a. Given the number of isomers including stereoisomers of alkane `C_(6)H_(14^(.))`
b. Given the decreasing order of stability at room temperature of the isomeric hexane.
c. Given the decreasing order of boiling points of the isomeric hexane.
d. Which of the isomeric hexanes gives two monochloro derivatives when chlorinated?

Explanation

a. Five structural isomeric hexanes are:
i. ii. iii.
iv. v.
None of them shows stereoisomerism (optical or geometrical).
b. More branching means more stable. Thus, the order of stability is: (v) gt (iv) gt (iii) gt (ii) gt (i).
c. More branching means compact or less surface area and thus has weaker interolecular van der Waals forces of attraction, so low boiling point. Thus, the order of the boiling point is: (i) gt (ii) gt (iii) gt (iv) gt (v).
d. Only (iv), 2,3-dimethyl butane, can two different monochlorinated compounds.

The isomeric hexane (i) gives three compounds out of which two are optically active.
The isomeric hexane (ii) gives five compounds out of which three are optically active.
The isomeric hexane (iii) gives three compounds out of which two are optically active.
The isomeric hexane (v) gives three compounds out of which only on is optically active.