Chapter 12, Problem 12.4P

Interpretation Introduction

Interpretation:

Two different ways of synthesizing the given compound via carbene addition by using a different alkene are to be provided.

Concept introduction:

A carbene is a species containing a carbon atom that has two bonds and a lone pair of electrons. Carbenes are typically highly electrophilic due to the lack of an octet and are ${\text{sp}}^{\text{2}}$ hybridized. The lone pair of electrons occupies a hybrid orbital, leaving the p orbital empty. Thus, carbenes resemble a carbocation and are generally highly electron-deficient.

Chloroform is a precursor to generate a carbene. When an alkyl trihalide is treated with a strong base in the presence of cyclohexane, a dihalocarbene is generated in two steps via $\text{α}$- elimination. The base first deprotonates the alkyl trihalide, which is weakly acidic. In step two, the halogen atom departs to generate a carbene.

In an electrophilic addition reaction, alkenes react with carbenes, forming a three-membered ring. The reaction consist of addition of the alkene to an electrophilic carbene. The lone pair can donate back so that a carbocation does not actually form in same step. The stereochemistry of the substituents in the alkene is conserved in the product.