2. Introduction
Carboxylic acids are compounds that contain the carboxyl group:
These compounds and their common derivatives make up the bulk of organic compounds.
Their common derivatives include acid halides:
acid anhydrides:
Ester:
and amides:
3. Introduction
Nomenclature of carboxylic acids
Two systems are used for naming carboxylic
acids: the common system and the IUPAC system.
Common names for carboxylic acids are derived
from Latin or Greek words that indicate one of
their naturally occurring sources.
Table 1 lists the common name, structure, source,
and etymology for some common carboxylic acids.
Employ the following steps to derive the IUPAC name for
a carboxylic acid:
1- Pick out the longest, continuous chain of carbon atoms
2- that contains the carboxyl group. The parent name for the compound comes from the alkane
name for that number of carbon atoms.
3- Change the ‐e ending of the alkane name to ‐oic and add the word “acid.”
4- Locate and name any substituents, labeling their placement by numbering away from the
carboxyl group.
Applying these rules gives the following compound the name 2‐ethyl‐4‐methylpentanoic acid.
4. Introduction
Acidity of carboxylic acids
Carboxylic acids show K a values in the order of 10 −4 to 10 −5 and thus readily
react with ordinary aqueous bases such as sodium hydroxide and sodium
bicarbonate. This acidity is due to two factors. First, the oxygen atom of the
carboxyl group bonded to the hydrogen atom has a partial positive charge on it
because of resonance.
Second, the anion that results from the removal of the hydrogen attached to
the carboxyl oxygen is resonance stabilized.
Substituting electron withdrawing groups such as halogens on the chain of the
R group(s) increases the acidity of the acid. This effect is strongest for
α‐substitutions and decreases rapidly as the electron withdrawing group is
moved further down the chain.
5. Preparation
Oxidation of alkenes
Alkenes are oxidized to acids by heating them with solutions of potassium
permanganate (KMnO 4) or potassium dichromate (K 2Cr 2O 7).
The ozonolysis of alkenes produces aldehydes that can easily be further oxidized
to acids.
6. Preparation
The oxidation of primary alcohols and aldehydes
The oxidation of primary alcohols leads to the formation of alde‐hydes that
undergo further oxidation to yield acids. All strong oxidizing agents (potassium
permanganate, potassium dichromate, and chromium trioxide) can easily oxidize
the aldehydes that are formed. Remember: Mild oxidizing agents such as
manganese dioxide (MnO 2) and Tollen's reagent [Ag(NH 3) 2
+OH −] are only strong
enough to oxidize alcohols to aldehydes.
7. Preparation
The oxidation of alkyl benzenes
Alkyl groups that contain benzylic hydrogens—hydrogen(s)
on a carbon α to a benzene ring—undergo oxidation to acids
with strong oxidizing agents.
Hydrolysis of nitriles
The hydrolysis of nitriles, which are organic molecules
containing a cyano group, leads to carboxylic acid formation. These hydrolysis
reactions can take place in either acidic or basic solutions.
8. Preparation
The carbonation of Grignard reagents
Grignard reagents react with carbon dioxide to yield acid salts, which, upon
acidification, produce carboxylic acids.
9. Reactions
Carboxylic acids undergo reactions to produce derivatives of the acid. The
most common derivatives formed are esters, acid halides, acid anhydrides,
and amides.
Esters are compounds formed by the reaction of carboxylic acids with
alcohols, and they have a general structural formula of:
The simplest method of preparation is the Fischer method, in which an alcohol
and an acid are reacted in an acidic medium. The reaction exists in an
equilibrium condition and does not go to completion unless a product is removed
as fast as it forms.
10. Reactions
The Fischer esterification proceeds via a carbocation mechanism. In this
mechanism, an alcohol is added to a carboxylic acid by the following steps:
1. The carboxyl carbon of the carboxylic acid is protonated.
2. An alcohol molecule adds to the carbocation produced in Step 1.
11. Reactions
Amide formation
Amides are compounds that contain the following group:
Substituted amides can contain the following groups:
Acid anhydride formation
Following is the anhydride group:
This group forms by reacting the salt of a carboxylic acid with an acyl halide.
Decarboxylation reaction
Decarboxylation is the loss of the acid functional group as carbon dioxide from a
carboxylic acid. The reaction product is usually a halocompound or an aliphatic
or aromatic hydrocarbon. The following illustration shows the sodalime method:
13. Pharmacological effect
Ibuprofen : is a medication in the nonsteroidal anti _ inflammatory drug
(NSAID) class that is used for treating pain ,fever ,and inflammation .
It use to close a patent ductus arteriosus in a premature baby .it typical begins
working whithin an hour.
Adverse effects include :
1) nausea
2) diarrhea
3)headache
4)rash
5)hypertension
In older hypertensive patient treated with hydrochlorothiazide ,ibuprofen at a
high daily dose was found to significantly increase systolic blood pressure.
14. Pharmacological effect
A method for the synthesis of ibuprofen in introductory organic chemistry
laboratory courses is reported. This experiment requires two 3-h lab sessions.
All of the reactions and techniques are a standard part of any introductory
organic chemistry course. In the first lab session, students reduce p-
isobutylacetophenone to an alcohol and then convert this alcohol to the
corresponding chloride. In the second session, students convert this chloride
to a Grignard reagent, which is then carboxylated and protonated to give
ibuprofen.
