310-7 - CH 310 N T Th 2-3:30 LECTURE 7 Textbook Assignment:...

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1 CH 310 N T Th 2-3:30 LECTURE 7 Textbook Assignment: Chapter 15 Homework (for credit): POW 3 posted- Today’s Topics: Organometallic Reagents Notice & Announcements: Exam 1: Monday, 9/22 7-9 PM Last Name: A-L WEL 1.308 Last Name: M-Z WEL 1.316 Organic Lecture Series 2 Organometallic Compounds • Organometallic compound: Organometallic compound: a compound that contains a carbon-metal bond • The focus will be on organometallic compounds of Mg, Li, and Cu – these classes illustrate the usefulness of organometallics in modern synthetic organic chemistry – the use of organometallics can bring about transformations that cannot be accomplished in any other way Organic Lecture Series 3 Grignard Reagents • Grignard reagent: Grignard reagent: an organomagnesium compound – prepared by addition of an alkyl, aryl, or alkenyl (vinylic) halide to Mg metal in diethyl ether or THF Mg + 1-Bromobutane Butylmagnesium bromide (an alkyl Grignard reagent) ether Br MgBr + ether Mg Br MgBr Bromobenzene Phenylmagnesium bromide (an aryl Grignard reagent)
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2 Organic Lecture Series 4 RMgX and RLi • Grignard reagents dissolve as coordination compounds solvated by ether – ethylmagnesium bromide, EtMgBr Organic Lecture Series 5 RMgX and RLi • Organolithium reagents – prepared by reaction of an alkyl, aryl, or alkenyl halide with lithium metal Cl + + 1-Chlorobutane Butyllithium pentane 2Li LiCl Li Organic Lecture Series 6 RMgX and RLi The carbon-metal bonds in RMgX and RLi are polar covalent 2.5 - 1.2 = 1.3 2.5 - 1.0 = 1.5 2.5 - 1.5 = 1.0 2.5 - 1.6 = 0.9 2.5 - 1.8 = 0.7 2.5 - 1.9 = 0.6 Difference in Electronegativity C-M Bond Percent Ionic character* 60 52 40 36 28 24 C-Li C-Mg C-Al C-Zn C-Sn C-Hg *Percent ionic character = E C -E M E C x 100 2.5 - 1.9 = 0.6 24 C-Cu Increasing Ionic Character
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3 Organic Lecture Series 7 • Reaction with proton donors: Reaction with proton donors: – RMgX and RLi are strong bases – they react readily with these proton acids CH 3 2 -MgBr H -OH 3 2 - H Mg 2+ OH - Br - Weaker base Stronger base Weaker acid Stronger acid
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This note was uploaded on 10/18/2008 for the course CH 310M taught by Professor Iverson during the Fall '05 term at University of Texas.

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310-7 - CH 310 N T Th 2-3:30 LECTURE 7 Textbook Assignment:...

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