Give simple chemical tests to distinguish between the following pairs of compounds. 

(i) Propanal and Propanone

(ii) Acetophenone and Benzophenone

(iii) Phenol and Benzoic acid

(iv) Benzoic acid and Ethyl benzoate

(v) Pentan-2-one and Pentan-3-one

(vi) Benzaldehyde and Acetophenone

(vii) Ethanal and Propanal

a )Tollen's test –Due to oxidizing nature of aldehydes they get easily oxidized, wheareas in case of ketones they are not readily

oxidizable. And tollens test exploits this fact, [Ag (NH₃)₂]⁺ is used as reagent Ag mirror is formed during this reaction

b) fehling test- aldehyde reduces the fehling solution to form red brow precipitate of Cu₂O. Fehling's solution is a chemical reagent used to differentiate between water-soluble carbohydrate and ketone functiona groups, and as a test for reducing sugars and non-reducing sugars, supplementary to the Tollens' reagent test.

2. Iodoform te

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a )Tollen's test –Due to oxidizing nature of aldehydes they get easily oxidized, wheareas in case of ketones they are not readily

oxidizable. And tollens test exploits this fact, [Ag (NH₃)₂]⁺ is used as reagent Ag mirror is formed during this reaction

b) fehling test- aldehyde reduces the fehling solution to form red brow precipitate of Cu₂O. Fehling's solution is a chemical reagent used to differentiate between water-soluble carbohydrate and ketone functiona groups, and as a test for reducing sugars and non-reducing sugars, supplementary to the Tollens' reagent test.

2. Iodoform test- Methyl ketones give positive iodoform test, so when acetophenone react with NaOI it forms Yellow ppt. ofIodoform. Whereas the benzophenone will not give ppt. of iodoform. Iodoform is CHI₃ tri iodo methane. It forms only in the case when NaOI is trated with methyl ketone.

C₆H₅COCH₃+NaOI ?  C₆H₅COONa+ CHI₃+NaOH

3. When phenol reacts with FeCl₃ it forms violet coloured complex, whereas the benzoic acid not,

 

4. When we add NaHCO₃ to acid solution it will produce effervescence of CO₂ gas, hence benzoic acid will give CO₂ gas and ethyl benzoate will not.

5. Iodoform test – as acetophenone is methyl ketone it will form

CHI₃ during iodoform test, Iodoform is CHI₃ tri iodo methane. It forms only in the case when NaOI is trated with methyl ketone, this is confirmatory test for methyl ketones.

6. Ethanal is methyl aldehyde, it gives positive iodoform test on reacting with NaOI, Whereas the propanal can't

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<p><strong>a )</strong>Tollen's test –Due to oxidizing nature of aldehydes they get easily oxidized, wheareas in case of ketones they are not readily</p><p>oxidizable. And tollens test exploits this fact, [Ag (NH₃)₂]⁺&nbsp;is used as reagent Ag mirror is formed during this reaction</p><div class="photo-widget-full"><div class="figure"><picture><source srcset="" media=" (max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/1749806710phpkAcpxS.jpeg" alt="" width="620" height="94" loading="lazy"></picture></div><div class="figure"><p><strong>b) </strong>fehling test- aldehyde reduces the fehling solution to form red brow precipitate of Cu₂O.&nbsp;Fehling's solution is a chemical&nbsp;reagent&nbsp;used to differentiate between water-soluble&nbsp;carbohydrate&nbsp;and&nbsp;ketone functiona groups, and as a test for&nbsp;reducing sugars&nbsp;and non-reducing sugars, supplementary to the&nbsp;Tollens' reagent&nbsp;test.<br>&lt;!- [if !supportLineBreakNewLine]-&gt;<br>&lt;!- [endif]-&gt;</p><div class="photo-widget-full"><div class="figure"><picture><source srcset="" media=" (max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/1749806753php8f2dWH.jpeg" alt="" width="666" height="108" loading="lazy"></picture></div><div class="figure"><p><strong>2.</strong> Iodoform test- Methyl ketones give positive iodoform test, so when acetophenone react with NaOI it forms Yellow ppt. ofIodoform. Whereas the benzophenone will not give ppt. of iodoform. Iodoform is CHI₃ tri iodo methane. It forms only in the case when NaOI is trated with methyl ketone.</p><p>C₆H₅COCH₃+NaOI&nbsp;? &nbsp;C₆H₅COONa+ CHI₃+NaOH</p><p><strong>3.</strong> When phenol reacts with FeCl₃&nbsp;it forms violet coloured complex, whereas the benzoic acid not, </p></div></div><p>&nbsp;<picture><source srcset="" media=" (max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/1749806828phpRfdn7h.jpeg" alt="" width="480" height="103" loading="lazy"></picture></p><p><strong>4.</strong> When we add NaHCO₃&nbsp;to acid solution it will produce effervescence of CO₂&nbsp;gas, hence benzoic acid will give CO₂&nbsp;gas and ethyl benzoate will not.</p><div class="photo-widget-full"><div class="figure"><picture><source srcset="" media=" (max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/1749806916phperSmZA.jpeg" alt="" width="384" height="172" loading="lazy"></picture></div><div class="figure"><p><strong>5. </strong>Iodoform test – as acetophenone is methyl ketone it will form</p><p>CHI₃&nbsp;during iodoform test, Iodoform is CHI₃&nbsp;tri iodo methane. It forms only in the case when NaOI is trated with methyl ketone, this is confirmatory test for methyl ketones.</p></div></div><div class="photo-widget-full"><div class="figure"><picture><source srcset="" media=" (max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/1749806969phpvVkbA7.jpeg" alt="" width="570" height="84" loading="lazy"></picture></div><div class="figure"><p><strong>6.</strong> Ethanal is methyl aldehyde, it gives positive iodoform test on reacting with NaOI, Whereas the propanal can't</p></div></div><div class="photo-widget-full"><div class="figure"><picture><source srcset="" media=" (max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/1749807022phpmlBL53.jpeg" alt="" width="433" height="114" loading="lazy"></picture></div></div></div></div>

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