Test: JEE Main 35 Year PYQs- Hydrocarbons - JEE MCQ

Acetylene reacts with the other three as:

In neopentane all the H atoms are same (1º).

Ease of replacement of H-atom 3° > 2° > 1°.

Alkenes combine with hydrogen under  pressure and in presence of a catalyst (Ni, Pt or Pd) and form alkanes.

Since it contains only two  types of H-atoms hence it will give only two mono  chlorinated compounds viz. 

 and 

Water adds directly to the more reactive alkene in presence of a  strongly acidic catalyst forming alcohols.
Addition occurs according to Markonikov’s rule.

NOTE : Addition follows Markownikoff’s rule.

2, 3-dichloro butane will exhibit optical isomerism due to the presence of two asymmetric carbon atom.

When alkyl benzene are oxidised with alkaline KMnO₄, (strong oxidising agent) the entire alkyl group is oxidised to –COOH group regardless of length of side chain.

The reaction follows Markownikoff rule which states that when unsymmetrical reagent adds across unsymmetrical double or triple bond the negative part adds to carbon atom having lesser number of hydrogen atoms.

FeCl₃ is Lewis acid. In presence of FeCl₃ side chain hydrogen atoms of toluene are substituted.

NOTE : ​group whichis o-, p- directing group so on nitration of toluene the – NO₂ group will occupy o-, p- positions.

on reduction with Sn/HCl they will form corresponding anilines in which –NO₂ group changes to –NH₂. The mixture now contains

anilines when diazotized and then treated with CuBr forms o-, p- bromotoluenes.

Completing the sequence of given reactions,

Thus ‘B’ is CH₃CHO Hence (d) is correct answer.

Alkynes  having terminal –C ≡ H react with Na in liquid ammonia to yield H₂ gas of the given compounds CH₃CH₂C ≡ CH can react with Na in liquid NH₃ so the correct answer is (b).

Writing the reaction we get

So we find  that CH₄ is produced in this reaction.

The given molecular formula suggests that the aldehyde formed will be acetaldehyde hence the alkene  will be

Compound must contain a vinyl group  in order to give formaldehyde as one of the product.

Anti addition of hydrogen atoms to the triple bond occurs when alkynes are reduced with sodium (or lithium) metal in ammonia, ethylamine, or alcohol at low temperatures. This reaction called, a dissolving metal reduction, produces an (E)- or trans-alkene.
Sodium in liq. NH₃ is used as a source of electrons in the reduction of an alkyne to a trans alkene.

When 1, 3-dimethylcyclopentene is heated with ozone and then with zinc and acetic acid, oxidative cleavage leads to keto - aldehyde.

5- keto – 2 – methylhexanal

Region 2 (blue flame) will be the hottest region of Bunsen flame shown in given figure

Volume of O₂ used =  = 75 ml

∴ From the reaction of combustion

1 ml C_xH_y requires =

So, 4x + y = 20
x = 3
y = 8