4. contains functional groups that undergo
nucleophilic acyl substitutions.
Background
are organic compounds having hydroxyl
group attached to the acyl group (RCO–).
can be distinguish from aldehydes and
ketones by the presence of a group
containing heteroatom.
CARBOXYLIC ACID DERIVATIVES
Has the structure of RCOZ
5. Background
Also known as acyl derivatives.
Many types of carboxylic acid derivatives,
the chapter focused on acid halides (acyl
halides), anhydrides, esters, amides,
thioesters, and acylphosphates.
Nucleophilic acyl substitution reactions
convert the carboxylic acid to one of the
derivatives.
formed when the hydroxyl group of the
carboxylic acid is replaced by a different
group.
6. Nomenclature
The name of the corresponding carboxylic acid is employed to
begin the nomenclature of acid halides. If the matching
carboxylic acid has a -oic acid or -ic acid ending, it is replaced
with -oyl followed by the first syllable of the halogen's name
and a -ide ending.
Esters: the oic or ic suffix in the acid name is replaced by ate.
e.g. CH3(CH2)2CO2C2H5 is ethyl butanoate (or ethyl butyrate).
Esters are named as though the alcohol's alkyl chain is an
alternative. This alkyl chain had no assigned number. The
name of the parent chain from the carboxylic acid portion of
the ester is then followed by a -e that have been removed and
replaced with the ending -oate.
7. Nomenclature
Anhydrides: The name of the related acid is used first,
then the word "anhydride" individually.
e.g. butanoic anhydride (CH3(CH2)2CO)2O) and
ethanoic propanoic anhydride (or acetic propionic
anhydride) (CH3COOCOCH2CH3).
When two carboxylic acid join and lose water, the
outcome is the acid anhydride functional group
(anhydride = without water). Like to carboxylic acid,
symmetrical acid anhydrides are called, but the
ending -acid is changed to -anhydride.
8. is a reaction where a nucleophile forms a new
bond with the carbonyl carbon of an acyl group
with accompanying breakage of a bond between
the carbonyl carbon and a leaving group.
single most important reaction of carboxylic acid
derivatives
transformation defines by and may be classified
as:
Nucleophilic substitution at an acyl group
Acylation of a nucleophile
1.
2.
Reaction
1. NUCLEOPHILIC ACYL SUBSTITUTION
9. -
Reaction
certain nucleophilic reagents reaction may assume other
names as well:
Hydrolysis - If Nuc-H is water
Alcoholysis - if Nuc–H is an alcohol
Aminolysis -if Nuc-H is ammonia and amines
acyl chlorides and bromides being the most reactive and
amides the least reactive.
In homogeneous solvent systems, reaction of acyl
chlorides with water occurs rapidly.
Amides react with water only in the presence of strong
acid or base catalysts and external heating.
1.
2.
3.
1. ACYL GROUP SUBSTITUTION
11. -
Reaction
also called as alkanoylation
used in avoiding the rearrangement
reactions which appears in the mechanism of
alkylating
for attaining this, the acylation reaction
primarily occurs, later the carbonyl group is
separated by the Clemmensen reduction
reaction or some related process.
example of this is the Fidel-Crafts acylation
reaction
ACYLATION REACTION
12. -
Reaction
Friedel-Crafts acylation, there is an addition of an
acyl group to an aromatic ring or in simple terms
ethanol or the acetyl group is added to the benzene.
The following reaction shows the mechanism.
FIDEL-CRAFTS ACYLATION REACTION
14. Reduction
At this point it will be useful to consider three kinds of reductions:
Catalytic Hydrogenation
Complex Metal Hydride Reductions
Diborane Reduction
1.
2.
3.
Reductions of carboxylic acid derivatives might be expected
to lead either to aldehydes or alcohols, functional groups
having a lower oxidation state of the carboxyl carbon.
Carboxylic acids themselves are reduced to alcohols by
lithium aluminum hydride.
15. Catalytic Hydrogenation
The exceptional reactivity of acyl halides, on the other hand, facilitates
their reduction under mild conditions, by using a poisoned palladium
catalyst similar to that used for the partial reduction of alkynes to
alkenes.
As a rule, the carbonyl group does not add hydrogen as readily as do
the carbon-carbon double and triple bonds.
It is fairly easy to reduce an alkene or alkyne function without
affecting any carbonyl functions in the same molecule through using a
platinum catalyst and increased temperature and pressure, it is
possible to reduce aldehydes and ketones to alcohols, but carboxylic
acids, esters and amides are comparatively unreactive.
16. Complex Metal Hydride Reductions
It is often abbreviated LAH, is the most useful for reducing carboxylic acid
derivatives due to its high reactivity, LAH easily reduces all classes of carboxylic
acid derivatives, generally to the –1 oxidation state.
The reductions of aldehydes and ketones to the electrophilic carbonyl carbon
atom. This hydride addition is the hydride-donating moiety being written as
AlH4(–). All four hydrogens are potentially available to the reduction, but when
carboxylic acids are reduced, one of the hydrides reacts with the acidic O–H to
generate hydrogen gas.
Lithium Aluminum Hydride (LiAlH4)
Aids, Esters, Anhydrides and Acyl Chlorides
These are all reduced to 1º-alcohols, and this method is superior to catalytic
reduction in most cases. Since acyl chlorides and anhydrides are expensive and
time consuming to prepare, acids and esters are the most commonly used reactants
for this transformation.
Irreversible Addition of Hydride
17. DIBORANE Reduction
The reducing characteristics of diborane (disassociated to BH3 in ether
or THF solution) were first introduced as addition reactions to alkenes
and alkynes.
This remains a primary application of this reagent, but it also effects
rapid and complete reduction of carboxylic acids, amides and nitriles.
Other than LAH, this reagent provides one of the best methods for
reducing carboxylic acids to 1º-alcohols.
In addition, diborane has been known to be an effective reagent for
reductions of aldehydes and ketones to borate esters.
18. Overview
The physical properties of the acyl derivatives are
depending on their Z group and the length of the R
alkyl chain
Carboxylic acid derivatives acyl group is bonded
with Z group
Nucleophilic acyl substitution converts carboxylic
acid to one of the derivatives
Heteroatoms are usually oxygen, nitrogen, sulfur,
or phosphorus
20. Quiz
1. Nucleophilic acyl substitution converts
carboxylic acid into?
2. It means "without water"
a. Aldehydes
b. Anhydride
c. Amine
d. Acid
3. Acyl group of the derivatives is bonded
into what group?
a. F group
b. Hydrogen group
c. Z group
d. Halogens
4. How aldehydes and ketones differs from
it's acyl derivatives?
a. Halogens
b. Aldehydes
c. Atom
d. Heteroatoms
5. It is a primary application of this reagent,
but it also effects rapid and complete
reduction of carboxylic acids, amides and
nitriles
a. Dihborane
b. Dehborane
c. Diborane
d. Deborane
21. Quiz
6. What is the molecular formula of the
Acyl derivatives?
a. RCOH
b. RCO-F
c. RCOZ
d. RCO-Z
7. It is often abbreviated LAH
a. lithium aluminum hydride
b. Lithium ammonium hydride
c. Lithium aluminum hydroxide
d. Lithium ammonium hydroxide
8. It is the single most important reaction of
carboxylic acid derivatives
a . Nucleophilic acyl substitution
b. Nucleoatom Acyl derivatives
c. Nucleophilic aldehydes derivatives
d. Acyl derivatives
9. It is an an addition of an acyl group to
an aromatic ring
a. Acylation reaction
b. Acylation derivatives
c. Aldehytion reaction
d. Aldyhytion derivatives
10. It is when the oic or ic suffix in the acid
name is replaced by ate.
a. Esters
b. Ethers
c. Ethyion
d. Ethylate
