Hydrocarbons - Class 12 MCQ

Boiling point depends upon intermolecular forces, favoured by no. of C-atoms & decreases with increases in branching

Corey-House reaction follows mechanism, which is used for preparation unsymmetrical alkanes.

Organic peroxides favour free redical mechanism

In the presence of peroxides, free radical mechanism or homolytic cleavage is favoured.

NH₂ - NH₂ acts as reducing agent & gives syn addition of H - atoms

 is a conjugated diene which gives 1,4-addition of H₂

Halogen derivatives, in the presence of Na & dry ethetr gives W urtz reaction following free radical mechanism

Conc. H₂SO₄ is used as dehydrating agent for alcohols following carbocation mechanism Hence, it is associated with rearrangement.

A : Intramolecular W urtz reaction

Electroph ilic addition is favoured by nucleophilic nature of alkenes, (c) has 6α-H , which increases nu cleophilicity

-OCH₃ has +R-effect, so, benzyl carbocation is more stable

Alkenes are more reactive than alkynes, but in vinylacetylene, HCl is added on alkyne as conjugated diene is formed which is more stable

NBS → free radical bromination    
KOH(alc) → Dehydro halogention
Hg(OAc)₂ ,PhCH₂OH → Mark. addition of alcohol

Exocylic π-bond is more reactive than endocyclic π-bond

Addition of Cl₂+H₂O is equivalent to HOCl, where Cl⁺ & OH^- are added by Mark, rule 

Diborane gives anti-Mark addition of H & OH, where H belongs to diborane & OH from oxidation

HCHO acts as electrophile in the presence of H⁺ ion.

Reaction shows carbocationc rearrangement by H^- shift

Hydrohalogenation follow electrophilic addition on nucleophilic alkene

Br₂ forms cyclic halonium ion which reacts with lone pair of N.

Conjugated dienes give Diels-Alder reaction with alkenes, which is known as cyclo-addition or (4+2) addition. It involves syn addition

Aromatic compounds are cyclic and planar following Huckel’s rule

It is anti-aromatic

^_CH₃ shows hyperconjugation, -OCH₃ shows +R-effect & -CF₃ shows inverse hyperconjugation

-OH is +R & -COOH is -R, So, nitration is governed by -OH group

H₂SO₄ protonates isobutylene & ter. carbocation is formed where -OCH₃ is +R substituent

H₃PO₂ is a reducing agent, it reduces Ph N₂⁺ benzene