16
votes
Accepted
Why doesn't aromatic substitution add at multiple positions in one reaction?
The rate of Aromatic substitution depends upon the activity of the aromatic system, because when the collision happens the aromatic system has to donate electrons to an electrophile.
In the example ...
- 3,161
15
votes
Why doesn't aromatic substitution add at multiple positions in one reaction?
During a electrophilic aromatic substitution, it is always possible to have multiple substitutions during one reaction. However, your example is not the ideal one for a discussion. As noted, Oscar ...
- 42.1k
12
votes
Accepted
Kolbe Schmitt followed by methylation
Collecting my comment thoughts together, there is an early demethylation step in this synthesis. Structure 1 is the result of carboxylation while methylation provides ester N. Friedel-Crafts ...
- 17.5k
12
votes
Accepted
Regioselectivity in Electrophilic Aromatic Substitution of Pyrrole and Indole
The traditional explanation for the reactivity of indole at C–3 is that attack at C–3 does not disrupt the aromaticity of the benzene ring in the cationic intermediate (see any organic chemistry book; ...
- 71.9k
11
votes
Accepted
Why is formyl chloride unstable while higher acyl chlorides are stable?
The simplest stable acyl chloride is ethanoyl chloride or acetyl chloride; methanoyl chloride (formyl chloride) is not stable at room temperature, although it can be prepared at –60 °C or below. (...
- 45.1k
10
votes
Meta-directing nature of anilinium cations
This does not answer your question exactly, but I hope this can shed some light on the anomalous behaviour of anilinium cations.
First of all, it is not true that the para-product is always favoured ...
- 5,735
9
votes
Accepted
Electrophilic substitution of benzene with conc. HNO₃ and HNO₂
Nitrosyl cation, $\ce{NO^+}$, is a better electrophile than molecular $\ce{HNO3}$ (you don't get $\ce{NO_2^+}$ in this system without sulfuric acid or other strong auxiliary acid) and so you get ...
- 62.6k
8
votes
Accepted
Why do resorcinol and iodine react to give 2-iodobenzen-1,3-diol?
Reading this question, I realized that OP is very new to organic chemistry, and in need for learning a lot about electrophilic aromatic substitution reactions. Thus, I recommend that OP should ...
- 42.1k
7
votes
Accepted
Electrophilic substitution on Borazole
Chiavarino, et al. [1] report that where electrophilic substitution occurs with carbocations (borazole more often undergoes addition), it does so on nitrogen. Nucleophiles such as methanol prefer ...
- 62.6k
5
votes
Why is formyl chloride unstable while higher acyl chlorides are stable?
More stable formyl compounds
While formyl chloride is unstable, formyl fluoride, with a stronger bond from the carbonyl carbon to the halogen, is marginally more stable. It can be made by a double ...
- 62.6k
5
votes
Accepted
Nitrobenzene - Aromatic Substitution Reactions
Of course, there must be some boundary as to whether or not nitrobenzene undergoes a particular electrophilic aromatic substitution (EAS) since nitro-group is very deactivating. I leave it to you to ...
- 42.1k
5
votes
Accepted
Reimer-Tiemann reaction on indole
The paper by Order and Lindwall [1] agrees with you that the R-T reaction gives indole-3-carboxaldehyde.
Since its isolation in 1903 by Hopkins and Cole (1), 3-indole aldehyde has been investigated ...
- 23k
5
votes
Accepted
Lactone acylation
The reaction of benzene and γ-butyrolactone with AlCl3 was reported by Truce and Olson1 in 1952. The authors found that the ratio of γ-phenylbutyric acid to α-tetralone was dependent ...
- 17.5k
5
votes
Accepted
Nitro-substitution
The reaction given in options (a) and (b) are called formation of nitrate esters. The following nitrate ester is called "ethyl nitrate",
Firstly, $\ce{HNO3}$ and $\ce{H2SO4}$ reacts to form ...
- 3,081
5
votes
Accepted
Major product of the nitration of benz[cd]indol-2(1H)-one
According to this patent here, N-ethyl 1,8-naphtholactam nitrates in the 4 position i.e. structure a. It seems entirely likely the N-unsubstituted material will do likewise.
- 23k
5
votes
Accepted
Electrophillic susbtitution of bromine on styrene and cinnamic acid in the presence of FeBr3, a Lewis acid
In electrophilic aromatic substitution the activation energy is very high ( as it should be, since the aryl carbocation transition state is very unstable)
The role of $\ce{FeBr_3}$ or any lewis acid ...
- 1,524
5
votes
Accepted
Electrophilic Substitution of Substituted Benzene
Friedel-Crafts reactions of anisole is known and the relevant acylation is performed in most academic institutions during undergraduate sophomore organic chemistry laboratories. For instance, Aluminum ...
- 42.1k
5
votes
Friedel-Crafts alkylation of fluorochloropropane
In the aforementioned question, Soumik Das has given acceptable reasoning (at least within our community, nobody has questioned his answer for five years). However, beside the fact that the Lewis acid ...
- 42.1k
5
votes
Accepted
Why electrophile doesn't attack COO- in 4-pentenoic acid?
It is entirely possible that the $\ce{I^+}$ end of a polarized iodine molecule does attack the carboxylate oxygen. But if it does, the resulting bond is weak and potentially quite reversible via the ...
- 62.6k
4
votes
Effect of chloromethyl substituent vs methyl substituent on yields of nitration
The following is the abstract of K.M. Zhang "Selective Nitration Of Benzyl Chloride And Its Application In The Synthesis Of Nitrobenzaldehyde"(link). The full pdf is behind paywall.
The selective ...
- 23k
4
votes
Accepted
Can anyone please help me how do you determine kinetically the fastest product of sulphonation of $\beta$ napthol?
Electrophile can substitute 2-naphthol ring on 3 possible positions: 1-position through intermediate I, 6-position through intermediate II, and 3-position through intermediate III (See following ...
- 42.1k
4
votes
Which is the major product of bromination of 3-(dimethylamino)benzamide, ortho or para?
Here's the 3D structure of the substrate:
As you can see, the $\ce{-N(Me)2}$ group is clearly larger than the $\ce{-CONH2}$ group. Also notice that the $\ce{-N(Me)2}$ group is planar with the benzene ...
- 6,348
4
votes
When we cannot use Friedel-Crafts acylation to insert alkyl group?
tBu-benzene is prepared exactly as you describe, see this preparation here. Follow this by nitration and reduction.
There is no obviously comparable strategy of acylation that can compete with this. ...
- 23k
4
votes
Accepted
What happens to the NMR of an alcohol when D2O is added?
In order to understand the probability of displacement of a H from any X-H bond (X is any atom), you need to know its pKa. The pKa values are as follows (ref.):
pKa of water = 14
pKa of OH (phenol) = ...
- 981
4
votes
Accepted
Bromination on the aromatic ring vs aliphatic chain
The key in this reaction is ketone in propiophenone is acting as Lewis base to $\ce{AlCl3}$ Lewis acid. If $\ce{AlCl3}$ is in catalytic amount, it activate $\alpha$-$\ce{H}$ in side chain sufficiently ...
- 42.1k
4
votes
Why are Friedel Crafts reaction not possible for molecules less activated than benzene?
Technically, the teacher's claim might be slightly modified. Deactivated benzenoid aromatics do fail to undergo Friedel-Crafts reactions, but according to a summary description from the University of ...
- 62.6k
4
votes
Is m-cresol or p-cresol more reactive towards electrophilic substitution?
To start, it is important that you understand that the methyl and hydroxy groups are activating only in the ortho and para positions. For example, if I were to substitute plain phenol, which contains ...
- 2,010
4
votes
Accepted
Electrophilic Substitution with Ceric Ammonium Nitrate and Lithium Bromide as reagents
First of all, the linked paper clearly points out the following:
Hint: In second step (A $\rightarrow$ B), combination of lithium bromide and cerium(IV) ammonium nitrate (CAN) is used as a ...
- 6,348
4
votes
Hell-Volhard-Zelinski Reaction
TL;DR: When $\ce{PBr3/PCl3}$ is not available as catalyst, red phosphorus is used which is reacted to bromine or chlorine to form the catalyst in situ.
Long answer:
Hell–Volhard–Zelinsky halogenation ...
- 26.8k
4
votes
Accepted
What is the electrophile in Perkin's condensation reaction?
The reaction mechanism shown on the Wikipedia page for the Perkin Reaction is perfectly clear.
The first step is deprotonation of acetic anhydride by acetate anion.
The second step is nucleophilic ...
- 23k
Only top scored, non community-wiki answers of a minimum length are eligible