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Question: $CH_3-CH_2-N \equiv N$...

CH3−CH2−N≡NCH_3-CH_2-N \equiv N

Answer

The given structure represents the ethyldiazonium cation (CH3−CH2−N+≡NCH_3-CH_2-\stackrel{+}{N} \equiv N). It is an extremely unstable compound that rapidly decomposes to an ethyl carbocation and nitrogen gas.

Explanation

Solution

The given structure is CH3−CH2−N≡NCH_3-CH_2-N \equiv N.

This represents the ethyldiazonium cation.

Explanation of the Solution:

  1. Identification: The compound is an alkyldiazonium cation, specifically ethyldiazonium cation. The group −N+≡N-\stackrel{+}{N} \equiv N is the diazonium group.
  2. Corrected Structure: The given structure is a simplified representation. To show the formal charge correctly, it should be written as: CH3−CH2−N+≡NCH_3-CH_2-\stackrel{+}{N} \equiv N The nitrogen atom directly bonded to the ethyl group has four bonds (one to carbon, three to the other nitrogen) and no lone pair, thus carrying a positive formal charge. The terminal nitrogen has three bonds (to the first nitrogen) and one lone pair, making it neutral.
  3. Stability: Alkyldiazonium cations are extremely unstable. Unlike arenediazonium salts (e.g., benzenediazonium chloride), which are resonance-stabilized by an aromatic ring and are stable at low temperatures (0-5 °C), alkyldiazonium cations lack such stabilization.
  4. Decomposition: Due to their high instability, alkyldiazonium cations rapidly decompose, even at very low temperatures, by eliminating a molecule of nitrogen gas (N2N_2). This decomposition generates a highly reactive carbocation. The decomposition of ethyldiazonium cation proceeds as follows: CH3−CH2−N+≡N→very fastCH3−CH2++N2↑CH_3-CH_2-\stackrel{+}{N} \equiv N \xrightarrow{\text{very fast}} CH_3-CH_2^+ + N_2 \uparrow The ethyl carbocation (CH3−CH2+CH_3-CH_2^+) formed is a primary carbocation and is highly unstable. It will immediately react with any available nucleophile (like water or halide ions) to form alcohols or alkyl halides, or undergo elimination (to form ethene), or rearrange to a more stable carbocation if possible. This leads to a mixture of products when primary aliphatic amines are treated with nitrous acid.