Question

Terminal alkene can be prepared by which of the following reagents?
(A) $Butan-2-ol.$
(B) $2-methylpropan-1-ol.$
(C) $2-methylpropan-2-ol.$
(D) None of these.

Answer 1

Hint : We know that in organic chemistry, the term "reagent" denotes a chemical ingredient (a compound or mixture, typically of inorganic or small organic molecules) introduced to cause the desired transformation of an organic substance. The one way to synthesize alkenes is by dehydration of alcohols, a process in which alcohols undergo $E1$ or $E2$ mechanisms to lose water and form a double bond.

Complete Step By Step Answer:
As we know alkynes are hydrocarbons containing a triple bond between any two adjoining carbon atoms. Alkenes can be prepared from alkynes by carrying out hydrogenation in the presence. The charcoal which is used in this reaction has been moderately deactivated. Lindlar catalyst is palladium on calcium carbonate which has been deactivated by lead acetate to stop further hydrogenation. These alkenes will have a cis form. To obtain a trans- alkene, these alkynes should be made to react with halogens. Alkenes are the hydrocarbons that contain a double bond between any two adjacent or adjoining carbon atoms. The structure of alkene is such that the number of hydrogen atoms is twice the number of carbon atoms. Alkenes have important industrial uses, and also play an important role in our everyday lives.
Thus, $2-methylprop-1-ene$ can be prepared from; $2-methylpropan-1-ol$ as:
$C{{H}_{3}}-CH\left( C{{H}_{3}} \right)-C{{H}_{2}}-OH\xrightarrow[acid]{\Delta }C{{H}_{3}}-\left( C{{H}_{3}} \right)C=C{{H}_{2}}+{{H}_{2}}O$
Therefore, the correct answer is option B.

Note :
Remember that It should be noted that the primary alcohols undergo bimolecular elimination while the secondary alcohols and tertiary alcohols undergo unimolecular elimination. The relative reactivity of alcohols in dehydration reaction is ranked as follows: Methanol $<$ primary $<$ secondary $<$ tertiary. Also Lucas' reagent is a solution of anhydrous zinc chloride in concentrated hydrochloric acid. This solution is used to classify alcohols of low molecular weight. The reaction is a substitution in which the chloride replaces a hydroxyl group.