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EK Orgo 3

Carbonyls and Amines

QuestionAnswer
carbonyl carbon double bonded to an oxygen, found in aldehydes, ketones, carboxylic acids, amides, and esters
2 important facts about carbonyls (1) planar stereochemistry (2) partial negative charge on the oxygen with partial positive charge on the carbon
carbonyl carbons readily undergo ______ attack nucleophillic
aldehydes and ketones typically undergo nucleophillic ______. addition
carbonyls other than aldehydes and ketones typically undergo nucleophillic _______. substitution
formaldehyde structure O || H-C-H
acetone structure O || CH3-C-CH3
physical properties of aldehydes and ketones -more polar and higher bp than alkenes/alkynes of similar MW -lower bp than corresponding alcohols (no H bonding) -excellent solvents for molecules that H bond with water -water soluble w/ up to 4 C's
enolate ion C=O dbl bond in aldehydes or ketones stabilized by resonance to alkene btw carbonyl C and alpha carbon
what happens when beta-carbon is also a carbonyl? enol form becomes more stable bc of internal H bonding and resonance (one carbonyl stays C=O and then the other is alkene form and the neg charged oxygen forms H bond)
the dicarbonyl ______ the acidity of the alpha hydrogen btw carbonyls increases
which are more acidic - aldehydes or ketones, and why? aldehydes are slightly more acidic than ketones bc it only has one e' donating group
how do e' donating groups on carbonyls affect acidity? e' donating grps cannot help distribute negative charge on the conjugate bases, making them less stable --> less acidic
what groups attached to the alpha carbon of a carbonyl will increase acidity? e' withdrawing groups (will help stabilize conjugate base and therefore increase acidity
tautomerization of ketone (keto-enol) alpha hydrogen moves from alpha carbon to the carbonyl oxygen - RXN AT EQUILIBRIUM NOT RESONANCE (exist at RT)
aldehydes react with alcohols to form... hemiacetals
ketones react with alcohols to form... hemiketals
hemiacetal formation catalyzed by acid or base where ROH acts as nucleophile and aldehyde undergos addition and can exist in equilibrium with ROH but too unstable to isolate
acetals or ketals formed when... second molar equivalent of ROH is added to the equilibrium of hemiacetal/hemiketal and R'OH in the presence of an acid to protonate OH group to produce good LG
blocking groups acetals and ketals - they are unreactive toward bases so aldehydes/ketones temporarily changed to acetal/ketal to prevent it from reacting with a base - often create ring with HOCH2CH2OH (five membered ring)
what happens when aldehydes/ketones dissolved in aqueous solution? they will establish equilbrium with their hydrate - geminal diol (two OH groups attached to previously carbonyl Carbon with its two substituents)
aldol condensation when aldehyde or ketone reacts with another aldehyde or ketone, catalyzed by acid or base
base catalyzed aldol condensation 1. base abstracts alpha-H 2. enolate ion attacks carbonyl C 3. resulting alkoxide ion removes H+ from water and regenerates catalyst and leaves aldol product
acid catalyzed aldol condensation 1. acid catalyzed tautomerization to an enol 2. carbonyl O is protonated (making carbonyl highly electrophillic) 3. enol can attack electrophile
with heat and a base, an aldol will ____ because ____ become and enal bc the aldol is unstable and the enal is stabilized by its conjugated double bonds
when do halogens add to ketones at the alpha carbon? presence of base or acid
in the presence of a base, halogenation of ketones at the alpha carbon results in.. halogenated carbonyl, halogen ion, and water - it is also difficult to prevent halogenation at more than one alpha position
in the presence of the acid, halogenation of ketones at the alpha carbon results in... halogenated carbonyl, halogen ion, and regenerated H+ acid
haloform rxn base + methyl ketone results in alpha carbon completely halogenated -> where base then attacks carbonyl and triple halogenated alpha carbon becomes a leaving group when C=O regenerated -> result in carboxylate ion and haloform
haloform definition HCX3
Wittig rxn converts ketone to alkene using phosphorous ylide
ylide neutral molecule that combines with negativly charged carbanion for use in the Wittig rxn - Phosphorous bound to 3 benzyl rings and a negatively charged carbon
steps in Wittig rxn negatively charged carbanion attacks carbonyl C of ketone/aldehyde forming betaine (nucleophillic addition) that quickly breaks down to an alkene with the R group on the ylide
a carbonyl cmpd with a dbl bond between alpha and beta C can is called _____ alpha beta unsaturated carbonyl
characteristics of the C-C dbl bond in alpha beta unsaturated carbonyl 1. beta carbon less susceptible to nucleophillic attack due to e' withdrawing capability of carbonyl 2. provides resonance when carbocation formed when all e' are at the O of the carbonyl bond
formic acid O || H-C-OH
acetic acid O || CH3-C-OH
benzoic acid O || benzene-C-OH
carboxylic acids like to be have as ____ in ____ rxns acids or substrates in nucleophillic substitution reactions
acidity of carboxylic acids... they are very strong for organic acids bc when dissociated, their conjugate base is stabilized by resonance
what types of group on the alpha carbon will increase the acidity of a carboxylic acid? e' withdrawing groups bc they help further stabilize conjugate base
physical properties of carboxylic acids high bp due to H bond dimers, if saturated and more than 8 carbons - solids, unsaturated impede crystal lattice structure and lower BP
when can carboxylic acids mix with water? <4 C's: soluble 5-10 C's: increasingly less soluble >10 C's: insobluble
carboxylic acids solubility in nonpolar solvents yes, soluble bc dimer form allows carboxylic acid to solvate w/o disrupting hydrogen bonds of the dimer
decarboxylation process in where carboxylic acid loses CO2, rxn is usually exothermic but has high activation energy
how is the activation energy of decarboxylation lowered? when the beta carbon is a carbonyl bc either the anion intermediate is sstabilized by resonance or the acid forms stable cyclic intermediate
what is needed to form acyl chlorides? carboxylic acids and inorganic acid chlorides (SOCl2, PCl3, and PCl5)
acyl chlorides act as what kind of acids? bronsted-lowry - they donate alpha hydrogen like aldehydes but the e' withdrawing Cl stabilizes conjugate base more than the H of an aldehyde
acyl chlorides are the most or least reactive of the carboxylic acid derivatives, and why? most reactive bc of the stability of the Cl- leaving group
what happens when any carboxylic acid derivative is in the presence of water? it will hydrolyze to give the corresponding carboxylic acid, and can occur under acidic or basic conditions
acid chloride + alcohol = ester
acid chloride + amine = amide
acid chloride + RCOOH = anhydride
alcohols + carboxylic acids = esters (via nucleophilic substitution), catalyzed by strong acid
esterification alcohols + carboxylic acids = esters
transesterification esters + alcohol = carboxylic acid way to trade alkoxy groups on an ester
acetoacetic ester synthesis production of ketone from acetoacetic ester due to strongly acidic properties
steps in acetoacetic ester synthesis 1. base is added to remove alpha H's 2. alkyl halide alkylates the resulting enolate ion 3. alkylacetoacetic ester is decarboxylated in presence of acid and heat resulting in ketone
amides are formed when... amine + carboxylic acids or one of its derivities
order of reactivity of carboxylic acid (most to least) acyl chloride > acid anhydride > carboxylic acid > ester > amide
important facts about nitrogen containing cmpds 1. they may act as Lewis base donating their lone pair of e's 2. they may act as a nucleophile where lone pair of e's attacks positive charge 3. N can take on 4th bond and become positively charged
what decreases amine basicity e' withdrawing substituents, steric hindrence, aromaticity
what increases amine basicity e' donating substituents
amine basicity from highest to lowest when functional groups are e' donating? 2 > 1 > ammonia
physical properties of ammonia and amines hydrogen bond capability of ammonia to 2 amines raise bp and increases solubility in water
what is special about chiral amines? at RT, the lone pair of e's moves rapidly and inverts configuration rapidly so molecule spends equal amt of time in each enantiomer
aldehydes/ketones + amines = imines/enamines + water (requires acid catalyst)
steps in condensation rxn with ketones 1. lone pair on amine attacks ketone or aldehyde in nucleophilic addition 2. OH grp is protonated by acid catalyst to make a good leaving group 3. unstable intermediate will produce enamine or imine
enamine formed when... secondary amine gives up its alpha hydrogen in condensation rxn with ketones where alkene with amine grp (enamine) forms
imine formed when... hydrogen lost from primary amine to make a C=N when water leaves unstable intermediate in condesnation rxn with ketones
imine products of condensation rxns can.. exist as a tautomer with its corresponding enamine
Wolff-Kishner rxn reduces ketone/aldehyde by removing oxygen and replaces it with 2 hydrogens - used for when molecule can't survive hot acid to reduce to alkane
steps in wolff-kishner reduction 1. lone pair of hydrazine N attacks ketone (Nu: addition) 2. acid protonates OH grp to make good LG 3. C=N formed to release water forming hydrazone and acid 4. hot strong acid added to deprotonate N of C=N to produce alkane, water, and N2 gas
amines can be alkylated with ___ in a _______ rxn alkylated with alkyl halides in a nuclephilic substitution rxn
amino groups are good or poor leaving groups? poor - they need to be converted to quarternary ammonium salt by repeated alkylations to be a good leaving group
what is the rxn mechanism to eliminate a quarternary ammonium salt? E2 mechanism with strong base
Hoffman elimination heating quarternary ammonium hydroxide and results in alkene
Hoffman product least stable alkene in the Hoffman elimination
Saytzeff product most stable alkene in the Hoffman elimination
nitrous acid + strong acid = HO-N=O + H+ --> [:N+=O:: <-> :N+-O:+] + H2O (product is nitrosonium ion)
primary amines + nitrous acid = diazonium salt
diazoniam group two Nitrogens triple bonded to each other as a functional group
diazotization of an amine rxn steps 1. nitrous acid protonated by strong acid 2. resulting nitrosonium ion reacts with primary amine 3. resulting N-nitrosonium (unstable) deprotonates to N-nitrosoamine and tautomerizes to diazenol 4. diazenol in acid dehydrates to diazonium ion
diazenol R-N=N-O-H (tautomer of RHN-N=O)
diazotization of an amine requires... aromatic primary amines
the diazonium grp can be replaced to the following.. OH group, halide, H, or -N=N-Ar
secondary amines + nitrosonium ion = N-nitrosoamine (amine N's lone pair still attacks positive charge on the nitrosonium ion and then water abstracts proton to form N-nitrosoamine)
amide caboxylic derivative containing nitrogen
amides behave as... weak acid or weak base
amides are hydrolyzed by... strong acids or strong bases
amides with a hydrogen attached are able to... hydrogen bond with each other
beta lactams cyclic amides, highly reactive due to large ring strain
Hoffman degradation primary amides react with stronly basic solns of Cl or Br to form primary amines with CO2 as the byproduct
steps in Hoffman degradation base abstracts H from 1-amide>(-)N attacks X2 >base abstracts H from resulting N-haloamide>rearrangment moves R grp to N (Br as LG) >OH- attacks C in isocyonate while lone pair abstracts H from H2O>resulting carbamic acid decarboxylated>>primary amine
isocyonate R-N=C=O, rearrangement that occurs in product of deprotnated product of N-haloamide and base (intermediate in Hoffman degradation rxn)
carbamic acid R-NH-COOH, formed when isocyanate reacts with water
advantage of Hoffman degradation over other methods of producing amines? other rxns rely on SN2 reaction which prevents production of amines on a tertiary carbon -- Hoffman degradation can produce amines w/ primary, secondary, or tertiary alkyl position
phosphoric acid O || OH-P-OH | OH
when heated, phosphoric acid forms... phosphoric anhydrides
phosphoric anhydrides + alcohols = esters
Created by: miniangel918 on 2010-12-21



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