Q.Match the terms mentioned in Column I with the terms in Column II. (More than one correlation is possible.)
Column I

Match: Organic Chemistry Terms

Concept: Structural features, hybridization, and reactive intermediates.

Each term in Column I corresponds to one or more definitions or examples in Column II based on fundamental organic chemistry principles.

Step 1 – Carbocation (i):

A carbocation is a positively charged carbon species with $sp^2$ hybridization and an empty $p$-orbital perpendicular to the plane of the three $sp^2$ bonds. It is also electron-deficient, so it accepts electron pairs.

Matches: (c) and (e).

Step 2 – Nucleophile (ii) and Electrophile (vi):

A nucleophile supplies a pair of electrons (Lewis base), while an electrophile receives a pair (Lewis acid).

Nucleophile matches: (f).

Electrophile matches: (e).

Step 3 – Hyperconjugation (iii):

Hyperconjugation is the stabilising interaction between a filled $\sigma$ bond (usually C–H) and an adjacent empty $p$-orbital on a positively charged carbon.

Matches: (b).

Step 4 – Isomers (iv): …

The question tests your understanding of core organic chemistry vocabulary. Each term in Column I represents either a reactive species, a structural feature, or a stabilisation mechanism. The key is to recognise what defines each concept at the electronic and structural level.

Let me work through each term systematically.

Matching each term

1. Carbocation (i)

A carbocation is a positively charged carbon species. The positive carbon has only three bonds (having lost an electron pair), so it adopts $sp^2$ hybridisation with a planar geometry. The unhybridised p-orbital remains empty.

Matches: (c) $sp^2$ hybridised carbon with empty p-orbital

This is the textbook definition of a carbocation's electronic structure.

2. Nucleophile (ii)

The name itself tells the story: "nucleus-loving." A nucleophile is electron-rich and seeks out positive centres. It must possess a lone pair or π-electrons that it can donate to form a new bond.

Matches: (f) Species that can supply a pair of electrons

Examples include $\ce{OH^-}$, $\ce{NH3}$, $\ce{CN^-}$, and alkenes.

3. Hyperconjugation (iii)

This stabilisation mechanism involves the overlap of a filled σ-bond (usually C–H) with an adjacent empty or partially filled p-orbital. In carbocations, the electrons in the C–H σ-bond delocalise slightly into the empty p-orbital of the positively charged carbon, spreading out the positive charge and lowering the energy.

Matches: (b) Conjugation of electrons of C–H σ bond with empty p-orbital present at adjacent positively charged carbon

This is the precise description of hyperconjugation in carbocations. The more C–H bonds adjacent to the carbocation centre (more α-hydrogens), the greater the stabilisation: tertiary > secondary > primary.

4. Isomers (iv)

Isomers are compounds with the same molecular formula but different structures. They can differ in connectivity (structural isomers) or spatial arrangement (stereoisomers).

Matches: (a) Cyclohexane and 1-hexene

Both have the formula $\ce{C6H12}$. Cyclohexane is a saturated ring; 1-hexene is an open-chain alkene. They are structural isomers.

5. $sp$ hybridisation (v)

When a carbon forms two σ-bonds, it uses $sp$ hybrid orbitals (50% s, 50% p character), leaving two unhybridised p-orbitals perpendicular to the bond axis. These p-orbitals form two π-bonds, giving a triple bond overall. The geometry is linear with bond angles of 180°. …