Question

Allyl chloride on dehydrochlorination will give:
(i) Propa-di-ene
(ii) Propylene
(iii) Alkyl alcohol
(iv) Acetyl chloride

Answer 1

An allylic carbon is a carbon atom which is bonded to a carbon atom that is in turn doubly bonded to another carbon atom and in case of allyl chloride the chlorine atom is attached to the allylic carbon. We need to find out on dehydrochlorination i.e. on removal of one molecule of $HCl$ what product is formed.

Complete step-by-step answer: Allylic carbon is the carbon atom which is bonded to a $s{p^2}$ hybridized carbon atom. In case of allyl chloride, a chlorine atom is attached to the allylic carbon. Hence the structure of allyl chloride is
${H_2}C = CH - C{H_2} - Cl$.
Dehydrochlorination is a type of elimination reaction that eliminates a molecule of hydrogen chloride from a given substrate resulting in the formation of an alkene.
Hence in the given substrate i.e. allyl chloride a molecule of hydrogen chloride is removed $(\,Cl$is removed from the $\alpha$carbon and $H$is removed from the $\beta$ carbon$)$resulting in the formation of an allene.
${H_2}C = CH - C{H_2} - Cl\,\,\xrightarrow{{ - HCl}}\,\,{H_2}C = C = C{H_2}$.
The IUPAC nomenclature of the product is Propa-di-ene, since it has three carbon atoms and two double bonds.

Additional Information: Dehydrochlorination is also known as $\beta$-elimination reaction as along with the $Cl$atom present at the $\alpha$ carbon the $H$ is removed from the $\beta$ carbon.

Hence the correct answer is (i) Propa-di-ene.

Note: For organic compounds you must know their general and IUPAC names so that you can identify the starting compound for any given reaction if the structures are not given. Also you must know what kind of reaction the given starting compound undergoes in the conditions given in the question.