Isomerism

Step 1: Concept
Optical activity requires an asymmetric carbon atom.
Step 2: Analysis
has a C-atom with four different groups.
Step 3: Conclusion
Different groups bonded to the chiral center enable optical activity.
Final Answer: (C)

Step 1: Theory
Newton's theory proposed light consists of particles called corpuscles.
Step 2: Denser Medium
The theory incorrectly predicted that denser media exert a greater attractive force, making light faster.
Step 3: Conclusion
Consequently, the speed is predicted to be slower (lesser) in a rarer medium compared to a denser one.
Final Answer: (b)

Concept: Resonance structures must have the same atomic arrangement; only electron distribution changes.

Step 1: In NO , nitrogen is the central atom bonded to two oxygens.

Step 2: Structure (I) maintains correct connectivity (O–N–O).

Step 3: Structure (II) changes connectivity (N not central), hence not a resonance form.
Conclusion:
Only structure (I) is valid.

Concept: Enols are formed by -hydrogen shift. Each -carbon can form an enol. Also, enols can show geometrical (E/Z) isomerism due to C=C bond.

Step 1: Write structure of 3-hexanone
CH –CH –CO–CH –CH –CH

Step 2: Identify -carbons
Two -positions exist (on both sides of carbonyl).

Step 3: Number of enols
Each -position gives one enol → total = 2

Step 4: Stereoisomerism
Each enol has C=C bond → shows E and Z isomerism. Conclusion:
Total enols = 4

Step 1: Understanding the Concept:
Ethyl acetoacetate exhibits keto-enol tautomerism.

Step 2: Detailed Explanation:
Ethyl acetoacetate (CH COCH COOC H ) exists in equilibrium with its enol form (CH C(OH)=CHCOOC H ). This dynamic equilibrium is called tautomerism.

Step 3: Final Answer:
Tautomerism

Concept: Benzene Hexachloride (BHC) BHC (hexachlorocyclohexane) exists in several isomeric forms:

Step 1: Identify insecticidal isomer
• Highly effective insecticide
• Acts on nervous system of insects

Step 2: Other isomers
• , , forms are less active or inactive
• -form is most stable but not insecticidal Final Answer: