Name the hydrocarbon which which is formed as mono-chloro derivative of C_8H_18

Question

Name the hydrocarbon which which is formed as mono-chloro derivative of C_8H_18

Answer 1

Octane is a straight chain 8 carbon alkane.  If you count the carbon atoms from the left, from 1 to 8, and you replace any one of the three H on C1 with a Cl, then you would call this 1-chlorooctane. If you replace any of the two H on C2 with Cl, then you have 2-chlorooctane. Likewise for any H on C3 or C4 woulkd be 3-chloro- or 4-chlorooctane respectively. The special case arises if you replace any of the two H on C5 counting from the left. This does not become 5-chlorooctane. According to IUPAC rules it is called 4-chlorooctane, because the Cl is on the 4th carbon from the end of the chain. Similarly, if you replace any of the two H on C6 and C7, the name is 3-chloro and 2-chlorooctane respectively. And finally if you replace any of the three H on C8, it is called 1-chlorooctane.