Predict the product(s) that would result when molecules (a)–(p) are allowed to react under the following conditions: (ii) PBr₃ If no reaction occurs, write 'no reaction.'
(c)

검증된 단계별 안내

Identify the functional groups in the given molecule. The structure shows a cyclohexane ring with two hydroxyl groups (OH) attached, indicating it is a diol.

Understand the role of PBr₃ in organic reactions. Phosphorus tribromide (PBr₃) is commonly used to convert alcohols into alkyl bromides by replacing the hydroxyl group with a bromine atom.

Determine which hydroxyl group will react with PBr₃. PBr₃ typically reacts with primary and secondary alcohols. In this molecule, both hydroxyl groups are secondary, so both can potentially react.

Predict the reaction mechanism. The reaction with PBr₃ involves the formation of a phosphite ester intermediate, followed by the substitution of the hydroxyl group with a bromine atom, resulting in the formation of an alkyl bromide.

Consider the stereochemistry of the reaction. The reaction with PBr₃ usually proceeds with inversion of configuration at the carbon atom bearing the hydroxyl group, due to the SN2 mechanism involved.

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주요 개념

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PBr₃ Reaction with Alcohols

Phosphorus tribromide (PBr₃) is commonly used to convert alcohols into alkyl bromides. The reaction involves the substitution of the hydroxyl group (OH) with a bromine atom (Br), resulting in the formation of an alkyl bromide. This reaction is typically used for primary and secondary alcohols, as it proceeds via an SN2 mechanism, which is less favorable for tertiary alcohols due to steric hindrance.

SN2 Mechanism

The SN2 mechanism is a bimolecular nucleophilic substitution reaction where the nucleophile attacks the electrophilic carbon from the opposite side of the leaving group, resulting in an inversion of configuration. This mechanism is favored in primary and secondary alcohols due to less steric hindrance, allowing the nucleophile to effectively approach the carbon atom. In the context of PBr₃ reactions, the bromide ion acts as the nucleophile, replacing the hydroxyl group.

Vicinal Diols

Vicinal diols are compounds with two hydroxyl groups attached to adjacent carbon atoms. In the given structure, the presence of vicinal diols can influence the reaction pathway, as they may undergo rearrangement or elimination under certain conditions. However, with PBr₃, each hydroxyl group can independently react to form the corresponding alkyl bromide, assuming no rearrangement occurs.

Predict the product(s) that would result when molecules (a)–(p) are allowed to react under the following conditions: (ii) PBr₃ If no reaction occurs, write 'no reaction.'(c)