8. CA and derivatives Flashcards
What are dicarboxylic acids? What are beta-dicarboxylic acids? What is a beta keto acid?
CA at each end of molec; they spont become cyclic anhydrides when heated. CA’s at beta C’s. Ketone at beta C
How to make CAs?
[O] of primary alc
For nuc acyl subst’n, after a nuc attacks, you could have multiple leaving groups. What makes a good leaving group? Trend on periodic table? Under which slns does nuc acyl subst’n occur?
lower pKa/weak bases (weak bases are most stable, low energy; it must accept e-), have to be stable once they leave molec; bigger = better b/c basicity dec as radius inc, more electroneg = better b/c LG will take e- and leave, forming resonance structures after leaving = better b/c resonance dec basicity. Inc down and right. Occurs in acidic or basic slns
What are cyclic amides called? beta vs gamma vs delta etc. How are they formed?
lactams. number of sides (beta = 4 sides, there is no alpha and there is no 3 sides). Formed by intramolec rxns of amino acids (ie. CA with amino group)
How does CA become amide?
when CA reacts w/ ammonia or amine in either acidic or basic solns
CONDENSATION RXN
How does CA become ester?
when CA reacts w/ alc + acid => Fischer esterification, best w/ primary alc
1) =OH takes H+
2) alc attacks carbonyl C –> -OH at top
3) methyl OH takes H from bonded alc –> becomes water
4) -OH at top goes back to carbonyl C and water = leaving group —> CONDENSATION RXN
5) =OH = deprotonated —> ester
How does CA become anhydride?
when CA reacts w/ another CA via condensation
Saponification
when long chain CA (ie. fatty acids) mix with a strong base and form a salt called soap
Ester hydrolysis of triacylglycerols using a strong base
Anhydrides are cleaved by a nuc. How does anhydride become amide + CA? ester + CA? 2 CA?
ammonia or amine = nuc; ether or alc = nuc; water = nuc
How does ester become alc + CA?
Hydrolysis: water attacks carbonyl and adjacent O grabs bonded water’s H, another water grabs doubled bonded OH and makes CA
Esters can be reduced to primary alcs by what?
LAH
Descending reactivity of CA derivatives towards nuc SUBSTITUTION (not nuc addn) attack
Acyl halides > anhydrides > CAs and esters > amides
They can react spont going down but need a catalyst going up
How do you know if a reagent will [O] -OH to ald/ket or CA intentionally?
If they really only want ald/ket, they will use a reagent specific for [O] to ald/ket. Otherwise, it’ll go straight to CA
Which substituents can cause e- w/drawing (and thus inc acidity) vs e- donating (and this dec acidity) on carboxyl group?
NO2 and halides vs NH2 and OCH3 b/c these destablize neg charge
Acyl derivatives
Cmpds that retain C=O from CA (ex: esters, amides, anhydrides, other CAs)
Beta dicarboxylic acids and beta keto acids spont undergo what rxn? What about gamma or delta dicarboxylic acids?
Decarboxylation. Gamma and delta = more difficult to decarboxylate
How can CAs become alkenes?
Reduce to alcs, then do elimination to become alkene (takes 2 steps)
Can NaBH4 reduce CAs?
Nope, not even to ald
What are cyclic esters called? Alpha vs beta vs gamma vs delta etc. How are they formed?
Lactones. Alpha = 3 sides, beta = 4 sides, gamma = 5 sides, etc. formed by intramolec rxns with hydroxycarboxylic acids ie. CA with alc)
Ways to make esters
1) CA + alc under acidic conditions aka Fischer esterification
2) anhydride + alc
3) transesterifcation
Induction
Refers to distribution of charge across sigma bonds. Electronegative atoms like more e- around them —> more neg (this less electronegative atoms = more pos)
Conjugated system
Alternating single bonds and multiple bonds; this allows pi e- to delocalized throughout unhybridized p orbitals OR heteroatoms with lone pairs of e-
Transesterification
When ester + alc reacts to make a diff ester + alc
Amides can be hydrolyzed under STRONG acidic or basic conditions into what? Describe mechanism
CA + amine
1) Carbonyl O = protonated —> =OH at top
2) water attacks carbonyl C of amide —> -OH at top, water at bottom
3) amino group steals H from water
4) -OH at top doubles bonds with C —> kicks out amino group, =OH at top again
5) =OH = deprotonated —> CA + amino group
How to name esters?
“R”yl “parent”oate
“R”yl = ester part “Parent”oate = CA part
How to convert CA and esters into alc with LAH
1) LAH attacks carbonyl C –> single bonds around carbonyl C
2) single carbonyl O becomes a double bond again with carbonyl C and kicks out -OR –> ald
3) more LAH attacks like BH4 –> alc product
