Chapter 19.12, Problem 32ATS

Interpretation Introduction

Interpretation:

The difficulty in the synthesis of the following two compounds has to be discussed.

                         

Concept Introduction:

• Benzene is a stable aromatic compound and it is the simplest form of the aromatic compounds. It is a very versatile compound that it furnishes various products with various reagents under different reaction conditions.
• The most common type of reactions that benzene undergoes is electrophilic substitution reactions. Benzene can be converted to various ranges of compounds with appropriate reagents and reaction conditions. One of the useful method one can adapt to introduce any kind of group or atom onto the benzene ring is electrophilic substitution reaction.
• The various types of electrophilic substitution reactions in benzene are – Chlorination, Bromination, Nitration, Sulfonation, Friedel Crafts Alkylation/Acylation etc.
• Apart from electrophilic substitution reactions benzene and its derivatives also undergo another special type of reactions namely Aromatic nucleophilic substitution reactions.
• A nucleophile, unlike an electrophile is a species that is electron rich and always attracted towards electron deficient site. A nucleophile is mobile unlike electrophile.
• In benzene compounds the site in the ring where there is deficient of electrons is attacked by the nucleophile. A new $\text{C-Nu}$  bond is formed where ‘Nu’ is the nucleophile and ‘C’ is aromatic ring Carbon. In this process the bond between aromatic Carbon and the substituent bonded with it is broken.
• Let the substituent be ‘X’ that then $\text{C-X}$  bond gets broken and $\text{C-Nu}$  bond is formed. The substituent ‘X’ is termed as ‘Leaving group’. A good leaving is large in size with high electron affinity that they are capable to grabbing the bond pair electron and leaving form the aromatic C atom. Halogens are known to be excellent leaving group.
• The overall reaction can be represented as follows –

                    

• The criteria for aromatic nucleophilic substitution reaction to occur are –
• The aromatic ring must contain a strong electron withdrawing group
• The aromatic ring must contain a leaving group
• The leaving group must be posited either ortho or para position to the strong electron withdrawing group.
• Aromatic compounds undergo a special type of reaction called addition – elimination reactions. A compound with leaving group when treated with a strong base under high or low temperature undergoes elimination – addition reaction where the leaving group is eliminated and a new group is added.

(b)

Interpretation Introduction

Interpretation:

The difficulty in the synthesis of the following two compounds has to be discussed.

                         

Concept Introduction:

• Benzene is a stable aromatic compound and it is the simplest form of the aromatic compounds. It is a very versatile compound that it furnishes various products with various reagents under different reaction conditions.
• The most common type of reactions that benzene undergoes is electrophilic substitution reactions. Benzene can be converted to various ranges of compounds with appropriate reagents and reaction conditions. One of the useful method one can adapt to introduce any kind of group or atom onto the benzene ring is electrophilic substitution reaction.
• The various types of electrophilic substitution reactions in benzene are – Chlorination, Bromination, Nitration, Sulfonation, Friedel Crafts Alkylation/Acylation etc.
• Apart from electrophilic substitution reactions benzene and its derivatives also undergo another special type of reactions namely Aromatic nucleophilic substitution reactions.
• A nucleophile, unlike an electrophile is a species that is electron rich and always attracted towards electron deficient site. A nucleophile is mobile unlike electrophile.
• In benzene compounds the site in the ring where there is deficient of electrons is attacked by the nucleophile. A new $\text{C-Nu}$ bond is formed where ‘Nu’ is the nucleophile and ‘C’ is aromatic ring Carbon. In this process the bond between aromatic Carbon and the substituent bonded with it is broken.
• Let the substituent be ‘X’ that then $\text{C-X}$ bond gets broken and  $\text{C-Nu}$ bond is formed. The substituent ‘X’ is termed as ‘Leaving group’. A good leaving is large in size with high electron affinity that they are capable to grabbing the bond pair electron and leaving form the aromatic C atom. Halogens are known to be excellent leaving group.
• The overall reaction can be represented as follows –

                    

• The criteria for aromatic nucleophilic substitution reaction to occur are –
• The aromatic ring must contain a strong electron withdrawing group
• The aromatic ring must contain a leaving group
• The leaving group must be posited either ortho or para position to the strong electron withdrawing group.
• Aromatic compounds undergo a special type of reaction called addition – elimination reactions. A compound with leaving group when treated with a strong base under high or low temperature undergoes elimination – addition reaction where the leaving group is eliminated and a new group is added.