11-Lewis Diagrams - 5.111 Lecture Summary #11 October 2,...

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5.111 Lecture Summary #11 October 2, 2009 Reading for today: 2.7,2.8 Reading for Lecture 11: Sections 2.9-2.11, 2.3, 2.12 LEWIS DIAGRAMS Lewis structures share the total number of valence electrons between atoms so that each atom achieves a noble gas configuration. Valence electrons for second row elements: 2s & 2p Cyanide Ion CN 1) [ C N ] 2) Total # of valence e - s plus the absolute value of total charge if negative ion 3) Total # of e - s if each atom had noble gas shell 4) # of bonding e - s 5) assign bonding e - s 6) multiple bonds 7) lone pairs Thionyl Chloride SOCl 2 SOCl 2 is a reagent used in organic and medicinal chemistry to convert carboxylic acid ( COOH ) groups to acid chloride ( COCl ) groups in molecules. One example of using SOCl 2 in the synthesis of pharmaceuticals is for novocaine, a local anesthetic drug used in dentistry and to reduce pain in intramuscular injections of other drugs, such as antibiotics. Li 2s 1 Be 2s 2 B 2s 2 2p 1 C 2s 2 2p 2 N 2s 2 2p 3 O 2s 2 2p 4 F 2s 2 2p 5 Ne 2s 2 2p 6 H 2 N C OH O SOCl 2 H 2 N C Cl O H 2 N C O O N C 2 H 5 C 2 H 5 novocaine
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5.111 Lecture Summary #11 October 2, 2009 1) Cl S O Cl 2) total # valence e - s 3) total # of e - s if each atom had noble gas shell 4) # of bonding e - s 5) assign bonding e - s 6) multiple bonds 7) lone pairs FORMAL CHARGE Formal charge is a measure of the extent to which an atom has gained or lost an electron in the process of forming an covalent bond. To assign a formal charge to an atom, we have to decide how many e - s an atom has in a molecule and compare it to how many e - s it has when it is a free atom. To assign a formal charge: 1) number of valence electrons on a free atom, V 2) subtract from it the # of e - s that are lone pairs, L V L 3) subtract from that 1/2 of # of e - s that it shares in molecule V – L – S/2 = FC
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11-Lewis Diagrams - 5.111 Lecture Summary #11 October 2,...

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