Chem 161-2011 Lecture 11 truncated, Chapter 7

Chem 161-2011 Lecture 11 truncated, Chapter 7 - CHEMISTRY...

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Chem 161-2011 Lecture 11 1 CHEMISTRY 161-2011 LECTURE 11 CHAPTER 7 MOLECULAR GEOMETRY AND BONDING THEORIES ANNOUNCEMENTS E-MAIL EXAMS How did we do?
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Chem 161-2011 Lecture 11 2 PLAN FOR TODAY Molecular Geometry The VSEPR model Electron-domain geometry and molecular geometry Deviation from ideal bond angles Geometry of molecules with more than one central atom Molecular Geometry and Polarity Valence Bond Theory Hybridization of Atomic Orbitals Hybridization of s and p orbitals Hybridization of s, p, and d oritals Hybridization in molecules containing multiple bonds Bonding Theories and Descriptions of Molecules with Delocalized Bonding
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Chem 161-2011 Lecture 11 3 VSEPR Valence Shell Electron Pair Repulsion Electron pairs surrounding a central atom keep as far away from each other as possible in order to minimize electron repulsion. Lewis structures provide two-dimensional geometry. VSEPR provides three-dimensional geometry, including molecular polarity. Similar molecular shapes often govern chemical and biological activity. e.g., Sulfanilamide and para-aminobenzoic acid: both antibiotics e.g., Colgate-Palmolive research Triclosan 2-Isopropoxyphenol: model compound for triclosan OH O Cl Cl Cl OH O
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Chem 161-2011 Lecture 11 4 Heroin Naloxone The receptor sites in human body proteins have three-dimensional shapes designed to accommodate certain molecules produced naturally in the body. Some drug molecules, e.g., heroin, fit into these receptor sites due to its shape. However, naloxone, which has a similar shape as morphine, can also fit the receptor site and block the action of heroin.
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Chem 161-2011 Lecture 11 6 A Strategy for Applying the VSEPR Method (1) Draw a Lewis structure of the molecule or polyatomic ion. (2) Determine the number of electron domains around the central atom. Electron domains Bonding electron pair (sigma bond) Non-bonding electron pair (lone pair) (Also, non-bonding electron (free radical)) Not domains T h e π bond of a double bond. T h e t w o π bonds of a triple bond. (3) Identify the electron group geometry, based on the number of electron domains. (4) Identify the molecular geometry, based on the atom positions (not based on the lone-pair electrons).
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Chem 161-2011 Lecture 11 7 Apply VSEPR on BeH 2 vs. BH 3 Discuss electron group geometries and bond angles. BeH 2 H Be H Linear, 180 o BH 3 H B H Trigonal planar, 120 o | H Apply VSEPR on CH 4 square planar vs. tetrahedral (use models) Discuss “electron domains” demonstrating almost equal electron group geometry CH 2 -O (single bond) CH 2 - (non-bonding electron group) CH 2 =O (double bond) Single bond is the reference point. Non-bonding electron group requires a little more room. Double bond requires even more room. H . . C — O: H H C : H H . . C = O: H
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Chem 161-2011 Lecture 11 8 BEHAVIOR OF POLAR MOLECULES IN AN ELECTRIC FIELD
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Chem 161-2011 Lecture 11 9 Polar and Non-Polar Bonds and Molecules Analogous to sled dog’s pulling in various directions in Susan Butcher’s Iditarod race in Alaska HCl has a polar covalent bond.
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This note was uploaded on 02/20/2012 for the course 160 161 taught by Professor Kim during the Fall '08 term at Rutgers.

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Chem 161-2011 Lecture 11 truncated, Chapter 7 - CHEMISTRY...

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