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

(i) Ethanal and Propanal

(ii) Benzoic acid and Phenol


(i) Distinguish test between ethanal and propanal:

 Iodoform Test: Ethanal gives iodoform test.

 CH3CHO + 4NaOH + 3I2 ---> CHI3 (Yellow ppt.) + HCOONa + 3NaI + 3H2O

Propanal does not give this test.

CH3CH2CHO + 4NaOH + 3I2 ---> No Reaction.

 

(ii) Distinguish test between Benzoic acid and Phenol:

 NaHCO3Test: When Benzoic acid reacts with NaHCO3, the brisk effervescence of CO2 gas evolved.

 

 
Phenol does not give this test.

C6H5OH + NaHCO3 -->  No Reaction

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An aromatic compound 'A' of molecular formula C7H7ON undergoes a series of reactions as shown below. Write the structures of A, B, C, D and E in the following reactions:


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A solution of (–) –1 – chloro –1 – phenylethane is toluene racemises slowly in the presence of a small amount of SbCl5, due to the formation of

  • carbanion

  • Carbene

  • Carbocation

  • Carbocation


C.

Carbocation


Because of the planar structure of carbonation, both retention and inversion can take place.
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Arrange the following compounds in order of decreasing acidity

  • II>IV>I>III

  • I>II>III>IV

  • III>I>II>IV

  • III>I>II>IV


C.

III>I>II>IV

Electron withdrawing group increases the acidic strength of the compounds by destabilising and stabilising the phenoxide ion formed respectively.

The presence of an electron withdrawing group increases the acidic strength by stabilising the phenoxide ion. On other hands, the presence of electron releasing group destabilises the phenoxide ion and decrease the acidic strength.

NO2>Cl>CH3>OCH3

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Select the ether among following that yields methanol as one the products on reaction with cold hydroiodic acid

  • 1-methoxybutane

  • 1-methoxybutane-2-methylpropane

  • 2-methoxy-2-methylpropane

  • methoxybenzene


C.

2-methoxy-2-methylpropane

According Zeise! method, when an ether reacts with cold HI, alkyl iodide and alcohol are formed. In case of asymmetrical ether, the alkyl halide is always formed from the smaller alkyl group provided no tertiary (3°) alkyl group is present and if any 3° alkyl group is present, the halogen gets attached with it. In case of alkyl aryl ethers, the products are always phenol and an alkyl halide.


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