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 Classification Tests for Hydroxyl-

And Carbonyl-Containing Compounds

Dupaya, Julian Victor M., Estacio, Jerwin Caesar A., Farnacio, Rebecca Ruth, Gabito, Jose

Luis F., Gallo, Cian Carlo M., Galvez, Joshua M.Group no.4, 2D-Medical Technology, Faculty of Pharmacy, University of Santo Tomas 

Abstract

Hydroxyl- or carbonyl- containing samples were given to the group for analysis. Hydroxyl group

refers to a functional group containing OH- when it is a substituent in an organic compound whereas

carbonyl group refers to a divalent chemical unit consisting of a carbon and an oxygen atom connected

by a double bond.  Hydroxyl group is the characteristic functional group of alcohols and phenols while

carbonyl group is the characteristic functional group of aldehydes and ketones. The samples were

analyzed through tests involving solubility of alcohols in water, Lucas Test, Chromic Acid Test (Jones

Oxidation), 2,4-Dinitrophenylhydrazone (2,4-DNP) Test, Fehling’s Test, Tollens’ Silver Mirror Test, and

Iodoform Test. Lucas Test differentiates primary, secondary, and tertiary alcohols. Chromic Acid Test is a

test for oxidizables or any compounds that possess reducing property 2,4-DNP Test is a test for

aldehydes and ketones. Fehling’s Test and Tollens’ Silver Mirror Test ar e tests for aldehydes. Iodoform

test is a test for methyl carbinol and methyl carbonyl groups.

Introduction

Hydroxyl group is used to

describe the functional group –OH when

it is a substituent in an organic

compound.  Hydroxyl groups areespecially important in biological

chemistry because of their tendency to

form hydrogen bonds both as donor and

acceptor. This property is also related to

their ability to increase hydrophilicity and

water solubility.  The hydroxyl group is

especially predominant in the family of

molecules known as carbohydrates. 

Hydroxyl group is the characteristic

functional group of alcohols and

phenols.

Figure 1 Structure of a Hydroxyl-

containing compound

 Alcohols are characterized by

one or more hydroxyl (−OH) groups

attached to a carbon atom of an alkyl

group (hydrocarbon chain). Alcohols

may be considered as organic

derivatives of water (H2O) in which one

of the hydrogen atoms has been

replaced by an alkyl group, typically

represented by R in organic structures.Because of hydrogen bonding,  alcohols

tend to have higher boiling points than

comparable hydrocarbons and ethers

 Alcohols, like water, can show either

acidic or basic properties at the O-H

group. With a pKa of around 16-19 they

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are generally slightly weaker acids than

water, but they are still able to react with

strong bases such as sodium hydride or

reactive metals such as sodium.  The

salts that result are called alkoxides. 

 Alcohols have an odor that is often

described as “biting” and as “hanging” in

the nasal passages.

There are three classifications of

alcohols by the carbon to which the

hydroxyl group is attached. Primary

alcohols are those in which the hydroxyl

group is attached to the carbon with only

one carbon attached. Secondaryalcohols are compounds in which the

OH- is attached to a carbon which has

two other carbons attached. Tertiary

alcohols are compounds in which a

hydroxyl group is attached to a carbon

with three attached carbons.

Phenols are aromatic compounds

in which a hydroxide group is directly

bonded to an aromatic ring system.They are very weak acids,  and like

alcohols,  form ethers and esters.  The

main phenols are phenol itself, cresol, 

resorcinol,  pyrogallol, and picric acid. 

Phenol itself (C6H5OH), also known as

carbolic acid, is a white, hygroscopic

crystalline solid, isolable from coal tar, 

but made by acid hydrolysis of cumene

hydroperoxide, or by fusion of sodium

benzenesulfonate with sodium

hydroxide. Formerly used as an

antiseptic, phenol has more latterly been

used to make bakelite and other resins,

plastics, dyes, detergents, and drugs.

The hydroxyl- containing

compounds used in the experiment are

ethanol, n-butyl alcohol, sec-butyl

alcohol, tert-butyl alcohol, isopropyl

alcohol, and benzyl alcohol.

Ethanol, C2H5OH, (also known as

ethyl alcohol, pure alcohol, grain

alcohol, or drinking alcohol) is the

second member of the aliphatic alcohol

series. It is a clear, colorless, volatile,

and flammable liquid which is

completely miscible with water and

organic solvents. It burns with a

smokeless blue flame that is not alwaysvisible in normal light. Ethanol has

widespread use as a solvent of

substances intended for human contact

or consumption, including scents,

flavorings, colorings, and medicines. In

chemistry, it is both an essential solvent

and a feedstock for the synthesis of

other products.

Figure 2 Structure of Ethanol

N-butyl alcohol (also known as n-

butanol, 1-Butanol or 1-butyl alcohol) is

a four carbon straight chain alcohol. It is

a volatile, clear liquid with a strong

alcoholic odor, and is miscible with

water. It is a highly refractive compound

which corrodes some plastics, and

rubbers. It is miscible with many organic

solvents, and incompatible with strong

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oxidizers. N-butanol is used as a direct

solvent and as an intermediate in the

manufacture of other organic chemicals.

Figure 3 Structure of n-butyl alcohol

Sec-butyl alcohol with the formula

CH3CH(OH)CH2CH3 (also known as

sec-butanol, 2-butyl alcohol, or 2-

butanol) is a flammable, colorless liquidthat is soluble in 12 parts water and

completely miscible with polar organic

solvent such as ethers and other

alcohols. 

Figure 4 Structure of sec-butyl

alcohol

Tert-Butanol, C4H10O is a

colorless liquid or white solid, depending

on the ambient temperature. It is the

simplest tertiary alcohol. and one of the

four isomers of  butanol. tert-Butanol is a

clear liquid with a camphor-like odor. It

is very soluble in water and miscible

with ethanol and diethyl ether.  It is

unique among the isomers of butanol

because it tends to be a solid at room

temperature, with a melting point slightly

above 25 °C. As a tertiary alcohol, tert-

butanol is more stable to oxidation and

less reactive than the other isomers of

butanol. tert-Butanol is used as a

solvent, as a denaturant for ethanol, as

an ingredient in paint removers,  as an

octane booster for gasoline,  as an

oxygenate gasoline additive,  and as an

intermediate in the synthesis of other

chemical commodities, other flavors and

perfumes.

Figure 5 Structure of tert-butyl

alcohol

Isopropyl alcohol (also propan-2-

ol, 2-propanol is a common name for a

chemical compound with the molecular

formula C3H8O. It is a colorless, flammable chemical compound with a

strong odor. It is the simplest example of

a secondary alcohol, where the alcohol

carbon is attached to two other carbons.

Being a secondary alcohol, isopropyl

alcohol can be oxidized to acetone, 

which is the corresponding ketone. 

Isopropyl alcohol dissolves a wide range

of non-polar compounds. It is also

relatively non-toxic and evaporatesquickly. Thus it is used widely as a

solvent and as a cleaning fluid,

especially for dissolving lipophilic

contaminants such as oil.

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Figure 7 Structure of Isopropyl

alcohol

Benzyl alcohol, C6H5CH2OH, is a

colorless liquid with a mild pleasant

aromatic odor. It is a useful solvent due

to its polarity, low toxicity, and low vaporpressure.  Benzyl alcohol is partially

soluble in water (4 g/100 mL) and

completely miscible in alcohols and

diethyl ether.  Like most alcohols, it

reacts with carboxylic acids to form

esters.  Benzyl alcohol is used as a

general solvent for inks,  paints, 

lacquers, and epoxy resin coatings. It is

also a precursor to a variety of esters,

used in the soap,  perfume,  and flavorindustries.  It is often added to

intravenous medication solutions as a

preservative due to its bacteriostatic and

antipruritic properties.

Figure 6 Structure of Benzyl alcohol

Carbonyl group is a divalent

chemical unit consisting of a carbon (C)

and an oxygen (O) atom connected by a

double bond. The group is a constituent

of carboxylic acids,  esters, anhydrides,

acyl halides, amides, and quinones, and

it is the characteristic functional group of

aldehydes and ketones. Carboxylic acid

(and their derivatives), aldehydes,

ketones, and quinones are also known

collectively as carbonyl compounds. 

 Aldehydes and ketones contain carbonyl

groups attached to alkyl or aryl groups

and a hydrogen atom or both. These

groups have little effect on the electron

distribution in the carbonyl group; thus,

the properties of aldehydes and ketones

are determined by the behaviour of the

carbonyl group. In carboxylic acids andtheir derivatives, the carbonyl group is

attached to one of the halogen atoms or

to groups containing atoms such as

oxygen, nitrogen, or sulfur. These atoms

do affect the carbonyl group, forming a

new functional group with distinctive

properties.

Figure 7 Structure of a Carbonyl-containing compound

 An aldehyde is an organic

compound containing a terminal

carbonyl group. This functional group, 

called an aldehyde group, consists of a

carbon atom bonded to a hydrogen

atom with a single covalent bond and an

oxygen atom with a double bond. Thus

the chemical formula for an aldehyde

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functional group is -CH=O, and the

general formula for an aldehyde is R-

CH=O. The aldehyde group is

occasionally called the formyl or

methanoyl group. The word aldehyde is

a combination of parts of the words

alcohol and dehydrogenated, because

the first aldehyde was prepared by

removing two hydrogen atoms

(dehydrogenation) from ethanol. 

Molecules that contain an aldehyde

group can be converted to alcohols by

the addition of two hydrogen atoms to

the central carbon oxygen double bond

(reduction). Organic acids are the resultof the introduction of one oxygen atom

to the carbonyl group (oxidation).

 Aldehydes are very easy to detect by

smell.  Some are very fragrant, and

others have a smell resembling that of

rotten fruit.

Figure 8 Structure of Aldehyde

Ketone features a carbonyl group

(C=O) bonded to two other carbon

atoms. They differ from aldehydes in

that the carbonyl is placed between two

carbons rather than at the end of a

carbon skeleton.  They are also distinct

from other functional groups,  such as

carboxylic acids,  esters and amides, 

which have a carbonyl group bonded to

a hetero atom. Ketone compounds have

important physiological properties. They

are found in several sugars and in

compounds for medicinal use, including

natural and synthetic steroid hormones. 

Figure 9 Structure of Ketone

Some of the carbonyl-containing

compounds used in the experiment are

benzaldehyde, n-butraldehyde,acetaldehyde, acetone and

acetophenone.

Benzaldehyde, C6H5CHO (also

known as benzenecarbonal) is a

colorless liquid aldehyde with a

characteristic almond odor. It boils at

180°C, is soluble in ethanol, but is

insoluble in water. It is formed by partial

oxidation of benzyl alcohol, and on

oxidation forms benzoic acid. It is called

oil of bitter almond, since it is formed

when amygdalin, a glucoside present in

the kernels of bitter almonds and in

apricot pits, is hydrolyzed, e.g., by

crushing the kernels or pits and boiling

them in water; glucose and hydrogen

cyanide (a poisonous gas) are also

formed. It is also prepared by oxidationof toluene or benzyl chloride or by

treating benzal chloride with an alkali,

e.g., sodium hydroxide. Benzaldehyde is

used in the preparation of certain aniline

dyes and of other products, including

perfumes and flavorings.

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Figure 10 Structure of Benzaldehyde

 Acetaldehyde, CH3CHO (also

known as ethanol) is a colorless liquid

aldehyde,  sometimes simply called

aldehyde. It is soluble in water and

ethanol. Acetaldehyde is made

commercially by the oxidation ofethylene with a palladium catalyst. It is

used as a reducing agent (e.g., for

silvering mirrors), in the manufacture of

synthetic resins and dyestuffs, and as a

preservative.

Figure 11 Structure of Acetaldehyde

N-butyraldehyde (also known as

butanal) is an organic compound with

the formula CH3(CH2)2CHO. This

compound is the aldehyde derivative of

butane.  It is a colourless flammable

liquid that smells like sweaty feet. It is

miscible with most organic solvents. n-

Butyraldehyde is used as an

intermediate in the manufacturing

plasticizers, alcohols, solvents and

polymers (such as 2-Ethylhexanol, n-

butanol, trimethylolpropane, n-butyric

acid, polyvinyl butyral, methyl amyl

ketone). It is also used as an

intermediate to make pharmaceuticals,

agrochemicals, antioxidants, rubber

accelerators, textile auxiliaries,

perfumery and flavors.

Figure 12 Structure of n-

Butyraldehyde

 Acetone (also known aspropanone) is the organic compound

with the formula (CH3)2CO. This

colorless, mobile, flammable liquid with

a characteristic sweetish smell is the

simplest example of the ketones. 

 Acetone is miscible with water and

serves as an important solvent in its

own right, typically as the solvent of

choice for cleaning purposes in the

laboratory.

Figure 13 Structure of Acetone

 Acetophenone is the organic

compound with the formula

C6H5C(O)CH3. It is the simplest

aromatic ketone.  This colourless,

viscous liquid is a precursor to useful

resins and fragrances.   Acetophenone

can be obtained by a variety of

methods. In industry, acetophenone is

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recovered as a by-product of the

oxidation of   ethylbenzene, which mainly

gives ethylbenzene hydroperoxide for

use in the production of  propylene oxide

Figure 14 Structure of Acetophenone

The hydroxyl- and carbonyl-

containing compounds were analyzed

by utilization of different tests such astesting the solubility of alcohols in water,

Lucas Test, Chromic Acid Test (Jones

Oxidation), 2,4-Dinitrophenylhydrazone

Test, Fehling’s Test, Tollens’ Silver

Mirror Test, and Iodoform Test.

Most organic compounds are not

soluble in water with the exception of

low molecular-weight amines and

oxygen-containing compounds likealcohols, carboxylic acids, aldehydes,

and ketones. Low molecular-weight

compounds are generally limited to

those with fewer than five carbon atoms.

Lucas Test often provides

classification information for alcohols, as

well as a probe for the existence of the

hydroxyl group. Substrates that easily

give rise to cationic character at the

carbon bearing the hydroxyl group

undergo this test readily; primary

alcohols do not give a positive result.

Since the Lucas Test depends on the

appearance of the alkyl chloride as a

second liquid phase, it is normally

applicable only to alcohols that are

soluble in the reagent. This limits the

test in general to monofunctional

alcohols lower than hexyl and certain

polyfunctional molecules.

Chromic Acid Test (Jones

Oxidation) detects the presence of a

hydroxyl substituent that is on a carbon

bearing at least one hydrogen, and

therefore oxidizable.

2,4-Dinitrophenylhydrazone Test

can be used to qualitatively detect the

carbonyl functionality of a ketone oraldehyde functional group.

Fehling’s Test and Tollens’ Silver

Mirror Test are used to detect

aldehydes. However, Fehling's solution

can only be used to test for aliphatic

aldehydes, whereas Tollens' reagent

can be used to test for both aliphatic

and aromatic aldehydes.

Iodoform Test is a test for methyl

carbinol (secondary alcohol with

adjacent methyl group) and methyl

carbonyl group.

Methodology

A. Solubility of Alcohols in Water

Five test tubes were labelled

accordingly and ten drops each of

ethanol, n-butyl alcohol, sec-butyl

alcohol, tert-butyl alcohol, and benzyl

alcohol were placed into the test tubes

by the use of a Pasteur pipette. 1-ml of

water was then added dropwise to the

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tube containing alcohol and the mixture

was shaken thoroughly after each

addition. If cloudiness resulted, 0.25-ml

of water at a time was added

continuously with vigorous shaking until

a homogeneous dispersion results. The

total volume of water added was noted.

If cloudiness resulted after the addition

of 2.0-ml of water, the alcohol is said to

be soluble in water. The results were

noted down.

B. Lucas Test

This test was performed on n-butylalcohol, sec-butyl alcohol, and tert-butyl

alcohol.

Lucas reagent was prepared by

dissolving 16 g of anhydrous zinc

chloride in 10-ml of concentrated

hydrochloric acid. The mixture was then

allowed to cool.

Two to three drops of the sample were

added to 1-ml of the reagent in a smallvial or test tube and the mixture was

shaken vigorously for a few seconds.

The mixture was allowed to stand at

room temperature. The rate of formation

of the cloudy suspension or the

formation of two layers were observed.

C. Chromic Acid Test (Jones

Oxidation)

This test was performed on n-butyl

alcohol, sec-butyl alcohol, tert-butyl

alcohol, n-butyraldehyde, benzaldehyde,

acetone, and acetophenone.

1 drop of liquid or a small amount of the

solid sample was dissolved in 1-ml of

acetone in a small vial or test tube. 2

drops of 10% aqueous Potassium

dichromate solution and 5 drops of

sulphuric acid were added into the

mixture.

D. 2,4-dinitrophenylhydrazone (or 2,4-

DNP Test)

This test was performed on acetone,

acetaldehyde, n-butyraldehyde,

benzaldehyde, and acetophenone.

The reagent was prepared by slowly

adding a solution of 3 g of 2,4-

dinitrophenylhydrazine in 15-ml of

concentrated sulphuric acid, while

stirring to a mixture of 20-ml of water

and 70-ml of 95% ethanol. The solution

was then stirred and filtered.

 A drop of a liquid sample was placed

into a small sample. 5 drops of 95%ethanol was added and well shaken.

 Afterwards, 3 drops of 2,4-DNP was

added and if no yellow or orange

precipitate formed, the solution was

allowed ro stand for at least 15 minutes.

E. Fehling’s Test 

This test was performed on

acetaldehyde, n-butyraldehyde,

acetone, benzaldehyde, and

acetophenone.

Fehling’s reagent was prepared by

mixing equal amounts of Fehling’s A

and Fehling’s B. Fehling’s A was

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prepared by dissolving 7 g of hydrated

copper (II) sulfate in 100-ml of water.

Fehling’s B was prepared by mixing 35

g of Potassium sodium tartrate and 10 g

of Sodium hydroxide in 100-ml water.

1-ml of freshly prepared Fehling’s

reagent was placed into each test tube.

3 drops of the sample to be tested was

added in to the tube. The tubes were

then placed in a beaker of boiling water

and changes within 10-15 minutes were

observed.

F. Tollens’ Silver Mirror Test 

This test was performed on

acetaldehyde, benzaldehyde, acetone,

n-butyraldehyde, and acetophenone.

The reagent was prepared by adding 2

drops of 5% Sodium hydroxide solution

to 2-ml of 5% Silver nitrate solution and

mixing thoroughly. Next, only enough

2% ammonium hydroxide (concentratedammonium hydroxide is 28%) was

added drop by drop and with stirring to

dissolve the precipitate. Adding excess

ammonia will cause discrepancies on

the result of the test.

Four test tubes with 1-ml of freshly

prepared Tollens’ reagent were

prepared. Two drops each of the

samples were then added. The mixture

was shaken and allowed to stand for 10

minutes. If no reaction has occurred, the

test tube was placed in a beaker of

warm water (35-50 oC) for 5 minutes.

Observations were recorded.

It was noted that if Tollens’ reagent is

left unused for a period of time, it may

form explosive silver. This was avoided

by neutralizing unused reagent with a

little nitric acid and discarded

afterwards.

G. Iodoform Test

This test was performed on

acetaldehyde, acetone, acetophenone,

benzaldehyde, and isopropyl alcohol.

Two drops of each sample was placedinto its own small vial or test tube. 20

drops of fresh chlorine bleach (5%

Sodium hypochlorite) was slowly added

while shaking to each test tube and

then, mixed. The formation of a yellow

participate was noted.

Results and Discussion

Table 1 Solubility of Alcohol in Water

 AlcoholCondensed

Structural Formula

 Amount of

Water (in ml)

needed to

produce a

homogeneou

s dispersion

Solubility

in Water

Ethanol CH3CH2OH 1 ml Miscible

N-butyl

alcoholCH3CH2CH2CH2OH 1.5 ml Miscible

Sec-butyl

alcohol1 ml Miscible

Tert-butyl

alcohol1 ml Miscible

Benzyl

alcoholN/A Immiscible

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  Table 1 shows alcohols such as

ethanol, n-butyl alcohol, sec-butyl

alcohol, tert-butyl alcohol, and benzyl

alcohol and their solubility in water.

Ethanol, n-butyl alcohol, sec-butyl

alcohol, and tert-butyl alcohol are all

miscible with water with the exception of

benzyl alcohol which exhibited

insolubility.

The table shows that all alcohols

are soluble in water except under C6.

There are different factors affecting

solubility. One of which is number ofcarbon atom wherein the higher the

number of carbon atoms, the more

insoluble the alcohol is in water. Another

factor is the branching of carbon chain

in which the more branching present,

the more soluble (with the same number

of carbons) it is. Lastly, the presence of

polar functional groups (-OH, -NH2, -

CO2H) also tends to affect alcohol

solubility in water. A compound withpolar functional group is more soluble in

water.

 As stated, all alcohols are soluble

in water except under C6. Hence,

ethanol, n-butyl alcohol, sec-butyl

alcohol, and tert-butyl alcohol are all

miscible with water. Ethanol has two

carbon atoms, while the other three all

have four carbons since they are all

derivatives of the alcohol, butanol.

Benzyl alcohol is immiscible with water

because it is an aromatic alcohol.

Ethanol is the most soluble

alcohol followed by tert-butyl alcohol,

sec-butyl alcohol, and n-butyl alcohol.

Ethanol exhibits fastest solubility

because it has only two carbon atoms

as compared to the butanol derivatives

having four carbon atoms. Tert-butyl

alcohol is the most soluble among the

butanol derivatives because it has the

most branching substituents present. 

Table 2 Reaction of Sample Compounds to

Lucas Test

SubstanceCondensed Structural

FormulaReaction Inference

n-butyl

alcoholCH3CH2CH2CH2OH

Clear

solutionMiscible

Sec-butyl

alcohol

Clear

solutionMiscible

Tert-butyl

alcohol

Formation

of two

layers with

cloudy

suspension

Immiscible

Table 2 shows the reaction of

butanol derivatives to Lucas Test. N-

butyl alcohol and sec-butyl alcohol

yielded a clear solution when subjected

to Lucas Test whereas tert-butyl alcohol

resulted to a cloudy immiscible

suspension which eventually formed two

layers.

Lucas Test differentiates primary,

secondary, and tertiary alcohols.

Reagents used include anhydrous ZnCl2 

and HCl. Positive result is based on

turbidity (alkyl chloride formation) andthe rate of the reaction was observed.

Tertiary alcohols form the second layer

in less than a minute. Secondary

alcohols require 5-10 minutes before

formation of second layer while primary

alcohols are usually unreactive. Based

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on Table 2, tert-butyl alcohol

immediately formed two layers; hence, it

is known to be a tertiary alcohol. Sec-

butyl alcohol when subjected to Lucas

test resulted to a clear solution although

theoretically, a secondary alcohol

dissolves to give a clear solution

(provided R does not have too many

carbon atoms in the chain.), then form

chlorides (cloudy solution) within five

minutes. N-butyl alcohol was unreactive

and is considered to be the primary

alcohol. Generally, the order of reactivity

of the alcohols toward Lucas reagent is

3°>2°>1° because the reaction rate ismuch faster when the carbocation

intermediate is more stabilized by a

greater number of electron donating

alkyl group bonded to the positive

carbon atom. This means that the

greater the alkyl groups present in a

compound, the faster its reaction would

be with the Lucas solution.

The reaction of alcohols with

halogen acids is a displacement

reaction in which the reactive species is

the conjugate acid of the alcohol R-

OH2+, and as might be expected, is

analogous to the replacement reactions

of organic halides and related

compounds with silver nitrate and iodide

ion. The effects of structure on reactivity

in these reactions are closely related.

Thus, primary alcohols do not react

perceptibly with hydrochloric acid even

in the presence of zinc chloride at

ordinary temperatures; chloride ion is

too poor a nucleophilic agent to effect a

concerted displacement reaction, on the

one hand, and the primary carbonium

ion is too unstable to serve as an

intermediate in the carbonium

mechanism, on the other. Hydrogen

bromide and Hydrogen iodide, which

have anions with nucleophilic reactivity

increasing in that order, are increasingly

reactive toward primary alcohols. These

are nucleophilicity orders to be expected

in hydroxylic solvents.

Tertiary alcohols react with

concentrated hydrochloric acid so

rapidly that the alkyl halide is visible

within a few minutes at room

temperature, at first as a milky

suspension and then as an oily layer.

The acidity of the medium is increased

by the addition of the anhydrous zinc

chloride (a strong Lewis acid), and the

reaction rate is increased further. Thisreaction is not a nucleophilic

displacement comparable to that

undergone by primary alcohols but

rather proceeds by way of a carbonium

ion intermediate. The high reactivity of

tertiary alcohols is a consequence of the

relatively great stability of the

intermediate carbonium ion. Allyl

alcohol, although a primary alcohol,

yields a carbonium ion that is relatively

stable because its charge is distributed

equally on the two terminal carbon

atoms. As might be expected, it reacts

rapidly with Lucas reagent with the

evolution of heat. Allyl chloride may be

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caused to separate by dilution of the

mixture with ice water.

Secondary alcohols are

intermediate in reactivity between

primary and tertiary alcohols. Although

they are not appreciably affected by

concentrated hydrochloric acid alone,

they react with it fairly rapidly in the

presence of anhydrous zinc chloride; a

cloudy appearance of the mixture is

observed within 5 minutes, and in about

10 minutes, a distinct layer is usually

visible.

Table 3 Reaction of Sample Compounds to

Chromic Acid Test

SubstanceCondensed

Structural FormulaReaction

n-butyl alcohol CH3CH2CH2CH2OHBlue-green

Solution

Sec-butyl alcoholBlue-green

Solution

Tert-butyl alcoholBlue-green

Solution

 AcetaldehydeRed-Orange

Solution

n-butyraldehyde Lime-Green

Solution

BenzaldehydeRed-Orange

Solution

 AcetoneBlue-green

Solution

acetophenoneBlue-green

Solution

Isopropyl AlcoholBlue-greenSolution

Chromic Acid Test/Dichromate

Test/Jones Test is a test for oxidizablesor any compounds that possess

reducing property (has an alpha acidic

hydrogen. Reagent used includes

chromium trioxide and concentrated

sulphuric acid.

Table 3 shows the reaction of n-

butyl alcohol, sec-butyl alcohol, tert-

butyl alcohol, n-butyraldehyde,

benzaldehyde, acetone, and

acetophenone to Chromic Acid test. N-

butyl alcohol. N-butyl alcohol, Sec-butyl

alcohol, tert-butyl alcohol, n-

butyraldehyde, acetone and

acetophenone resulted to a blue-green

or lime-green solution whereas

acetaldehyde and benzaldehyde

resulted to a red-orange solution.

Primary, secondary alcohols and

aldehydes give a positive visible result.

Positive result exhibits a lime-green or

blue-green solution; hence, n-butyl

alcohol, sec-butyl alcohol, and n-

butyraldehyde all formed either lime-

green or blue-green solutions. Chromic

acid test involves redox reaction.

Primary, secondary alcohols and

aldehydes undergo oxidation and

chromium undergoes reduction (from

Cr +6  to Cr +3). Primary, secondary

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alcohols and aldehydes will reduce the

orange-red chromic acid/sulfuric acid

reagent to an opaque green or blue

suspension of Cr(III) salts in 2-5

seconds. A primary alcohol reacts with

chromic acid to yield aldehyde, which is

further oxidized to carboxylic acid. A

secondary alcohol reacts with chromic

acid to yield ketone, which does not

oxidize further. A tertiary alcohol is

usually unreactive.

Table 4 Reaction of Sample Compounds to

2,4-DNP Test

Substance CondensedStructural Formula

Reaction

 AcetaldehydeYellow

precipitate

n-butyraldehyde Yellow

solution

Benzaldehyde

Orange-

Yellow

precipitate

 Acetone Orange-Red

precipitate

acetophenoneOrange-Red

precipitate

2,4-Dinitrophenylhydrazone (2,4-

DNP) test is a test for carbonyl groups It

gives a positive result for aldehydes and

ketones. Its mechanism is condensationor addition and elimination. The test

involves nucleophilic addition of NH2  to

C=O and elimination of H2O. Reagents

used include 2,4-dinitrophenylhydrazine,

ethanol, and H2SO4. Positive result is

the formation of a orange-red precipitate

(conjugated carbonyl compounds) or

yellow precipitate (non-conjugated

carbonyl compounds).

Table 4 shows the reaction of

acetaldehyde, n-butyraldehyde,

benzaldehyde, acetone, and

acetophenone to 2,4-DNP test. All the

samples exhibited positive result

because they all formed either a yellow

or an orange precipitate. Hence, 2,4-

DNP test proved that the samples are

carbonyl-containing compounds and are

either aldehydes or ketones.

The reaction of 2,4-DNPH with

aldehydes and ketones in an acidic

solution is a dependable and sensitive

test. Most aldehydes and ketones

yield dinitrophenylhydrazones that are

insoluble solids. The precipitate may beoily at first and become crystalline on

standing. A number of ketones,

however, give dinitrophenylhydrazones

that are oils. A further difficulty with the

test is that certain allyl alcohol

derivatives may be oxidized by the

reagent to aldehydes and ketones,

which then give a positive result. If the

dinitrophenylhydrazone appears to be

formed in very small amount, it may be

desirable to carry out the reaction on the

scale employed for the preparation of a

derivative and to make an estimate of

the yield. The melting point of the solid

should be checked to be sure it is

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different from that of 2,4-

dinitrophenylhydrazine (MP 198oC). If

necessary, this hydrazone derivative

can be recrystallized from a solvent

such as ethanol. Solvents containing

reactive carbonyl groups should not be

used, as they may result to formation of

another hydrazone.

The color of a 2,4-

dinitrophenylhydrazone may give an

indication as to the structure of the

aldehyde or ketone from which it is

derived. Dinitrophenylhydrazones of

aldehydes or ketones in which the

carbonyl group is not conjugated withanother functional group are yellow.

Conjugation with a carbon-carbon

double bond or with a benzene ring

shifts the absorption maximum towards

the visible and is easily detected by an

examination of the ultraviolet spectrum.

However, this shift is also responsible

for a change in color from yellow to

orange-red. In general, then, a yellow

dinitrophenylhydrazone may beassumed to be unconjugated. However,

an orange or red color should be interpreted

with caution, since it may be due to

contamination by an impurity.

Table 5 Reaction of Sample Compounds to

Fehling’s Test 

SubstanceCondensed

Structural FormulaReaction

 Acetaldehyde Brick-Redprecipitate

n-butyraldehyde Brick-Red

precipitate

BenzaldehydeNo

Decolorization

 AcetoneNo

Decolorization

acetophenoneNo

Decolorization

Fehling’s Test is a test for

aldehydes. Reagents include CuSO4,

NaOH ( Cu2+

  in alkaline solution).

Positive result is the formation of brick-

red precipitate.

 As shown in Table 5,

acetaldehyde and n-butyraldehyde

exhibited positive result. Acetaldehyde,

in particular turned from blue to muddy

green then formed a brick-red

precipitate upon heating. These three

sample compounds which exhibited

positive result to Fehling’s test are all

aldehydes.

Fehling’s test involves redox

reaction wherein aldehyde is oxidized to

carboxylic acid and ketones do not

undergo oxidation. Copper is reduced

(from Cu2+

to Cu+).

Table 6 Reaction of Sample Compounds toTollens’ Silver Mirror Test 

SubstanceCondensed

Structural FormulaReaction

 Acetaldehyde Silver Mirror

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n-butyraldehydeSilver Mirror

Benzaldehyde Silver Mirror

 AcetoneBlack

Solution

acetophenoneBlack

Solution

Tollens’ Silver Mirror test is a test

for aldehydes. The preparation of

Tollens reagent is based on the

formation of a silver diamine complex

that is water soluble in basic solution. As

shown in Table 6, acetaldehyde, n-

butyraldehyde, and benzaldehyde

exhibited positive result of formation of

silver mirror whereas acetone and

acetophenone do not. Acetone resulted

to a black solution while acetophenoe

formed a black precipitate. They areboth negative for Tollens’ Silver Mirror

test. The test proved that acetaldehyde,

n-butyraldehyde, and benzaldehyde are

aldehydes.

The test often results in a smooth

deposit of silver metal on the inner

surface of the test tube, hence the name

“silver mirror” test. In some cases,

however, the metal forms merely as agranular gray or black precipitate,

especially if the glass is not scrupulously

clean. The reaction is autocatalyzed by

the silver metal and often involves an

induction period of a few minutes.

Table 7 Reaction of Sample Compounds to

Iodoform Test

Substance

Condensed

Structural

Formula

Reaction

 AcetaldehydeYellow

precipitate

Benzaldehyde

Brownish-

Red Oily

Droplet

 AcetoneYellow

precipitate

acetophenoneYellow

precipitate

Isopropyl

alcohol

Yellow

precipitate

Iodoform Test is a test for methyl

carbinol (secondary alcohol with

adjacent methyl group) and methyl

carbonyl groups. Reagents include 10%

KI and NaClO. Positive result is

exhibited by the formation of yellow

crystals or precipitate. Table 7 shows

that among the sample compounds

tested, acetaldehyde, acetone,

acetophenone, and isopropyl alcohol

exhibited positive result. Compounds

with a methyl group next to a carbonyl

group give a positive result with the

iodoform (tri-iodomethane) test. Ethanol

and secondary alcohols with a methylgroup attached to the same carbon as

the  –OH group will also give a positive

iodoform test. This is because the iodine

oxidizes the alcohols to a carbonyl

compound with a methyl group next to

the carbonyl group.

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When a - methyl carbonyl

compounds react with iodine in the

presence of a base, the hydrogen atoms

on the carbon adjacent to the carbonyl

group (a hydrogens) are subsituted by

iodine to form tri iodo methyl carbonyl

compounds which react with OH -  to

produce iodoform and carboxylic acid

(2):

References

BOOKS:

Bayquen, A., Sarile, A. et al. (2014). Laboratory

Manual In Organic Chemistry. Quezon City,

Philippines. C & E Publishing Inc. Pg. 107-112

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