How can gas chromatography determine what mechanism a reaction underwent? For example, I was to synthesize an alkyl halide using 1-propanol, NaBr, and sulfuric acid. I know its a substitution reaction, but how can gas chromatography tell me whether its SN1 or SN2 substitution?

2 answers

  1. You will get a mixture of products in the case of SN1 as the + ion formed can rearrange or eliminate to form an alkene.

    In the case of SN2 there is no rearrangement although there may be competing E2 reaction to give an alkene.

    Thus by running a GC with a mixture of expected products and then comparing this with the reaction mixture it is possible to decide if the reaction was SN1 or SN2.

    I will leave you to decide which are the rearrangement products from the SN1 and the competing elimination product in the SN2.

  2. My products were traced by the GC and when given back to me, there are numerous peaks and a list of different areas of the peaks. I still don't get how the peaks and areas given can help me determine what mechanism it was.

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