无机化学课件：20 group IVA

1、Group IV A or 14Carbon, Silicon, Germanium, Tin, Lead CarbonGraphiteDiamondFullereneBucky Tube Graphite - diamond100 kbar, 12002800 KCr, Fe or NiGraphite Soft and black and the stable,common,form of carbon.Very light and resistantMore 2D like; sp2 Orbitals. Atom is at the corners of fused hexagon in

2、 parallel layersStrong bonds within layers and weak bond between layersGood conductor of electricityDiamondAbrasiveGemDiamond Hard and transparent and the unusual form of carbon. Strong thermal conductivity More 3D like behavior; sp3 orbital. Atom is bound to four other carbon atoms in a regular rep

3、etitive pattern.Strong covalent bonding in 3 dimensionsBad electrical conductor (Diamonds are not forever!) It will turn into graphite (given time). (Faster if you heat it up or bombard it with high energy ions.)Fullerenes C60 Discovered in 1985 by Harry KrotoUniversity of Sussex, England Richard Sm

4、alley and Robert Curl JrRice University, Texas 1996 Nobel Prize in ChemistryH.Kroto R. Smalley R. CurlSmalleys apparatus for generating and detecting buckyball. Schematic of a mass spectrometer “.in the field of Observation, chance only favors the prepared mind”Louis PasteurC60Bucky Ball; fullerene

5、J.R. Heath, S.C. OBrien, H.W. Kroto, R.F. Curl, R.E. Smalley, Nature 318 , 162, (1985)FullereneC60 - A third allotropic form of very stable spheres(1985) - Formed when graphite is evaporated in an inert atmosphere. - Assumed C60 consists of 12 pentagons and 20 hexagons with carbon atoms at each corn

6、er, as a soccer ball. - Names New carbon ball C60 Buckminsterfullerene ( R.Buckminster Fuller : The geodesic dome 1967 ) Buckyball All have 12 pentagonal faces, 145.5 pm on a side. C60 has 20 hexagonal faces, 139 pmT= 5K on a side. The C=C between two pentagons is electron rich, The pentagons themse

7、lves are electron poor. The LUMO of C60 is triply degenerate. Fullerides C60-1 to 6, C603- are superconducting below T = 28K. Fullerenes may encapsulate metal atoms or small clusters. Clusters lose 3 electrons to the fullerene. La C60 is La3+ C603-.The Fullerenes Molecular forms of CarbonWhat is hap

8、pening in current research with Buckyball? Model of C60 docked in the binding site of HIV-1 protease Fullerene Pyrrolidine and Osmium Tetroxide derivatives of C60. C50-containing soot ( 90 g) was synthesized in a modified graphite arc-discharge process in which 0.013 atm of CCl4 was added to 0.395 a

9、tm of helium. The products in the toluene extract from the soot were isolated with multistage high-performance liquid chromatography . and 2 mg of C50Cl10 with 99.5% purity was obtained. The C50Cl10 thus obtained is moderately soluble in some organic solvents, e.g., carbon disulfide, toluene, and be

10、nzene, as a lemon yellowcolored solution. Science, Vol 304, Issue 5671, 699 , 30 April 2004Rational Side of Materials Chemistry:Rational Doping:C60 insulator Semiconductor SuperconductorLa2CuO4 Magnetic insulator Bad Metal SuperconductorKK3C60Nanotubes C1,000,000 and beyond Discoverer: Sumio Iijima

11、Carbon Nanotubes (CNT) 1991 multiwalled CNTcoaxial cylinders with a hollow core 1993 single-walled CNT Roll up sheets of hexagonsNanotubes C1,000,000 and beyond Diameter 1-30 nm Length microns Interlayer Spacing 0.347 nm Graphite interlayer spacing 0.337 nmIBMDo C60 and CNT really exist? NUS Surface

12、 Science LaboratorySeeing is believing Yacobson and Smalley Richard Smalley Image GalleryArc Discharge Catalytic Decomposition H, CH4 or COTemperature Programmable FurnaceQuartz TubeCatalystCO/ CH4CNTCo/La2O3600-750 oC2COC + CO2CH4C + 2H22-dimensional hexagonal lattice of carbonsp2 hybridized carbon

13、 atomsBasis for C-60 (bucky balls), nanotubes, and graphiteAmong strongest bonds in natureWhat is graphene?A. K. Geim & K. S. Novoselov. The rise of graphene. Nature Materials Vol 6 183-191 (March 2007)A Two dimensional crystalIn the 1930s, Landau and Peierls (and Mermin, later)showed thermodynamics

14、 prevented 2-d crystals in free state.Melting temperature of thin films decreases rapidly with temperature - monolayers generally unstable. In 2004, experimental discovery of graphene- high quality 2-d crystalsPossibly, 3-d rippling stabilizes crystalRepresentation of rippling in graphene. Red arrow

15、s are 800nm long.How to make grapheneStrangely cheap and easy.Either draw with a piece of graphite, or repeatedly peel with Scotch tapePlace samples on specific thickness of Silicon wafer. The wrong thickness of silicon leaves graphene invisible.Graphene visible through feeble interference effect. D

16、ifferent thicknesses are different colors.Samples of grapheneGraphite films visualized through atomic force microscopy.Transmission electron microscopy image c) Scanning electron microscope image of graphene.Electrons in grapheneElectrons in p-orbitals above and below planep-orbitals become conjugat

17、ed(共轭的） across the planeElectrons free to move across plane in delocalized（不受限制的） orbitalsExtremely high tensile strength（抗张强度）http:/wiki/Aromaticity-Graphene and graphite are great conductors along the planes.Synthesis of GrapheneChemical Vapor Deposition (CVD)thermal decomposition of hexagonal -Si

18、CCombustion of Mg in CO2!Electrolysis in Ionic Liquidcarbon fibers CarbidesPreparation of Metal Carbides:Direct combination of the elements or the metal oxide with carbon at high temperature.Reaction of the heated metal with gaseous hydrocarbon.Reaction of acetylene with electropositive metals in li

19、quid ammonia.Structure of CarbidesC4- methanide: produces predominantly CH4 on hydrolysis. eg:Be2C and Al4C3C22-, acetylide (ethynide): alkali metals, M2IC2, alkaline earth metals,MIIC2, and the lanthanoids LnC2 and Ln2C3.CaC2 + N2 CaCN2 + C 1000+ oC石灰氮；碳氮化钙;碳酰亚氨钙；氰氨基钙cyanamide - can be trimerized t

20、o melamineInterstitial CarbideWhere the carbon-metal electronegativity difference is smaller, as in transition metal carbides, MxCy compounds are called interstitial carbides. eg., WC. Bonding is more covalent, properties are metallic.Compounds of CarbonStructure： CO(6+8=14e-) and N2（27=14e-）Isoelec

21、tronic, similar structure。One bondTwo bond:C O:OxidesMonooxide (CO):C O:Properties of CO： as ligand，forming carbonyl complexes Fe(CO)5, Ni(CO)4, Co2(CO)8 C as coordinating atom。 Reductant：Highly toxicDioxide (CO2) ：O C O ：structure：O=C=OOC=O bond length 124pm as in CH3-C-CH3C O bond length 113pmC-O

22、bond length in CO2: 116pmC：spSolid state:Dry iceCarbidesDirect Combination of the elements above2000 C.Reaction of the metal oxide with carbon at high temperatures.Reaction of heated metal with gaseous hydrocarbon.Reaction of acetylene with electropositive metals in liquid ammonia. Carbonates CO2 so

23、luble in H2O，mostly as CO2H2O，A few as H2CO3Structure of CO32-：CO32-(6+38+2=32e-) and BF3(5+39=32e-)are isoelectronic。C：sp22-71-332104.4 HCOH COH=+K11-2-23-3104.7 COH HCO=+KThermal stability of carbonate：H2CO3MHCO3 Ge Sn Pb C. There are no germanium analogues to the silicones. The exceptional stabil

24、ity of the Si-O bond is not duplicated in the Ge-O bond.Stability of the M(II) state: Pb Sn Ge Si C.Ability to catenate: C Si Ge Sn Pb. For the alkane analogues: SinH2n+2 n = 8; GenH2n+2 n = 5.Hydrides of germanium are not pyrophoric and are unaffected by acid/base, unlike the silanes. Hydrides of t

25、in and lead are of marginal stabilityProperties： Reaction with Base Reaction with HF2.Silicic acid and silicates H4SiO4 silicic H2SiO3 metasilicic xSiO2yH2O polysilicicProperties：12210132106.1107.1 SiOH-=，low solubility，biacidKKPreparation：Silica gel containing small amount of CoCl2will change color

26、 at different H2O contents。Silicic acid as gelSilica gel-H2O2NaClSiOH2HClSiONa3232+(g)2NH2NaClSiOHCl2NHSiONa332432+soluble：Na2SiO3 、K2SiO3insoluble: with characteristic color。silicatesSi sp3Tetrahedral arrangement of Si-Osilica Structure of silica：halides SiX4 SiF4 SiCl4 SiBr4 SiI4State g l l shydro

27、lysis：Mp low high Hydride (silane SinH2n+2)property：simplest：SiH4pyrophoricity：hydrolysis：strong reductant：low thermal stability：Silicon Carbide（SiC）：Hydroxides of Tin and LeadHNO3or HAcH+standingH+-26Sn(OH)32)(s,SnOH-w4Sn+ex. OH-ex. OH-3Pb(OH)2)(s,Pb(OH) w2Pb+ex. OH-ex. OH-24Sn(OH) 2)(s,Sn(OH)w2Sn+

28、 ex. OH-ex. OH-c-HNO3 )(s,SnOH- Sn 32Not sol in A or BwOH4NOSnOH)(4HNOSn22323+c-Sn(II) as reductantIdentification of Sn2+,Hg2+Identification Reaction of Bi3+Sn0.136Sn 0.154 Sn/V24A-+E-Sn0.91Sn(OH)0.93-Sn(OH)/V24-26B-EPb(IV) as oxidantPb0.58PbO0.25PbO /VPb0.126Pb1.45PbO /V2B22A-+EEOHNaClPbONaClOPb(OH)222+22-422O2H5Pb2MnO4H2Mn5PbO+2222O2HClPbCl)4HCl(PbO+c2224422O2HO)2Pb(HSOSO4H2PbO+224422O2HO2PbSOSO2H2PbO(Pb3O4)-red can be seen as：4HNOPbOPb342+O2H)(PbO)2Pb(NO2223+brown(Pb2O3)：orange seen as：PbOPbO2(PbO)：orange yel