What reactants combine to form 3-chlorooctane?

The following reactants combine to form 3-chlorooctane in POOR YIELD.

1. Oct-2-ene + hydrogen chloride

CH₃CH=CHCH₂CH₂CH₂CH₂ CH₃ + HCl → CH₃CH₂CHClCH₂CH₂CH₂CH₂CH₃
(+2-chlorooctane)

2. Oct-3-ene + hydrogen chloride

CH₃CH₂CH=CHCH₂CH₂CH₂CH₃ + HCl → CH₃CH₂CHClCH₂CH₂CH₂CH₂CH₃
(+ 4-chlorooctane)

3. Octane + hydrogen chloride + ultraviolet light

CH₃CH₂CH₂CH₂CH₂CH₂CH₂CH₃ + HCl → CH₃CH₂CHClCH₂CH₂CH₂CH₂CH₃
(+ 1-chloro-, 2-chloro-, and 4-chlorooctane)

And here are three combinations that give 3-chlorooctane in GOOD YIELD.

4. Octan-3-ol + hydrogen chloride

CH₃CH₂CHOH CH₂CH₂CH₂CH₂ CH₃ + HCl → CH₃CH₂CHClCH₂CH₂CH₂CH₂CH₃ + H₂O

5. Octan-3-ol + thionyl chloride + pyridine

CH₃CH₂CHOH CH₂CH₂CH₂CH₂ CH₃ + SOCl₂ + C₅H₅N → CH₃CH₂CHClCH₂CH₂CH₂CH₂CH₃ + SO₂ + C₅H₅NHCl

6. Octan-3-ol + phosphorus trichloride + pyridine

CH₃CH₂CHOH CH₂CH₂CH₂CH₂ CH₃ + PCl₃ + C₅H₅N → CH₃CH₂CHClCH₂CH₂CH₂CH₂CH₃ + H₃PO₃ + C₅H₅NHCl

In the last two cases, the pyridine acts as a base. It reacts as a base to neutralize the HCl as it forms.

Here’s a video on the preparation of alkyl halides from alcohols and thionyl chloride.