Phenols Reactivity MDCAT Quiz is a very critical topic for MDCAT students because it focuses on the diverse chemical reactions phenolic compounds undergo as a result of the hydroxyl group (-OH) attached to an aromatic ring. Phenols exhibit a difference in behavior compared to alcohols, and this property makes their behavior in reactions vital to understanding organic chemistry and to make predictions in the outcome of reactions within the MDCAT exam.
Electrophilic Aromatic Substitution: Phenols undergo electrophilic aromatic substitution reactions because the hydroxyl group on the aromatic ring is electron-donating. The presence of the hydroxyl group makes the benzene ring more reactive toward electrophiles, such that phenols react with reagents like bromine (Br₂), chlorine (Cl₂), and nitric acid (HNO₃). For example, bromination of phenol gives 2,4,6-tribromophenol. The position of substitution is influenced by the activating effect of the -OH group, which directs electrophiles to the ortho and para positions relative to itself.
Acid-Base Reactions: Phenols are weak acids and can undergo acid-base reactions with bases like sodium hydroxide (NaOH) to form phenoxide salts. The hydroxyl group releases a proton (H⁺) to form the phenoxide ion (C₆H₅O⁻), which is stabilized by resonance with the benzene ring. The phenoxide ion is a strong nucleophile and can participate in nucleophilic substitution reactions. This ability to act as an acid distinguishes phenols from alcohols, which are generally less acidic.
Reduction Reactions: The phenols can be reduced to hydrocarbons. A common reducing agent is hydrogen gas (H₂) in the presence of a catalyst, which reduces the phenol to an alkane. This type of reaction is important for the conversion of phenolic compounds into other organic molecules for further chemical processes.
Formation of Esters: Phenols can react with carboxylic acids or acid chlorides to form phenolic esters. In this reaction, the hydroxyl group of the phenol reacts with the carbonyl group of the carboxylic acid to form an ester and release water. This reaction is usually catalyzed by an acid, such as sulfuric acid (H₂SO₄). Thus, phenyl acetate is formed when phenol reacts with acetic acid.
Understanding the reactivity of phenols is essential for MDCAT students, as these reactions are fundamental in organic chemistry and play a role in both laboratory synthesis and industrial applications.
Quiz: Test Your Knowledge of Phenols Reactivity
Our MDCAT Quiz on phenols reactivity will help you test your knowledge of various chemical reactions that phenols undergo, including electrophilic substitution, acid-base reactions, reduction, and ester formation. The quiz provides practical questions to reinforce your understanding and prepare you for reactivity-based questions in the MDCAT exam.
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Free Flashcard: Key Insights on Phenols Reactivity
Our Free Flashcard set on phenols reactivity provides a concise summary of the key reactions that phenols undergo, such as electrophilic substitution and esterification. These flashcards will help you quickly memorize and recall essential information for the MDCAT exam.
Phenols undergo __________ reaction with bromine.
Electrophilic substitution
When phenol reacts with zinc, it forms __________.
Cyclohexene
Phenols react with __________ to form esters.
Acid chlorides
The reaction of phenol with sodium hydroxide gives __________.
Sodium phenoxide
Phenols react with __________ to form phenolic acids.
Halogens
The reaction of phenol with zinc dust at high temperature gives __________.
Cyclohexene
Phenols react with alkyl halides in the presence of a base to form __________.
Alkylphenols
The reactivity of phenol with electrophiles is enhanced by __________.
Electron-donating groups
Phenols can undergo __________ reaction with halogens.
Substitution
When phenol reacts with nitric acid, it forms __________.
Nitrobenzene
The phenol group can undergo __________ reaction with acyl chlorides.
Friedel-Crafts acylation
In the presence of a strong oxidizer, phenols can be oxidized to __________.
Quinones
Phenols react with formaldehyde to give __________.
Phenol formaldehyde
When phenol reacts with sodium, it forms __________.
Sodium phenoxide
The reaction of phenol with a halogen like chlorine is an example of __________.
Electrophilic substitution
The reactivity of phenols in nucleophilic substitution is higher due to __________.
The delocalization of electrons
Phenols are highly reactive due to the presence of the __________ group.
Hydroxyl (-OH)
When phenol reacts with an alkyl halide in the presence of a base, it forms __________.
Ether
Phenols undergo __________ reaction with oxidizing agents like potassium permanganate.
Oxidation
The reaction of phenol with halogenated compounds typically results in __________.
Electrophilic substitution
The reaction of phenol with acetic anhydride gives __________.
Esters
The reactivity of phenols is generally greater in the presence of __________ groups.
Electron-withdrawing
Phenols can undergo __________ reaction to form diphenylmethane.
Friedel-Crafts reaction
The reaction of phenol with bromine forms __________.
2,4,6-Tribromophenol
When phenol reacts with alkali, it forms __________.
Sodium phenoxide
In phenols, the reactivity towards electrophiles increases when substituents are present in the __________ position.
Ortho or para
Phenols can be used as __________ agents in chemical reactions.
Reducing
When phenol reacts with acyl chlorides, it forms __________.
Phenolic acid
In electrophilic aromatic substitution reactions, phenols react faster due to __________.
Resonance stabilization
Phenols can undergo __________ reaction with diazonium salts.
Electrophilic substitution
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