Exercise 11: CARBOXYLIC ACIDS Flashcards by Blueberry Cheesecake

 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

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also contains and acyl group (RCO–)
with a hydroxyl group attached to it

CARBOXYLIC ACIDS

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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

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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

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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

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the - is a more excretable form

 this process of ethanol metabolism therefore prevents the accumulation of
the -

acetate metabolite, toxic acetaldehyde metabolite

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TEST FOR CARBOXYLIC ACIDS

• REACTION WITH WATER AND INDICATOR
• REACTION WITH SODIUM HYDROXIDE
• REACTION WITH SODIUM CARBONATE
• ESTERIFICATION REACTION
• REACTION WITH NEUTRAL FERRIC CHLORIDE

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REACTION WITH WATER & INDICATOR

acetic acid

blue to red
pink solution

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REACTION WITH WATER & INDICATOR

stearic acid

blue to red
orange solution

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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

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REACTION WITH WATER & INDICATOR

 acidity of carboxylic acids can
be detected through

pH
measurement, the use of pH
paper or pH indicators

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REACTION WITH SODIUM HYDROXIDE

acetic acid

soluble, clear colorless solution

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REACTION WITH SODIUM HYDROXIDE

stearic acid

insoluble, clear colorless solution with insoluble white layer

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carboxylic acids react with - forming water-soluble salts as products (neutralization)

strong bases (such as sodium hydroxide or
potassium hydroxide)

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REACTION WITH SODIUM CARBONATE

acetic acid

positive

no change after heating

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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)

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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