Titanous Ions Destroy Perchlorates. Joseph E. Earley, Sr. Giulio Amadei and Daniel Tofan Georgetown University Washington, DC 20057

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1 Titanous Ions Destroy Perchlorates Joseph E. Earley, Sr. Giulio Amadei and Daniel Tofan Georgetown University Washington, DC 20057

2 Summary Last year, in New Orleans, we reported that, in ethanolic media, Ti III reduces perchlorate rather rapidly. Evidence indicates an intermediate with two Ti III centers. We have designed catalysts based on these results. (Patent applied for.) Development exist. opportunities

3 Perchlorato-Cu II complex Lewis, Hatfield, Hodgson, Inorg. Chem. 13, 1974, 147.

4 Two Old Ligands COOH N N COOH OH HOOC HEDTA NH OH N H HO DADP3

5 Two New Ligands H 2 N NH H N OH OH N H HN NH NH HN HN NH 2 TADP3 CYCAPAB

6 Ligands Influence Spectra ε (M -1 cm -1 ) Ti(III) Ti(III)-HEDTA Ti(III)-TADP3 Ti(III)-CYCAPAB Ti(III)-DADP λ (nm)

7 Suggestions of Dinuclear Ions Pecsok & Fletcher (Inorg. Chem. 1962, 1, 155) observed that absorption between 730 nm and 800 nm (due to polymers?) slowly developed in Ti(III) solutions of ph 3.9. Absorption observed in this spectral region for our systems suggests the presence of dinuclear Ti(III) species. Absorption at 778 nm of Ti III complexes followed the trend: TADP3 > CYCAPAB > DADP3 HEDTA >> Aquoion.

8 The Ti III L- ClO 4 Reaction With reductant in excess, the initial product is chlorate, the final product is chloride. With perchlorate in excess, disappearance of Ti III is exponential in time. First order rate constant is proportional to perchlorate concentration.

9 Acid Catalysis Pseudo-first order rate constants increase as [H + ] increases. Curvature indicates contribution from a rate-law term second order in [H + ]. k obs = k 0 + k [H + ] 2 At [H + ] = 432 mm, rate constants (k) are: TADP3 (158) > CYCAPAB (86) > DADP3 (48) HEDTA (44) > H 2 O (1) Species that absorb strongly at 778 nm react rapidly, suggesting a dinuclear complex as intermediate.

10 Acid Catalysis Is Nonlinear 850 TADP3 680 k x 10 6 (s -1 ) CYCAPAB HEDTA DADP3 Ti(III) [H+] (mm)

11 An Unusual Kinetic Feature Each run yields a first-order rate constant. But, strangely enough, the value of that constant increases as [Ti III ] increases. A mechanism involving a dinuclear intermediate models this behavior.

12 Mechanistic Model Ti III + L Ti III L k 1f, k 1r 2 Ti(III)L Ti 2 L 2 k 2f, k 2r Ti 2 L 2 + ClO 4 - ClO k 3 k 1f = 1000; k 1r = 2000; k 2f = 1000; k 2r = 0.1; k 3 = 0.1; Initial particles = 8000.

13 The Model Fits 3 Rate Constant x 10 4 sec Observed CKS Model [Ti(III)] total x 10 3 / M

14 Synthesis of Functionalized TADP3 11,23-Dihydroxicarbonyl-25,26-dihydroxy-3, 7, 15, 19-tetraazatriciclo[ ,13]hexacosa-1(25), 9(26), 10, 12, 21, 23-hexaene COOH 2+ COOH HOOC O H OH H O [13] H 2 N NH 2 Pb(ClO 4 ) 2, NaOH CH 3 CN N O N Pb Pb N O N COOH [13a] 1- NaBH 4, MeOH 2- Io n Exchange Chromatography NH H N OH N H OH HN COOH * n HBr [14] 13 C-NMR (DMSO d 6 ): 168.1; 154.2; 133.1; 121.3; 120.2; 44.08; 42.00; Elemental Analysis: Found: C: 32.98; N: 6.54; Br: 36.71; H: Calculated [C 24 H 34 N 4 O 6 *4HBr*3H 2 O] C: 33.17; N: 6.45; Br: 36.78; H: 7.03.

15 TADP3-PVA Semi-Solids * OH n * Polyvinyl alcohol is the solid support of choice (<MW> Kdal, 97% hydrolyzed) Preliminary experiments showed that perchlorate ions are reduced by Ti(III) more rapidly in a PVA environment than in water. TADP3-(COOH) 2 is a modified ligand suitable to be covalently bound to the support.

16 Attachment of TADP3DC to PVA COOH OH Ar NH H N OH N H OH HN * n * DMF, H 2 O * O n O * * 4HBr C 2 H 5 -C=N=C-(CH 2 ) 2 -N(CH 3 ) 2 COOH

17 Assay of Functionalization of PVA Spectrophotometric determination of substituted benzene rings (λ max = 298 nm) is a rapid and reproducible method to assay the degree of PVA functionalization (~10%) Cross-linking of PVA chains is likely to occur, due to the presence of two p-cooh groups on the ligand.

18 Results Ti III is stable in the presence of PVA (in.2m acid) for more than two weeks. Ti III reacts with perchlorate more than two orders of magnitude faster in the presence of PVA than in its absence. The PVA surface environment favors reaction.

19 Heterogeneous Catalysis In.2 M acid,ti III absorbed on ligand-modified PVA, reacts with perchlorate more than two orders of magnitude faster than does Ti III absorbed on PVA. Ti III is in excess over ligand. The PVA-fixed ligand is an effective catalyst.

20 A New Chemical Principle Ligands that favor dinuclear complex-formation, when attached to a semisolid support with an alcohol-like surface, act as effective catalysts for reduction of perchlorate ions by Ti III. The sample system increases rate > fold.

21 Prospects Ti IV can be reduced to Ti III chemically electro-chemically photo-chemically Flow and batch systems can be developed to use this new chemical principle for destruction of perchlorates.

22 Advantages Titania (TiO 2 ) is cheap, abundant and environmentally benign. Optimization of ligand, support-system, and regeneration method can yield rapid, cheap, and safe methods of perchlorate disposal.

23 Contact Information Kelli Watson, esq. Technology Development Serv. Georgetown University Washington, DC (phone: ) Joseph E. Earley, Sr., Department of Chemistry, Georgetown University (phone )

AQA A2 CHEMISTRY TOPIC 4.10 ORGANIC SYNTHESIS AND ANALYSIS TOPIC 4.11 STRUCTURE DETERMINATION BOOKLET OF PAST EXAMINATION QUESTIONS

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