Chem2O6 - 1997/98

1. The digitoxin derivative shown below is a metal chelating agent that is specific for ATPase and has potential use in radio-imaging.

(i) Identify the functional groups present in this compound.
(ii) Identify a methyl group, and a primary, secondary, or tertiary carbon (if there are any present).
(iii) Identify a primary, secondary, or tertiary alcohol (if any are present).
(iv) Identify a primary, secondary, or tertiary amide (if any are present).

2. Consider the following three organic molecules:

(a) Give the hybridization of each of the atoms (excluding hydrogens) in each molecule.

(b) In which direction do the lone pairs on the N atoms in the three structures point relative to the plane of the rings?

(c) A cyclic array of 6 electrons (or 6 electrons in overlapping 2p orbitals is said to be aromatic:

    (i) Would you expect thymine, adenine, or imidazole to be aromatic? If so, what resonance structures would you have to write in order to obtain 6 electrons in a cycle?
    (ii) The first sites of protonation of adenine by a strong acid (e.g. HCl) are N(1), N(3), and N(7), NOT the NH₂ group as one might expect. Write one or more resonance structures that would account for this.

3. Show the direction (LHS or RHS) that you would expect the following equilibria to lie:

(i) CH₃CN + C₆H₅^- [CH₂CN]^- + C₆H₆

(ii) CH₂CH₂ + OH^- CH₂CH^- + H₂O

(iii) OH^- + CH₃NH₂ CH₃NH^- + H₂O

(iv) CH₃SH + CH₃^- CH₃S^- + CH₄

(v) CH₃CH₂O^- + C₆H₅COOH CH₃CH₂OH + C₆H₅COO^-

(vi) (C₂H₅)₂NH₂⁺ + HCO₂^- (C₂H₅)₂NH + HCO₂H

4. The following equilibria all lie on the right hand side of the equation:

    NH₂^- + CH₃COOCH₃ NH₃ + ^-CH₂COOCH₃
    ^-CH₂COOCH₃ + CH₃COCH₃ CH₃COOCH₃ + ^-CH₂COCH₃
    ^-CH₂COCH₃ + CH₃OH CH₃COCH₃ + CH₃O^-
    CH₃O^- + CH₃NO₂ CH₃OH + ^-CH₂NO₂

(i) Identify which compounds are weaker acids than methanol.

(ii) Identify which compounds are weaker bases than methoxide ion.

(iii) Identify which compounds are weaker acids than acetone (2-propanone).

(iv) Identify which compounds are weaker bases than acetone anion.

(v) Identify which is the strongest acid and which is the strongest base.

25sep97; wjl