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I was solving some questions on amines when I happened to see the below question:

propan-1-amine + ($\ce{NaNO2 + HCl}$)= a mixture of products (originally, the mixture in brackets on the reactant side was just written as $\ce{HNO2}$)

The mixture contains:

a. 1-Propanol

b. 2-Propanol

c. Cyclopropane

d. All of these

The answer happened to be "d. All of these". I could understand the formation of 1-propanol and 2-propanol but not cyclopropane. The answer given in the textbook wasn't clear and I couldn't understand. It said that the carbocation intermediate had something to do with it which I couldn't follow.

Can someone explain what is behind all this?

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1 Answer 1

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  • Diazotisation of primary amines gives the diazonium salt which decomposes to the primary cation and $\ce{N2}$. From this, in aq. $\ce{HCl}$, you directly get the primary alcohol, primary chloride and primary nitro by immediate trapping of the primary cation by ions in solution and the terminal alkene by 1,2 elimination.
  • A cation shift to give the secondary cation also occurs to give secondary alcohol and secondary chloride.
  • The cyclopropane arises from a 1,3-elimination of the primary cation.

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pics from reference 1

References

  1. Amines with Nitrous Acid - chem.libretexts.org
  2. Nitrosation, diazotisation, and deamination by J. H. Ridd Q. Rev. Chem. Soc., 1961, 15, 418-441 DOI: https://doi.org/10.1039/QR9611500418
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  • $\begingroup$ Reaction equations added $\endgroup$
    – Waylander
    Commented May 6, 2020 at 13:59

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