Explore topic-wise InterviewSolutions in .

(i) deactivates the ring by inductive effect.

(iii) decreases the charge density at ortho and para position of the ring relative to meta position by resonance.

• All ortho and para directing groups possess nonbonding electron pair on the atom which is directly attached to the aromatic ring; however, methyl group is an exception. 
• Methyl (or alkyl groups) is ortho and para directing, although it has no nonbonding electron pair on the key atom. This is explained on the basis of special type of resonance called hyperconjugation or no bond resonance.

Deactivating group  is NO₂

Chlorination of methane is a free radical reaction which occurs by the following mechanism.

Step I: Chain Initiation step The reaction is initiated by homolytic cleavage of Chlorine molecule in the presence of light or heat. The Cl-Cl bond is weaker than the C-C and C-H bond and hence is easiest to break. 

Cl-Cl ------> Cl. + Cl. 

  Chlorine free radicals

Step II: Chain Propagation step Chlorine free radicals attacks the methane molecules and takes the reaction in the forward direction by breaking the C-H bond to generate methyl free radicals with the formation of HCl. 

(a) CH₄ + Cl.-------->  CH₃ + H-Cl 

The methyl radicals attack the second molecule of chlorine to form CH₃-Cl with the liberation of another Cl by homolysis of Cl₂ molecule 

(b) CH₃ + Cl-Cl ------> CH₃-Cl + Cl. 

The chlorine and methyl free radicals repeats steps (a) and (b) respectively and thereby setup a chain of reactions. 

The propagation steps (a) and (b) are those which directly gives principal products, but many other propagation steps are possible.

Two such steps shown here explains how more halogenated products are formed 

 CH₃Cl + Cl. ------>  CH.₂Cl + HCl 

CH. ₂Cl + Cl-Cl -------> CH₂Cl₂ + Cl

Step III: Termination 

The reaction stops after some time due to consumption of reactants and / or due to the following side reactions : 

(a) Cl. + Cl. --------> Cl-Cl 

(b) CH.₃ + CH.₃ ---------> H₃C-CH₃ 

(c) CH.₃ + Cl. H₃C-Cl 

Though in (c) CH₃-Cl , the one of the product is formed but free radicals are consumed and the chain is terminated.

The energy differences between staggered and eclipsed forms of ethane is just 12.55 kj mol^_1 which is easily met by collisions of the molecules at room temperature. Therefore, it is not possible to isolate either pure staggered or pure eclipsed ethane at room temperature.

(i) Kolbe's reaction : In this reaction, an aqueous solution of sodium or potassium salt of carborylic acid on electrolysis gives alkane having even number of carbon atoms at anode.

2CH₃COO–Na + +2H₂O → CH₃–CH₃ + 2CO₂ + H₂ + 2NaOH

Ethane

(ii) Wurtz reaction : In this reaction, alkyl halides on treatment with sodium in dry ether gives higher alkanes, preferably containing even number of carbon atoms.

CH₃Br + 2Na + BrCH₃ \(\underset{ether}{\stackrel{dry}{\rightarrow}}\)

CH₃ – CH₃ + 2 NaBr Ethane

Staggered form of ethane is more stable than the eclipsed form because the force of repulsion between hydrogen atoms on adjacent C atom is minimum. The energy difference between the staggered form and the eclipsed form of ethane is just 12.55 kJ mol^-1 . Therefore, it is not possible for these two forms of ethane to isolate at room temperature.

(a) (2-Propyl) cyclohexane.

(b) 2, 3-dimethylbutane

(i) H–C ≡ C – H > H₂C = CH₂ > H₃C–CH₃

(ii) HC ≡ CH > CH₃–C ≡ CH ≫ CH₃–C ≡ C–CH₃.

H₂C = CH₂ + H₂ \(\underset{523-573\,K}{\stackrel{Nickel}{\rightarrow}}\) H₃C–CH₃

There is one mono substituted benzene and three di substituted benzene i.e. ortho, para and meta.

(a) A is correct, R is correct and R is a correct explanation of A.

These are sigma (σ) bonds.

The different molecular arrangements arising as a result of rotation around carbon carbon single bonds are called conformational isomers or rotational isomers and the phenomenon is called conformational isomerism.

Because of low reactivity.

Organic compounds containing only carbon and hydrogen are called hydrocarbons.

The reactivity of halogens towards alkanes varies as 

Fluorine > Chlorine > Bromine > Iodine 

i.e., F > Cl > Br > I.

Alkanes are saturated aliphatic hydrocarbons containing carbon to carbon single bonds.

The hydrocarbons containing only carbon – carbon single bonds saturated hydrocarbons.

Arenes are aromatic hydrocarbons. General formula of arenas is C_nH_2n-6.

Petroleum and natural gas are the major sources of aliphatic hydrocarbon while coal is an important source of aromatic hydrocarbons. The oil trapped inside the rocks is known as petroleum. PETRA –ROCK, OLEUM –OIL. The oil in the petroleum field is covered with a gaseous mixture known as natural gas. The main constituents of the natural gas are methane, ethane, propane and butane.

The hydrocarbons which contain at least one carbon to carbon double bond or triple bond are called unsaturated hydrocarbons.

• Benzene is both, toxic and carcinogenic (cancer causing). 
• In fact, it might be considered “the mother of all carcinogens” as a large number of carcinogens have structures that include benzene rings. 
• In liver, benzene is oxidized to an epoxide and benzopyrene is converted into an epoxy diol. These substances are carcinogenic and can react with DNA and thus, can induce mutation leading to uncontrolled growth of cancer cells.

Correct option is: Correct option is (B) \(C_{10}H_{22}\)

\(C_{10}H_{22}\), follow the general formula of alkene, (\(C_{n}H_{2n+2}\))

where n = 10

Correct option is (B) C₁₀H₂₂

Chain isomerism.

1. Alkanes are aliphatic saturated hydrocarbons containing carboncarbon and carbon-hydrogen single covalent bonds.

2. They have a general formula C_nH_{2n + 2} where, ‘n’ stands for number of carbon atoms in the alkane molecule.

Correct option is: (B) \(C_n H_{2n + 2}\)

The general formula of alkanes are \(C_n H_{2n + 2}\)

for alkenes - \(C_n H_{2n}\)

for alkynes - \(C_n H_{2n - 2}\)

Correct option is (B) C_nH_{2n + 2}

The general formula of alkanes is C_nH_2n+2