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27 Cards in this Set
- Front
- Back
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carbonyl
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C=O
think: planar sterochemistry (susceptible to chemical attack) partial Positive charge on C (partial neg on O = easily protonated) aldehydes and ketones - nucleophilic addition other carbonyls - nuclephilic substitution |
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aldehydes and ketones physical properties
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cant H-bond with each other, therefore lower boiling points to ROH, but higher than alkanes and alkenes
good solvents for things that can H-bond up to 4 C = soluble in H2O |
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keto-enol tautomerization
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a proton shift from alpha-carbon to carbonyl oxygen (double bond switches to between Cs)
both tautomers exist at room temp (but ketone/aldehyde is normally favoured) |
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Chemical properties of aldehydes and ketones
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react in nucleophilic addition or as Bronstead-Lowry acid donating an alpha-H
(alpha-carbon anions are stabilized by resonance = enolate ion) aldehydes more acidic (bc ketone has 2 e-donating alkyl groups) aldehydes slightly more reactive (same reason as above) |
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Aldehydes/ketones plus ROH
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Hemiacetal/hemiketal formation (ROH adds to =; have OH group and OR group)
add 2nd molar equiv ROH get acetal/ketal (two OR groups) 1st is acid/base catalyzed 2nd is acid catalyzed (protonate OH to make better LG) use either as blocking groups (unreactive towards bases; add H+ after to remove) similar rxn when dissolved in H2O - but get hydrates (geminal diols - two OH groups) |
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aldol condensation
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1. base abstracts a-H = enolate
2. enolate acts as nucleophile and attacks other carbonyl (aldol addition) 3. alkoxide removes H+ from H2O (stronger base bc electron donating alkyl group) = aldol 4. aldol is unstable and looses an H2O to form a double bond = enal (stabalized b/c conjugated =) |
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Halogenation of ketone
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X2 adds to a-carbon in presence of acid (true catalyst) or base (forms water)
if with base, a-carbon will become completely halogenated - reacts with base to form carboxylic acid and halogorm (HCX3) - haloform reaction |
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haloform reaction
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if halogenation of methyl ketone with base, a-carbon will become completely halogenated - reacts with base to form carboxylic acid and haloform (HCX3)
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Wittig reaction
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converts a ketone or aldehyde to an alkene
use phosphorus ylide - neutral molecule with neg-charged carbanion |
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physical properties of carboxylic acids
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strong double bonds to form dimer = significantly increases boiling point by doubling molec weight of molecs leaving liquid phase
saturated more than 8 C = solids unsat. (think f.a.) impede crystal lattice structure = lower melting point (liquid at rm temp) 4C miscible < 10 C insoluble also soluble in nonpolar bc dimer (undisrupted) |
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decarboxylation of carboxylic acid
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usually exothermic, BUT high Ea
Ea lower when beta-carbon is carbonyl (anion intermediate stabilized by resonance OR cyclic intermediate) CO2 can leave first (anion, then add H+) OR H+ can add first (cyclic) then lose CO2 final products are tautomers |
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acyl group
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R-C=O
I acyl chlorides stronger acid than aldehydes because Cl is electron withdrawing and stabilizes conjugate base |
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esterfication
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alcohols react with carboxylic acids (nucleophilic substitution)
ROH + RCOOH --> RCOOR + H2O catalyzed by strong acid (protonates hydroxyl group) same reaction b/w glycerol and f.a. to make triglycerides... |
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transesterfication
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esters plus ROH - substitutes one alkoxy group with another - equilibrium results, but controlled by adding an excess of alcohol
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nitogen bonds
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can be three or four
when takes four bonds, it has a positive charge when three bonds, has lone pair** |
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nitrogen reactions
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may act as lewis base (donating lone pair e-)
may act as a nucelophile where lone pair attacks positive charge can take on 4th bond, becoming positively charged |
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order of basicity of amines when functional groups are electron donating
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secondary
primary ammonia bulky functional groups can hinder ability to donate lone pair however... aromatic amines are weaker b/c lone pair can delocalize |
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amine and ketone or aldehyde
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condensation (lose H2O) to produce IMINES and ENAMINES
amine acts as nucleophile w lp = addition acid protonated H2O - elimination with H from either amine if primary = imine OR alpha-H if secondary = enamine (therefore difference is where double bond ends up) = BUT exist as tautomers note- if too much acid in first step, protonates amine, becomes poor nucleophile |
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Wolff-Kishner reaction
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replace =O of ketone or aldehyde with two H
- same as imine/enamine formation, BUT use hydrazine instead - addition, protonation, elimination H2O, then strong hot base added to deprot N |
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hydrazine
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H2N - NH2
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reduction of aldehyde or ketone
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2 methods:
hot acid in presence of amalgamated zinc (w Mg) BUT some won't survive Wolff-Kishner Reduction - uses hydrazine in imine/enamine like rxn |
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alkylation of amines
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use alkylhalides - loses H to HX with each addition of R-X
once get to quaternary ammnium salt, can get alkene via Hofmann Elimination |
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Hoffmann elimination
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alkene from quaternary ammonium salt
major product is the LEAST stable alkene (Hoffmann product) (vs more stable = Sayteff product) - eliminate N(CH3)3 and H2O (because use stron base) |
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nitrous acid
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H-O-N=O
weak acid, dehydrated by strong acid to Nitrosonium ion ==> +N=O |
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amides
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can behave as weak acid or base
less basic than amines b/c carbonyl is electron withdrawing can hydrogen bond with each other if N has H |
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lactams
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cyclic amides
beta = 4 member ring gamma - 5 member ring delta - 6... highly reactive due to ring strain |
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Hofmann degredation
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primary amides react with strgonly basic solutions of chlorine or bromine to form primary amines w CO2 as byproduct
deprotonation of amide X2 rearrangement to isocyanate decarboxylation advantage - isnt affected by steric hindrance like other methods relying on Sn2 (therefore alkyls produced can be 1*, 2* or 3*) |
