Which of the following molecules is chiral?

Options

A. `CH_(3)CH=C=CHCH_(3)`
B. `CH_(3)CH=CHCH=CH_(2)`
C. `CH_(3)CH_(2)CH=C=CH_(2)`
D. `CH_(2)=CHCH_(2)CH_(2)`

Answer

A

Explanation

It is a chiral molecule that does not possess a tatrahedral atom with four differenr ligands. A molecule is chiral if it is not superposable on its mirror image. The presence of a tetrahedral atom with four different ligands (such as chiral carbon atom) is only one locus that can confer chirality on a molecule. Most of the chiral molecules that we come across do have such stereocenters but many chiral molecules are known that do not posses chiral carbon atoms.
Allenes are compounds whose molecules contain the following double bond sequence:

The plane of the `pi` bonds of allenes are perpendicular to each other. This geometry of the `pi` bonds causes the ligands bonded to the end carbon atoms to lie in perpendicular planes.Because of this allenes with different substituents on the end carbon atoms are chiral as their molecules do not possess any symmetry element such as plane of symmetry.

Allenes do not shown cis-trans isomerism.