Choose the correct mechanistic pathway for each of the following questions: A. an El process
B. an SN2 process
C. an E2 process
D. an SN1 process
a. Chlorination of a 1° alcohol using Thionyl Chloride
b. Alkene formation via POCl3 reaction with a 2º alcohol

Chlorination of a 1° alcohol using Thionyl Chloride - an SN2 process

Alkene formation via POCl3 reaction with a 2º alcohol - an El process

Explanation:

For a primary alcohol, the chlorination occurs by SN2 mechanism. Remember that the order of SN2 mechanism is methyl > primary > secondary > tertiary. This means that a primary alkyl halide will undergo nucleophillic  substitution by SN2 mechanism.

For a secondary alkyl halide, we normally expect that the mechanism will be E2. When we use POCl3 and pyridine, the alkyl halide passes through a carbocation intermediate which is characteristic of an E1 mechanism.