The Characterization of Hydrocarbons

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The last test performed was the permanganate test. 10 drops of colorless test compound were placed in separate test tubes. 3 drops of purple 0.1% aqueous KMnO4 and 2 drops of colorless 10% aqueous NaOH were added in the test tubes, and then warmed in the water bath. In this test, only cyclohexene, toluene and naphthalene reacted with the reagent as observed from its change of colors. Cyclohexene changed into a brown color solution. Toluene and naphthalene both changed into a blue green color solution. Cyclohexane was the same with the color of the reagent.

Results

Tabulation of data and results

Compounds

Nitration test (upper layer)

Bromine test

Permanganate test

Cyclohexane

colorless

1 drop (orange color)

Same with the reagent

Cyclohexene

brown color

20 drops (colorless)

brown color solution

Toluene

yellowish color

1 drop (orange color)

blue green color solution

Naphthalene

white powder

1 drop (red-orange color)

blue green color solution

In the nitration test, the noted color was based on the color of upper or the organic layer of the solution. The number of drops noted in the bromine test were the number of drops of bromine in dichloromethane used until the test compounds changed its color. In permanganate test, the color of the test compound solutions after the test were compared to the purple color of the used reagent which was the 10% KMnO4.

Discussion

Nitration test

Bromine test

An addition reaction occurred when halogens (Br or Cl) are added to alkenes. One bromine atom added to each side of the double bond, which opened to form two new single bonds. The reaction occurred when the 20 drops of orange color of the bromine reagent disappeared in the cyclohexene test compound, and formed colorless 1, 2-dibromocyclohexane. The greater the amount of bromine that must be added to the solution, the more unsaturated the compound is. Only unsaturated hydrocarbon can react with bromine. [pic 19][pic 20]

Cyclohexane did not react with bromine due to the fact that it does not composed of a double bond. It is composed of carbon-carbon single bonds, so addition of bromine will not occur. Toluene and naphthalene also cannot react with bromine, but it can with the presence of a catalyst such as FeBr3-. [pic 21][pic 22]

[pic 23][pic 24][pic 25]

,[pic 26][pic 27][pic 28][pic 29]

[pic 30]

Permanganate test