Question

The most appropriate reagent for the following conversion is CCOC1C=CC=CC1O Oc1ccccc1 (A) \(\mathrm{Cu} / 300^{\circ} \mathrm{C}\) (B) conc. \(\mathrm{H}_{2} \mathrm{SO}_{4}\) (C) Red P/HI (D) NaI in Acetone

Short answer

Based on our analysis, the most appropriate reagent for the given conversion from ethyl phenyl ether to phenol is \( \displaystyle (C) \ \text{Red P/HI} \) as it can break the ether bond and form an alcohol.

Step-by-step solution

Translate SMILES Notation to Molecular Structure

For ease of understanding the chemical conversion, we should first translate the given SMILES notations into molecular structures. Starting compound (CCOC1C=CC=CC1O): Ethyl phenyl ether (C8H10O) \( \displaystyle \begin{array} { c c } \text { Structure: } & \\ \text { O } & \\ | & \\ \text { C } - \text { C } & \\ & | \\ \text { C } & \\ \quad / | \backslash & \\ \text { C } = \text { C } - \text { C } \\ \quad \backslash / & \\ \text { C } \end{array} \) Target compound (Oc1ccccc1): Phenol (C6H6O) \( \displaystyle \begin{array} { c } \text { Structure: } \\ \text { O } \\ | \\ \text { C } - \text { C } \\ \quad / | & \\ \text { C } & \\ \quad \backslash / & \\ \text { C } \end{array} \)

Analyze the Conversion

We want to convert ethyl phenyl ether (C8H10O) to phenol (C6H6O). To achieve this, we need to remove the ethyl group (-C2H5) attached to the oxygen atom and replace it with a hydrogen atom. Let's analyze the given reagents: (A) \(\displaystyle \mathrm{Cu}\ /\ 300^{\circ} \mathrm{C}\) Catalytic hydrogenation is used to reduce alkene or alkyne functionalities to alkanes but is not necessary here as our target compound has the same level of unsaturation as the starting compound. (B) conc. \(\displaystyle \mathrm{H}_{2} \mathrm{SO}_{4}\) Concentrated sulfuric acid is a strong dehydrating agent and can form ethers by combining two alcohols, but our aim is to break the ether bond and convert it into a phenol, which is an alcohol. (C) Red P/HI Red phosphorus and hydroiodic acid (Red P/HI) can break the ether bond and produce an alcohol with the help of an iodohydrin intermediate. It appears the most suitable candidate for our conversion. (D) NaI in Acetone Sodium iodide in acetone is a mild nucleophile reagent that can halogenate and convert alkyl chlorides or bromides into alkyl iodides, but it is not useful here as we want to break the ether bond and form a phenol.

Select the Most Appropriate Reagent

Based on our analysis, reagent (C) Red P/HI seems the most appropriate choice to achieve the desired conversion from ethyl phenyl ether to phenol by breaking the ether bond and forming an alcohol. So, the correct answer is (C) Red P/HI.

Key concepts

SMILES Notation in Organic Chemistry

The Simplified Molecular Input Line Entry System (SMILES) is a notation system used to represent a chemical structure in a linear text form. It serves as a shorthand way to depict molecules and reactions in a consistent and machine-readable format.

SMILES notation allows chemists to quickly communicate complex molecular structures through simple strings of ASCII characters. Each character or group of characters represents atoms, bonds and other features of the molecule's three-dimensional structure.

For instance, in the exercise, the starting compound was given in SMILES as CCOC1C=CC=CC1O, which is ethyl phenyl ether, while the target compound was Oc1ccccc1, known as phenol. These notations help students and researchers visualize structures without drawing them and play a critical role in computational chemistry for database searching and molecular modeling.

Alcohol and Ether Conversion

Converting alcohols to ethers, or breaking ethers back down to alcohols, is part of routine synthetic organic chemistry. An Ether, such as ethyl phenyl ether presented in the original exercise, is a compound in which an oxygen atom is connected to two carbon-containing groups. An Alcohol has an -OH group attached to a carbon atom.

For converting ethers to alcohols, chemists often employ strong acids or other cleaving agents that break the C-O bond in ethers, liberating an alcohol. However, this conversion must be done carefully to avoid over-reacting or affecting other parts of the molecule. This is why the selection of reagents is crucial. In the given exercise, the Red P/HI reagent is most suitable because it can efficiently break the ether bond and convert it into the desired alcohol, phenol, without unnecessary changes to the remaining structure of the molecule.

Reagent Selection for Chemical Reactions

Choosing the right reagent is essential in organic chemistry to ensure the desired reaction proceeds efficiently and yields the correct product. Each reagent has specific properties and reactivities that make it suitable for certain transformations and unsuitable for others.

When selecting a reagent, a chemist evaluates factors such as reactivity, selectivity, cost, safety, and environmental impact. For instance, in the exercise, the selection of Red P/HI is based on its specific ability to cleave ether bonds and its compatibility with the other functional groups present in the molecule.

Understanding the mechanism of a reaction can also aid in the selection process. Reagents can act as acids, bases, oxidizing agents, reducing agents, nucleophiles, electrophiles, and more. Correct reagent selection and its subsequent effect on a reaction can often make the difference between a successful synthesis and a failed one.