The final product of the following reaction is :\$C_6H_5COONa + NaOH \xrightarrow{CaO, heat} ? \$

In this reaction, a sodium salt of higher fatty acid undergoes decarboxylation. In this reaction, the carboxyl group is removed from fatty acid forming benzene as a product along with sodium carbonate.

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>>Class 11
>>Chemistry
>>Hydrocarbons
>>Aromatic Hydrocarbon
>> $Benzene-Structure and Stabi...$

Benzene-Structure and Stability

Q: Benzene reacts with \$CH_3Cl\$ in the presence of anhydrous \$AlCl_3\$ to form:

Benzene reacts with \$CH_{3}Cl\$ in presence of anhydrous \$AlCl_{3}\$ to give Toulene. This is fridel crafts Alkylation and an electrophillic substitution.

Q: Which one of the following is aromatic?

According to Huckel's rule, an aromatic compound must have (4n + 2)\$\pi\$ electrons that form an uninterrupted π electron cloud. In addition, it must be planar and cyclic. If the compound is not planar and cyclic then it is also not aromatic. The cycloheptatrienyl (tropylium) cation is aromatic because it also has 6 electrons in its pi system. It is planar, cyclic and has conjugated system.

Q: How will you convert benzene into p - nitrobromobenzene?

Electrophilic aromatic substitution of benzene with bromine in presence of ferric bromide gives bromobenzene. Nitration with conc nitric acid and concentric sulphuric acid gives a mixture of ortho bromo nitrobenzene and para bromo nitrobenzene which are separated by fractional distillation.

Q: Among the above, the number of aromatic compound(s) is/are :

(A) is non-aromatic as it is not planar.(B) is antiaromatic as it contains conjugated system of \$4n\$ \$\pi\$ electrons or 2 \$\pi\$ electrons.(C) is aromatic as it contains conjugated system of \$4n+2\$ \$\pi\$ electrons (2 \$\pi\$ electrons). It is cyclic and planar.(D) is non-aromatic as \$\pi\$ electrons are not fully conjugated.(E) is aromatic as it contains conjugated system of \$4n+2\$ \$\pi\$ electrons (6 \$\pi\$ electrons). It is cyclic and planar.(F) is anti aromatic as it contains conjugated system of \$4n\$ \$\pi\$ electrons (4 \$\pi\$ electrons). It is cyclic and planar.(G) is aromatic as it contains conjugated system of \$4n+2\$ \$\pi\$ electrons (6 \$\pi\$ electrons). It is cyclic and planar.(H) is aromatic as it contains conjugated system of \$4n+2\$ \$\pi\$ electrons (6 \$\pi\$ electrons). It is cyclic and planar. These are \$\pi\$ electrons present in one ring. \$\pi\$ electrons present in other ring are not counted.(I) is aromatic as it contains conjugated system of \$4n+2\$ \$\pi\$ electrons (14 \$\pi\$ electrons). It is cyclic and planar. the number of aromatic compound(s) is \$5\$.

Q: Benzene reacts with acetyl chloride in presence of anhydrous aluminium chloride to form :

The given reaction is Friedel-Craft's acylation reaction. In this reaction, the acyl group substitutes one of the hydrogen atoms on benzene to form acetophenone.

Q: Benzene reacts with \$CH_{3}COCl\$ in the presence of \$AlCl_{3}\$ to give

Benzene reacts with \$CH_{3}COCl\$ in the presence of \$AlCl_{3}\$ to give \$C_{6}H_{5}COCH_{3}\$. This reaction is called Friedel-Crafts Acylation reaction.

Q: How will you convert benzene into \$m - \$nitrochlorobenzene?

Nitration of benzene with conc nitric acid and conc sulphuric acid gives nitrobenzene. Chlorination with chlorine in presence of anhydrous aluminum chloride gives meta nitro chlorobenzene.

Q: What product are formed when the following compound is treated with \$Br_2\$ in the presence of \$FeBr_3\$?

m-xylene on bromination with bromine in presence of ferric bromide gives 1-bromo-2,4-dimethylbenzene.This is represented by option C which shows a pair of identical compounds.This is an electrophilic aromatic substitution reaction and since methyl group is ortho para directing, the substitution occurs at a position which is ortho to one methyl group and para to other methyl group.

Q: What are the necessary conditions for any system to be aromatic?

The necessary conditions for any system to be aromatic are planar, conjugated ring system with delocalisation of (4n+2)π electrons, where, n is an integer.

Chemistry

definition

Structure of benzene

All six carbon-carbon bonds in benzene are of the same length, at 140 (pm).
The C-C bond length are greater than a double bond (135 pm) but shorter than a single bond (147 pm).
This intermediate distance is consistent with electron delocalization the electrons for CC bonding are distributed equally between each of the six carbon atoms.

definition

Concept of benzene ring resonance

Benzene is a hybrid of various resonating structures .The hybrid structure is represented by inserting a circle or a dotted circle in the hexagon.The circle represents the six electrons which are delocalised between the six carbon atoms of the benzene ring.