Acetonitrile, CH₃CN, is an important solvent. The chemical is normally available as a by-product of the manufacture of acrylonitrile, CH₂=CHCN, the building block of polyacrylonitrile, a widely used polymer. Recently, however, the demand for acrylonitrile dropped, so the supply of acetonitrile diminished to a point where users of the solvent were concerned. For that reason new methods were sought for the synthesis of CH₃CN, and a new “green” method was reported. Step 1: reaction of ethanol (C₂H₅OH) with ammonia to give ethylamine (C₂H₅NH₂) and water. Step 2: reaction of ethylamine and oxygen (over a ruthenium oxide/aluminum oxide catalyst) to give acetonitrile and water.
(a) Draw Lewis electron dot structures for ethanol, ethylamine, acetonitrile, and acrylonitrile. Specify the molecular geometry around each C atom and, as appropriate, around the O or N atoms.
(b) Write balanced equations for each step in the synthesis of acetonitrile from ethanol.
(c) Calculate the atom economy for the synthesis of acetonitrile from ethanol. (Atom economy is discussed in Applying Chemical Principles, 4.1, Green Chemistry and Atom Economy, page 207.)