Experiment Six: Synthesis of Bromohydrin – Flashcards
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What are we adding to the C=C in this reaction?
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OH and Br
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what does it mean that the OH adds Markovnikov?
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the OH adds to the more substituted side
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what does it mean to say that Br adds anti-markovnikov?
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the Br adds to the less substituted side
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What type of stereoselectivity occurs in addition of Br and OH?
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anti OH is 180 degrees away from Br
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What acts as the electrophile?
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halogen
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what acts as the nucleophile?
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water
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What is our source of Br?
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NBS N-Bromosuccinimide easy to handle, solid electrophile source
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What is the difference between adding Br and OH syn or anti?
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steric interactions and very different chemical properties
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What are our reactants?
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1-methylcyclohexene (liquid) water (co-solvent) (liquid) THF (co-solvent) (liquid) NBS (solid)
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What is added last in the reactant mixture?
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liquid 1-methylcyclohexene
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What is the intital color of the reactant mixture?
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yellow due to unreacted Br
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what is the ending color of the reaction mixture?
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clear due to the fact that all the Br is reacted
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How do we quench the reaction following the color change?
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add water
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How do we extract the organic layer from the aqueous layer?
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place it test tube and use pipet to trasfer bottom organic layer to new test tube
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what does the organic layer contain?
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1-methyl-2-bromocyclohexanol (product) and the succinimide byproduct THF and H2O solvent
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How do we remove water from organic layer?
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using magnesium sulfate drying agent
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How do we separate succinimide byproduct from product?
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using chromatographic purification
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what is the purpose of chromatographic purification?
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to separate organic molecules of different polarity
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what medium is used for chromatographic purification?
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silica gel
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how does chromatographic purification work?
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the polar OH bonds on the surface of the silica gel attract the polar succinimide by product to the surface and prevent passage cyclohexonal is nonpolar and can pass through
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How do we proceed with chromatographic purification?
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prepare chromatographic column with silica gel, then use pipet to transfer organic layer into column rinse test tube with dicholormethane and transfer remaining organic layer add dicholormethan to column use pipet bulb to push cyclohexanol and dicholormethane through the silica gel
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How do we remove the dicholormethane?
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rotary evaporation
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what should the product look like after rotary evaporation?
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colorless liquid
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what are we looking for in the IR spectrum for this experiment?
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the absence of C=C and the presence of C-OH
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What is the beilstein test?
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tests for the presence of halogens copper wire flame test should glow green/blue for Br
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What is the jones test?
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test for the presence of secondary alcohols (regiochemistry)
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For the jones test what does the orange/red color indicate?
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(-) the OH is tertiary
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for the jones test what does the green color indicate?
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(+) the OH is secondary
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In this we reaction, what are the states of our reactants and products?
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liquid reactant --> liquid product
