Classification Test for Hydro

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University of Santo TomasFaculty of Pharmacy

Organic Chemistry Laboratory

Classification Tests for Hydrocarbons

Liza Marie Antonio, Maria Esperanza R. Apolinario, Polene Bernardo,Keith Canlas, Anna Mae C. Chicote

Group 2 2C Pharmacy Organic Chemistry Laboratory

ABSTRACTThe organic compounds hexane, heptane, cyclohexane, cyclohexene, benzene, and toluene were subjected

different physical and chemical tests to differentiate their intrinsic physical properties and chemical properties in ter

of structure and behavior. The physical state, color, and odor were observed by simple physical observati

Miscibility was tested by introducing a drop of the sample to 1 ml concentrated HS 2O4. Flammability was tested

placing 3-5 drops of the sample to an evaporating dish and lighting it with a match. Active unsaturation was tes

using the Baeyer¶s and Bromine test. Aromaticity was determined by subjecting the samples through nitrati

Oxidation was tested by introducing 2% KMnO4 solution and 10% NaOH solution to the samples. All orga

compounds showed immiscibility in concentrated HS2O4 and flammability in the ignition test. All samples exc

cyclohexane were not actively unsaturated. The aromatic compounds are benzene and toluene. All are not oxidi

except cyclohexene.

INTRODUCTION

Hydrocarbons are family of organic compound,composed entirely of carbon and hydrogen. Theyare the organic compounds of simplestcomposition and may be considered the parentsubstances from which all other organiccompounds are derived [1]. Hydrocarbons areclassified as either aliphatic or aromatic on thebasis of their sources and properties. Aliphatichydrocarbons are derived by chemical

degradation of fats or oils. Aromatichydrocarbons constituted a group of relatedsubstances obtained by chemical degradation of certain pleasant-smelling plant extracts. Aliphatichydrocarbons are divided into three main groupsaccording to the types of bonds they contain:alkanes, alkenes, and alkynes. Alkanes have onlysingle bonds, alkenes contain a carbon-carbondouble bond, and alkynes contain a carbon-carbon triple bond. Aromatic hydrocarbons arethose that are significantly more stable than theirLewis structures would suggest. They areclassified as either arenes, which contain abenzene ring as a structural unit, ornonbenzenoid aromatic hydrocarbons, whichpossess special stability but lack a benzene ringas a structural unit [2]. Saturated hydrocarbonsare the simplest type of organic compounds.They are hydrocarbons in which all carbon-carbonbonds are single bonds and contain the maximumnumber of hydrogen atoms for each carbonatom. An example of a saturated hydrocarbon isan alkane. Unsaturated hydrocarbons containcarbon-carbon multiple bonding and contain lessthan the maximum number of hydrogen per

carbon.Saturated and unsaturated hydrocarbhave similar physical properties, but they diffetheir chemical properties [3]. Saturahydrocarbons are chemically inert to some exteon the other hand unsaturated hydrocarbons very reactive hydrocarbons. Their high reactivis due to the presence of pi-bond in thstructure and this serves as location whchemical reactions can occur [4]. The objecti

of this experiment is to (1) differentihydrocarbons in terms of their intrinsic physproperties and chemical properties in termsstructure and behaviour (2) to analyze hydrocarbon and determine if it is saturatactively unsaturated, aromatic or an arene.

EXPERIMENTAL

A. Samples used1. Hexane (CH3CH2CH2CH2CH2CH3)



2. Heptane(CH3CH2CH2CH2CH2CH2CH3)

3. Cyclohexane (C6H12)

4. Cyclohexene (C6H10)

5. Benzene (C6H6)

6. Toluene (C7H8)

B. Procedures

1. Observation of the PhysicalState, Color and Odor

The physical state, color and odor

of the sample were observed at roomtemperature. The odor was observed with awafting motion.

2. Solubility in concentratedH2SO4

A drop of the sample wascautiously added to about one mL of concentrated H2SO4. The color change andwarming effect was observed.

3. Ignition Test

Three to five drops of the liquid sam

was placed in a small evaporating dish a

lighted with a match. Only pinch amount of

solid sample was used. The color of the flame

was observed.

4. Test for Active UnsaturatioA. Baeyer¶s TestFive drops of the sample w

placed in a dry test tube. Two drops of KMnO4 solution was added. The test tube wshaken vigorously and the rate and extentwhich the reagent is decolorized was observThe formation of the brown precipitation was anoted and had been compared to water as negative control. Decolorization of the reagenimmediate if it occurred within 1 minute.

B. Bromine TestFive drops of the sample w

placed in a dry test tube. Add 10 drops of 0.Br2 in CCl4 reagent. The test tube was shavigorously and the rate and extent (color chanby which the reagent is decolorized wobserved; the bromine color was discharged. Twas then compared to water as negative contIf the reagent failed to decolorized withinminute, exposure of the reagent to sunlight wadvised.

5. Test for Aromaticity:Nitration

Two mL of concentrated HNOplaced in an Erlenmeyer flask. Immerse the flin an evaporating dish containing water agradually add two mL of conc. H2SO4. Tresulting mixture was cooled to rotemperature. This will serve as the nitratmixture. Five drops of the sample was placed idry test tube. Eight drops of the nitrating mixtwas added and shake the test tube to enscomplete mixing. Note the formation of a yeloily layer or droplet. Then dilute it with 20 droof water. If no apparent change was observwithin a minute, place the test tube in a wabath (~50oC) for ten minutes. Dilute with drops of water.

6. Basic OxidationTo four drops of the sample in

test tube, eight drops of 2% KMnO4 solutand Three drops of 10% NaOH solution wadded. Each tube was warmed in a wabath for 2 minutes and the color change athe formation of a brown precipitate wobserved.



RESULTS AND DISCUSSION

Table 1: Results of the Observation of the Physical

Properties, Color and Odor of the Samples

Test compounds Physical Stateat RT

Color Odor

Hexane Liquid Clear,

colorless

Odorless

Heptane Liquid Clear,colorless

Odorless

Cyclohexane Liquid Clear,colorless

Odorless

Cyclohexene Liquid Clear,Colorless

Gas-likeodor

Benzene Liquid Colorless Rugby-like odor

Toluene Liquid Clear,colorless

Rugby-like odor

Based on Table 1, all of the samples arecolorless and are in the liquid state at roomtemperature. This means that most hydrocarbonsare in the liquid state and colorless. Aliphatichydrocarbons based on Table 1 are odourlesshydrocarbons while aromatic hydrocarbonspossess different odor property.

Table 2: Results of Solubility in concentrated H2SO4

Test compounds Solubility inconcentrated

H2SO4

Inference

Hexane Formed 2layers

immiscible

Heptane Formed 2layers

immiscible

Cyclohexane Formed 2layers

immiscible

Cyclohexene Turned Yellow immiscible

Benzene Formed 2layers

immiscible

Toluene Formed 2layers

immiscible

Based on Table 2, all samples exccyclohexene formed 2 layers when concentraH2SO4 was added to each sample. Tformations of 2 layers indicate that the sampleimmiscible in concentrated H2SO4. On the othand cyclohexene is the only compound tturned yellow in the presence of concentraH2SO4. The solubility of organic compound concentrated H2SO4 indicates whether the sam

is a very weak base which can be protonated oneutral compound which cannot be protonatThe dissolution of compounds in H2SO4 produheat or a change in color of the solution in case of cyclohexene.

Table 3: Results of Ignition Tests

Testcompounds

Result of Ignition Test

Inference

Hexane Flammable No soot, luminous

Heptane Flammable No soot,

luminousCyclohexane Flammable No soot,

luminous

Cyclohexene Flammable No soot, yelloluminous

Benzene Flammable With soyellow lumino

Toluene Flammable With soot,yellow lumino

Based on Table 3, all the compounds

flammable. This means that most hydrocarbare flammable compounds. Unsaturahydrocarbons produced more luminous flacompared to saturated hydrocarbons namhexane, heptanes and cyclohexane. Tcompounds that did not have soot are also luminous this means that there is luminositythe presence of soot. Aromatic compounproduced soot due to incomplete combustwhich causes the formation of unburned carbComplete combustion is indicated by a bluenon-luminous flame and there is more heat thlight, which means that the carbon is complet

oxidized. The more carbon atoms are there icompound, the more luminous it will be whsubjected to combustion. In contrast, incomplcombustion is indicated by a yellow or luminoflame and there is much light than hetherefore the carbon is not completely oxidized



Table 4: Test for Active Unsaturation

Testcompound

Baeyer¶sTest

BromineTest

Inference

Hexane did notdecolorized

did notdecolorized

notactivelyunsatura

-ted

Heptane slowly

decolorized

did not

decolorized

not

activelyunsatura-ted

Cyclohexa-ne

slowlydecolorized

slowlydecolorized

notactivelyunsatura

-ted

Cyclohexe-ne

immediatelydecolorized(violet tobrown)

immediatelydecolorized(orange to

white)

activelyunsatura

-ted

Benzene did notdecolorized

did notdecolorized

notactively

unsatura-ted

Toluene did notdecolorized

did notdecolorized

notactivelyunsatura

-ted

A. Baeyer¶s TestThe rate at which the samples decolorized

was observed in the addition of 2% KMnO4.Based on table 4, Cyclohexene was the only

compound that immediately decolorized orreacted with KMnO4 at a fast rate. From violetcyclohexene turned into a brown precipitate andwent under a redox reaction. The aromaticcompounds however did not decolorized.

B. Bromine TestThe rate and the change in color of the

compound were observed upon the samples¶ reaction with 0.5% Br. Only cyclohexeneimmediately decolorized and reacted with 0.5%Br. Like the Baeyer¶s test the aromaticcompounds did not decolorized.

Table 5: Test for Aromaticity

Test compounds Test forarmaticity in

nitration

Inference

Hexane no yellow layer notaromati

Heptane no yellow layer notaromati

Cyclohexane with yellowlayer

Notaromati

Cyclohexene no yellow layer notaromati

Benzene with yellowlayer

aromati

Toluene with yellowlayer

aromati

Based on table 5, Benzene and Tolue

are aromatic compounds. This was indicated

the formation of a yellow layer upon doing reaction.

Table 6: Test for Basic Oxidation

Testcompounds

Test for BasicOxidation

Inferenc

Hexane not decolorized not

oxidized

Heptane not decolorized not

oxidized

Cyclohexane not decolorized not

oxidized

Cyclohexene Immediatelydecolorized

oxidized

Benzene not decolorized not

oxidized

Toluene not decolorized not

oxidized

Based on table 6, cyclohexened is the o

compound that decolorized and reacted throug

redox reaction.



REFERENCES

[1] Davis, Thomas W. "Hydrocarbons."Microsoft® Student 2009 [DVD]. Redmond, WA:Microsoft Corporation, 2008. 9/14/11[2] hydrocarbon. (2010). EncyclopædiaBritannica. Encyclopaedia Britannica Ultimate

Reference Suite. Chicago: EncyclopædiaBritannica. 9/14/11[3]http://www.chem.latech.edu/~deddy/chem12

1/Alkanes.htm 9/14/11[4] http://www.citycollegiate.com/organic8.htm9/14/11[4]

Classification Test for Hydro

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