CLASSIFICATION TESTS FOR HYDROCARBONS USING SOLUBILITY, IGNITION, NITRATION, BAEYER’S TEST, BROMINE TEST AND BASIC OXIDATION TEST Jasher Christian Boado, Alyanna Cacas, Phoebe Calimag, Caryl Angelica Chin, Haidee Cosilet, John Francis Creencia Group 2, 2BMT, Faculty of Pharmacy, University of Santo Tomas ABSTRACT Hydrocarbons are classified as saturated, actively unsaturated, aromatic or an arene based on various classification tests involving test for solubility in concentrated H2SO4, ignition, active unsaturation using Baeyer’s test and Bromine test, aromaticity using nitration test, and basic oxidation test. This experiment aims to differentiate the intrinsic physical and the chemical properties of hydrocarbons, and to determine if it is saturated, actively unsaturated, aromatic or an arene. The sample compounds hexane, heptane, cyclohexane, cyclohexene, benzene and toluene were analyzed for their physical state in room temperature, color, and odor. Using solubility test, a drop of a sample was added cautiously into 1ml of concentrated H2SO4. Using the Baeyer’s Test and/or Bromine test in which 2 drops of 2% KmnO4 solution and 10 drops of 0.5% Br2 in CCl4 reagent, respectively, was added into 5 drops of a sample in a dry test tube, was shaken vigourously until the reagent is decolorized compared with water. Using Nitration test, 8 drops of nitrating mixture was added into 5 drops of a sample in a dry test tube, was observed for the formation of a yellow oily layer or droplet and was diluted with 20 drops of water. Using Basic Oxidation test, 8 drops of 2% KmnO4 solution and 3 drops of 10% NaOH solution was added into 4 drops of a sample in a dry test tube and was heated in a water bath for 2 minutes. A sample was described as immiscible or immisicible using solubility test, as actively unsaturated using Baeyer’s and Bromine tests, as aromatic using nitration test and as an arene using basic oxidation test. INTRODUCTION Hydrocarbons are the simplest organic bonds attached to it. Thus, a hydrocarbon that is compounds containing only the elements carbon saturated has all sigma bonds however it is actively and hydrogen. They can be classified in many unsaturated when it has both sigma bond and pi ways. One, a hydrocarbon skeleton can be acyclic bonds. Moving on, aromatic hydrocarbons can be (open chained) or cyclic (closed chain). Two, a classified as an arene when it contains an alkyl side hydrocarbon can be classified as aliphatic or chain (Brown & Poon, 2014). aromatic based on its sources and properties. Aliphatic (from the Greek: aleiphar meaning fat or The sample compounds used in this oil) describes a hydrocarbon that resembles long experiment are hexane, heptane, cyclohexane, carbon-chain molecules derived from animal fats, cyclohexene, benzene and toluene. Hexane, C6H14, but more conviniently, when the chemical structure is a chemical made from crude oil. Heptane, C7H16, contains no ring. Aromatic describes a hydrocarbon is a chemical derived from the fractional distillation that resembles pleasant smelling plant extracts, but of petroleum. Cyclohexane, C6H12, is a colorless more conviniently, when the chemical structure liquid cycloalkane that is made by passing benzene contains a ring (Carey, 2014). Aliphatic and hydrogen under pressure over a heated Raney o hydrocarbons can be divided into an alkane, alkene nickel catalyst at 150 C or by the reduction of or alkyne based on the types of bonds they contain. cyclohexanone. Cyclohexene, C6H10, is a colorless Alkanes are saturated hydrocarbons that contain liquid cycloalkene that is prepared by dehydration of only carbon-carbon single bonds. Alkenes and cyclohexanol by thermal reaction of ethylene- Alkynes are unsaturated hydrocarbons that contain propylene-butadiene. Benzene, C6H6, is a liquid a carbon-carbon double bond or triple bond, aromatic hydrocarbon found in gasoline and other respectively. As mentioned, “saturated” is a way to fuels (National Center for Biotechnology describe a bond, meaning each carbon (a Information, n.d.). Toluene, C7H8, is a liquid tetravalent atom) contains the maximum number of aromatic hydrocarbon that occurs naturally in crude 5 drops of the sample was placed in a oil and in the tolu tree (ATSDR, 2011). dry test tube. Then, 2 drops of 2% KmnO4 solution was added into it and The objectives of this experiment are to was shaken vigorously. The extent of differentiate the intrinsic physical and the chemical decolorization of the reagent was properties of hydrocarbons using these compunds, observed. and to determine if they are saturated, actively unsaturated, aromatic or an arene. b. Bromine test MATERIALS AND METHODS 5 drops of the sample was placed in a The sample compounds used in this dry test tube. Next, 10 drops of 0.5% experiment are hexane, heptane, cyclohexane, Br2 in CCl4 reagent was added into it cyclohexene, benzene and toluene. The reagents and was shaken vigorously. The extent used in the different classification tests are of decolorization of the reagent was concentrated H2SO4, concentrated HNO3, 2% observed or when the red-brown KmnO4 solution, 0.5% Br2 in CCl4 reagent, and 10% bromine was discharged. Optionally, a NaOH solution. blue litmus paper on a glass rod was put on the mouth of the test tube and Members of the group were assigned tasks any color changed was noted. Then the and collected the materials used in the experiment. sample was compared with water as a negative control. A. Physical State, color, and odor E. Nitration test The sample compounds hexane, heptane, cyclohexane, cyclohexene, benzene and toluene A nitrating mixture was prepared by adding were observed and noted for their physical state as 2ml of concentrated HNO3 and 2ml of concentrated solid, liquid or gas at room temperature, for their H2SO4 in an erlenmeyer flask immersed in an color and for their appearance as either clear or evaporating dish containing water. The sample was turbid. Next, the odor was described by wafting the cooled at room temperature. hand over the mouth of the test tube containing a sample. 5 drops of the sample was placed in a dry test tube. Then, 8 drops of the nitrating mixture was B. Solubility in Concentrated H2SO4 added on the sample and was shaken. Any formation of a yellow oily layer or droplet was A drop of the sample compound was added observed and was diluted with 20 drops of water. A in a test tube containing 1 ml of concentrated sample that resulted in no apparent reaction was H SO A sample was described as immiscible or o 2 4. heated in a water bath at approximately 50 C for 10 misicible when they form a layer or not. minutes and was observed. C. Ignition Test F. Basic Oxidation test 3 drops of the liquid sample was placed in a 4 drops of the sample was placed in a dry small evaporating dish and was observed as test tube. Then, 8 drops of 2% KmnO4 solution and flammable or not by putting a lighted match on it. 3 drops of 10% NaOH solution was added into it The flame was observed as either luminous or non- and heated in a water bath for 2 minutes. Any color luminous, and if it produced soot or not. change and formation of a brown precipitate was observed. D. Tests for active unsaturation a. Baeyer’s test RESULTS AND DISCUSSION Table 1: Results HEXANE HEPTANE CYCLOHEXANE CYCLOHEXENE BENZENE TOLUENE Condensed structural formula Physical Liquid Liquid Liquid Liquid Liquid Liquid state at RT Appearance Clear Clear Clear Clear Clear Clear Color Colorless Colorless Colorless Colorless Colorless Colorless Odor Plastic balloon- Chlorine odor Detergent-like Acetone-like Flowery odor Rugby-like like Solubility in Formation of a Formation of a Formation of a Formation of an Formation of Formation concentrated black layer clear oily layer clear oily layer orange layer a yellow of a clear H2SO4 green layer oily layer Inference Immiscible Immiscible Immiscible Immiscible Immiscible Immiscible Ignition test Luminous Luminous flame Luminous flame Luminous flame Luminous Luminous flame flame with flame with soot soot Inference Flammable Flammable Flammable Flammable Flammable Flammable Baeyer’s test No formation No formation of No formation of Formation of No formation No of brown brown suspension brown brown of brown formation of suspension suspension suspension suspension brown suspension Bromine test No change No change No change Reddish Brown No change No change to colorless Inference Not actively Not actively Not actively (+) actively Not actively Not actively unsaturated unsaturated unsaturated unsaturated unsaturated unsaturated Nitration Formation of a Formation of a Formation of a Black Formation of Formation clear oily layer clear oily layer clear oily layer a yellow oily of a yellow layer oily layer with brown ppt Inference Aliphatic Aliphatic Aliphatic Not aromatic Aromatic Aromatic Basic No precipitate No precipitate No precipitate Bluish green to No Bluish black oxidation brown precipitate precipitate Inference Not an arene Not an arene Not an arene Not an arene Not an arene Arene A. Physical State, Color, and Odor Generally, saturated hydrocarbons specifically alkanes are not as reactive as other The Physical properties of hydrocarbons hydrocarbons. The reasons are alkanes do not determine thier reactivity. Aliphatic hydrocarbons: have double or triple bonds that can react with acid alkane (CnH2n+2), cycloalkane (CnH2n), alkene to form carbocations and they have no leaving (CnH2n-2) and alkyne (CnH2n-4) consist only of weak groups making them incapable of E1, E2, SN1 or dispersion forces. This forces account for their low SN2 reactions. However, unsaturated hydrocarbons boiling points thus they exist in such physical state specifically alkenes are more reactive than alkanes at room temperature. They are less dense than because they can undergo addition reactions water, thus they are non-polar and soluble in each (Carey, 2014). Thus, sulfuric acid reacts differently other (Brown & Poon, 2014).