Synthesis Of Cyclohexene Lab Report 2h2yh

Synthesis of Cyclohexene The Dehydration of Cyclohexanol Acid Catalyzed

Organic Chemistry I.

Introduction The acid-catalyzed dehydration of alcohols is a potentially useful technique for preparing alkenes, the overall general reaction being shown in general equation .The success of this reaction, called dehydration, requires the presence of a strong acid, such as aqueous H2SO4.The mechanism (Note 1) for this reaction depends on the class of alcohol being dehydrated, and the one shown in equation (2) is for 2º and 3º alcohols The –OH group in an alcohol is a poor leaving group but is converted to a better one by protonation of oxygen to given an oxonium ion. The oxonium ion undergoes decomposition by loss of a molecule of water to give a carbocation intermediate whose formation is the rate-determining step. This mechanism is referred to as an E1mechanism. Compelling evidence for the intervention of a carbocation intermediate comes from the observation that secondary carbocations derived from certain 2º alcohols may undergo molecular rearrangement to a more stable carbocation. Which will results in the formation of rearranged, isomeric alkenes.

Materials Sulfuric Acid

2 –Ring Stands

Distillational Column

1-Round Bottom Flask

Thermometer

Heating Mantle

Gloves

Reflux Condenser

T-Adaptor

I-Adaptor

J-Adaptor (inlet)

Magnetic Stirrer

Cyclohexanol 2-Hose

1-3 Kneck Round Bottom Flask Graduated Cylinder

Water

Procedures Measure out the cyclohexanol (25 mL) and determine its mass. Place it into a round bottomed flask no less than 100mL volume. Add 5 mL of concentrated H2SO4 and a boiling chip. Cork the flask and gently swirl the mixture. Use a collection flask or beaker that is no less than 50 mL in volume. Gently heat the mixture using a heating mantle and continue heating. Distill the mixture until about 5mL of liquid remains in the round bottom flask. The distillate will be a mixture of water and cyclohexene. Of 5% Iodine in trans1,2diiodocyclohexane. Note the color of each solution after addition of the iodine solution. A positive result for the formation of cyclohexene is indicated by a clear colorless solution upon addition of iodine to your product.

Results From the results of this experiment we have indicated that we have synthesis cyclohexene from the dehydration of cyclohexanol. And a clear colouration indicated that we have made cyclohexene, once we added iodine and a little result of the mixture. The results also showed 2 layers in the round bottom flask. From this result we have to calculate the theoretical yield.

Conclusion In conclusion of the synthesis of cyclohexene from cyclohexanol by acid catalyzed it the over all reaction The overall reaction is cyclohexanol (R-OH). Sulfuric acid is present as a catalyst which promotes the reaction but is not consumed in it. The hydroxyl group in R-OH is a poorleaving group because it would have to leave as a hydroxide ion (HO-). Therefore, an acid is used to protonate the alcohol (step 1) and form R-OH2+ (see Figure 2). The water is the leaving group in this reaction (step 2) and the product is a secondary carbocation. In the following step (step 3), a molecule of water deprotonates the carbocation at either of the adjacent carbons. The remaining electrons flow towards the positive charge producing a –bond between the carbons and forming a double bond.