Methyl magnesium chloride reacts with water to give methane.
\(\underset { (Methylmagnesiumchloride) }{ { CH }_{ 3 }MgCl } +{ H }_{ 2 }O\rightarrow \underset { (Methane) }{ { CH }_{ 4 } } +MgCl(OH)\) 

When a solution of bromo benzene and iodo methane in dry ether is treated with metallic sodium, toluene is formed.
\({ C }_{ 6 }{ H }_{ 5 }Br+2Na+IC{ H }_{ 3 }\overset { ether }{ \longrightarrow } { C }_{ 6 }{ H }_{ 6 }{ CH }_{ 3 }+NaBr+NaI\)
Bromo benzene    Iodo methane       Toluene
The process is named as Wurtz-Fitting reaction.

Benzene can be reduced to 1, 4-cyclohexadiene by treatment with Na or Li in a mixture of liquid ammonia and alcohol. It is the convenient method to prepare cyclic dienes.

The addition of HBr to an alkene in the presence of organic peroxide, gives the anti Markovniko's product. This effect is called peroxide effect.

\(\underset { Ethanol }{ { C }_{ 5 }{ H }_{ 5 }{ O }_{ 4 } } \overset { Conc.{ H }_{ 2 }{ SO }_{ 4 } }{ \underset { 430-440K }{ \longrightarrow } } \underset { \overset { (A) }{ Ethene } }{ { CH }_{ 2 }={ CH }_{ 2 } } \overset { { H }_{ 2 } }{ \underset { Ni,298K }{ \longrightarrow } } \underset { \overset { (B) }{ Ethane } }{ { CH }_{ 3 }-{ CH }_{ 3 } } \)

The structure of benzene is best described in terms of the molecular orbital theory. All the six carbon atoms of benzene are sp² hybridized. Six sp² hybrid orbitals of carbon linearly overlap with six one is orbitals of hydrogen atoms to form six C - H sigma bonds. Overlap between the remaining Sp² hybrid orbitals of carbon forms six C-C sigma bonds

All the bonds in benzene lie in one plane with bond angle 120°. Each carbon atom in benzene possess an un hybridized p-orbital containing one electron. The lateral overlap of their p-orbital produces 3 \(\pi\)-bond The six electrons of the p-orbitals cover all the six carbon atoms and are said to be delocalised. Due to delocalization, strong -bond is formed which makes the molecule stable. Hence unlike alkenes and alkynes benzene undergoes substitution reactions rather addition reactions under normal conditions.

Among anthracene and cyclopentadiene - anthracene is aromatic in nature.

Anthracene		Cyclopentadiene
1.	Planar structure	Planar structure
2.	Contains 14 delocalised \(\pi\) electrons (4n + 2 = 14\(\pi\)e-)	Contains 4 non-delocalised \(\pi\) electrons
3.	Hence aromatic	Hence non-aromatic

(i) Preparation of alkene by dehydration of alcohol:
When an alcohol is heated at 430-440 K with excess of concentrated sulphuric acid, a molecule of water from alcohol is removed and an alkene is formed. is reaction is called elimination reaction.
\({ C }_{ 2 }{ H }_{ 5 }OH\overset { Conc.{ H }_{ 2 }{ SO }_{ 4 } }{ \underset { 430-440K }{ \longrightarrow } } { CH }_{ 2 }={ CH }_{ 2 }\)
Ethanol                          Ethene
Ethene can also be prepared in laboratory by catalytic dehydration of alcohol.
\({ C }_{ 2 }{ H }_{ 5 }OH\overset { { A1 }_{ 2 }{ O }_{ 3 } }{ \underset { 623K-723K }{ \longrightarrow } } { CH }_{ 2 }={ CH }_{ 2 }\)
Ethanol                         Ethene
(ii) Preparation of ethene by Kolbe's electrolytic method:
When an aqueous solution of potassium succinate is electrolyzed between two platinum electrodes, ethene is produced at the anode.
\(\overset { { CH }_{ 2 }-COOK }{ \underset { { CH }_{ 2 }-COOK }{ | } } \overset { Electrolysis }{ \longrightarrow } \overset { { CH }_{ 2 }-{ COO }^{ - } }{ \underset { { CH }_{ 2 }-{ COO }^{ - } }{ | } +2 } { K }^{ + }\)
Potassium Succinate
At anode
\(\overset { { CH }_{ 2 }CO{ O }^{ - } }{ \underset { { CH }_{ 2 }CO{ O }^{ - } }{ | } \rightarrow } \overset { { CH }_{ 2 } }{ \underset { { CH }_{ 2 } }{ || } } +{ CO }_{ 2(g) }+{ 2e }^{ - }\)
                   Ethene
(iii) When alkene is treated with halogens like chlorine or bromine, addition takes place rapidly and forms 1,2- dihalo alkane (or) vicinal dihalide.
\({ CH }_{ 2 }={ CH }_{ 2 }\overset { { \\ CI }_{ 2 } }{ \longrightarrow } \overset { { CH }_{ 2 }- }{ \underset { CI }{ | } } \overset { { CH }_{ 2 } }{ \underset { CI }{ | } } \)
                         1,2 dichloroethane     

Isomerism:
Presence of double bond in alkene provides the possibility of both structural and geometrical isomerism.
Structural Isomerism:
The first two member's ethene C₂H₄ and propene C₃H₆ do not have isomers because the carbon atoms in the molecules can be arranged only one distinct way.
However from the third member of alkene family butene C₄H₁₀ structural isomerism exists.
(i) CH₃-CH = CH-CH₃  1-Butene
(ii) CH₂=CH-CH₂-CH₃ 2-Butene
(iii) \({ CH }_{ 2 }=\overset { \underset { | }{ { CH }_{ 3 } } }{ C } -{ CH }_{ 3 }\) 2-Methyl-1-propene
structures (i) & (ii) are position isomers. structures (i) & (iii), (ii) & (iii) are chain isomers. 
Geometrical isomerism:
It is a type of stereoisomerism and it is also called cis-trans isomerism. Such type of isomerism results due to the restricted rotation of doubly bounded carbon atoms.
if the similar groups lie on the same side, then the geometrical isomers are called C is-isomers. When the similar groups lie on the opposite side, it is called a Trans isomer.
for example: the geometrical isomers of 2-Butane is expressed as follow

The exothermic nature of alkane combustion reaction explains the extensive use of alkanes as fuels. Methane present in natural gas is used in home heating. Mixture of propane and butane are known, as LPG gas which is used for domestic cooking purpose. GASOLINE is a complex mixture of many hydrocarbons used as a fuel for internal-combustion engines.
Carbon black is used in the manufacture of ink, printer ink and black pigments. .It is also used as fillers.

Step 1: Generation of CI+ electrophile.

Step 2: Attack of the electrophile on the benzene ring to form arenium ion:

Step 3: Rearomatisation of arenium ion:

An alkyne shows acidic nature only if it contains terminal hydrogen atom. This can be explained by considering the sp hybrid orbitals of carbon atom in alkynes. The percentage of s-character of sp hybrid orbital (50%) is more than Sp² hybrid orbital ofalkenes (33%) and sp3 hybrid orbital of alkanes (25%). Because of this, carbon atom becomes more electronegative, thus facilitating donation of H+ ions to bases. So hydrogen attached to triply bonded carbon atoms is acidic in nature.
(i) \(\underset { (1-Butyne) }{ CH_{ 3 }-{ CH }_{ 2 }-C } \equiv CH+{ CuCl }_{ 2 }+\underset { (Silver\quad bitynide) }{ { 2NH }_{ 4 }OH } \longrightarrow { CH }_{ 3 }-{ CH }_{ 2 }-C\equiv C-Cu\downarrow 2{ NH }_{ 4 }{ NO }_{ 3 }+2{ H }_{ 2 }O\)(ii) \({ CH }_{ 3 }-{ CH }_{ 2 }-C\equiv CH+{ CuCl }_{ 2 }+2{ NH }_{ 4 }\longrightarrow { CH }_{ 3 }-{ CH }_{ 2 }-C\equiv C-C\downarrow 2{ NH }_{ 4 }{ NO }_{ 3 }+2{ H }_{ 2 }O\)
(iii) 
\(\underset { (2-Butyne) }{ { CH }_{ 3 }-C\equiv C-{ CH }_{ 3 } } +2Ag{ NO }_{ 3 }+2{ NH }_{ 4 }OH+2{ NH }_{ 4 }OH\longrightarrow No\quad reaction\quad due\quad to\quad absence\quad of\quad acidic\quad hydrogen\)

(i) Nitration:

(ii) Halogenation:

(iii) Sulphonation:

(iv) Friedel Craft's Alkylation:

(v) Friedel Craft's Acylation:

Preparation of benzene:
(i) Industrial preparation of benzene from coal tar:
Coal tar is a viscous liquid obtained by the pyrolysis of coal. During fractional distillation, coal tar is heated and distills away its volatile compounds namely benzene, toluene, xylene in the temperature range of 350 to 443 K. These vapours are collected at the upper part of the fractionating column
(ii) From acetylene:
Acetylene on passing through a red - hot tube trimerises to give benzene.

(iii) Laboratory methods of preparing benzene and toluence
(a) Decarboxylaation of aromatic acid.
When sodium benzoate in heated with sodalime, benzene vapours distil over.
C₆H₅COONa + NaOH \(\overset { CaO }{ \longrightarrow } \)C₆H₆ + Na₂CO₃
Sodium benzoate               Benzene
(b) Preparation of benzene from phenol
When phenol vapours are passed over zinc dust, then it is reduced to benzene.
C₆H₅OH + Zn \(\rightarrow\) C₆H₆ + ZnO
 Phenol             Benzene
(c) Wurtz - Fittig reaction:
When a solution of bromobenzene and iodomethane in dry ether is treated with metallic sodium, toluene is formed.
C₆H₅Br + 2Na + ICH₃ \(\overset { ether }{ \longrightarrow } \) C₆H₆CH₃ + NaBr + Nal
Bromobenzene  Iodo methane  Toluene
(d) Friedel Craft's reaction:
When benzene is treated with methyl chloride in the presence of anhydrous aluminium chloride, toluene is formed.
C₆H₆ + CH₃CI \(\overset { anhydrous\quad AICI_{ 3 } }{ \longrightarrow } \)C₆H₅CH₃ + HCI
Benzene Chloromethane            Toluene