Chapter 5, Problem 26P

(a)

Interpretation Introduction

Interpretation:

The condensed structural formula and systematic name should be given for the molecular formula of ${\text{C}}_{\text{6}}{\text{H}}_{\text{12}}$ compound.

Concept introduction:

A condensed structural formula is a system of writing organic structures in a line of text.

Isomer: A molecule having the same molecular formula but with different chemical structure is called isomer.

Constitutional Isomers: A molecule having same molecular formula with different structural formulas (Difference in the connectivity of the molecule is called constitutional isomer).

Any organic molecule can be named by using certain rules given by IUPAC (International Union for Pure and applied chemistry).IUPAC name consists of three parts, namely Prefix, suffix and root word.

Prefix- Represents the substituent present in the molecule and its position in the root name.

Suffix- Denotes the presence of functional group if any in the molecule.  It can be an alkene, alkyne, alcohol, carboxylic acid, alcohol etc.  To add suffix to name a compound, the suffix “-ane” in the parent alkane is replaced by the respective suffix, which corresponds to the functional group present in the given compound.  For carboxylic acid, suffix “-oic” will be added, for alcohol, suffix “-ol” will be added and so on

Root word - Represents the longest continuous carbon skeleton of the organic molecule.

Alkenes:

Alkenes are a class of hydrocarbons. The carbon-carbon double bond is called as alkenes and it is also called as olefins.

(b)

Interpretation Introduction

Interpretation:

The E and Z isomer of the alkene has to be identified.

Concept introduction:

E and Z isomerism:

The two similar groups (or higher priority groups) are in same side in double bond of alkenes is called as cis isomer (or Z-isomer). Two similar groups (or higher priority groups) are opposite side in double bond of alkenes is called as trans isomer (or E-isomer).

Example:

(c)

Interpretation Introduction

Interpretation:

The most stable alkene has to be identified.

Concept Introduction:

Stability of alkene:

Stability of alkene depends on the following factors,

The smallest heat hydrogenation of alkene is more stable. The number of hydrogens bonded to its ${\text{sp}}^{\text{2}}$ carbons decreases the stability of an alkene increases. The number of substituent increases the stability of the alkene is increases (heat hydrogenation decreases).

Stability of Cis–trans alkene:

The two similar groups (or higher priority groups) are in same side in double bond of alkenes is called as cis isomer (or Z-isomer). Two similar groups (or higher priority groups) are opposite side in double bond of alkenes is called as trans isomer (or E-isomer).

In cis alkene, molecule are close to each other, hence electron clouds interfere each other therefore strain in the molecule so cis alkene is less stable. Whereas molecule is away from each other, hence electron clouds are will not interfere each other therefore less strain in the molecule, so trans alkene is stable.