The purpose of this lab is to produce cyclohexene through the acid catalyzed elimination of water from cyclohexanol (dehydration) BACKGROUND AND THEORY:
Dehydration of alcohols, such as cyclohexanol, to give alkenes, such as cyclohexene, is an important transformation and is an elimination reaction. Strong acids such as sulfuric (H2SO4) and phosphoric acid (H3PO4) catalyze this reaction.
Dehydration of an alcohol can follow the E2 or E1 mechanism. However, in each case, acid is required as a catalyst, because –OH is a strong base and poor leaving group, whereas water (H2O) is a weak base but a better leaving group. Adding strong acids, such as sulphuric acid to the mixture allows protonation of the –OH group to give a by-product of water as a leaving group. Once protonation occurs, the mechanism followed usually depends on the R group. An example of E1 mechanism is as follows
An example of E2 mechanism is as follows
Reaction Mechanism for cyclohexenol to cyclohexene
This mechanism shows that the lone pairs on the oxygen attack the Hydrogen Ion from sulfuric acid making a by product of HSO4 - , the Oxygen will then break it’s bond with the benzene ring to form a carbocation. The Hydrogen on the adjacent Carbon will be attacked by the HSO4 to fulfill the S needs, and form H2SO4. The carbon’s can now form a C=C bond. PROCEDURE
First, set up a fractional distillation apparatus. Place 10mL of cyclohecanol into a 50mL – flask (round bottom) and add 5mL or 85% phosphoric acid. Make sure a boiling stone is added to control the mixture as it boils. Place the flask in a fractional distillation and heat the mixture for 10 minutes at a steady temperature and gradually increase every 10 minutes afterwards. Table 1: Table of physical constants
Reagent/Compound| Formula/Structure| Molecular Weightg/mol| Densityg/mL| Boiling Point °C| Melting Point°C| Saftey Hazards| Cyclohexanol| C6H12O| 100.158 | 0.962 | 160.84| 25.93|...