Chapter 6, Problem 46P

(a)

Interpretation Introduction

Interpretation:

The product formed when cis- and $\text{trans-2-butene}$ reacts with $\text{HCl}$ should be determined. The stereoisomers formed should be indicated.

Concept introduction:

Addition of hydrogen halides:

In the addition of hydrogen halides over alkenes, first the ${\text{H}}^{\text{+}}$ gets bonded to carbon and forms most stable carbocation which then the halide ion bonds with carbocation that results in formation of product.

Carbocation: carbon ion that bears a positive charge on it.

Carbocation stability order:

Stereoisomers: Two compounds with same molecular formula but different in their orientation are considered as isomers.

The presence of atom with non-super impossible mirror image is defined as enantiomers which are given $\text{R and S}$ configuration based on the atoms bonded with them.

R and S nomenclature: it is used to assign the molecule using CIP rules.

The CIP rules are as follows:

Select the chiral carbon and assign the numbers according to the decreasing atomic mass of atoms attached to it.

If the numbering follows clockwise direction then the molecule is termed as R and if it follows anti-clockwise direction then molecule is termed as S.

Chiral or Asymmetric carbon: Carbon bonded with four different substituents with it is termed as chiral or asymmetric carbon.

(b)

Interpretation Introduction

Interpretation:

The product formed when cis- and $\text{trans-2-butene}$ reacts with $H_2$ and $\text{Pd/C}$ should be determined. The stereoisomers formed should be indicated.

Concept introduction:

Addition of$H_2$:

Catalytic hydrogenation in presence of $\text{Pd/C}$ is an example for syn addition of hydrogen.

For cyclic reactants, the addition of $H_2$ will form cis enantiomers since two hydrogens adds to one side of the double bond.

(c)

Interpretation Introduction

Interpretation:

The product formed when cis- and $\text{trans-2-butene}$ reacts with ${\text{H}}_{\text{2}}{\text{O+H}}_{\text{2}}{\text{SO}}_{\text{4}}$ should be determined. The stereoisomers formed should be indicated.

Concept introduction:

Acid Catalyzed addition of water: When water is added to alkene in the presence of an acid, the product formed will be an alcohol.

The electrophile ${\text{H}}^{\text{+}}$ adds to the nucleophile alkene that results to form carbocation intermediate. Then water adds to the carbocation and forms protonated alcohol. Finally, it loses a proton and finally an alcohol is formed.

Nucleophile: It donates pair of electrons to positively charged chemical substrate resulting in the formation of chemical bond.

Electrophile: It is positively charged species which seeks for negative charge and hence accepts pair of electrons from negatively charged species (Nucleophiles) which results in the formation of chemical bond.