Reduction of 9 Flourene 03 12 2015 What s the big difference between lithium aluminum hydride and sodium borium hydride The aluminum and the boron they are in the same group so they have similar properties such as same valence shell electrons However Al is bigger H usually has 1 electron But these reducing agents are producing H That extra electron comes from The Al of the Boron The electronegativy correlates with reducing strength Since Al is bigger the valence shell electrons are further away from it So Boron is the weakest reducing agent because it does not give up those electrons as easily since they are closer to the nucleus o Won t react with ethanol o Li with ethanol might actually reduce it and cause it to explose H2 gas Our reduction We re going to take the 9 flourenol and then we re going to take sodium boron hydride o First we will get boroxide salt o 4 ketones for every 1 borohydride We will then add acid to get our alcohol 9 flouronol is a very bright yellow o So you ll know if the reaction worked or not Procedure change we will not use 10 mg of NaBH o We ll use 20 mg because of water in the air reacting with it since people leave the bottle open 100 mg of product roughly crude product Recrystalllize it o Not super straight forward o One pure solvent doesn t do the job No one solvent that fits all solvent rules o Sometimes the ratio is unknown it s dependent upon purity of the substance o How we ll do it tube Add crude to 1 ml of methanol Bring to a boil in a test Add distilled water dropwise until just cloudy Will only take a few drops Make distilled water the water bath so that they are the same temperature Just a little bit has precipated out of solution Add 1 drop of methanol But don t worry about just don t do it because it takes some dexterity Take test tube out of the product o Isolate do melting point yield and IR Looking for disappearance of the carbonyl peak 3600 area fluorine is still there Solid hydrogen bonding is weaker than liquid hydrogen bonding so the OH peak will be small Great yield is 60 40 50 is good Aldol reaction If you have a carbonyl compound like acid aldehyde o The alpha proton to that carbonyl compound has a pka between 18 and 20 Which means that if you take a base like NaOH you can remove that proton o This is so acidic than an average alkane proton is because of the resonance stability offered by the carbonyl oxygen o The net result of this is that we have a nucleophilic carbon o You can use it to attack an electrophilic carbon o Take an enolate plus acid aldehyde you get a new carbon carbon bond plus some water In essence it s a carbon c bond forming reaction Acid aldehyde sodium hydroxide there you go A really complex aldol reaction o Acid aldehyde react it with propanone Mixed or cross because its two different carbonyl compounds o By adding one carbon because there are now two carbonyl carbons that can serve as the electrophilic carbon also two alpha protons If we aren t careful we will get a mixture of different products and not the one you want o Need to control a mixed aldol reaction Add enolate first Acid aldehyde be the enolate first But if you add sodium hydroxide it will react with itself because of the equilibrium Keq 10 to the 4 equals products over reactants Way on the Reactant side When you want the enolate to react with something else and only something else Then you have to shift the eq to the products side This is done by using a very powerful base This gives us the same enolate but it has a K eq of 10 17 so heavy on the products side o An example of a mix aldol reaction Happens all the time takes place in glycolsis Takes place 24 7 in every cell 365 It s a mixed aldol reaction Our reactionc We will take acetephenone mix it with p anisaldehyde with a lil sodium hydroxide o Initial product is a betahydroxy something o This beta hydroxyl ketone very rapidly undergoes dehydration o So the final product we get trans p anisalesetaphanone We are mixing acetephenone with p anisaldehyde o You re not supposed to do it o And we re using a weaker base o Why can we get away with it There are two issues with a mixed 2 two carbonyl carbons that can be electrophiles 2 there are two possible enolates o There is only one alpha proton source so only one possible enolate o It s less hindered Both have benzene rings but one has a methyl group while the either has a hydrogen o The aldehyde is easier to attack sterically speaking o So the enolate will have a easier time attacking the aldehyde than the ketone o Once it form the betahydroxy Why rapid dehydration Dehydration is very thermodynamically favorable It s a long extended conjugation 75 yield 03 12 2015 03 12 2015