Chapter 16, Problem 16.60P

Interpretation Introduction

(a)

Interpretation: The product formed by the reaction of given diene with one equivalent of $\text{HI}$ is to be drawn.

Concept introduction: Diene is a hydrocarbon that contains two $\text{C}=\text{C}$ double bonds in a compound. Conjugated diene consists of two double bonds that are separated by a single bond, whereas isolated diene also consists of two double bond but they are separated by two more carbon atoms.

Answer to Problem 16.60P

The products formed by the given reaction are,

Explanation of Solution

Conjugated dienes undergoes electrophilic addition to gives a mixture of products that is $1,2-\text{addition}\text{product}$ and $1,4-\text{addition}\text{product}$, whereas isolated diene give one product followed by markovnikov’s rule.

Markovnikov addition of $\text{HI}$ results in the formation of $1,2-\text{addition}\text{product}$, whereas addition of $\text{HI}$ to the two end carbons of the diene result in the formation of $1,4-\text{addition}\text{product}$.

The given reaction is shown below.

Figure 1

The given diene is a conjugated diene. The attack of ${\text{H}}^{+}$ on the given diene results in the formation of stable carbocation. In the next step, iodide ion as a nucleophile will attack on the carbocation to form constitutional isomers. Thus, the product formed by the reaction of given diene with one equivalent of $\text{HI}$ is shown below.

Figure 2

Therefore, the products formed by the given reaction are $3-\text{iodo}-2,3-\text{dimethylbut}-1-\text{ene}$ and $1-\text{iodo}-2,3-\text{dimethylbut}-2-\text{ene}$.

Conclusion

The products formed by the given reaction is $3-\text{iodo}-2,3-\text{dimethylbut}-1-\text{ene}$ and $1-\text{iodo}-2,3-\text{dimethylbut}-2-\text{ene}$.

Interpretation Introduction

(b)

Interpretation: The Diels-Alder product formed by the given reaction including stereochemistry is to be drawn.

Concept introduction: A chemical reaction that involves $\left[4+2\right]$ cycloaddition is called Diels-Alder reaction. The reactant molecules that give rise to product are diene and dienophile. Adduct of Diels-Alder reaction exist in two isomeric forms endo and exo.

Answer to Problem 16.60P

The Diels-Alder product formed by the given reaction is,

Explanation of Solution

The given reaction is shown below.

Figure 3

Diels-alder reaction is a cycloaddition reaction in which two molecules combine to form a new ring. In this type of reaction, syn addition takes place. It is a reaction between diene with a dienophile to yield a cyclohexene. They have syn stereochemistry. The stereochemistry of dienophile in endo isomer is same as that of bridging ring system, whereas in exo isomer, it is in opposite.

Thus, the Diels-Alder product formed by the given reaction including stereochemistry is shown in Figure 4.

Figure 4

Conclusion

The Diels-Alder product formed by the given reaction including stereochemistry is shown in Figure 4.

Interpretation Introduction

(c)

Interpretation: The Diels-Alder product formed by the given reaction including stereochemistry is to be drawn.

Concept introduction: A chemical reaction that involves $\left[4+2\right]$ cycloaddition is called Diels-Alder reaction. The reactant molecules that give rise to product are diene and dienophile. Adduct of Diels-Alder reaction exist in two isomeric forms endo and exo.

Answer to Problem 16.60P

The Diels-Alder product formed by the given reaction including stereochemistry is,

Explanation of Solution

The given reaction is shown below.

Figure 5

Diels-alder reaction is a cycloaddition reaction in which two molecules combine to form a new ring. In this type of reaction, syn addition takes place. It is a reaction between diene with a dienophile to yield a cyclohexene. They have syn stereochemistry.

Thus, the Diels-Alder product formed by the given reaction including stereochemistry is shown in Figure 4.

Figure 6

Conclusion

The Diels-Alder product formed by the given reaction including stereochemistry is shown in Figure 6.

Interpretation Introduction

(d)

Interpretation: The product formed by the reaction of given diene with one equivalent of $\text{HBr}$ is to be drawn.

Concept introduction: Diene is a hydrocarbon that contains two $\text{C}=\text{C}$ double bonds in a compound. Conjugated diene consists of two double bonds that are separated by a single bond, whereas isolated diene also consists of two double bond but they are separated by two more carbon atoms.

Answer to Problem 16.60P

The products formed by the given reaction are,

Explanation of Solution

Conjugated dienes undergoes electrophilic addition to gives a mixture of products that is $1,2-\text{addition}\text{product}$ and $1,4-\text{addition}\text{product}$, whereas isolated diene give one product followed by markovnikov’s rule.

Markovnikov addition of $\text{HBr}$ results in the formation of $1,2-\text{addition}\text{product}$, whereas addition of $\text{HBr}$ to the two end carbons of the diene result in the formation of $1,4-\text{addition}\text{product}$.

The given reaction is shown below.

Figure 7

The given diene is a conjugated diene. The attack of ${\text{H}}^{+}$ on the given diene results in the formation of stable carbocation. In the next step, iodide ion as a nucleophile will attack on the carbocation to form constitutional isomers. Thus, the product formed by the reaction of given diene with one equivalent of $\text{HBr}$ is shown below.

Figure 8

Therefore, the products formed by the given reaction is $6-\text{bromo}-1,6-\text{dimethylcyclohex}-1-\text{ene}$ and $3-\text{bromo}-1,2-\text{dimethylcyclohex}-1-\text{ene}$.

Conclusion

The products formed by the given reaction is $6-\text{bromo}-1,6-\text{dimethylcyclohex}-1-\text{ene}$ and $3-\text{bromo}-1,2-\text{dimethylcyclohex}-1-\text{ene}$.