solvent lead to an SN2 reaction mechanism instead of SN1? I thought that halogens were weak nucleophiles, and only ...
-1
votes
0answers
13 views
Why is a thioester more reactive than an ester? [duplicate]
I'm curious as to why a thioester is more reactive than an ester when it comes to reactivity towards nucleophilic attack.
I know that the two factors affecting the reactivity towards nucleophilic ...
-4
votes
2answers
35 views
Addition reaction(Haloalkane) [closed]
In these reactions if two reagent is given how to decide who is going to react with the compound.HBr is a strong acid
CH3OH is a weak base.So HBr dissociate easily but CH3OH is reacting with the given ...
1
vote
1answer
50 views
Displacement of leaving groups in organic reactions
When I initially learned about substitution reactions, there would be times where a poor leaving group had to be changed into a better one in order to proceed with a substitution reaction. For ...
1
vote
1answer
36 views
Do bulky bases participate in substitution reactions?
I see how bulky bases influence the regioselectivity of E2 and E1 reactions. I do not see very much content on the involvement of bulky bases in substitution reactions.
I know that bulky bases like t-...
1
vote
0answers
38 views
Electronic effects of substituents in the benzyne mechanism
On the topic of nucleophilic aromatic substitution (S$_N$Ar) reactions, the benzyne mechanism is discussed. When considering the position of substitution, electronic and steric factors are mentioned. ...
-1
votes
1answer
64 views
Converting a thioester to an amide
What reagents can I use for the following transformation? I think this has something to do with formation of an iminium salt and reductive amination, but I'm not so sure.
9
votes
3answers
324 views
How does ring size affect SN2 reactions?
Suppose we have to compare the $\mathrm{S_N2}$ reactivity order for cyclopropyl and cyclopentyl chloride. How can we do that?
I think that cyclopentyl should be more reactive towards $\mathrm{S_N2}$ ...
2
votes
1answer
55 views
Why do *tert*-butyl ethers in diluted sulfuric acid undergo elimation instead of solvolysis?
My organic textbook states the pathway for propyl tert-butyl ether in dilute sulfuric acid will follow E1 with a tertiary carbocation intermediate. It mentions that Sn1 will only occur with good ...
12
votes
1answer
198 views
Rearrangement with sodium iodide (ring opening)
I'm not able to figure out the mechanism for this reaction. I don't see how sodium iodide in acetone could lead to rearrangement, and surprisingly ring opening!
What is this reaction called, if it ...
2
votes
0answers
279 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 ...
-2
votes
1answer
94 views
Organic reaction with Na2S2O4 [closed]
Question:
In the first step due to cooperating Inductive and resonance effect C6H5N2 + will be attached at the ortho position of methyl group for which para position is occupied by Amine group ...
1
vote
0answers
46 views
Why ammonium salts can not undergo substitution
Why is ammonium salt, such as RNH3+, can not react with nucleophiles like HI to give RI and NH4+? The reaction is pretty much like the substitution of alcohol in acid condition.
In my opinion, NH3 (...
2
votes
0answers
97 views
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- ...
1
vote
1answer
45 views
Formation of acid chlorides
In Sn2 nucleophilic substitution reactions,the attacking nucleophile or leaving group is eliminated. The weaker base is eliminated. Then how do acid chlorides form as OH- is a stronger base than Cl–.
3
votes
1answer
70 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 ...
1
vote
0answers
54 views
What is the product formed when 4-chlorobut-1-ene is treated with acetic acid?
My teacher did like this forming a really unstable cyclopropyl group but this is the correct answer instead. My question is why the product will be even formed?
In the mechanism that my teacher had ...
1
vote
1answer
668 views
Does neopentyl halide undergo SN1?
Carbocation formed from neopentyl halide is primary in nature. So it is not stable. Although it undergoes rearrangement reaction to form tertiary one, now it can undergo SN1 easily. So if we say it ...
1
vote
0answers
108 views
Competition of H2O and NH3 leaving groups in nucleophilic acyl substitutions
I've learned in several textbooks, that in the nucleophilic acyl substitution $\ce{H2O}$ is a better leaving group than $\ce{NH3}$. This can be explained by the "thumb rule" of the $\mathrm{p}K_\...
0
votes
2answers
224 views
Which will give faster Sn2 reaction
In $\ce{H2C=CH-Br}$ and $\ce{H3C-CH2-Br}$, which will react faster towards a SN2 reaction?
According to me, as double bond exhibit -I effect, hence the 1st should do a faster reaction. Am I right or ...
1
vote
1answer
92 views
Can someone confirm and/or correct my logic regarding this mechanism?
In the picture, Ethyl 2-oxocyclopentanecarboxylate (I) reacts with ethyl 2-(4-chloromethylphenyl)propionate (II) in the presence of KOH in hot DMF to afford ethyl 2-[4-(1-ethoxycarbonyl-2-...
2
votes
1answer
212 views
Are SN2 reactions in equilibrium?
I'm learning about SN2-reactions, and my text book gives the following examples of these reactions:
$$\ce{HO^- +CH_3Br -> CH_3OH + Br^-}\tag{1}$$
$$\ce{I^- +CH_3Br -> CH_3I + Br^-}\tag{2}$$
...
1
vote
1answer
89 views
What is the product of the reaction of diol with tosyl chloride followed by lithium aluminum hydride?
This question is about the structure of products X and Y.
According to me, the answer should be only A (as OTs will substitute on benzylic carbon).
But in the answer key, they have given B and D.
...
4
votes
2answers
131 views
Can the alkyl-oxygen bond in lactones be cleaved in an SN2 reaction?
I understand that nucleophiles typically attack the electrophilic carbonyl carbon of the lactone and open the ring through a nucleophilic acyl substitution. Has there ever been the case where the ...
1
vote
2answers
407 views
Reactivity of meta- and para-bromo-nitrobenzene towards nucleophilic substitution
Among 1-bromo-3-nitrobenzene and 1-bromo-4-nitrobenzene, which would be more reactive towards nucleophilic substitution?
From what I can infer, the answer should have been 1-bromo-3-nitrobenzene. ...
3
votes
0answers
40 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 ...
3
votes
2answers
209 views
Reaction of NaOD/D2O with semicarbazone
I managed to solve the question till D but I'm stuck at the last reaction.
I tried to find its solution and the source suggest it as
6
votes
0answers
76 views
The effect of the groups at para position on SN2 reactivity
Compare the SN2 reactivity order for:
The benzyl group stabilises the transition state of SN2 reaction using the π system of the benzene ring for conjugation with the p- orbital of the ...
5
votes
0answers
121 views
Attack of ethoxide on epichlorohydrin
I eliminated the possibility of the first two options since they included an alcohol and the solvent has not been specified so we do not know whether it is polar protic or polar aprotic.
As for the ...
10
votes
2answers
568 views
Mechanism for reaction of aryl diazonium with potassium iodide
I’m working on a synthesis problem that requires me to draw the arrow mechanism for the second half of the Sandmeyer reaction. Basically it’s the halogenation of an aryl diazonium compound. Typically ...
12
votes
1answer
358 views
Why does a six-membered ring contract in this SN1 reaction?
I was watching this video on Khan Academy (YouTube link) regarding SN1 mechanisms and carbocation rearrangements and came across this mechanism.
At around timestamp 4:20 in the video, why does step 2 ...
0
votes
0answers
45 views
Why do halohydrins in base react to give epoxides rather than a substitution or elimination reaction?
The halohydrin reaction in base is well known for making epoxides. However I am confused as to why the base does not simply perform SN2 on the bromine atom, or an E1 on an adjacent carbon atom.
4
votes
0answers
49 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 ...
3
votes
1answer
40 views
Which attack occurs first: nucleophilic acyl substitution or nucleophilic substitution?
If there is a compound with a site for nucleophilic acyl substitution (i.e. an ester group or the like) as well as a nucleophilic substitution (i.e. a bromine group or the like), will a nucleophile ...
6
votes
0answers
347 views
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 ...
1
vote
0answers
72 views
Mechanism for the formation of an alkyl halide from alcohol and phosphorus trihalide [duplicate]
I was reading about synthesis of alkyl halides from $\ce{PX3}$. I want to know the mechanism for this reaction. According to Solomons and Fryhle, no rearrangement takes place in case of $\ce{PBr3}$ , ...
12
votes
1answer
395 views
Order of halide nucleophilicity in DMF
The order of nucleophilicity for halide family in DMF is: $\ce{Cl- > Br- > I-}$. I understand the reason for this must be that DMF, being a polar aprotic solvent, is unable to solvate the ...
4
votes
0answers
390 views
What is the SNi mechanism of the reaction of moist silver oxide with a halide?
I was told by my teacher that the following reaction proceeds through SNi:
Moist $\ce{Ag2O}$ is basically $\ce{AgOH}$, what role does it play in this reaction's mechanism? I think this is what ...
6
votes
1answer
84 views
Mechanism for the conversion of an unsaturated alkyl halide to an alcohol
Question:
Predict the mechanism for the following reaction:
Attempt:
I thought it will proceed through SN1 mechanism as $\ce{H_2O}$ is involved (solvolysis). So I proceeded with the ...
4
votes
2answers
70 views
Do alkyl halides with an alpha nitrogen atom undergo SN1 reaction?
Today, in my organic chemistry class, I learnt about the nucleophilic substitution reaction. The notes have stated that:
Alkyl halides with $\alpha$ oxygen atom can also undergo SN1 reaction ...
