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116 terms

Kaplan MCAT OChem Ch. 10: Carb Acid Derivatives

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types of carb acid derivatives
acyl halides

anhydrides

amides

esters
types of carb acid derivatives
OH of carbonyl group replaced with:

-X

-OCOR

-NH2

-OR
acyl halides
AKA acid or alkanoyl halides
acyl halides
most reactive of carb acid derivatives
acyl halides
change -oic acid to "-oyl halide"
acetyl chloride
ethanoyl chloride:

http://www.chemguide.co.uk/mechanisms/addelim/ethanoylcl.GIF
benzoyl chloride
http://upload.wikimedia.org/wikipedia/commons/6/6a/Benzoyl_Chloride.png
n-butanoyl-chloride
http://www.lookchem.com/300w/casimage/2011-01-08-16/5856-79-1.gif
acyl group
RCO-
synthesis of acyl halide
carb acid + SOCl2 => SO2 + HCl
acyl halides
most common is acid chloride
synthesis of acyl halide
can also used PCl3 or PCl5 (or PBr3)
rxn of acyl halides
all rxns occur via Nu acyl sub.
hydrolysis (rxn of acyl halides)
acid halide back into carb acid
hydrolysis (rxn of acyl halides)
acid halide + water => carb acid + HCl (makes acid halides dangerous)
aldehyde and ketones
since don't have LG => undergo Nu add.
hydrolysis
cleavage by water
conversion into esters (rxn of acyl halides)
acyl halides into this , proceeding through tetrahedral intermediate, using alcohol as Nu

picks up H in sol => HCl as side product.
conversion into amides
acyl halides + amines => this
conversion into amides
lone pair on Nu amines (ammonia) attack carbonyl group of acyl chloride, displaces chloride
conversion into amides
side product is ammonium chloride (salt), formed from excess ammonia and HCl
imine
formed from ketones + amines
types of Nu acyl sub
hydrolysis

conversion into esters

conversion into amides
friedel-crafts acylation
type of EAS
friedel-crafts acylation (rxn of acyl halides)
Nu - aromatic ring
Electrophile - carbonyl (acyl cation or acylium ion (RCO+)
friedel-crafts acylation (rxn of acyl halides)
product = alkyl aryl ketone
reduction (rxn of acyl halides)
acid halides => alcohols

or

acid halides => selectively to aldehydes
reduction (rxn of acyl halides)
uses bulky reagent that only has one hydride to transfer (LiAlH(OC(CH3)3)3
anhydride
formed from condensation of two acid molecules w/ loss of water
anhydride nomenclature
also called acid anhydrides
anhydride nomenclature
condensation dimers of carboxylic acids w/ gen formula RCOOCOR
acetic anhydride
most common anhydride:

http://upload.wikimedia.org/wikipedia/commons/b/bf/Acetic_anhydride-2D-skeletal.png

dimer of acetic acid
succinic anhydride
http://upload.wikimedia.org/wikipedia/commons/b/be/Succinic_anhydride-2D-Skeletal.png
maleic anhydride
http://upload.wikimedia.org/wikipedia/commons/6/62/Maleic_anhydride_structure.png
phthalic anhydride
http://0.tqn.com/d/chemistry
/1/0/_/N/1/Phthalic_anhydride.jpg
anhydride
product of condensation rxn between two carb acids
snythesis of anhydride
OH group of one attacks carbonyl electrophile of another
snythesis of anhydride
another way is rxn of acid chloride w/ carboxylate anion
snythesis of cyclic anhydride
by heating carb acids
snythesis of cyclic anhydride
driven by inc. stability of newly formed ring
snythesis of cyclic anhydride
5 to 6 ring easily made
intramolecular rxn
more likely to occur than between those of separate molecules
types of reactions of anhydrides
hydrolysis

conversion into amides

conversion into esters and carb acids
rxns of anhydrides
more stable than acid chlorides => less reactive
rxns of anhydrides
will produce carb acid side product (instead of HCl like acid halides)
rxns of anhydrides (cyclic)
cause ring opening and forming new func. groups
hydrolysis of anhydrides
break up anhydrides into two eq. of carb acids by exposing them to water (Nu)
hydrolysis of anhydrides
to be useful, must be symm
hydrolysis of anhydrides
LG is carb acid (not as good as LG as halogen in acyl halide)
conversion into amides ( anhydrides )
cleaved by ammonia
conversion into amides ( anhydrides )
final products are amide and ammonium salt (carboxylate anion)
conversion into amides ( anhydrides )
LG is carb acid, but since in basic environment (ammonia => two react => salt (ammonium carboxylate)
acid chlorides
can be converted into any of other derivatives
anhydrides
can make any other less reactive derivatives (esters and amides )
esters
can be converted into amides
conversion into esters and carb acids ( anhydrides )
alcohol (Nu) + anhydride => these
acylation (anhydrides )
anhydride + aromatic (w/ AlCl3 or other Lewis Acid catalyst)
amides
general formula is RCONR2
amides
ending in -amide
amides
alkyl subs on N atom listed as prefixes, and location specified w/ letter N
peptide bond
amide linkage that possesses DB character from resonance
amides
most stable carb acid derivative
synthesis of amides
acid chlorides w/ amines
synthesis of amides
OR acid anhydride w/ ammonia
synthesis of amides
loss of H required
synthesis of amides
only primary and secondary amines will undergo this rxn
rxns w/ amides
since very stable => bound well to carbonyl
rxns w/ amides
acidic or basic conditions
types of rxns w/ amides
hydrolysis

hoffman rearrangement

reduction
hydrolysis of amide
under acidic condition (extreme) via Nu sub
hydrolysis of amide
acidic conditions allow carbonyl O to become protonated => Nu attack by water => carb acid and ammonia
hydrolysis of amide
basic conditions the carbonyl oxygen is not protonated and Nu is OH ion
hoffman rearrangement (amide)
amides to primary amines w/ loss of carbon as CO2
hoffman rearrangement (amide)
initial reactants are Br and NaOH => sodium hypobromite
hoffman rearrangement (amide)
involves formation of nitrene
hoffman rearrangement (amide)
...
hoffman rearrangement (amide)
...
nitrene
nitrogen analog of carbene
nitrene
nitrene is attached to carbonyl and only has 6 electrons
nitrene
an electrophile => resolved through by rearranging to isocyanate => hydrolyzed to form amine w/ CO2 leaving
isocyanate
nitrene rearranges to this form

has DB on either side of carbon
reduction (amide)
this is reduced by LAH w/ no loss of carbon
ester nomenclature
dehydration prod. of carb acid and alcohols
ester nomenclature
named as alkyl or aryl alkanoates
(fischer esterification) synthesis of esters
under acidic conditions, mix of carb acids and alcohols will condense (losing water) into esters
synthesis of esters
can also be obtained from reaction of acid chlorides or anhydrides w/ alcohols
synthesis of esters (phenolic aromatic))
can also be obtained from reaction of acid chlorides or anhydrides w/ alcohols, although less reactive than aliphatic => add a base catalyst
types of reaction w/ esters
hydrolysis

conversion to amides

transesterification

grignard addition

condensation rxns

reduction
hydrolysis of esters
produces carb acids and alcohols
hydrolysis of esters
since products are equally reactive -> can drive rxn forward by using either acidic or basic conditions
hydrolysis of esters
under basic conditions:
1. C=O not protonated
2. OH is Nu
triacylglycerols
called fats
triacylglycerols
are esters of long-chain carb acids (free fatty acids) and glycerol (alcohol)
saponfication (ester)
process by which fats are hydrolyzed under basic conditions to produce soaps
acidification (ester)
soap regenerates triacylglycerols
conversion of amides (ester)
N bases (like ammonia) attacks carbonyl C=> displaces an alkoxide to yield an amide and an alcohol side product
transesterfication
other alcohols as Nu => displace alkoxy group
transesterfication
transforms one ester into another
grignard reagents (ester)
RMgX, equivalent to R- Nu
grignard addition (ester)
neg. charged C of Grignard reagent + carbonyl of ester => ketone (carbonyl reformed and aloxy group leaves) => catch is that it's more reactive, so attacked by more Grignard reagents
grignard addition (ester)
to get around ketone problem => two eq. of Grignard reagent used => tertiary alcohols (intermediate ketone can be isolated only if alkyl group are bulky to prevent further attack)
grignard addition
first round - Nu sub
second round - Nu add (carbonyl => alcohol)
claisen condition (condensation rxns, esters)
two moles of ethyl acetate react under basic conditions => B-keto ester
claisen condition (condensation rxns, esters)
also called acetoacetic ester (common name)
claisen condition (condensation rxns, esters)
like aldol condensation
claisen condition (condensation rxns, esters)
proceeds by adding enolate anion to carbonyl of another ester => displaces ethoxide ion
claisen condition (condensation rxns, esters)
mech by which long hydrocarbon chains of are synthesized in bio systems
reduction of esters
reduced to primary alcohols w/ LAH (not NaBH4 since weaker and selective)
reduction of esters
allows for selective reduction in molecules w/ multiple func groups
phos acid and the mono/diesters
are acidic, usually exist as anions
phos acid and the mono/diesters
like all esters, can be cleaved under acidic conditions into parent acid and alcohols
phospholipids (phosphoglycerides)
many living systems as covered in phosphate ester in this form: glycerol attached to two carb acids and one phos. acid
phospholipids
main component of cell membrane
phospholipids/carbohydrates polymers
form backbone of nucleic acids
ATP
facilitates many bio rxns by releasing P groups (via hydrolysis) to other compounds, inc their reactivity => downhill free energy => thermodynamically favorable
phosphodiester bonds
holding the DNA backbone together, connecting nucleotides w/ covalent linkages