Question
This anion (“ANN-eye-on”) is reduced in the most common redox couple for dye-sensitized solar cells. For 10 points each:
[10h] Name this hyper·valent anion used as a model system for three-center, four-electron bonding. Thio·sulfate reduces this ion, dissociating one of its covalent bonds, in a common colori·metric redox titration.
ANSWER: tri·iodide [or I3-- (“I-three-minus”); reject “iodide”]
[10e] Hyper·valent species like tri·iodide violate this basic principle of chemical bonding. According to this rule, the sum of lone pairs and bonding pairs of electrons on every main-group atom is four.
ANSWER: octet rule
[10m] Photo·chemists use tri·iodide to simulate the hyper·valent transition state of this organic reaction mechanism. In this concerted mechanism, donation of a lone pair into a sigma-star orbital coincides with leaving group departure.
ANSWER: SN2 [or bimolecular nucleophilic substitution; prompt on substitution or nucleophilic substitution]
Data
| Team | Opponent | Part 1 | Part 2 | Part 3 | Total |
|---|---|---|---|---|---|
| Chicago A | Brown A | 0 | 10 | 0 | 10 |
| Chicago B | Stanford A | 0 | 10 | 10 | 20 |
| Claremont A | Virginia A | 0 | 10 | 0 | 10 |
| Columbia A | Chicago C | 10 | 10 | 0 | 20 |
| Cornell A | Florida A | 0 | 10 | 0 | 10 |
| Cornell B | Harvard A | 10 | 10 | 10 | 30 |
| Duke A | Ohio State A | 0 | 10 | 10 | 20 |
| Florida B | UC Berkeley B | 0 | 10 | 10 | 20 |
| Georgia Tech A | WUSTL A | 0 | 10 | 0 | 10 |
| Illinois A | Yale B | 0 | 0 | 0 | 0 |
| Imperial A | Columbia B | 0 | 10 | 0 | 10 |
| Indiana A | UC Berkeley A | 0 | 10 | 0 | 10 |
| Iowa State A | South Carolina A | 0 | 10 | 0 | 10 |
| Minnesota A | Texas A | 10 | 10 | 10 | 30 |
| Minnesota B | Vanderbilt A | 0 | 10 | 0 | 10 |
| NYU A | Johns Hopkins A | 0 | 10 | 10 | 20 |
| North Carolina A | Northwestern A | 10 | 10 | 10 | 30 |
| Penn A | McGill A | 0 | 10 | 10 | 20 |
| Penn State A | WUSTL B | 0 | 10 | 10 | 20 |
| Purdue A | Michigan A | 0 | 10 | 10 | 20 |
| Rutgers A | Georgia Tech B | 0 | 0 | 0 | 0 |
| Rutgers B | Houston A | 0 | 10 | 0 | 10 |
| Toronto A | MIT A | 0 | 10 | 10 | 20 |
| Yale A | Maryland A | 0 | 10 | 10 | 20 |