Compound A undergoes the reaction sequence: A --[dilute NaOH, low temperature, excess]-- B --[OH⁻, heat]-- C. Compound B gives a positive Tollens' test and a positive iodoform test. Which of the following could be compound A?

Question

Compound A undergoes the reaction sequence: A --[dilute NaOH, low temperature, excess]--> B --[OH⁻, heat]--> C. Compound B gives a positive Tollens' test and a positive iodoform test. Which of the following could be compound A?

Accepted Answer

CH3CHO (acetaldehyde). A + dil NaOH (low T, excess) -> B. B gives +ve Tollens' (aldehyde present) and +ve iodoform (CH3CO or CH3CHOH). The aldol condensation of acetaldehyde (CH3CHO) with itself gives 3-hydroxybutanal: CH3CH(OH)CH2CHO. This compound has an aldehyde group (positive Tollens') and a -CHOH-CH3 moiety (positive iodoform). Heating with OH⁻ gives crotonaldehyde (dehydration — aldol condensation product). This fits perfectly. Therefore A = CH3CHO.

Compound A undergoes the reaction sequence: A --[dilute NaOH, low temperature, excess]--> B --[OH⁻, heat]--> C. Compound B gives a positive Tollens' test and a positive iodoform test. Which of the following could be compound A?

Solution

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