Using any aromatic -amino acid as the example answer the following questions: 1. Draw the Fisher projections of possible stereo isomers and designate their configurations. Which of them takes part in molecules of peptides building?
2. Draw the structure of this -amino acid in isoelectric point (IEP). In what region of pH the IEP is situated?

)benzene and toluene form nearly ideal solutions. consider an equimolar solution of benzene and toluene. at 20 °c the vapour pressures of pure benzene and toluene are 9.9 kpa and 2.9 kpa, respectively. the solution is boiled by reducing the external pressure below the vapour pressure. calculate (i) the pressure when boiling begins, (ii) the composition of each component in the vapour, and (iii) the vapour pressure when only a few drops of liquid remain. assume that the rate of vaporization is low enough for the temperature to remain constant at 20 °c.