Q78E - Organic Chemistry (Mcmurry)

Question

Melamine, used as a fire retardant and a component of the writing surface of white boards, can be prepared from s-trichlorotriazine through a series of SNAr reactions with ammonia. The first substitution takes place rapidly at room temperature. The second substitution takes place near 100 °C, and the third substitution requires even higher temperature and pressure. Provide an explanation for this reactivity.

Step-by-Step Solution

Answer

Step-by-Step Solution

Step 1: SNAr reactions

It is the aromatic nucleophilic substitution in which the nucleophile addition of the group occurs in the aromatic ring and it disturbs the aromaticity of the ring and the rate of the reaction depends upon the position where substitution is attached.

Step 2: SNAr reactions of melamine

Melamine is prepared from s-trichlorotriazine from nucleophilic aromatic substitution and the first substitution takes place rapidly at room temperature. The second substitution takes place near 100 °C, and the third substitution requires even higher temperature and pressure because this allows the substitution of three different nucleophiles like chlorine onto the same triazine core and cyanuric chloride has temperature-dependent differential reactivity for the displacement of chlorides with nucleophiles during SNAr so react at three different temperature to form product as shown below: