Chem272E2Lecture(1) (1)

Chem272E2Lecture(1) (1) - Experiment #2: Nucleophilic...

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Experiment #2: Nucleophilic Substitution Rx: Competing Nucleophiles We will look at S N 1 and S N 2. Results will matter. I. Announcements a) Find a “buddy” and compare results! b) New techniques learned here: Gas Chromatography. II. Theory a) Compare nucleophilicities of Cl - and Br - in aqueous, acidic mixture. Present in equimolar amounts as their salts: NH 4 Cl, NH 4 Br in H 2 SO 4 /H 2 O Caution!! b) In protic solvents: I - > Br - > Cl - > F - Larger charged species less slowed down by solvent!! c) Substrates used: 1- butanol, 2 – butanol, 2-methyl-2-propanol (t-butanol) X - + ROH RX + OH - OH - is a poor leaving group Perform in acidic solution: Fast protonation ROH + H + ROH + H Displacement (or ionization of H 2 O) by S N 1 and S N 2 . Need heat for 1 ° , 2 ° substrates X - + ROH + R X + H 2 O H 4) What should we see? 1 – butanol should react by S N 2 H + CH 3 CH 2 CH 2 CH 2 OH CH 3 CH 2 CH 2 CH 2 -OH 2 + H-X
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CH 3 (CH 2 ) 2 CH 2 X + H 2 O The relative amounts of 1 – chlorobutane and 1 – bromobutane will show which halide is the better nucleophile!! t – butanol should react by
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This note was uploaded on 07/03/2011 for the course CHEM 121 taught by Professor Matt during the Spring '11 term at Edmonds Community College.

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Chem272E2Lecture(1) (1) - Experiment #2: Nucleophilic...

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