Question

Given below are two statements:

Statement I: Ozonolysis followed by treatment with Zn, H₂O of cis-2-butene gives ethanal.

Statement II: The product obtained by ozonolysis followed by treatment with Zn, H₂O of 3, 6-dimethyloct-4-ene has no chiral carbon atom.

In the light of the above statements, choose the correct answer from the options given below

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Answer 1

Answer: (C)

Statement I is true but Statement II is false

Answer 2

Statement I (cis‑2‑butene):

Ozonolysis of cis‑2‑butene proceeds via the formation of an ozonide which, on reductive work‐up with Zn/H₂O, cleaves the C=C bond forming two molecules of $\mathrm{CH_3CH=O}$ (ethanal).

Result: Statement I is true.

Statement II (3,6‑dimethyloct‑4‑ene):

The structure of 3,6‑dimethyloct‑4‑ene is symmetric:

$\text{CH}_3\text{-CH}_2\text{-C(CH}_3\text{)H-CH=CH-C(CH}_3\text{)H-CH}_2\text{-CH}_3$

Ozonolysis cleaves the double bond (between C4 and C5) giving two identical fragments:

$\text{CH}_3\text{-CH}_2\text{-C(CH}_3\text{)H-CHO}$

In this aldehyde, the carbon bearing the methyl substituent (the former C3 in fragment) is attached to four different groups:

• $\mathrm{CH_2CH_3}$
• $\mathrm{CH_3}$
• $\mathrm{CHO}$
• $\mathrm{H}$

Thus, it is a chiral center.

Result: Statement II is false.

Conclusion: Only Statement I is correct.