A few Midterm practice problems…

1. Find the pH, [H₃O⁺], [OH^-], and pOH for a:
1. 0 .050M KOH solution.
2. 0.030M HCl solution.
2. A Lineweaver-Burk plot gave a slope of 0.0561 and a y-intercept of 0.387.
1. Calculate V_max for this reaction
2. Calculate K_M for this reaction.
3. If the enzyme concentration used was 10^-6M, use your calculated V_max to determine the enzyme turnover number.
3. The pKa’s for aspartic acid are 2.09, 3.86 (side chain), and 9.82.
1. For a pH of 3.0 draw the Lewis structures of the two most concentrated forms of aspartic acid. Show all atoms, bonds, charges, and lone pairs.
2. For a pH of 3.0, determine the relative fractions of the two most concentrated forms.
3. Explain the difference in the overage charges for an aspartic acid ion when it is in the stomach at a pH-1.5 vs being in a cell at a physiological pH of 7.4. Fully support your answer.
4. Alkaloids are N-containing organic compounds that occur in nature. Research by students in the chemistry labs at Winthrop is currently demonstrating a new synthetic route to make nicotine (which is an alkaloid) through a pathway that has never been done before.
1. To extract nicotine from ground tobacco into an aqueous solution, predict whether it would be preferable to use an acidic or basic aqueous solution. Use Henderson-Hasselbalch, solubility, and your knowledge of nitrogen-containing compounds to develop and to support your prediction.
2. Once nicotine has been extracted into an aqueous solution, predict how the pH should be adjusted to get the nicotine to partition into the organic layer of the organic solvent added to the solution. Fully explain and support your prediction.
5. Compare the log P’s for 1-butanol, 1-decanol, glycerol, water, and pentane.
6. Indinavir is a potent inhibitor of the HIV-1 protease, and is used in the treatment of AIDS. It has a log P value of 2.7. 5.00 mL of 1-octanol was vigorously mixed with 200.0 mL of water and 1 mmole of Indinavir was added during mixing. Calculate the number of mmoles of Indinavir that partition to each of the two phases in the mixture.
7. The rate constant for the decomposition of HI at 573K is 2.91 x 10^-6M/sec. The rate constant for this reaction at 673K is 8.38 x 10^-4M/sec.
1. Determine the activation energy for this reaction in units of kJ/mole.
2. For a temperature of 573K, use your answer for the activation energy to predict the fraction of collisions with sufficient energy to react.
3. For a temperature of 573K, determine the collision frequency factor.
8. Draw the mechanism and clearly show what occurs when ethanol reacts with ethanoic acid. Draw the structures of all reactants and products.