Below is an incomplete reaction scheme. Choose the correct major product from the following options.[Fill in the blank]Single choice
A
A.
B
B.
C
C.
D
D.

Question

Below is an incomplete reaction scheme. Choose the correct major product from the following options.[Fill in the blank]

BlackTom AI · Accepted Answer

Ozonolysis of an alkyne breaks the C≡C bond and converts each alkynyl carbon into a carboxyl group; in practice an internal alkyne R–C≡C–R' is cleaved to give two carboxylic acids RCO2H + R'CO2H. For diphenylacetylene (Ph–C≡C–Ph) this gives two molecules of benzoic acid (PhCO2H). The overall stoichiometry can be written conceptually as:
Ph–C≡C–Ph + [O] → 2 PhCO2H.
Step-by-step reasoning:
1. Identify the substrate: the drawn substrate is diphenylacetylene (a phenyl ring on each side of a C≡C triple bond).
2. Key concept: ozonolysis of alkynes effects oxidative cleavage of the triple bond, producing carboxylic acids on both carbons. Unlike alkenes, where reductive workup (e.g., (CH3)2S) can stop at aldehydes/ketones, ozonolysis of alkynes proceeds to oxidized carboxylic acids under typical ozone conditions.
3. Apply to this substrate: each phenyl-substituted alkyne carbon becomes a benzoic acid unit, so the major organic product corresponding to the aryl fragment is benzoic acid (PhCO2H).
Why the other options are incorrect:
- A (benzaldehyde): would be expected from ozonolysis of a stilbene (an alkene) with reductive workup; that cleavage yields aldehydes/ketones for alkenes, not for alkynes here.
- B (benzyl alcohol): is the reduced form of benzaldehyde and is not produced by ozone cleavage of an aryl–alkyne.
- D (acetophenone): would result from cleavage next to a methyl substituent (e.g., Ph–C≡C–Me giving PhCOCH3) but does not match the symmetrical diphenylacetylene substrate.
Conclusion: ozonolysis of diphenylacetylene gives benzoic acid as the major product; therefore option C is correct.

Below is an incomplete reaction scheme. Choose the correct major product from the following options.[Fill in the blank]Single choice

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