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ANALYSIS OF HYDROCARBONS(Alkanes, Alkenes, Alkynes and Aromatics)

INTRODUCTIONHYDROCARBONS are the simplest organic compounds consisting of the C and H atoms only. Hydrocarbons are generally insoluble in water because of their non-polarity. They are generally classified either as aliphatic or aromatic hydrocarbons. Aliphatic hydrocarbons are derived by chemical degradation of fats or oils. These are hydrocarbons which does not contain a benzene ring. Aliphatic hydrocarbons can further be classified either as Saturated or Unsaturated hydrocarbons.Saturated hydrocarbons are whose compounds of carbon and hydrogen having only single bond between carbon to carbon bond with the standard formula C(n)H(2n+2). ALKANES are compounds containing at least 2 carbons that are bonded through single covalent bond. Also called as PARAFFINS- derived from Latin word meaning little activity that sates that alkane compounds are very unreactive compare to alkene and alkyneR C C R

Unsaturated hydrocarbons are those compounds of carbon and hydrogen that contains one double or triple bond between carbon atoms (carbon-carbon ).ALKENES are compounds containing carbon that are bonded through double bonds. Also called as OLEFINS forming oily liquids on reaction with chlorine gas.R C C RALKYNES are compound containing carbon bonded through triple bonds. Also called as ACETYLENES ( C2H2 ) simplest alkyne R C C R

Aromatic hydrocarbons are obtained by chemical degradation of certain pleasant smelling plant extracts. They are compound containing special six carbons arranged in a ring formation with three alternating double bonds. Aromatic hydrocarbons can further be classified as Alkylated or Non-alkylated hydrocarbons.Alkylated hydrocarbons contains an alkyl group. It is formed when an aromatic ring with an alkyl halide undergoes alkylation.Non-alkylated hydrocarbons has no alkyl substituent attached to it and is less reactive than the alkylated one

Many hydrocarbons occur in nature like petroleum, asphalt, natural gas, etc. In addition to making up fossil fuels, they are present in trees and plants.

PARALLEL CHEMICAL TESTA chemical test perform in a way that different parameters are observed simultaneously.

There are three tests that can be performed to identify hydrocarbons. These are the Nitration test, Bromine Test and the Permanganate test.

NITRATION TEST is used to test the aromacity of the compound. A positive result yields a yellow oil or precipitate describing an aromatic hydrocarbon.BROMINE TEST detects the presence of unsaturation or phenols in the compound. The positive result is a colorless solution.OXIDATION TEST/ PERMANGANATE TEST detect the presence of unsaturation. The positive result yields a brown precipitate or a blue green solution.Objectives To be able to differentiate various types of hydrocarbonsTo be able to device a scheme to distinguish one hydrocarbon from the otherCharacterize an unknown hydrocarbon through parallel chemical testsMaterials Test tubes Test tube rackDropperBeaker1:1 H2SO4 HNO3 (Nitrating reagent)5% Br2 in CH2Cl22% aq. KMnO4HexaneCyclohexeneNaphthalene Toluene 10% NaOHUnknown liquids ProcedureHexane(5 drops)Cyclohexene(5 drops)Napthalene(5 drops)Toluene(5 drops)Unkown #1(5 drops)Unkown #2(5 drops)Unkown #3(5 drops)Unkown #4(5 drops)Record observationNitratingMixture(8 drops)Place in warm water bath for 8 minutes Add 20 dropsof H2O

Nitration TestBromine Reagent(5 drops)Hexane(5 drops)Cyclohexene(5 drops)Napthalene(5 drops)Toluene(5 drops)Unkown #1(5 drops)Unkown #2(5 drops)Unkown #3(5 drops)Unkown #4(5 drops)Record observationBromine TestHexane(5 drops)Cyclohexene(5 drops)Napthalene(5 drops)Toluene(5 drops)Unkown #1(5 drops)Unkown #2(5 drops)Unkown #3(5 drops)Unkown #4(5 drops)Record observationKMnO4(1 drop)10 % NaOH(4 drops) Place in warm water bath for 2 minutesPermanganate Test14Set-up

Test tube Test tube rackRESULTSHydrocarbonNitration Reaction test Bromine Reaction test Permanganate Reaction testHexane---Cyclohexene-++Naphthalene+--Toluene+--1+--2+--3---4-+

+Group 1HydrocarbonNitration Reaction testBromine Reaction testPermanganate Reaction testHexane---Cyclohexene-++Naphthalene--+Toluene+--5+--6--+7-++8--+Group 2 18HydrocarbonNitration Reaction testBromine Reaction testPermanganate Reaction testHexane--+Cyclohexene-++Naphthalene+-+Toluene+--9+--10-++11--+12+-+Group 3HydrocarbonNitration Reaction testBromine Reaction testPermanganate Reaction testHexane---Cyclohexene-++Naphthalene+--Toluene+--13+--14-++15---16+--Group 4HydrocarbonNitration Reaction testBromine Reaction testPermanganate Reaction testHexane---Cyclohexene-++Naphthalene+-+Toluene+--17+-+18+--19---20-++Group 5HydrocarbonNitration Reaction testBromine Reaction testPermanganate Reaction testHexane---Cyclohexene-++Naphthalene+-+Toluene+--21+--22+-+23-++24---Group 6HydrocarbonNitration Reaction testBromine Reaction testPermanganate Reaction testHexane---Cyclohexene-++Naphthalene+--Toluene+--25+--26-+-27---28+--Group 7Hydrocarbon Nitration Reaction testBromine Reaction testPermanganate Reaction testHexane---Cyclohexene-++Naphthalene+--Toluene+--29+--30-++31---Group 8HydrocarbonNitration Reaction testBromine Reaction testPermanganate Reaction testHexane---Cyclohexene-++Naphthalene+--Toluene+-+32+--33---34-++Group 9Nitration TestBromine TestOxidation TestHexane---Cyclohexene-++Naphthalene+--Toluene+-+DISCUSSION OF RESULTSThere are three tests that were performed in the analysis of hydrocarbons. These are the Nitration test, Bromine Test and the Permanganate test.NITRATION TEST is used to test the aromacity of the compound. A positive result yields a yellow oil or precipitate describing an aromatic hydrocarbon.BROMINE TEST detects the presence of unsaturation or phenols in the compound. The positive result is a colorless solution.OXIDATION TEST/ PERMANGANATE TEST detect the presence of unsaturation. The positive result yields a brown precipitate or a blue green solution.

SATURATED ALIPHATIC HYDROCARBON(HEXANE) C6H14Hexane only has a C-C single bondStraight or branched carbon thus opposite to aromaticsMost aliphatic compounds are flammableCharacterize by a substitution reactionColorless liquid with petrolic odor

SATURATED ALIPHATIC HYDROCARBONHEXANE Bromine test (-)The structure shows that the compound is aliphatic since it only contains a single bond between carbons and will not yield a colorless solution.

Nitration Test (-)The structure of hexane is not characterized by an aromatic ring.

Permanganate/oxidation test (-)the same as the bromine test it detects the presence of double and triple bond furthermore it test the presence of alkyl groupsUNSATURATED ALIPHATIC HYDROCARBON (CYCLOHEXENE)UNSATURATED -hydrocarbons containing either double or triple bondALIPHATIC - hydrocarbons joined together in straight or branched chains HYDROCARBON - Simplest organic compound containing carbon and hydrogen - The carbon serves as its backbone where hydrogen is attach - They are characterize by addition or bond rupture reactions

CYCLOHEXENECommercially used as a starting material in the production of chemicals, polymers ( plastics, rubbers, resins ).Properties :- more reactive than alkanes ( saturated aliphatic hydrocarbons) - strong oxidizers react vigorously with them- low toxicity but acts as asphyxiants- physical state in room temperature changes by increase in molecular weight ( gaseous to waxy solid )Asphyxiants gas/ vapor that can cause unconsciousness and/or death if inhaled CYCLOHEXENEcolorless liquid with a sharp smellinsoluble in water and less dense than water produced by partial hydrogenation of benzene not very stable upon long term storage with exposure to light and air for it forms peroxides inhalation of high concentration may have narcotic effecthighly flammable C6H10

NITRATION TEST ( - )C6H10 + HNO3 + H2SO4 NO REACTIONSince nitration tests for the presence of aromatic in a solution and cyclohexene does not exhibit aromatic structure, cyclohexene yields a negative result because when treated with nitric and sulfuric acid there was no formation of yellow oil or precipitate nitrate test only reacts with aromatic compounds

BROMINE TEST ( + )C6H10 + Br2 C6H10Br2 (1,4-dibromocyclohexane )

Cyclohexene has the presence of carbon-carbon double bond that indicates that is has unsaturation. The solution bromine decolorizes as it was mixed with cyclohexene indicating a positive result.Decoloration of bromine happens because bromine undergoes electrophilic addition to the double bonds of cyclohexene

OXIDATION/PERMANGANATE TEST ( + )C6H10 + KMnO4( potassium permanganate ) C6H10(OH)2 (1,2dihydroxicyclohexANE) + MnO2(manganese dioxide )

- cyclohexene has the presence of unsaturation because there is a double bond between carbon-carbon atoms- when cyclohexene was treated with potassium permanganate there was the presence of a brown precipitate- permanganate converted the cyclohexene into a diol- cyclohexene stated postive in permanganate test

NON-ALKYLATED AROMATIC HYDROCARBON(NAPHTHALENE)

NON-ALKYLATED hydrocarbon that has no alkyl substituent attached to itAROMATIC hydrocarbon with alternating double and single bonds between carbon atoms forming ring/rings. An aromatic hydrocarbon is also called an arene.Characteristics of aromatic hydrocarbons:Cyclic the contributing atoms are connected forming a ring/ringsCoplanar all contributing atoms are in the same plane Hckels rule Number of delocalized -electrons should be 4n+2 where n=0,1,2Total number of delocalized -electrons should be even but not a multiple of 4 Delocalized conjugated system an arrangement of alternating single and double bonds

NAPHTHALENEwhite crystalline solidsimplest polycyclic aromatic hydrocarbon (fused aromatic rings)from coal tar and crude oilbyproduct of fuel burning either fossil fuel or biomassused as insecticide, pest repellant and was once a widely used ingredient for mothballs

NaphthaleneC10H8

NITRATION TEST ( + )

CyclicCoplanar Hckels rule Delocalized conjugated system

NO2HNO3H2SO4Substantial resonance stabilizationBROMINE TEST ( )UNSATURATION unsaturated compound is a chemical compound that contains carbon-carbon double bonds or triple bondsPHENOL chemical compounds consisting of a hydroxyl group (OH) directly bonded to an aromatic hydrocarbon

Br2NO REACTIONNaphthalene is an unsaturated compound, so why did it test negative?

Since naphthalene is an aromatic compound, it is stable and will resist addition reaction with bromineIt has 3 resonance structures

10 electrons of naphthalene aredelocalized and it has substantialresonance energy

Aromatic compounds can react with bromine via substitution reaction rather than the addition reaction which will produceHBr (Hydrogen Bromide) gasFor the reaction to occur there must be presence of heat and catalyst

OXIDATION/PERMANGANATE TEST ( )

Naphthalene is an aromatic compound, therefore it is stable and will not react with KMNO4Since naphthalene is a non-alkylated hydrocarbon, it will not test positiveThis would only test positive if the reaction occurs with aromatic hydrocarbons that contain alkyl substituents at a very high temperature, because then it can react with the alkyl substituent

KMNO4NO REACTIONALKYLATED AROMATIC HYDROCARBON (TOLUENE)ALKYLATED hydrocarbon contains an alkyl substituentAROMATIC - hydrocarbon with alternating double and single bonds between carbon atoms forming ring/ringsTOLUENEalso known as Methylbenzenecolorless liquid with a paint thinner like odorwater insoluble aromaticflammableobtained from petroleum and coal tarused as solvent for gums and lacquers, in high octane fuels such as medicines, dyes, explosives and detergents

NITRATION TEST ( + )

methyl group acts as the activating groupproduces poly substituted nitro-products

BROMINE TEST ( - )

negative since Br2 is not electrophilic enough to attack the benzene ring of Toluenea catalyst (FeBr2) is required for the reaction to follow through

OXIDATION TEST ( +)

The methyl group in the side chain of the aromatic ring is oxidized to become a carboxyl group in the presence of a strong oxidizing agent which in this case is KMnO4.

EXPERIMENTAL ERRORSInaccurate quantities of reagentsContamination of droppers used to transfer reagentsContamination of test tubesUNKNOWNSHEXANE 8 11 15 19 24 27 31 33 CYCLOHEXENE 7 10 14 20 23 26 30 34NAPHTHALENE 6 12 16 17 22 28 32 TOLUENE 5 9 13 18 21 25 29

REINFORCEMENT EXERCISE Indicate which sample best suits the description

The hydrocarbon structure above will yield yellow oil when subjected to Nitration test since it is an aromatic hydrocarbon. It will decolorize KMnO4 because it contains an alkyl substituent indicating that it is an alkylated aromatic hydrocarbon.

The sample above is aliphatic and it will turn the bromine solution to colorless because it is unsaturated containing a C-C triple bond, thus, it is an Unsaturated Aliphatic hydrocarbon.

The hydrocarbon sample above will yield yellow oil with HNO3 / H2SO4 because it is an aromatic and will not decolorize KMnO4 because there is no an alkyl group attached to it and is therefore a Non-alkylated aromatic hydrocarbon.CONCLUSIONThrough the help of Nitration, Bromine and Permanganate tests, different hydrocarbons were differentiated from one another. Parallel chemical test was used to compare the unknowns to the known chemicalsSAMPLEAROMATICALIPHATICALKYLATEDNON-ALKYLATEDSATURATEDUNSATURATEDNITRATION TEST+- + --+PERMANGANATE TEST BROMINE TEST Referenceshttp://cameochemicals.noaa.gov/react/28http://chemistry.about.com/od/chemistryglossary/g/Aliphatic-Hydrocarbon-Definition.htmhttp://www.elmhurst.edu/~chm/vchembook/500hydrocarbons.htmhttp://cameochemicals.noaa.gov/react/29http://en.wikipedia.org/wiki/Aromaticity http://en.wikipedia.org/wiki/Naphthalene http://npic.orst.edu/factsheets/naphgen.htmlhttp://chemistry.tutorvista.com/organic-chemistry/toluene.html?view=simple