Chapter 7, Problem 54P

Interpretation Introduction

Interpretation:

The structures of the compounds A, B, and C 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.

▸ The reaction in which hydrogen is added to the compound in the presence of catalyst is known as hydrogenation.

▸ The number of moles of hydrogen absorbed will be equal to the number of double bonds.

▸ Hydrogenation of alkenes or alkynes is an addition reaction that leads to the formation of alkanes. It is done in the presence of reducing agents such as ${\text{H}}_2/Ni$.

▸ Infrared spectroscopy is a simple, instrumental technique, which helps to determine the presence of various functional groups.

▸ It depends on the interactions of atoms or molecules with the electromagnetic radiation.

▸ The molecules which have dipole moment are IR active and the molecules which do not have dipole moment are IR inactive.

▸ The change in number of pairs of hydrogen atoms of a given compound and the acyclic compound which has the number of carbon atoms same as the number of carbon atoms in the given compound, is known as the Index of hydrogen deficiency.

▸ The Index of hydrogen deficiency can be denoted by IHD.

▸ The Index of hydrogen deficiency can be calculated by using the formula given below:

$\begin{array}{c}\text{IHD}=\text{rings}+\pi \text{bonds}\\ =\text{C}-\frac{\text{H}}{2}-\frac{\text{X}}{2}+\frac{\text{N}}{2}+1\end{array}$

Here, C represents the number of carbon atoms, H represents the number of hydrogen atoms, N represents the number of nitrogen atoms and X represents the number of halogen atoms.

▸ The molecules which are non-superimposable or not identical with their mirror images are known as chiral molecules.

▸ A pair of two mirror images which are non-identical is known as enantiomers which are optically active.

▸ The objects or molecules which are superimposable with their mirror images are achiral objects or molecules and these objects have a centre of symmetry or plane of symmetry.

▸ The achiral compounds in which plane of symmetry is present internally and consists of chiral centres are known as meso compounds but they are optically inactive.

▸ The stereoisomers which are non-superimposable on each other and not mirror images of each other are known as diastereomers.

▸ Chiral molecules are capable of rotating plane polarized light

▸ The molecules which are superimposable or identical with their mirror images are known as achiral molecules, and achiral molecules are not capable of rotating the plane-polarised light.