University:
Massachusetts Institute of Technology
Course:
3.091SC | Introduction to Solid State Chemistry
Academic year:

2024
Views:

165

Pages:

4
Author:

Camilla Castro

3.091 OCW Scholar Self-Assessment Exam Organic Materials Solution Key Final Exam, Problem #5 The skeletal structure of the amino acid, alanine, is given below as it exists as the neutral zwitterion. To the right is shown its titration curve in aqueous solution. The abscissa expresses concentration in terms of degree of protonation, so that at a value of 0.5 the neutral zwitterion is the only species present, at a value of 0 alanine is totally deprotonated, and at a value of 1.0 alanine is totally protonated. γ α alanine β (a) What is the hybridization of each of the thre e carbons in alanine? α β γ (b) Indicate on the titration curve (1) the pKa for protonation of the zwitterion, (2) the pKa for deprotonation of the zwitterion, and (3) the isoelectric point. (c) Draw the skeletal structure of alanine when it is solvated in an aqueous solution at extreme acidity, i.e., pH < 1. (d) For an aqueous solution of alanine calculate the ratio of the concentration of neutral alanine zwitterion to the concentration of deprotonated anion when the pH is 8.091. Final Exam, Problem #6 (d) The dipeptide, alanylserine shown below, is derived from alanine and serine. (ii) Draw the skeletal structure of each constituent amino acid as it would be present in an aqueous solution of extreme basicity, i.e., pH > 12. alanine serine (e) The figure below shows various features of the tertiary structure along a length of protein in aqueous solution. © source unknown. All rights reserved. At each of the four numbered positions, name one chemical change to the environment of the protein that would destabilize the associated feature in the tertiary structure. Explain the relevant chemistry. Final Exam, Problem #13 (a) Name the type of polymerization reaction that will convert 6-aminohexanoic acid into nylon 6. 6-aminohexanoic acid nylon 6 (b) Write the reaction that converts two molecules of 6-aminohexanoic acid into a dimer of nylon 6. (c) Calculate the molecular weight of nylon 6 for which the degree of polymerization, n, is 3091. (d) Is it possible to convert nylon 6 into an elastomer? If so, describe how, i.e., specify the necessary change in the chemistry. If not, explain why this is the case.