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CHEM 0320: Notes
What are the different ways to synthesize aldehydes and ketones
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1. oxidation of alcohol, PCC, jones, MnO2
2.Ozonolysis
3. Markovnikov hydration of alkynes
4.Hydroboration of alkynes |
polarization of carbonyl functional group
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makes aldehydes and ketones have a higher boiling point, are also more miscible in water
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there are three different regions of reactivity in aldehydes and ketones
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the oxygen is attacked by electrophiles
the carbon double bonded to the oxygen is attacked by nucleophiles |
strong bases as nucelophiles
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makes the reaction irreversible
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acetalization
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equlibrium reaction, thermodynamically driven
driving forces: excess EtOH, remove H2O w drying agent |
what is the difference between an acetal and an ether
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you can do this with aldehydes and ketones but not acids or esters
doing this with cyclic molecules gives you diols |
what happens when you acetalize a diol
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you get a cyclic acetal
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what are the applications of acetalization
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bugs - reeversible formation is important
powerful pheromones
used as protective groups in synthesis because they can formed reversibly |
rules with bisulfite adduct reactions
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must use cyclic ketone or aldehyde, doesn't work with acyclic ketones.
used for extractions |
ylide |
a negatively charged carbon atom is attached to a positively charged heterotatom
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bayer villager oxidation: migratory aptitudes
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me< 1o <2o <3o
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keto enol tautomerism
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equalibrium strongly prefers keto over enol form but the enol form can be stabilized by H bonding and additional delocalization
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dean-stark
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technique removes water as an aziotrope
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alkylation of enolates
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if limiting amounts of MeI are used, a poly alkylation occurs.
Doing an irreversible deprotonation means one final product and higher yield of said product |
Problems with enolate equlibration
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can react as a base and deprotonate the product
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aldols |
reactions are reversible
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non enolizable aldehyde
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an aldehyde with no alpha hydrogens (alpha hydrogens bond to alpha carbons- carbon bonded to functional group)
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amides |
amide bonds are quite stable, mroe stable than esters, acid chlorides and anhydrides but less stable than
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alkylation
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a great way to form a ketone
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alodol condensation
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useful because it combines two carbon carbon groups and leaves an aldehyde/ketone
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formic acid
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planar |
carboxylic acids
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the carboxyl group is polar, form dimer readily, lose hydrogens readily
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addition-elimination reaction
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eliminating the leaving group and replacing it with the nucleophile
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tetrahedral intermediate
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the first species formed after an addition - elimination reaction
catalyzed by acid base
the acid first protonates the carbonyl oxygen, the second protonation make the leaving group a better leaving group |