06 Alkane and alkene

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CUNY College of Staten Island *

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250

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Chemistry

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Jan 9, 2024

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Alkane and Alkene 1. Purpose (5pts) The purpose of the lab was to observe the reactions of the different solutions with purified ligroin, unpurified ligroin, and cyclohexene in order to identify unknown substances by their specific reaction. 2. Reaction equation (5pts)

3. Procedure and Observation (20pts) 3.1) Bromine in Nonaqueous Solution. Treat 1.0 mL samples of purified ligroin, unpurified ligroin and cyclohexene with 5-6 drops of a 3% solution of bromine in dichloromethane. If the bromine color persists, illuminate the solution. When 5 to 6 drops of 3% bromine in dichloromethane was added to the tubes the purified ligroin was a red/orange color, the unpurified ligroin was also a red/orange color, and the cyclohexene was colorless. 3.2) Bromine Water. Measure 3 mL of a 3% aqueous solution of bromine into each of three tubes, then add 1-mL portions of purified ligroin to two of the tubes and 1 mL of cyclohexane to the third. Shake each tube and record the initial results. Put one of the ligroin-containing tubes in the desk out of the light and expose the other to bright sunlight or hold it close to light. When a change is noted, compare the appearance with that of the mixture kept in the dark. When bromine water was added to the 2 purified ligroin tubes they had a thin orange layer on top and the bottom layer was yellow. The cyclohexene tube developed a thin orange layer on top, a clear middle layer, and a yellow bottom layer. When one of the purified ligroin tubes was exposed to light, the top orange layer became a foggy white and the bottom layer stayed yellow. The one kept in the dark stayed the same as its initial observation. 3.3) Acid Permanganate Test. To 1-mL portions of purified ligroin, unpurified ligroin, and cyclohexene add a drop of an aqueous solution containing 1% potassium permanganate and 10% sulfuric acid and shake. If the initial portion of reagent is decolorized, add further portions. When the potassium permanganate and the sulfuric acid were added to the substances the purified ligroin developed a thin pink top layer with a clear bottom layer, the unpurified ligroin developed a thin dark orange top layer with a cloudy clear bottom, and the cyclohexene developed a thin brown top layer with a clear bottom layer. 3.4) Sulfuric Acid. Cool 1-mL portions of purified ligroin and cyclohexene in ice, treat each with 1 mL of concentrated sulfuric acid, and shake. Observe and interpret the results. After cooled and treated with concentrated sulfuric acid the purified ligroin stayed clear and became cold, and the cyclohexene became black and turned hot. Both of the substances reacted. 3.5) Prepare 1-mL portions of purified ligroin and cyclohexene. Add 5 drops of NBS solution in each of them. Observe the results. When 5 drops of NBS solution was added to the purified ligroin it stayed clear and when added to the cyclohexene it became cloudy clear.

3.6) Test for unsaturation. Followed Test 3.1 for Unknowns - Unknown #1 was a red/orange color - Unknown #2 was a red/orange color - Unknown #3 was colorless/clear Followed Test 3.3 for Unknowns - Unknown #1 had a thin pink top layer with a clear bottom layer - Unknown #2 had a thin dark orange top layer with a cloudy clear bottom layer - Unknown #3 had a thin brown top layer with a clear bottom layer 4. Result and Explanation (10pts) The unknowns were able to be identified based off of their results in test 3.1 and 3.3. Unknown #1 was the purified ligroin because based off test number 3.1 it mimicked the same reaction in color change as when testing the known substances. In test 3.1 it became a red/orange color and to further separate and identify it from the unpurified ligroin, in test 3.3 it demonstrated the same thin pink top layer as the purified ligroin in the known substance test. Unknown #2 was identified as the unpurified ligroin because even though it resulted in the same color change as the purified ligroin in test 3.1, it was able to be differentiated in test 3.3 when the thin orange top layer appeared mimicking the identified unpurified ligroin appearance in the known test. Unknown #3 was concluded to be cyclohexene because it was automatically clear in the first test showing no color change, but to further prove and identify it, in test 3.3 the unknown #3 matched exactly to the same thin brown top layer that was shown for cyclohexene in the known test 3.3. Post lab questions. P 244, 1,2,3(30 pts) 1. Structure formed when cyclohexene is dissolved in concentrated sulfuric acid: 2. Structure: The stereochemistry of the compound is achiral.

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