Test: Alkanes & Alkenes(9- Sep) - JEE MCQ

Zn reacts with 2,3 - dibromobutane to give alkene. As trans 2-butene is more stable than cis 2-butene(owing tosterric hinderancce), former is major product.

• Statement I: 2-bromobutane reacts with (CH₃)₃COK in tertiary butanol to give 1-butene as the major product. This is due to the E2 elimination reaction taking place, resulting in the formation of the alkene.


• Statement II: The very strong base (CH₃)₃COK in tertiary butanol is capable of bringing about E2 elimination reactions. This type of reaction occurs when a strong base removes a proton from a beta carbon, leading to the formation of a double bond and the elimination of a leaving group.


• Therefore, both Statement I and Statement II are correct. However, Statement II is not the direct explanation of Statement I, as it does not explicitly connect the strong base with the formation of 1-butene.


• Hence, the correct answer is Option B: Both Statement I and Statement II are correct and Statement II is not the correct explanation of Statement I.

In organic chemistry, an electrophilic addition reaction is an addition reaction where, in a chemical compound, a π bond is broken and two new σ bonds are formed. The substrate of an electrophilic addition reaction must have a double bond or triple bond.

As shown in the above mechanism 1-butene and 2-butene cannot be formed by this free radical. release of 1 hydrogen radical gives 2-methyl propene as disproportionated product.

Hence, the correct option is C.

They form vicinal glycols as shown below:

Hammond's postulate states that the transition state of a reaction resembles either the reactants or the products, to whichever it is closer in energy. In an exothermic reaction, the transition state is closer to the reactants than to the products in energy

The correct answer is option c

Thus, a racemic mixture is obtained. A racemic mixture is one that has an equal amount of left and right handed enantiomers of a chiral molecule.

As there is no hydrogen at adjacent position for E₂ elimination.

The correct answer is Option D.
The more intermolecular mass is added, the higher the boiling point. Intermolecular forces of alkenes get stronger with increase in the size of the molecules. In each case, the alkene has a boiling point which is a small number of degrees lower than the corresponding alkane.

Boiling point depends upon intermolecular interactions which over here is more in cis due to its net dipole moment . The dipole moment enables electronic interactions which hold molecules together . Trans 2-Butene has more symmetry thanits cis isomer which results in better packing and hence higher melting point .