16 votes
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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 ...
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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 ...
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11 votes
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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 ...
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11 votes
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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; ...
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9 votes
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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 ...
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8 votes
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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 ...
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7 votes
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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. (...
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7 votes

Kinetic isotope effect in nitration of benzene

Page 513 of Organic Reaction Mechanisms by Bansal references the work of Melander in Arkiv för Kemi, 2, 211 (1950). This states that the rates of nitration for benzene vs benzene-d6 are about the same,...
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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 ...
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7 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 ...
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6 votes

Friedel-Crafts synthesis - How is HCl produced?

You could perform the electrophilic aromatic substitution with acetyl chloride as well instead of acetic anhydride - in the first case it is evident where $\ce{HCl}$ comes from. However, the mechanism ...
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5 votes
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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 ...
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5 votes
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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 ...
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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 ...
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5 votes
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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 ...
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4 votes

Kinetic isotope effect in nitration of benzene

This is an example of an inverse kinetic isotope effect. When a transition state increases in coordination then differences gained from vibrational bending energy for the $\ce{C-D}$ vs $\ce{C-H}$ ...
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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 ...
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4 votes
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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 ...
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4 votes
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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 ...
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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 ...
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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 ...
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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 ...
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4 votes
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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 ...
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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.
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4 votes
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Can't aluminium chloride do electrophilic substitution as an electrophile?

The reaction wouldn't happen because you forget that $\ce{Cl2}$ is also present in the solution (because $\ce{AlCl3}$ is a strong lewis acid). An acid-base reaction is way faster than an aromatic ...
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3 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. ...
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Solvent Effects in Friedel–Crafts Reaction

On Friedel-Crafts-acylation reactions, two types of Friedel-Crafts-acylation mechanisms, namely an ion pair mechanism and a dipolar ion mechanism, have been proposed (Ref.1). Normal acylations are ...
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3 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 ...
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Why are Friedel Crafts reaction not possible for molecules less activated than benzene?

OP quote: I know that Friedel Crafts alkylation reaction are not possible for aniline and phenol since they form complexes with Lewis Acids. This is true partially for Lewis acids (Note: I said ...
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3 votes
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Validity of the leveling effect of water in nitration reactions

What you have gone wrong in this question is you completely disregard the fact that mentioned stronger acids than water are all in aqueous medium, in other words, dissolved in water. Thus, fast acid-...
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