09-03 - 9/7/2010 Choose the answer that has the shape of...

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Unformatted text preview: 9/7/2010 Choose the answer that has the shape of the following compounds correctly identified. CH3 Choose Choose the answer that has the shape of the following compounds correctly identified. CH3 A. B. C. D. pyramidal planar pyramidal planar shape planar pyramidal pyramidal planar VSEPR planar pyramidal What What hybrid orbitals are used to form the C-H and O-H bonds? CH3 Valence Shell Electron Pair Repulsion theory summary VSEPR: Electron pairs assume a geometry that minimizes their repulsion. hybrid examples electron electron orbitals groups geometries 2 linear trigonal planar tetrahedral sp sp2 H molecular geometries linear trigonal planar planar pyramidal 3 4 sp3 H C H H tetrahedral trigonal pyramidal Csp2―Hs Osp3―Hs H O H bent Using VSEPR what shape would be predicted for the amino group in the following structure? trigonal trigonal H planar H H Using VSEPR what shape would be predicted for the amino group in the following structure? trigonal trigonal H planar H H N C O A. trigonal planar B. trigonal pyrimidal C. neither of these D. both of these both The position of atoms cannot change in two resonance structures. H trigonal pyrimidal N C O A. trigonal planar B. trigonal pyrimidal C. neither of these D. both of these both H N C H trigonal pyrimidal trigonal planar H H H N C O H N C O trigonal trigonal planar trigonal trigonal planar H H H N C O H C C H trigonal pyrimidal H H O This This is resonance structure! This is not a resonance structure! Why? H 5 H 6 1 9/7/2010 The nitrogen in an amide cannot be both planar and pyramidal at the same time. trigonal trigonal H planar H H N C O A. trigonal planar B. trigonal pyrimidal C. neither of these D. both of these both H N C trigonal pyrimidal There are still seats open in CHE 327 Organic Chemistry Laboratory. CHE 327 Lab Section L11 L21 L22 L32 Time Wed. 8:20‐12:30 Wed. 1‐5 Wed. 1‐5 Thu. 8:20‐12:30 # of Seat Available 1 2 1 2 trigonal trigonal planar H H H N C O trigonal H pyrimidal O H However, VSEPR is ambiguous in its prediction. It predicts both a planar and pyramidal shape depending upon the importance of the double bonded structure. If you want to take it in fall, please email: che327@notes.cc.sunysb.edu 7 What is the "molecular glue" that holds atoms together to give molecular structures such as rapamycin? rapamycin? HO O electrostatics attraction + repulsion + hydrogen atom H· nuclei - repulsion electrons - hydrogen atom H· N O O O O O O OH O O O rapamycin 9 10 electrostatics attraction What is the “glue” that holds the hydrogen atoms together to form H2? A. The attraction of e1 to e2. + repulsion + hydrogen atom H· H· nuclei - repulsion electrons - B. The attraction of n1 to n2. to to to C. The attraction of n1 to e1 and the attraction of n2 to e2. to to D. The attraction of n1 to e2 and the attraction of n2 to e!. hydrogen atom H· + H· n1 e1 H· + H· e2 n2 energy energy H—H 11 H—H 12 2 9/7/2010 The classical electrostatic model for bonding was very successful but it had some difficulties. A new theory for chemical bonding was necessary. 1. the circulating electrons did not emit light. 2. the electron did not collapse into the nucleus. What was this new theory of chemical bonding? A. Gravitational theory. B. Quantum theory. C. Nuclear theory. D. String theory. H· H· H· H· energy H H 13 13 energy H H 14 What was a major understanding that allowed the development of Quantum theory? A. electrons have no mass. B. protons have no mass. C. electrons have wave properties. D. neutrons can be ignored. an electron = a particle a wave When it was postulated that electrons have wave properties the difficulties of the classic electrostatic model disappeared and quantum or wave mechanics was developed. H· H· H· H· energy H H 15 energy H H 16 16 How has quantum mechanics increased our understanding of molecules; their bonding and how they react? How has quantum mechanics increased our understanding of molecules; their bonding and how they react? quantum mechanics H· atomic 1s orbital 17 18 3 9/7/2010 How has quantum mechanics increased our understanding of molecules; their bonding and how they react? Atomic s, p orbitals and their hybrids. quantum mechanics x y atomic 2s orbital + higher energy d and f atomic orbitals 19 x y H· 3 atomic 2p orbitals Z Z 1 s orbital 3 p orbitals 20 How are the orbitals arranged about a sp hybridized atom? How are the orbitals arranged about a sp hybridized atom? 2 sp hybrid orbitals 1 s orbital 3 p orbitals 21 2 sp hybrid orbitals pz + py atomic orbitals 22 How are the orbitals arranged about a sp hybridized atom? How are the orbitals arranged about a sp hybridized atom? sp hybridized atom 2 sp hybrid orbitals pz + py atomic orbitals 23 2 sp hybrid orbitals pz + py atomic orbitals 24 4 9/7/2010 Consider the combination of one s atomic orbital and two p atomic orbitals. How many sp2 hybrid orbitals will result from the combination of one s atomic orbital and two p atomic orbitals? A. 1 B. 2 C. 3 s px y z x y z x py pz 25 pz 26 How many sp2 hybrid orbitals will result from the combination of one s atomic orbital and two p atomic orbitals? A. 1 B. 2 C. 3 How are the hybrid orbitals arranged about a sp2 hybridized atom? x y z How will these 3 sp2 hybrid orbitals be arranged in space? y z x interorbital angle = 120° 120° an pz sp2 hybridized hybridized atom pz A. xy plane B. xz plane C. yz plane 27 28 How many hybrid orbitals are on an sp3 hybridized atom? How many hybrid orbitals are on an sp3 hybridized atom? s px y z interorbital angle = 109.5° 109.5° x y z x py an sp3 hybridized atom hybridized pz 29 30 5 9/7/2010 31 6 ...
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This note was uploaded on 12/05/2010 for the course CHE 321 taught by Professor Fowler/sampson during the Fall '08 term at SUNY Stony Brook.

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