Chapter 14.SE, Problem 27AP

Interpretation Introduction

a) 1 mol Br₂ in CH₂Cl₂

Interpretation:

The products expected to be formed when 1,3-cyclohexadiene reacts with one mole of bromine in CH₂Cl₂ are to be given.

Concept introduction:

Conjugated dienes are treated with bromine in CH₂Cl₂ undergo both 1,2 and 1,4 addition of bromine to yield different products.

To give:

The product expected to be formed when 1,3-cyclohexadiene reacts with one mole of bromine in CH₂Cl₂.

Answer to Problem 27AP

The products expected to be formed when 1,3-cyclohexadiene reacts with one mole of bromine in CH₂Cl₂ are 3,6-dibromocyclohexene and 3,4-dibromocyclohexene.

Explanation of Solution

1,3-cyclohexadiene is a conjugated diene. When treated with one mole of bromine in CH₂Cl₂ it yields 3,6-dibromocyclohexene by 1,4 addition and 3,4-dibromocyclohexene by 1,2 addition reaction.

Conclusion

The products expected to be formed when 1,3-cyclohexadiene reacts with one mole of bromine in CH₂Cl₂ are 3,6-dibromocyclohexene and 3,4-dibromocyclohexene.

Interpretation Introduction

b) O₃ followed by Zn

Interpretation:

The product expected to be formed when 1,3-cyclohexadiene is treated with ozone followed by zinc is to be given.

Concept introduction:

Alkenes and dienes form ozonide when treated with ozone. The addition of ozone takes place to the double bonds. On reduction the ozonide cleaves and an oxygen atom becomes doubly bonded to each of the original alkene carbons to yield carbonyl compounds as products.

To give:

The product expected to be formed when 1,3-cyclohexadiene is treated with ozone followed by zinc is to be given.

Answer to Problem 27AP

The products expected to be formed when 1,3-cyclohexadiene is treated with ozone followed by zinc are glyoxal and succindialdehyde.

Explanation of Solution

Ozone adds to both the double bonds in 1,3-cyclohexadiene to form an ozonide. When treated with Zn and acetic acid the ozonide breaks to yield carbonyl compounds. The carbons that have oxygen in the products are joined through double bonds in the reactant.

Conclusion

The products expected to be formed when 1,3-cyclohexadiene is treated with ozone followed by zinc are glyoxal and succindialdehyde.

Interpretation Introduction

c) 1 mol HCl in ether

Interpretation:

The products expected to be formed when 1,3-cyclohexadiene is treated with one mole of HCl in ether is to be given.

Concept introduction:

Conjugated dienes when treated with one mole of HCl in ether undergo both 1,2 and 1,4 addition of HCl to yield different products. With unsubstituted cyclic conjugated 1,3-dienes a single product is produced in both types of addition.

To give:

The products expected to be formed when 1,3-cyclohexadiene is treated with one mole of HCl is to be given.

Answer to Problem 27AP

The product expected to be formed when 1,3-cyclohexadiene is treated with one mole of HCl is 3-chlorocyclohexene.

Explanation of Solution

Both 1,2 and 1,4 addition of HCl to 1,3-cyclohexadiene leads to the formation of the same product, 3-chlorocyclohexene, as it is an unsubstituted conjugated 1,3-diene.

Conclusion

The product expected to be formed when 1,3-cyclohexadiene is treated with one mole of HCl is 3-chlorocyclohexene.

Interpretation Introduction

d) 1 mol DCl in ether

Interpretation:

The products expected to be formed when 1,3-cyclohexadiene is treated with one mole of DCl are to be given.

Concept introduction:

Conjugated dienes when treated with one mole of DCl in ether undergo both 1,2 and 1,4 addition of DCl to yield different products.

To give:

The products expected to be formed when 1,3-cyclohexadiene is treated with one mole of DCl.

Answer to Problem 27AP

The products expected to be formed when 1,3-cyclohexadiene is treated with one mole of DCl are 3-chloro-4-deuteratedcyclohexene and 3-chloro-6-deuteratedcyclohexene.

Explanation of Solution

1,3-cyclohexadiene is a conjugated diene. When treated with one mole of DCl it yields 3-chloro-4-deuteratedcyclohexen by 1,2 addition 3-chloro-6-deuteratedcyclohexene by 1,4 addition reaction.

Conclusion

The products expected to be formed when 1,3-cyclohexadiene is treated with one mole of DCl are 3-chloro-4-deuteratedcyclohexene and 3-chloro-6-deuteratedcyclohexene.

Interpretation Introduction

e) 3-Buten-2-one (H₂C=CHCOCH₃)

Interpretation:

The product expected to be formed when 1,3-cyclohexadiene is treated with 3-buten-2-one is to be given.

Concept introduction:

In Diels-Alder reaction, a dienophile reacts with a diene to yield a cyclic adduct. The reaction takes place through 1,4 addition of the dienophile into the diene through a cyclic transition state. During the reaction the diene and dienophile orient themselves on top of one another and so an endo product results.

To give:

The product expected to be formed when 1,3-cyclohexadiene is treated with 3-buten-2-one.

Answer to Problem 27AP

The product expected to be formed when 1,3-cyclohexadiene is treated with 3-buten-2-one is

Explanation of Solution

The diene, 1,3-cyclohexadiene and the dienophile 3-buten-2-one arrange themselves one on the top of the other and react through the formation of a cyclic six member transition state to yield the endo product.

Conclusion

The product expected to be formed when 1,3-cyclohexadiene is treated with 3-buten-2-one is

Interpretation Introduction

f) Excess O_sO₄, followed by NaHSO₃

Interpretation:

The product expected to be formed when 1,3-cyclohexadiene is treated with excess OsO₄ and then with NaHSO₃ is to be given.

Concept introduction:

The reaction given involves hydroxylation of the double bonds in the diene. When a diene is treated with OsO₄, a single step addition of OsO₄ to each of the double bonds takes place to give a cyclic osmate. The cyclic osmate gets cleaved when treated with NaHSO₃ yields a tetraol.

To give:

The product expected to be formed when 1,3-cyclohexadiene is treated with excess OsO₄ and then with NaHSO₃.

Answer to Problem 27AP

The product expected to be formed when 1,3-cyclohexadiene is treated with excess OsO₄ and then with NaHSO₃ is cyclohexane-1,2,3,4-tetraol.

Explanation of Solution

When 1,3-cyclohexadiene is treated with excess OsO₄ the addition of OsO₄ takes place to both the double bonds in it. The addition occurs with syn stereochemistry to yield a cyclic osmate. The cyclic osmate then gets cleaved when treated with NaHSO₃ to yield the tetraol.

Conclusion

The product expected to be formed when 1,3-cyclohexadiene is treated with excess OsO₄ and then with NaHSO₃ is cyclohexane-1,2,3,4-tetraol.