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Chemistry LibreTexts

2.8: Solutions for Selected Problems

  • Page ID
    202258
  • Exercise 2.1.1:

    MBq1pt1.png

    Exercise 2.1.2:

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    Exercise 2.1.3:

    At neutral pH, lysine would normally be protonated. It would noy have a lone pair on the nitrogen to coordinate a metal ion.

    MBq1pt3.png

    Exercise 2.4.6:

    The pKa of an α-position is typically about 20, although it can vary depending on what other groups are nearby. That is too high to build up a significant amount of the deprotonated species in water, which has a pKa (in water) of 14.

    Exercise 2.4.7:

    1. The pKa of the side chain of histidine is about 6.0; upon changing from pH 7 to pH 5, this group would become protonated and positively charged. The positive charge would be more stabilising (or less destabilising) toward Fe2+ than Fe3+; the reduction potential would increase.
    2. The pKa of the side chain of histidine is about 3.7; upon changing from pH 4 to pH 3, this group would become protonated and positively charged. The positive charge would be more stabilising (or less destabilising) toward Fe2+ than Fe3+; the reduction potential would increase.
    3. The pKa of the side chain of histidine is about 4.2; upon changing from pH 4 to pH 5, this group would become deprotonated and negatively charged. The negative charge would be more stabilising (or less destabilising) toward Fe3+ than Fe2+; the reduction potential would decrease.

    Exercise 2.5.1:

    Ti4+ and Ca2+

    Exercise 2.5.2:

    F- and HO-

    Exercise 2.5.3:

    1. Co2+ with NO2-
    2. Mg2+ with CH3CO2-
    3. Cu+ with RS-
    4. Fe2+ with N2
    5. Zn2+ with imidazole

    Exercise 2.5.4:

    Choose the best match for the following metal ions.

    1. Fe3+ with asp
    2. Cu+ with met
    3. Zn2+ with his
    4. Cu2+ with his
    5. Co3+ with glu

    Exercise 2.5.5:

    Choose the amino acid residue that would have the effect on the metal ion as described, based on HSAB principles.

    1. Increase the reduction potential of Cu2+: met.
    2. Decrease the reduction potential of Fe3+: glu.
    3. Make Cu+ easier to oxidise: his.
    4. Make Fe2+ easier to oxidise: asp.
    5. Make Fe3+ easier to reduce: cys.

    Exercise 2.7.1:

    a) 0 β b) 1.73 β c) 2.83 β d) 3.87 β e) 4.89 β f) 5.92 β

    Exercise 2.7.2:

    a) approx. 4 β b) approx. 4 β c) approx. 2 β d) approx. 3 β

    e) approx. 5 β f) approx. 0 β g) approx. 6 β