Chapter #9 Flashcards
(22 cards)
amides, esters, and anhydrides are all formed via a ____ reaction with carboxylic acids
condensation reaction (dehydration reaction, specifically)
what types of amines can act as nucleophiles with carboxylic acids?
primary or secondary (must have a hydrogen to lose)
tertiary amines do not have the hydrogen to lose
do amides participate in hydrogen bonding?
depends on the number of alkyl groups they have bonded
compare amide to carboxylic acid boiling point
same or lower
how are esters obtained?
CA + alcohol
anhydride + alcohol
what is the first step of the fischer esterification problem?
protonation of the carbonyl oxygen.
compare ester to carboxylic acid boiling points?
esters do not partake in hydrogen bonding so usually have lower boiling points
why do cyclic anhydrides form when just in heat?
the reaction is driven by the increased stability of the newly formed ring (favors making new 5 or 6 membered rings)
intermolecular anhydride formation favors _____ membered rings
5 or 6 membered
compare boiling points of anhydrides and their related carboxylic acids
anhydrides usually have much higher boiling point because of their much greater weight.
compare the reactivities of carboxylic acid derivatives and explain
- anhydrides: resonance stabilization and three electron-withdrawing oxygen atoms (most electrophilic)
- esters and carboxylic acids: lack one of the carbonyl oxygens that the anhydrides have
- amides: have an electon-donating amino group
describe steric effects and reactivity
the size and substitution of the leaving group can affect the ability of a nucleophile to access the carbonyl carbon.
steric hindrance can be used to control _____
where a reaction occurs in a molecule
Ex: protecting groups
induction
distribution of charge along sigma bonds
what makes some cyclic anhydride derivatives more susceptible to hydrolysis?
ring strain (both
what type of strain leads B-lactams to be susceptible to hydrolysis?
torsional strain (eclipsing interactions) and angle strain (less than 109.5 degrees)
transesterification
an alcohol reacts with an ester and displaces the esterifying group on an ester.
one ester is changed for another
under what conditions are amides hydrolyzed
acidic conditions
can also occur in basic conditions but hydroxide ion would be the nucleophile and the result would be a carboxylate anion.
how do strongly acidic or strongly basic conditions catalyze the hydrolysis of an amide?
strongly acidic: protonate the carbonyl oxygen which makes the carbonyl carbon more electrophilic
strongly basic: increase hydroxide ion concentration which increase likelihood of nucleophilic attack
what are the names of the lactams in order?
beta, gamma, delta, epsilon
anhydrides, particularly cyclic anhydrides, will form spontaneously from dicarboxylic acids when ____.
heated
will amide react with just water?
no, very unreactive so need strong base or acid solution.
