Analysis of Hydrocarbons

Analysis of Hydrocarbons
Leoncito, Alyssa Lynn, Libatique, Keith Martin P., Ligot, Nestlhyn B.*, Lim, Jamie Therese T.
Department of Psychology, University of Santo Tomas, Manila, Philippines
Abstract
Four organic samples: hexane, cyclohexene, napthalene and toulene were given to serve as reference standards to characterize and distinguish four unknown given samples. Nitration, bromine and basic oxidation testswere conducted to classify the different samples from being an aliphatic, or aromatic, saturated or unsaturated and alkylated or non-alkylated hydrocarbons. The physical state and color were noted by simple physical observation. The unknown samples were characterized and differentiated by using the three different tests to distinguish hydrocarbon from each type.
Introduction
There are millions of organic compounds that are already known. One type of which is the mostcommon and the simplest type that is only composed of hydrogen and carbon atom, the hydrocarbons.All hydrocarbons are insoluble in water due to their relatively non-polarity. Instead, they mix withrelatively non-polar solvents like dichlromethane or carbon tetrachloride.
Hydrocarbons can be characterize on the way in which carbon atoms are connected, the aliphaticand aromatic hydrocarbons. Aliphatic hydrocarbons, from the Greek word aleiphar (fat or oil), are longcarbon-chain molecules which are usually found in animal fats and plant oils. In aliphatic hydrocarbons,carbon atoms are joined together in straight chains, branched chains, or non-aromatic rings. Aliphatics undergo free-radical substitution reactions. The aromatic hydrocarbon or arene, are characterized byhaving molecular structures which are called benzene rings. They are characterized by ionic substitution reactions due to their opposition to addition reactions because of their aromacity, the possession of aclosed loop of electrons and a manifestation of cyclic delocalization and low reactivity of resonance.
Another means of classification rely upon the type of bonding that exists between carbons.Saturated hydrocarbons contains only single carbon-carbon bonds and unsaturated hydrocarbons that contains two or more C-C bonds, or benzene-like rings. Saturation refers to the fact that each carbonhas its maximum number of bonds to hydrogen. Alkanes, with the general formula of CnH2n+2, andcycloalkanes, where the carbon atoms are joined up in a ring and with the general formula of CnH2n,are classified as saturated with a single C-C bond. On the other hand, unsaturated hydrocarbons arehighly reactive and undergo addition reactions to their multiple bonds. Alkenes, with double C=C bondsand a general formula of CnH2n, and Alkynes, which have triple bonded C atoms and a general formulaof CnH2n-2, are classified as unsaturated hydrocarbons. The presence of a double or triple bond in themolecule opens up many more possibilities for isomerism compared with single bonded molecules.Hydrocarbons can also be grouped if there is an alkyl substitution that has happened to thecompound. Alkylated hydrocarbons undergo alkylation in which there is a transfer of an alkyl group from one molecule to another. Hydrocarbons that do not undergo alkylation are called non-alkylatedhydrocarbons.
The samples that were given to serve as standards are hexane, cyclohexene, naphthalene and toluene.
Hexane is an organic compound made of the elements carbon and hydrogen. It is primarily produced through the refining of petroleum. It has many uses, including that of a vegetable solvent, cleaning agent, and thermometer liquid. Its toxicity is considered to be relatively low, though the effects of extremely high exposure can include irritation, dizziness, headache, and slight nausea. Hexane’s physical properties are well known. It is most commonly encountered as a colorless liquid. It has a melting point of roughly -139.54°F (-95.3°C) and a boiling point of 154.04°F (67.8°C). It has a molar mass of 86.18 grams per mole (g/mol). It is also a non-polar molecule, meaning that it is not soluble in water. Hexane is a relatively simple molecule. As the hex- prefix indicates, it has six carbon atoms. These carbon atoms are accompanied by 14 hydrogen atoms, giving it the molecular formulaC6H14. The carbons are chained in a row, one following the next. Each carbon has at least two hydrogen atoms attached to it, except for the first and last carbon that have three. Due to its exclusive carbon-hydrogen makeup and the fact that hexane only has single molecular bonds, it can be classified as a straight-chain alkane.
Hexane is also easily represented visually. When drawn as a Kekulé structure, it is a line of six C’s, each of which has four line-bonds. H’s (hydrogens) surround the central carbon chain. The condensed structure is written as CH3CH2CH2CH2CH2CH3. The line structure is a simple line with five segments. Figure 1.Condensed structural formula of Hexane
Cyclohexene is a hydrocarbon with the formula C6H10. This cycloalkene is a colorlessliquid with a sharp smell. It is an intermediate in various industrial processes. Cyclohexene is not very stable upon long term storage with exposure to light and air because it formsperoxides.
Cyclohexene is produced by the partial hydrogenation of benzene, a process developed by Asahi Chemical Company. It is converted to cyclohexanol, which is dehydrogenated to give cyclohexanone, a precursor to caprolactam. Cyclohexene is also a precursor toadipic acid, maleic acid, dicyclohexyladipate, and cyclohexeneoxide. Furthermore, it is used as a solvent. Figure 2.Cyclohexene
Naphthalene is an organic compound with formula C10H8. It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass.[1] As an aromatic hydrocarbon, naphthalene 's structure consists of a fused pair of benzene rings. It is best known as the main ingredient of traditional mothballs.
A naphthalene molecule can be viewed as the fusion of a pair of benzene rings. As such, naphthalene is classified as a benzenoid polycyclic aromatic hydrocarbon (PAH). There are two sets of equivalent hydrogen atoms: the alpha positions are positions 1, 4, 5, and 8 on the drawing below, and the beta positions are positions 2, 3, 6, and 7.
Two isomers are possible for mono-substituted naphthalenes, corresponding to substitution at an alpha or beta position. Usually, electrophiles attack at the alpha position. The selectivity for alpha over beta substitution can be rationalized in terms of the resonance structures of the intermediate: for the alpha substitution intermediate, seven resonance structures can be drawn, of which four preserve an aromatic ring. For beta substitution, the intermediate has only six resonance structures, and only two of these are aromatic. Sulfonation, however, gives a mixture of the "alpha" product 1-naphthalenesulfonic acid and the "beta" product 2-naphthalenesulfonic acid, with the ratio dependent on reaction conditions. The 1-isomer forms predominantly at 25 °C, and the 2-isomer at 160 °C.
Naphthalene can be hydrogenated under high pressure in the presence metal catalysts to give 1,2,3,4-tetrahydronaphthalene or tetralin(C10H12). Further hydrogenation yields decahydronaphthalene or decalin (C10H18). Oxidation with chromate or permanganate, or catalytic oxidation with O2 and a vanadium catalyst, gives phthalic acid.
Most naphthalene is derived from coal tar. From the 1960s until the 1990s, significant amounts of naphthalene were also produced from heavy petroleum fractions during petroleum refining, but today petroleum-derived naphthalene represents only a minor component of naphthalene production. Figure 3. Naphthalene
Toluene is also known as methylbenzene, phenylmethane and toluol. It was originally extracted from the tropical Colombian tree of Myroxylon balasamum which has an aromatic extract known as tolu balsam. However, toluene is also a naturally occurring compound in crude though in very low levels. It is also a by-product in the production of gasoline and coke (fuel) from coal. Toluene is a colorless and clear liquid with a distinct smell, characteristic of the aromatic hydrocarbon family of chemical compounds including benzene.
Toluene is typically stable under normal usage and storage conditions but the container may burst when heated or subjected to high temperature and mishandling. It can be highly reactive especially in the presence of heat and flame. It is chemically incompatible with strong oxidizing agents, sulfuric and nitric acids, nitrogen tetraoxide, and chlorine. When heated and made to react with a nitro group, toluene can give rise to dintrotoluene and eventually, into the volatile and explosive trinitrotoluene. It reacts strongly with oxidizing agents and may produce heat or potentially ignite or explode when not handled properly. Figure 4.Toluene

The objectives of the experiment was to differentiate hydrocarbons based on their reactions to different chemical tests and to identify four unknown hydrocarbons through parallel test with standard hydrocarbons. Three tests: nitration, bromine and permanganate tests were used to determine the type of hydrocarbon of a given sample.
Nitration is a chemical reaction in which a nitro (=NO2)) group is added to a hydrocarbon compound replacing a hydrogen. In nitration, H2SO4 and HNO3 are reacted with the samples. Simple aromatic hydrocarbon will react with the warm sulfuric acid to form a sulfonic acid which will dissolve and then precipitated when =NO2 is reacted. Yellow globules indicate that a hydrocarbon is aromatics, if no yellow globules are present, the hydrocarbon is aliphatic.
In bromine test, alkenes and alkynes will readily add bromine across the multiple bonds unless there are electron withdrawing groups on the multiple bond. One observes the rapid disappearance of the red-brown bromine color. Aromatic compounds can react with bromine more slowly to give bromine substitution and the formation of HBr. A colorless solution in bromine test will indicate an unsaturated aliphatic hydrocarbon; a colored solution will indicate a saturated solution.
Results and Discussion
Hydrocarbons react differently due to their distinctness in properties. The basis for determining the type of hydrocarbon is the difference in their reactionsl. Nitration, bromine, and permanganate test was used in this experiment to identify the type of hydrocarbon of he unknown samples.
Standard Tests Hexane Cyclohexene Naphthalene Toluene Seat No. 21 Seat No. 22 Seat No. 23 Seat No. 24
Nitration Test Negative colorless solution Negative yellowish solution Positive yellow oil Positive
Yellow oil Negative
Colorless solution Negative
Colorless solution Negative
Colorless solution Negative
Colorless solution
Bromine Test Negative darkred solution Negative yellowish solution Negative
Bright red solution Negative
Red orange solution Negative light red solution Negative
Yellowish Solution Negative
Red orange solution Negative darkred solution
Permanganate Test Negative purple solution Positive clear solution with brown ppt Negative
Purple solution Negative
Purple solution with ppt Negative
Purple solution Positive clear solution with brown ppt Negative
Purple solution Negative purple solution
Table 1. Result of Standard and Unknown Samples. In the Nitration test performed, hexane

Ano yung reaction ng each 4 compunds sa nitration, bromine, permanganate. Figures muna, yung dapat na reaction tapos yung reaction ng naging experiment.

Figure 3. Chemical reaction of alkenein Bromine Test
Due to their C=C double bonds in cyclohexene,which can be broken, alkenes react readily withbromine to produce saturated dibromoalkanes.
Figure 4. Chemical reaction of aromatic compounds in nitration
A nitrite compound attached to benzene wasproduced as seen in the chemical reaction of benzene from a nitrating mixture composed of conc.
HNO
3 and conc. H
2
SO
4
, and with aid of heat.Nitrobenzene as well as p
-nitrotoluene both gave ayellow oily layer above a colorless solution. Thisindicated that both compounds possess aromaticity.

Experimental
Four unknown samples were given to each group for classification, using four standard hydrocarbons for reference producing 8 test tubes per test. 10 drops of each were used for three tests, namely, Nitration, Bromine, and Permanganate Test.
A. Nitration Test
Preparation of sample hydrocarbons. 5 drops of nitrating agent was added, followed by 10 drops of water. A yellow oil precipitate yielded a positive result, if otherwise, a negative one. Results were noted down.
B. Bromine Test
Preparation of sample hydrocarbons. A bromine reagent was mixed until an orange color persist. A maximum of 50 drops was limited. A colorless solution produces a positive result, and an orange color produces a negative result. Results were noted down.
C. Permanganate Test
Preparation of sample hydrocarbons. 5 drops of 1M KMnO4 and 5 drops of NaOH were added to the samples. Each test tube was subjected to a two-minute warm water bath. A positive result will have a brown precipitate and if none, a negative result . Results were noted down.

References:
Stoker, S. Organic and BiologicalChemistry. 1998. Houghton MifflinCompany. www.chemistry.com www.orgchem.colorado.edu www.chemistry explained.com
Article Source: http://EzineArticles.com/2214472

References: Stoker, S. Organic and BiologicalChemistry. 1998. Houghton MifflinCompany. www.chemistry.com www.orgchem.colorado.edu www.chemistry explained.com Article Source: http://EzineArticles.com/2214472