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Chapter 16 Group 16 Elements

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Chapter 16 Group 16 Elements Chapter 16 Group 16 Elements Physical Properties The elements Halides, oxohalides, oxides, salts of oxoacids Metal sulfides, polysulfides, polyselenides, polytellurides Compounds of sulfur and selenium with nitrogen 1 • Dioxygen makes up 21% of the Earth’s atmosphere and 47% of the Earth’s crust is composed of O-containing compounds (water, limestone, silica, silicates). • Sulfur occurs around volcanoes and hot springs, iron pyrites fool’s gold (FeS 2), and other minerals. • Selenium and Tellurium are relatively rare and occur in only a few minerals • Polonium is omitted because its abundance is only 3 × 10 −7 ppb, giving a negative number on the log scale. Relative abundances of the group 16 elements in the Earth’s crust Production of sulfur in the US from 1980 to 2008 2 Uses of sulfur and sulfuric acid 3 ∆ o Given the fH (Na 2O,s) = -414 kJ/mol, determine the + 2- enthalpy change for the process: 2Na (g) + O (g) Na 2O(s) Hint: Create an appropriate Born-Haber cycle and look up the necessary values for each of the steps. ∆ o 2 aH (Na) 2Na (s) + ½ O 2(g) 2Na (g) + O (g) ∆ o aH (O) ∆ o fH (Na 2O,s) ∆ o 2 IE (Na) EA H 1(O) 1 ∆ o EA H 2(O) ∆ Ho(Na O,s) lattice 2 + 2- Na 2O (s) 2Na (g) + O (g) 4 Chemistry of oxygen MnO 2 or Pt catalyst 2H 2O2 O2 + 2H 2O ∆, MnO 2 catalyst 2KClO 3 3O 2 + 2KCl + - 2- Describe bonding in [O 2] , O 2, [O 2] , [O 2] using MO theory. + - O2 + PtF 6 [O 2] [PtF 6] + - 2O 2F2 + 2BF 3 2[O 2] [BF 4] + F 2 Chemistry of ozone and ozonide ∆ o -1 3/2 O 2(g) → O3(g) fH (O 3,g,298 K) = +142.7 kJ mol + - o O3(g) + 2H (g) + 2e ⇌ O2(g) + H 2O(l) E = +2.07 V − The structures of O 3 and [O 3] , and contributing resonance structures in O 3. − • The O O bond order in O 3 is taken to be 3/2. 2KOH + 5O 3 2KO 3 + 5O 2 + H 2O (Ozonide salts) Phosphite ozonide 5 Sulfur: allotropes S6 S7 S8 catena -S S8 + 24F 2 → 8SF 6 S8 + 4Cl 2 → 4S 2Cl 2 S8 + 4Br 2 → 4S 2Br 2 SF 6 2+ structure of [S 2I4] 6 2- Polysulfides, [S x] , and polythionates are formed from reaction of sulfur with hot aqueous alkali polythionate Vulcanization – soft rubber is toughened by cross-linking polyisoprene chains. Hydrocarbons are dehydrogenated when heated with sulfur and further reaction with alkenes occur. Other reactions of sulfur: - - - 1/8 S 8 + CO O=C=S 1/8 S8 + CN N=C=S ⇌ NΞC-S Na 2SO 3 + 1/8S 8 –H2O, 373 K Na 2S2O3 S8 + 3AsF 5 –liquid SO 2 [S 8][AsF 6]2 + AsF 3 2+ [S 8] is red and undergoes a change in ring conformation… 2+ [S 8] 7 2+ [S 19 ] 2+ S8 • transannular interactions • Cross ring S-S separations smaller than the sum of van der Waals radii • Two 7-membered, puckered rings • Delocalized bonding connected by a 5-atom chain • Charge localized on the three- coordinate S Selenium 4SeCl 2 + 4Ph 3PSe Se 8 + 4Ph 3PCl 2 Inorganic Chemistry By Egon Wiberg, Nils Wiberg, Arnold Frederick Holleman 8 tellurium 4+ 2ReCl 4 + 15Te + TeCl 4 –heat in sealed tube → 2[Te 8][ReCl 6] Production of H 2O2 BaO 2 + H 2SO 4 → BaSO 4 + H2O2 2[NH 4][HSO 4] – electrolytic oxidation, “-H2” [NH 4]2[S 2O8] 2[NH 4][HSO 4] + H 2O2 H2O2 stabilizer catalytic cycle used in the industrial manufacture of hydrogen peroxide 9 H2O2 H2O2 + - o H2O2 + 2H + 2e ⇌ 2H 2O E = +1.78 V + - o O2 + 2H + 2e ⇌ H2O2 E = +0.70 V Cl 2 + H 2O2 → 2HCl + O 2 10 Peroxo complexes − µ 2− [V(O 2)2(O)(bpy)] [Mo 2(O 2)4(O) 2( -OOH) 2] 11 Polysulfanes: H 2SX n = 2 2H 2S + Sn nCl 2 H2Sn+2 + 2HCl 2- Polysulfides: [S X] 2- [S 6] 2- [Mn(S )(S )] 2- [Zn(S 4)2] 5 6 µ 4- 2- [(S 6)Cu( -S8)-Cu(S 6)] [AuS 9] 12 2- 2- Polyselenides and polytellurides: [Se x] and [Te x] DMF* 3Se + K 2Se 2 K2[Se 5] *DMF = Dimethylformamide = 4Se + K 2Se 2 + 2[Ph 4P]Br [Ph 4P] 2[Se 6] + 2KBr DMF, 15-crown-5 3 Se + K 2Se 2 [K(15-crown-5)] 2[Se 5] 1,2-diaminoethane, crypt-222 2K + 3 Te [K(crypt-222)] 2[Te 3] 2- 2- [Te 5] [Te 8] O 141 pm 103° F F 13 Sulfur fluorides and oxofluorides S2F10 SOF 2 14 Sulfur chlorides and oxochlorides 206 pm 1/4S 8(l) + Cl 2(g) - S2Cl 2 193 pm Reaction Chemistry S 2Cl 2 2SO 2 + S 2Cl 2 + 3Cl 2 4SOCl 2 Cl-S-S 108° SO 3 + SCl 2 SOCl 2 + SO 2 Internal dihedral angle = 84° 2SCl 2 S2Cl 2 + Cl 2 Reaction Chemistry of SOCl 2 RCO 2H + SOCl 2 RC(O)Cl + SO 2 + HCl SOCl 2 SO 2Cl 2 15 TeF SeF 4 4 Se 4Cl 16 Tellurium halides 16 2− = MO diagram for octahedral [ECl 6] (E Se or Te) Oxides of Sulfur SOCl 2 + Ag 2S -430 K S2O + 2AgCl HS 7H + SOCl 2 → S8O S8 ----CF 3C(O)OOH → S8O 17 - [(SO ) N ]- [SO 2N3] 2 3 3 18 Gas phase form of SO 3 also exists as a trimer of SO 4 units. Solid state form exists as polymeric chains Oxides of selenium and tellurium [Te O F ]3- 3 6 3 SeO 3 tetramer 19 Oxoacids and their salts: S H2S + HSO 3Cl -low temp- H2S2O3 + HCl ClSO 3H ClSO 3H H2O2 -HCl H2SO 5 -HCl H2S2O8 20 2− H SO (g) [S 2O6] 2 4 H2SO 4 (l) Sulfur-Nitrogen Compounds 21 Potential diagrams (values in V) for sulfur, selenium and tellurium at pH = 0. 22.
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