Question

What starting reagent should I use to synthesize chlorocyclohexene? What starting reagent should I use to synthesize 2-chloro-2-methylpropane? The options for starting reagents are 3-methyl-1-butanol, benzyl alcohol, cyclohexanol, and 2-methyl-2-propanol.

Alcohol Halogenation Procedure

Enter the synthesis lab [left-hand desk]. Click on Alcohol Halogenation on the chalkboard.

Decide on the appropriate starting reagent[s] to synthesize chlorocyclohexane. Use ether as solvent.

Build the experimental setup. Use a heater, condenser and nitrogen gas. Add the appropriate organic reagents to a flask, and move the flask to the stir plate. Add the inorganic reagent.

You will monitor the reaction on the chalkboard and with TLC. Since you'll be running two syntheses in this experiment, you'll need to organize your TLC plate results so that you know what result belongs to which compound, as you did in earlier experiments.

Run a TLC plate before you start the reaction, and save it. Some reactants may not show up on TLC so make sure that you check the contents of the reaction vessel on the chalkboard.

Note the time on the laboratory clock. Start the reaction by turning on the stir plate. Advance the laboratory clock by an interval of 1 minute and run another TLC plate and check the chalkboard. Save every TLC plate that you run.

Repeat this step until you note the appearance of product on the TLC plate or on the chalkboard. Note the time and calculate the time to the first appearance of product.

If no product has appeared by 10 minutes, then advance the clock by intervals of 10 minutes until product appears. Note the time.

Continue running TLC plates until there is no more starting reagent visible on the TLC plate and the starting reagent has disappeared from the chalkboard. Save your last TLC plate to your book.

Take screenshots of your TLC plates.

Clean up.

Repeat the procedure to synthesize 2-chloro-2-methylpropane.

Answer 1

For the first question that "What starting reagent should I use to synthesize chlorocyclohexene?" answer is cyclohexanol.

I think in this experiment an alkene (cyclohexene) will be prepared by dehydration of an alcohol (cyclohexanol) using an acid catalyst such as phosphoric acid. This is one of the most common methods of preparing alkenes and whatever you will get in crude product is contaminated with water, unreacted alcohol, phosphoric acid and some side products. Washing with water removes most of the impurities. Treatment with sodium carbonate solution removes traces of acid and a final wash with water removes any remaining carbonate.
The mechanism of the dehydration of cyclohexanol probably involves the formation of a carbocation.
This carbocation can react in any of the ways shown below:

1. With water to yield cyclohexanol - the starting material. Guys you should Note that all the steps in this reaction are reversible
2. by losing a proton to yield cyclohexene;
3. with cyclohexanol to yield dicyclohexyl ether.
Dicyclohexyl ether then is a probable side product of the dehydration of cyclohexanol. It is immiscible with water is likely to co-distill and may therefore be present in the first distillate. To remove dicylcohexy ether completely a second distillation of the product is usually carried out.

For second question "What starting reagent should I use to synthesize 2-chloro-2-methylpropane?" answer is 2-methyl 2-propanol.

In a 100 mL separatory funnel place anhydrous t-butyl alcohol (12.4 g, density 0.78 g cm^-3), and concentrated hydrochloric acid (21 mL) and shake the mixture very frequently during 20 minutes. After each shaking, relieve any internal pressure by opening the stopcock of the inverted separatory funnel.

Allow the mixture to stand for a few minutes after the period of shaking until the layers have separated sharply; separate the two layers and set aside the aqueous acid layer in a beaker. Pour the layer containing the halide product into a clean, dry conical flask and dry with a mixture of anhydrous magnesium sulfate and sodium carbonate in the stoppered flask. Filter the liquid through a small funnel supporting a fluted filter paper into a dry pre-weighed test-tube. Record the weight of the t-butyl chloride, calculate the yield and submit the entire sample for grading.