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EK Orgo 3
Carbonyls and Amines
| Question | Answer |
|---|---|
| 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
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