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Help me answer: From amongst the following alcohols the one that would react fastest with conc .HCl and anhydrous ZnCl2, is

From amongst the following alcohols the one that would react fastest with conc .HCl and anhydrous ZnCl2, is

  • Option 1)

    1-Butanol

  • Option 2)

    2-Butanol

  • Option 3)

    2-Methylpropan-2-ol

  • Option 4)

    2-Methylpropanol

 
Answers (3)
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option 2

 

The reagent, conc.HCl and anhydrous ZnCl2 is Lucas reagent, which is used to distinguish between 1°, 2° and 3° alcohols.

3° alcohol + Lucas reagent → Immediate turbidity.
2° alcohol + Lucas reagent → Turbidity after 5 mins.

1° alcohol + Lucas reagent → No reaction.
Thus, the required alcohol is 2-methylpropan-2- ol, i.e.

As we learnt in 

Test of alcohol Lucas test -

ZnCl_{2}+conc.HCl\:\:is\:called\:Lucas\:reagent

- wherein

1^{\circ}alcohol\rightarrow Cloudiness\:appears\:on\:heating

2^{\circ}alcohol\rightarrow Cloudiness\:appears\:after\:5\:minutes

3^{\circ}alcohol\rightarrow Cloudiness\:appears\:immediately

 

 Tertiary alcohol reacts fastest with Lucas reagent.


Option 1)

1-Butanol

This option is incorrect

Option 2)

2-Butanol

This option is incorrect

Option 3)

2-Methylpropan-2-ol

This option is correct

Option 4)

2-Methylpropanol

This option is incorrect

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