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71 terms

Kaplan MCAT OChem Ch. 9: Carboxylic Acids

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carb acid
pKa 3-6
alcohol
pKa = 16
carb acid
H bond donor and acceptor in same functional group => large intermolecular forces and high BP
carb acid
highest priority
formic acid
methanoic aci


http://upload.wikimedia.org/wikipedia/commons/5/58/Formic-acid-2D.png
acetic acid
ethanoi acid


http://upload.wikimedia.org/wikipedia/commons/f/fd/Acetic-acid-2D-flat.png
propionic acid
propanoic acid

http://upload.wikimedia.org/wikipedia/commons/b/b4/Propionic_acid_chemical_structure.png
cyclic carboxylic acid
cycloalkane carboxylic acids
salts of carb acids
cation + acid ending w/ -ate
oxalic acid (2C)
IUPAC: ethanedioic acid
malonic acid (3C)
IUPAC: propanedioic acid
succinic acid (4C)
IUPAC: butanedioic acid
glutaric acid (5C)
IUPAC: pentanedioic acid
adipic acid (6C)
IUPAC: hexanedioic acid
pimelic acid (7C)
IUPAC: heptanedioic acid
phys. properties of carb acids
H-bonding

acidity
H-bonding of carb acids
polar and form really well H bonds w/ each other since two diff. points participating in H bonding => dimers (pairs of molecules connected by two H bonds)
H-bonding of carb acids
multiple H bonding:
1. elevate BP (also inc. w/ MW) and MP (higher than alcohol)
acidity of carb acids
due to resonance stabilization of carboxylate anion (conjugate base)
acidity of carb acids
more stable conj. base => proton likely leaves => stronger acid
acidity of carb acids
sub. near this influence its acidity
acidity of carb acids
EW groups => absorb neg. charge => inc this
acidity of carb acids
EDG => donate add. electron density => destabilize neg charge => less this
acidity of carb acids
closer the sub gruop => great its effect on this
acidity of dicarb acids
more acidic than carb acids
acidity of dicarb acids
proton leaves => carboxylate anion formed => second carb group less acidic (since double neg species is unfavorable is second proton is deprotonated)
beta-dicarb acids
notable for high acidity of alpha carbon between two carbonyls (pKa = 10)
beta-dicarb acids
loss of acidic H atom => carbanion => stabilized by EWG effect of two carboxyl groups

this also applies to molecules that shared this structure
types of synthesis of carb acids
oxidation rxns

carboxylatin of organometalic reagents

hydrolysis of nitriles
oxidation rxns (carb acids)
these are prepared via oxidation of aldehydes, primary alcohols and certain alkylbenzenes
carb acids
most oxidized func group
oxidation rxns (carb acids)
oxidant usually KMnO4
oxidation rxns (carb acids)
2ndary and 3rd alcohols can't be oxidized to carb acids because of valence limitations
carboxylation of organometallic reagents
like Grignard reagents, react w/ CO2 to form this
carboxylation of organometallic reagents
conversion of tertiary alkyl halides into this
carboxylation of organometallic reagents
rxns adds one caron atom to the chain
carboxylation of organometallic reagents
in 2nd rxn, Nu is a carbanion that's coordinated w/ pos. charged Mg and electrophile is carbon of CO2
hydrolysis of nitrile
AKA cyanides, func group -C≡N
-C≡N (cyanide) (hydrolysis of nitrile)
carries neg charge on carbon atom => great Nu but not great base
-C≡N (cyanide) (hydrolysis of nitrile)
displaces primary and secondary halides in Sn2
hydrolysis of nitrile
can do this under either acidic or basic conditions => carb acids and ammonia (ammonium salts)

NOTE: all carb acid derivatives may be hydrolyzed to their parent carb acid
hydrolysis of nitrile
allows for conversion of alkyl halides into carb acids
hydrolysis of nitrile
additional carbon is introduced into the chain
rxns w/ carb acids
soap formation

Nu Acyl Sub

Decarboxylation
types of Nu Acyl Sub rxns (rxns w/ carb acids )
reduction

ester formation

acyl halide formation
soap formation (rxns w/ carb acids)
long chain carb acid + NaOH or KOH => RCOO-(Na+ or K+)(soap) + water
soap formation (rxns w/ carb acids)
can solvate nonpolar organic compounds in aq. sol since possess nonpolar tail and polar carboxylate head
soap formation (rxns w/ carb acids)
soap molecules placed in aq. sol => arrange themselves into micelles
micelles
spherical structures where polar heads outwards (solubilized by water) and nonpolar hydrocarbon chains oriented toward inside of sphere (protected from solvent, nonpolar molecules can dissolve in hydrocarbon interior of this)
reduction (Nu Acyl Sub rxns)
this by LAH => alcohols
reduction (Nu Acyl Sub rxns)
aldehyde can be intermediate but eventually goes to alcohols
reduction (Nu Acyl Sub rxns)
occurs by Nu add. of H- to carbonyl group
carb acids
can't be further oxidized, but can be reduced
ester formation
hybrid between carb acid and ether
ester formation
make this when carb acid + alcohols under acidic conditions
ester formation
condensation rxn, so water is a side product
ester formation
in acidic conditions, O in carbonyl is protonated => enhance polarity of bond => more positive C => able to be attacked by Nu
ester formation
condensation occurs most pardily w/ primary alcohols
ester formation (common name)
named as same manner as carb salts (cation + acid ending w/ -ate)
acyl halides
also called acid halides
acyl halides formation
carbonyl groups bonded to halides
acyl halides formation
reagents used is SOCl2 (thionyl chloride)
acid chlorides
reactive; EWG power of Cl- => carbonyl attacked more
acid chlorides
used as intermediates from carb acid to esters and amides
acid chlorides
among the highest energy (least stable and most reactive) members of carbonyl family
decarboxylation
loses a carbon in form of CO2
decarboxylation
B-keto acids may spon. decarboxylate when heated => carboxyl group is lost and replaced w/ hydrogen
decarboxylation
electrophile and Nu in same molecule => rxn proceeds through a six membered ring transition state
decarboxylation
initial enol form tautomerizes to the more stable keto form
more stable the CB
more likely the proton will leave
stability of CB (3 factors)
1. periodic trends (EN, thus induction)
2. size of anion
3. resonance