Question

From amongst the following alcohols the one that would
react fastest with conc. HCl and anhydrous ZnCl2, is
(a) 2-Butanol (b) 2- Methylpropan-2-ol
(c) 2-Methylpropanol (d) 1- Butanol

Answer 1

The one that would  react fastest with conc. HCl and anhydrous ZnCl2, is  2-Methylpropanol.

option (C) is correct.

Explanation:

The reagent, concentrated 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.

                                  CH3

                                      |

                          CH3 -- C -- CH3

                                       |

                                    CH3

Thus the one that would  react fastest with conc. HCl and anhydrous ZnCl2, is 2-Methylpropanol.