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

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