Chapter9

Chapter9 - Final Examination: Chem 140A Important...

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Final Examination: Chem 140A Important Information The Final Examination will be held next week - Either Monday or Friday depending on the class. The exam will cover all the material from lectures, problem sets, chapters, midterm questions (including Bonus questions etc.). CHAPTERS 1 to 9.
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Chapter 9 – Further Reactions of Alcohols and the Chemistry of Ethers
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Alkoxides We’ve talked about alkoxides and we’ve used them in reactions: As bases in elimination reactions with sterically hindered haloalkanes, and as nucleophiles in S N 2 reactions. How are they made? Bases will convert an alcohol into an alkoxide depending on the strength of the base. Alkali metals react with alcohols to generate alkoxides and hydrogen by reduction.
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Alcohols with Strong Acids The OH group of an alcohol must be converted into a better leaving group for alcohols to participate in substitution or elimination reactions as the leaving group. Protonation is one way of achieving this – i.e. turning the OH into “water” as a leaving group. Primary alcohols can react to give a haloalkane. Bromo and Iodo via S N 2. Secondary and tertiary alcohols can react to give S N 1 and E1 reactions. Note that if the conjugate base is a good nucleophile, it will attack. If you want a different nucleophile involved look at other methods for activating the OH as a leaving group.
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Carbocation Rearrangement Rearrangement occurs because the carbocation is more stable on tertiary carbons than on secondary ones.
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Carbocation Rearrangement
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Carbocation Rearrangement
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Esters
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Haloalkanes from Alcohols via Inorganic Esters A method for forming a haloalkane from an alcohol that avoids some of the complications in using an acid-catalyzed conversion.
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Chloroalkane Synthesis Converting alcohols into chloroalkanes. Again we first form an inorganic ester and Cl- acts as the nucleophile. The formation of the ester, is the generation of the leaving group. This is a related process to the formation of sulphonates that we have used already. Remember the use of TsCl to make OH a good leaving group! Importantly, the alkyl sulphonate can be isolated and kept for reaction later.
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Ethers Simple ethers are common solvents, and therefore have common names, some of which we are already experts on!
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Crown Ether – Cyclic polyethers The size of the cavity in a crown ether can be changed to fit different metal ions. Shape recognition. The study of these compounds and their incapsulation abilities forms some
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This note was uploaded on 04/05/2012 for the course CHEM 140A taught by Professor Whiteshell during the Winter '04 term at UCSD.

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Chapter9 - Final Examination: Chem 140A Important...

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