Question

Explain with suitable equations conventional and green synthesis of carbaryl. Also mention the principle of green chemistry involved. 

Answer 1

Conventional route:
Carbonyl is prepared on large scale by treating methyl-isocynate with 1-napthol, anine is treated with phosgene to get methyl-isocynate. Carbaryl is produced by treating methyl isocynte with 1-napthol 

- With using napthol-1 methylcarbomoyl chloride:

- In these route of synthesis of carbaryl highly toxic substance such as phosgene, methyl isocynate and methylcarbamoyl chloride are used. 

Green route:
1. Napthol treated directly with equal quantity of phosgene is alkaline medium to get chloroformate which is then treated with methylamine to give carbary alternatively, 1-napthol is first converted to its chloroform, which is then treated with methylamine to give desired product.

2. Greener route synthesis also uses exactly the same reagent, but these are taken in different sequence. Hence, this sequence avoids the proportion of methyl isocynate. But use of phosgene and methyl amine is still needs to be avoided.