Exercise 11: CARBOXYLIC ACIDS

Question 1

 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

Answer 1

CARBOXYLIC ACIDS

Question 2

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

Answer 2

CARBOXYLIC ACIDS

Question 3

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

Answer 3

nucleophilic substitution

halo, alkoxyl,
amino, and acyloxy

Question 4

the most common reaction to synthesize carboxylic acids is through the
(using

 this chemical process also occurs biologically in the - on ethanol
metabolism

Answer 4

oxidation of primary alcohols, potassium dichromate or potassium
permanganate)

liver

Question 5

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

Answer 5

alcohol dehydrogenase, CYP450
enzyme)

aldehyde dehydrogenase

Question 6

the - is a more excretable form

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

Answer 6

acetate metabolite, toxic acetaldehyde metabolite

Question 7

TEST FOR CARBOXYLIC ACIDS

Answer 7

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

Question 8

REACTION WITH WATER & INDICATOR

acetic acid

Answer 8

blue to red
pink solution

Question 9

REACTION WITH WATER & INDICATOR

stearic acid

Answer 9

blue to red
orange solution

Question 10

carboxylic acids exhibit acidic property in

 the reaction involves the - from the carboxyl group
and the stability of the conjugate base

Answer 10

aqueous solution

release of protons

Question 11

REACTION WITH WATER & INDICATOR

 acidity of carboxylic acids can
be detected through

Answer 11

pH
measurement, the use of pH
paper or pH indicators

Question 12

REACTION WITH SODIUM HYDROXIDE

acetic acid

Answer 12

soluble, clear colorless solution

Question 13

REACTION WITH SODIUM HYDROXIDE

stearic acid

Answer 13

insoluble, clear colorless solution with insoluble white layer

Question 14

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

Answer 14

strong bases (such as sodium hydroxide or
potassium hydroxide)

Question 15

REACTION WITH SODIUM CARBONATE

acetic acid

Answer 15

positive

no change after heating

Question 16

carboxylic acids react with - , a water-soluble salt is still formed but together with a
by-product of carbon dioxide liberated as gas

Answer 16

weak bases (such as sodium
bicarbonate)

Question 17

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

Answer 17

effervescence

Question 18

ESTERIFICATION REACTION results

acetic acid

Answer 18

pear-like odor

Question 19

ESTERIFICATION REACTION results

benzoic acid

Answer 19

nutty-like odor

Question 20

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

Answer 20

acid catalyst
(Fischer esterification)

Question 21

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

Answer 21

electrophilic

nucleophile

Question 22

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

Answer 22

water, protonated
ester

characteristic
fruity-like odor

Question 23

REACTION WITH NEUTRAL FERRIC
CHLORIDE

acetic acid

Answer 23

turbid orange solution
reddish brown precipitate

Question 24

REACTION WITH NEUTRAL FERRIC
CHLORIDE

Tartaric acid

Answer 24

turbid orange solution
reddish brown precipitate

Question 25

 function of test: can be used to detect presence of carboxylic acid

Answer 25

REACTION WITH NEUTRAL FERRIC
CHLORIDE

Question 26

 reagent: neutral ferric chloride (ferric chloride in)

Answer 26

sodium carbonate

Question 27

REACTION WITH NEUTRAL FERRIC
CHLORIDE
 positive result:

Answer 27

reddish brown/brick red precipitate

Question 28

the carboxylic acid is neutralized using
- to produce ammonium
carboxylate while - is released
through heating; ammonium carboxylate is then
reacted with - producing ferric carboxylate

Answer 28

ammonium hydroxide, excess ammonia gas

ferric chloride

Question 29

SPECIAL TEST FOR CITRIC AND TARTARIC ACIDS

citric acid

Answer 29

green solution brown precipitate

Question 30

SPECIAL TEST FOR CITRIC AND TARTARIC ACIDS

tartaric acid

Answer 30

violet solution
brown precipitate

Question 31

is tricarboxylic acid
and has tricarboxylic acid, no enantiomer form

 is dicarboxylic acid
that has two enantiomer forms:

Answer 31

citric acid

tartaric acid, D-
tartaric acid and L-tartaric acid

Question 32

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

Answer 32

Chapman and Smith

potassium
permanganate

manganese dioxide

Question 33

FERRIC HYDROXAMATE TEST
ethyl acetate

Answer 33

pale yellow green solution

dark maroon solution

Question 34

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

Answer 34

esters

R1C=OOR2

Question 35

 an important test to identify esters is known as

Answer 35

ferric hydroxamate
test

Question 36

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

Answer 36

hydroxylamine

phenol

enol

Question 37

HYDROLYSIS REACTION

acetic anhydride

Answer 37

blue to red
evolution of heat

Question 38

HYDROLYSIS REACTION

acetamide

Answer 38

red to blue
evolution of gas

Question 39

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)

Answer 39

acid anhydrides

amides

Question 40

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

Answer 40

acetic anhydride

acetamide