Chapter 12, Problem 12.29P

Interpretation Introduction

(a)

Interpretation:

How the given compound with specified stereochemistry can be produced from an alkene is to be shown, along with the reagents used and special conditions if any.

Concept introduction:

A cyclopropyl group can be introduced in a compound by reacting the corresponding alkene (or alkyne) with a carbene. A carbene is a species with only two groups, typically hydrogen or halogen atoms bonded to a carbon. The carbon atom also carries a lone pair of electrons or sometimes two unpaired electrons. This pair of electrons makes the carbene extremely reactive. Carbenes add to an alkene or alkyne by simultaneously forming bonds with the two carbon atoms from the double (or triple) bond. One bond is formed by the lone pair on the carbene and the other by the $\text{π}$ bond pair from the initial double (or triple) bond.

The stereochemistry of the double bond is preserved in the reaction as it is a concerted addition. If the alkene has a cis configuration, the two similar substituents on the double bond end up on the same side of the cyclopropyl ring in the product. If it is a trans alkene, the similar substituents on the double bond end up on opposite sides of the ring in the product.

Carbenes are generated in situ, typically by irradiating a mixture of the alkene and diazomethane with UV light or by treating a mixture of the alkene and haloform (trihalomethane) with a strong base like an alkoxide.

Interpretation Introduction

(b)

Interpretation:

How the given compound with specified stereochemistry can be produced from an alkene is to be shown along with the reagents used and special conditions if any.

Concept introduction:

A cyclopropyl group can be introduced in a compound by reacting the corresponding alkene (or alkyne) with a carbene. A carbene is a species with only two groups, typically hydrogen or halogen atoms bonded to a carbon. The carbon atom also carries a lone pair of electrons or sometimes two unpaired electrons. This pair of electrons makes the carbene extremely reactive. Carbenes add to an alkene or alkyne by simultaneously forming bonds with the two carbon atoms from the double (or triple) bond. One bond is formed by the lone pair on the carbene and the other by the $\text{π}$ bond pair from the initial double (or triple) bond.

The stereochemistry of the double bond is preserved in the reaction as it is a concerted addition. If the alkene has a cis configuration, the two similar substituents on the double bond end up on the same side of the cyclopropyl ring in the product. If it is a trans alkene, the similar substituents on the double bond end up on opposite sides of the ring in the product.

Carbenes are generated in situ, typically by irradiating a mixture of the alkene and diazomethane with UV light or by treating a mixture of the alkene and haloform (trihalomethane) with a strong base like an alkoxide.

Interpretation Introduction

(c)

Interpretation:

How the given compound with specified stereochemistry can be produced from an alkene is to be shown along with the reagents used and special conditions if any.

Concept introduction:

A cyclopropyl group can be introduced in a compound by reacting the corresponding alkene (or alkyne) with a carbene. A carbene is a species with only two groups, typically hydrogen or halogen atoms bonded to a carbon. The carbon atom also carries a lone pair of electrons or sometimes two unpaired electrons. This pair of electrons makes the carbene extremely reactive. Carbenes add to an alkene or alkyne by simultaneously forming bonds with the two carbon atoms from the double (or triple) bond. One bond is formed by the lone pair on the carbene and the other by the $\text{π}$ bond pair from the initial double (or triple) bond.

The stereochemistry of the double bond is preserved in the reaction as it is a concerted addition. If the alkene has a cis configuration, the two similar substituents on the double bond end up on the same side of the cyclopropyl ring in the product. If it is a trans alkene, the similar substituents on the double bond end up on opposite sides of the ring in the product.

Carbenes are generated in situ, typically by irradiating a mixture of the alkene and diazomethane with UV light or by treating a mixture of the alkene and haloform (trihalomethane) with a strong base like an alkoxide.