Does m -xylene or p -xylene react more rapidly with Cl 2 + FeCl 3 ? Explain your answer.

Welcome back, everyone between Resorcinol and hydro Chone, which one will have a higher reaction rate with bromine and iron three bromide justify your answer. So let's go ahead and draw the two structures. First of all, we have resource. No, that's benzene with two hydroxy substituents meta relative to each other. Now, hydroquinone, it is a similar structure, but now the two hydroxy substitutions are parra relative to each other, which one will have a high reaction rate with bromine. Well, we have to recall that hydroxy subs are Ortho para directors. So we want to analyze each structure. The first one is resource and the second one is hydrogen. Let's begin with. The first hydroxy group were resource and we understand that there are two orthopedics and one par position. So these are the positions at which we're going to observe the electro grammatic substitution relative to the first hydroxy group. Now let's analyze the second one. Once again, we are going to have two Ortho positions in one par position and we can notice that all of these positions coincide, meaning the two hydroxy substituents are directing to exactly same carbons for the electro aromatic substitution. Now for hydroquinone, we can perform the same analysis Ortho Ortho. And now the power of position is already substituted, it's already substituted, right. So we don't need to analyze it. And now relative to the other hydroxy substituent, we have Ortho and Ortho and they do not coincide, meaning our answer would be resource. No. Now what is the reason? Well, the two hydroxy substituents are activating and directing bromine to exactly same positions, right. The hydroxy subscriptions are activating and directing to the same positions off the benzene ring. So that double activation essentially increases the rate of an electro pilic aromatic substitution reaction. Thank you for watching.

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19. Reactions of Aromatics: EAS and Beyond

EAS:Synergistic and Competitive Groups

Organic Chemistry

19. Reactions of Aromatics: EAS and Beyond

EAS:Synergistic and Competitive Groups

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3:16 minutes

Problem 69

Textbook Question

Does m-xylene or p-xylene react more rapidly with Cl₂ + FeCl₃? Explain your answer.

Verified step by step guidance

Step 1: Understand the reaction mechanism. The reaction between xylene and Cl₂ in the presence of FeCl₃ is an electrophilic aromatic substitution. FeCl₃ acts as a Lewis acid catalyst, generating the electrophile Cl⁺, which will attack the aromatic ring.

Step 2: Analyze the structure of m-xylene and p-xylene. Both are dimethylbenzene derivatives, but the positions of the methyl groups differ. In m-xylene, the methyl groups are located at the 1 and 3 positions, while in p-xylene, they are at the 1 and 4 positions.

Step 3: Consider the electron-donating effects of the methyl groups. Methyl groups are electron-donating via hyperconjugation and inductive effects, increasing the electron density of the aromatic ring. This makes the ring more reactive toward electrophilic attack. The positions of the methyl groups influence the distribution of electron density.

Step 4: Evaluate the steric hindrance. In m-xylene, the methyl groups are closer together, which can create steric hindrance and reduce the accessibility of certain positions on the ring for electrophilic attack. In p-xylene, the methyl groups are farther apart, reducing steric hindrance and making the ring more accessible for reaction.

Step 5: Conclude based on reactivity. Due to the reduced steric hindrance and more evenly distributed electron density, p-xylene reacts more rapidly with Cl₂ + FeCl₃ compared to m-xylene. The para position allows for easier electrophilic attack.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Electrophilic Aromatic Substitution

Electrophilic aromatic substitution (EAS) is a fundamental reaction mechanism in organic chemistry where an electrophile replaces a hydrogen atom on an aromatic ring. The reactivity of the aromatic compound is influenced by the substituents already present on the ring, which can either activate or deactivate the ring towards further substitution. Understanding EAS is crucial for predicting how different xylene isomers will react with electrophiles like Cl2 in the presence of a catalyst.

Substituent Effects

Substituent effects refer to how different groups attached to an aromatic ring influence its reactivity and orientation during electrophilic substitution reactions. Electron-donating groups (EDGs) enhance reactivity by stabilizing the positive charge in the intermediate, while electron-withdrawing groups (EWGs) decrease reactivity. In the case of m-xylene and p-xylene, the position of the methyl groups affects the electron density on the ring, thus impacting their reactivity with Cl2.

Steric Hindrance

Steric hindrance is the prevention of chemical reactions due to the spatial arrangement of atoms within a molecule. In the context of xylene isomers, the position of the methyl groups can create steric effects that influence how easily the electrophile can approach and react with the aromatic ring. For example, p-xylene may experience more steric hindrance compared to m-xylene, affecting the rate of reaction with Cl2 and FeCl3.

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