Give the reagents and observations to distinguish the following pairs of compounds: (i) CH2CH=CH2 and CH3C≡CH (ii) CH3CHO and CH3COCH3 (iii) CH3CH2NH2 and CH3CONH2

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5. (c) Give the reagents and observations to distinguish the following pairs of compounds:

• (i) $\text{CH}_2\text{CH}=\text{CH}_2$ and $\text{CH}_3\text{C}\equiv\text{CH}$

  • Reagent: $\boxed{\text{Ammoniacal silver nitrate (Tollens' reagent)}}$ or $\boxed{\text{Ammoniacal copper(I) chloride}}$.
  • Observation for $\text{CH}_3\text{C}\equiv\text{CH}$ (propyne): With Tollens' reagent, a $\boxed{\text{white precipitate}}$ of silver acetylide is formed. With ammoniacal copper(I) chloride, a $\boxed{\text{red precipitate}}$ of copper(I) acetylide is formed.
  • Observation for $\text{CH}_2\text{CH}=\text{CH}_2$ (propene): $\boxed{\text{No observable reaction}}$.

• (ii) $\text{CH}_3\text{CHO}$ and $\text{CH}_3\text{COCH}_3$

  • Reagent: $\boxed{\text{Tollens' reagent (ammoniacal silver nitrate)}}$ or $\boxed{\text{Fehling's/Benedict's solution}}$.
  • Observation for $\text{CH}_3\text{CHO}$ (ethanal): With Tollens' reagent, a $\boxed{\text{silver mirror}}$ is formed. With Fehling's/Benedict's solution, a $\boxed{\text{brick-red precipitate}}$ of copper(I) oxide is formed.
  • Observation for $\text{CH}_3\text{COCH}_3$ (propanone): $\boxed{\text{No observable reaction}}$.

• (iii) $\text{CH}_3\text{CH}_2\text{NH}_2$ and $\text{CH}_3\text{CONH}_2$

  • Reagent: $\boxed{\text{Nitrous acid (prepared from } \text{NaNO}_2 \text{ and dilute } \text{HCl} \text{ at } 0-5^\circ\text{C})}$.
  • Observation for $\text{CH}_3\text{CH}_2\text{NH}_2$ (ethylamine): $\boxed{\text{Effervescence (evolution of nitrogen gas)}}$ is observed.
  • Observation for $\text{CH}_3\text{CONH}_2$ (ethanamide): $\boxed{\text{No effervescence}}$.

6. (a) An organic compound S reacted with ozone (ozonolysis) to give compounds Q and R. Both Q and R react with $\text{NaOH}/\text{I}_2$ to produce a yellow precipitate with antiseptic smell. Q reacts with HCN to produce the compound $\text{CH}_3\text{C}(\text{CH}_3)\text{OHCN}$ while R gives a silver mirror with Tollens reagent.

• (i) Write the structural formulae and names of Q, R, S and the yellow precipitate

  • Q:

    • Formula: $\boxed{\text{CH}_3\text{COCH}_3}$
    • Name: $\boxed{\text{Propanone}}$

  • R:

    • Formula: $\boxed{\text{CH}_3\text{CHO}}$
    • Name: $\boxed{\text{Ethanal}}$

  • S:

    • Formula: $\boxed{\text{CH}_3\text{C}(\text{CH}_3)=\text{CHCH}_3}$
    • Name: $\boxed{\text{2-methylbut-2-ene}}$

  • Yellow precipitate:

    • Formula: $\boxed{\text{CHI}_3}$
    • Name: $\boxed{\text{Triiodomethane}}$

• (ii) Write equations to show the reactions of Q with $\text{NaOH}/\text{I}_2$ Q is propanone ($\text{CH}_3\text{COCH}_3$). The reaction with $\text{NaOH}/\text{I}_2$ is the iodoform test.