last updated Friday, October 30, 2015

Meeting 11 (Condensed Key)

1. a. The reaction uses water as solvent and a recyclable catalyst (Pd/C). Aside of that, most of the other chemicals are not that dangerous either (i.e., potassium carbonate)

b. The potassium carbonate deprotonates the phenol making it more water-soluble and easier to undergo an oxidative addition. In addition, the carbonate ion also serves as ligand in the ligand exchange part of the catalytic cycle.

c. Elemental palladium metal on carbon is used as catalyst. It goes through a sequence of oxidations and reductions during the reaction. It can easily be recovered after the reaction and be recycled.

d. The addition of hydrochloric acid protonates the phenolate resulting in the precipitation of the neutral phenol. In addition, the carbonate is protonated leading to the formation of carbon dioxide.

 Ph-Ph-O^-  +       H⁺   ------>    Ph-Ph -OH
          CO₃^2-  +  2 H⁺  ------>     H₂O  +  CO₂

e. A mixture of methanol and water (1:1) is ultimately used for recrystallization. The crude is first dissolved in methanol. After the catalyst is removed, water is added and the mixture reheated. The addition of water increases the polarity of the solution and causes the weakly polar product to precipitate.

f. The compound displays six signals in the 1H-NMR spectrum. Three doublets (two for the protons on the para-subst. ring and one for the ortho protons of the mono-subst. ring), two triplets (meta and para protons of the mono-subst. ring) and one broad singlet for the phenol group.

g. The CI spectrum should display less fragmentation than the EI spectrum. The parent peak (=molecular ion peak) should be at m/z=171 ([M+H])