Chapter 21, Problem 116CP

(a)

Interpretation Introduction

Interpretation: Under conditions, a plausible mechanism for the given conversion has to be proposed.

Concept Introduction:

Benzyne mechanism: A strong base abstract the proton from ortho to the leaving group in aromatic ring, followed by loss of leaving group which forms benzyne intermediate. This benzyne intermediate is highly unstable it undergoes nucleophilic attack and protonation which leads to the formation of the product.

Example:

Chloro benzene is converted to a phenol in the presence of base by the use of benzyne mechanism.

The mechanism of phenol sequence of arrow pushing pattern is given.

Enolate formation:

 For any given transformation, the following mandatory observations have to be made clear to predict the synthetic scheme:

• Observe whether there is any change in the carbon skeleton.
• Observe whether there is any change in the location of the functional group.
• Predict the synthetic scheme in such a way that these two observations have to be achieved within the minimum chemo selective steps.

(b)

Interpretation Introduction

Interpretation: The structure of the side product has to be proposed.

Concept Introduction:

Enolate formation:

 For any given transformation, the following mandatory observations have to be made clear to predict the synthetic scheme:

• Observe whether there is any change in the carbon skeleton.
• Observe whether there is any change in the location of the functional group.
• Predict the synthetic scheme in such a way that these two observations have to be achieved within the minimum chemo selective steps.