ch 21: carboxylic derivatives Flashcards
acyl group
R-C=O
carboxylic derivatives
carboxylic acid
ester
acyl phosphate
thioester
acid chloride
amide
nitrile
anhydride
what are carboxylic acid derivatives are stabilized by?
resonance
what are cyclic esters called?
lactones
what is the hydridization of C and N in an nitrile?
sp hybridized making it linear
- C is electrophilic
anhydrides
removing one molecule of H2O from two carboxylic acid molecules forms an anhydride
physical properties of amides
primary and secondary amides have N-H bonds. so they are capable of intermolecular hydrogen bonding and have higher MP and BP than esters and tertiary amides
nucleophilic acyl substitution
common characteristic reaction of carboxylic acid derivatives
KNOW MECHANISM
what is reactivity related to?
leaving group ability
- more reactive, better leaving group
conversion of leaving groups
the more reactive types can be readily converted into the less reactive ones
- hard to go in the other direction
reactivity of leaving group ranking
most reactive -> least reactice
1. acid chloride
2. anhydride
3. acyl phosphate
4. thioester
5. ester
6. carboxylic acid
7. amide
how to determine what will leave in nucleophilic acyl substitution?
depends if the nucleophile or Z is a better leaving group
- for a reaction to occur, Z must be a better leaving group than nucleophile
what happpens when acid chlorides react with oxygen nucleophiles?
they form anhydrides, carboxylic acids, and esters
how to form anhydride with acid chloride?
use carboxylate anion as nuclephile
how to form carboxylic acid with acid chloride?
use H2O as nucleophile
how to make ester with acid chloride?
use ROH as nucleophile
what can acid chlorides react with to make amides?
NH3, primary or secondary amines
- 2 equivalents of NH3 is used
1. nucleophile
2. snags HCL by-product to form ammonium salt
reactions of anhydrides
nucleophilic attack occurs at one C=O and the second C=O becomes part of the leaving group
why type of anhydride is typically used for anhydride reactions?
symmetrical anhydrides
acetylations
reactions that results in the transfer of an acetyl group
- usually make acetic anhydride
KNOW MECHANISM
reactions of esters
- esters are hydrolyzed with H2O in the presence of acid or base to from carboxylic acids or carboxylate anions
- esters react with NH3 and amines to form primary, secondary, tertiary amides
mechanism of acid-catalyzed hydrolysis
- addition of nucleophile H2O
- elimination of leaving group ROH
KNOW MECHANISM
saponification
base hydrolysis of esters
- the OH ends up as part of the product
KNOW MECHANISM
what does base hydrolysis of esters form?
carboxylate anion that is resonance stabilized
- once that happens, it can be protonated to form carboxylic acids
