Chapter 23, Problem 23P

Interpretation Introduction

Interpretation:

The structural formulas and names of the compounds identified from a reaction sequence are to be predicted.

Concept Introduction:

Electrophiles are electron deficient species which has positive or partially positive charge. Lewis acids are electrophiles which accept electron pair.

Nucleophiles are electron rich species which has negative or partially negative charge. Lewis bases are nucleophiles which donate electron pair.

Free radical is an atom, molecule or ion that has unpaired electrons which makes it highly chemically reactive.

Substitution reaction: A reaction in which one of the hydrogen atoms of a hydrocarbon or a functional group is substituted by any other functional group is called substitution reaction.

Elimination reaction: A reaction in which two substituent groups are detached and a double bond is formed is called elimination reaction.

Addition reaction: It is the reaction in which unsaturated bonds are converted to saturated molecules by the addition of molecules.

Cholesterol is essential for human life. In the human body, it is produced as an intermediate in the biosynthesis of all steroids. In a molecule of cholesterol, there is no internal plane of symmetry, and hence, every carbon atom is different, and each chiral carbon has four different groups. A single unit of cholesterol consists of eight tetrahedral chirality centres.

Cholestane is a group of saturated tetracyclic triterpenes. They contain $27-\text{carbon}$ atom rings. Cholestene is a derivative of cholestane with a double bond.

The reaction of alkenes with peroxide acids to form epoxides is called epoxidation reaction. In this reaction, the double bond between $\text{C}=\text{C}$ is converted to an epoxide.

Reactions of steroids are greatly influenced by steric hindrance. Most steroids prefer reaction at $\beta -$ position, but some reagents attack at $\alpha -$ position if it is sterically favourable (lower steric hindrance).