Exercise 11: CARBOXYLIC ACIDS Flashcards
organic compounds containing a carboxyl (R-COOH) functional group
occur widely in nature, often combined with other functional groups,
just like in fats, oils, and waxes
important components of many, food, and medicines
many of these substances are best known in their common names
based on Latin and Greek words describing their sources
CARBOXYLIC ACIDS
also contains and acyl group (RCO–)
with a hydroxyl group attached to it
CARBOXYLIC ACIDS
other functional groups could be
attached to the acyl group through
- reaction,
that is, replacing the hydroxyl group
with substituents such as -
these compounds are therefore
considered as carboxylic acid
derivatives
nucleophilic substitution
halo, alkoxyl,
amino, and acyloxy
the most common reaction to synthesize carboxylic acids is through the
(using
this chemical process also occurs biologically in the - on ethanol
metabolism
oxidation of primary alcohols, potassium dichromate or potassium
permanganate)
liver
ethanol is metabolized into acetaldehyde through an enzyme known as
(this process can also occur through
then acetaldehyde is further metabolized into acetic acid through an
enzyme known as
alcohol dehydrogenase, CYP450
enzyme)
aldehyde dehydrogenase
the - is a more excretable form
this process of ethanol metabolism therefore prevents the accumulation of
the -
acetate metabolite, toxic acetaldehyde metabolite
TEST FOR CARBOXYLIC ACIDS
• REACTION WITH WATER AND INDICATOR
• REACTION WITH SODIUM HYDROXIDE
• REACTION WITH SODIUM CARBONATE
• ESTERIFICATION REACTION
• REACTION WITH NEUTRAL FERRIC CHLORIDE
REACTION WITH WATER & INDICATOR
acetic acid
blue to red
pink solution
REACTION WITH WATER & INDICATOR
stearic acid
blue to red
orange solution
carboxylic acids exhibit acidic property in
the reaction involves the - from the carboxyl group
and the stability of the conjugate base
aqueous solution
release of protons
REACTION WITH WATER & INDICATOR
acidity of carboxylic acids can
be detected through
pH
measurement, the use of pH
paper or pH indicators
REACTION WITH SODIUM HYDROXIDE
acetic acid
soluble, clear colorless solution
REACTION WITH SODIUM HYDROXIDE
stearic acid
insoluble, clear colorless solution with insoluble white layer
carboxylic acids react with - forming water-soluble salts as products (neutralization)
strong bases (such as sodium hydroxide or
potassium hydroxide)
REACTION WITH SODIUM CARBONATE
acetic acid
positive
no change after heating
carboxylic acids react with - , a water-soluble salt is still formed but together with a
by-product of carbon dioxide liberated as gas
weak bases (such as sodium
bicarbonate)
the reaction is accompanied by the
formation of -, indicating the
release of carbon dioxide from the solution
this chemical reaction is used to
differentiate carboxylic acids from other
weak acids such as phenols
effervescence
ESTERIFICATION REACTION results
acetic acid
pear-like odor
ESTERIFICATION REACTION results
benzoic acid
nutty-like odor
alcohols react with carboxylic acid in the presence of an
during the synthesis, the acid catalyst promotes the protonation of the
carbonyl oxygen which makes the carbonyl carbon electrophilic
the alcohol then acts as the nucleophile that attacks the electrophilic
carbonyl carbon
acid catalyst
(Fischer esterification)
during the synthesis, the acid catalyst promotes the protonation of the
carbonyl oxygen which makes the carbonyl carbon -
the alcohol then acts as the - that attacks the electrophilic
carbonyl carbon
electrophilic
nucleophile
this would in turn produce a by-product of - and a; the ester would then be deprotonated (chemical reaction is in equilibrium)
production of an ester is indicated by the presence of - because esters are known to exhibit such property
water, protonated
ester
characteristic
fruity-like odor
REACTION WITH NEUTRAL FERRIC
CHLORIDE
acetic acid
turbid orange solution
reddish brown precipitate
REACTION WITH NEUTRAL FERRIC
CHLORIDE
Tartaric acid
turbid orange solution
reddish brown precipitate
function of test: can be used to detect presence of carboxylic acid
REACTION WITH NEUTRAL FERRIC
CHLORIDE
reagent: neutral ferric chloride (ferric chloride in)
sodium carbonate
REACTION WITH NEUTRAL FERRIC
CHLORIDE
positive result:
reddish brown/brick red precipitate
the carboxylic acid is neutralized using
- to produce ammonium
carboxylate while - is released
through heating; ammonium carboxylate is then
reacted with - producing ferric carboxylate
ammonium hydroxide, excess ammonia gas
ferric chloride
SPECIAL TEST FOR CITRIC AND TARTARIC ACIDS
citric acid
green solution brown precipitate
SPECIAL TEST FOR CITRIC AND TARTARIC ACIDS
tartaric acid
violet solution
brown precipitate
is tricarboxylic acid
and has tricarboxylic acid, no enantiomer form
is dicarboxylic acid
that has two enantiomer forms:
citric acid
tartaric acid, D-
tartaric acid and L-tartaric acid
special test for identification citric acid
and tartaric acid was established by
when citric acid is boiled with a very
alkaline solution of -, it will yield a green
solution of alkaline manganate
when tartaric acid is treated with the
same solution, brown precipitate of
- will be produced
Chapman and Smith
potassium
permanganate
manganese dioxide
FERRIC HYDROXAMATE TEST
ethyl acetate
pale yellow green solution
dark maroon solution
are organic compounds with the general formula of- ,
where R1 may be hydrogen, alkyl or aryl groups and
R2 may be an alkyl or aryl group but must not be a hydrogen
are very common in nature and are known to have
characteristic pleasant odors unlike carboxylic acids
this property enables to be utilized as perfuming or flavoring
agents, aside from them being used as organic solvents
esters
R1C=OOR2
an important test to identify esters is known as
ferric hydroxamate
test
esters when heated with - produce
hydroxamic acids that reacts with ferric ion to form
intensely colored complexes, commonly dark maroon in
color
this test is related to the- test wherein compounds
with high enolic character gives colored complexes with
ferric ion
therefore, a preliminary test must be performed to check
if the carbonyl compound being tested produces
enough - to form colored complexes with ferric ion,
which could lead to a false positive result
hydroxylamine
phenol
enol
HYDROLYSIS REACTION
acetic anhydride
blue to red
evolution of heat
HYDROLYSIS REACTION
acetamide
red to blue
evolution of gas
are organic compounds with two acyl groups (R-C=O) joined together by an oxygen atom
are organic compounds with general structure of a nitrogen
atom bonded to the carbonyl carbon atom (RC=ONH2)
acid anhydrides
amides
can be
hydrolyzed into two molecules
acetic acid
produces
carboxylate salt and free
ammonia
the pH of the products formed
can be tested to confirm their
presence after the hydrolysis
reaction
acetic anhydride
acetamide
