How to calculate the theoretical yield dehydration of 2-octene. In this experime

Question

How to calculate the theoretical yield dehydration of 2-octene. In this experiment you will synthesize trans-2-octene using 2-octanol. This is an acid-catalyzed dehydration of an alcohol via E1 mechanism. This type of reaction works better for secondary and tertiary alcohols than primary ones. Besides the major product of the reaction, trans2-Octene, minor products are formed:1-Octene and cis-2-Octene. Pre lab question: Write the chemical reaction showing the mechanism for the acid-catalized dehydration of 2-Octanol.Show structures of all products formed. Experimental procedure Weigh 1.7 grms of 2-Octanol into a 5 mL reaction vial Add 1 mL of concentrated phosphoric acid Place spin vane in the vial Attach Hickman still head into 5 mL reaction vial Attach air condenser onto top of reaction vial and below collar of Hickman still head Place reaction apparatus into a sand bath and heat to 150-160 degreeC As liquid collects into the Hickman still head remove air condenser and transfer liquid with disposable pipette into a 3 mL vial Continue heating 5 mL reaction vial until 2 mL of liquid has been transferred to 3 mL vial. Liquid in vial becomes yellow. Isolation and purification of product: Using disposable pipette, remove bottom aqueous layer in 3 mL vial Add 0.2 grams of sodium chloride into 3mL vial with prosuct Seal vial and shake strongly. Liquid product should be clear. If not, add more sodium chloride Transfer product into a pre-weighed vial with cap Weigh capped vial with product Characterization of product Determine the weight of your product Obtain an infrared spectrum of your product and 2-Octanol

Explanation / Answer

Lets summarize the data from given experiment.

In order to get theoretical yield of the 2-octene, we need the amount of the reactants in term of moles and from their moles we first predict limiting reactant since it is the reactant which is consumed in reaction completely and gives maximum yield. The maximum yield is called as theoretical yield.

Reaction:

H3PO4 + C8H18O -- > C8H16   +   H2O + H3PO4    

Here phosphoric acid acts as catalyst since it is generated at the end of the reaction.

And the yield so depends on the mass of octanol.

From the data we got the value of mass of octanol = 1.666 g

Calculation of moles of octanol

We know n =m/ Molar mass

n is mol , m is mass in g

Lets plug in the value of molar mass

n = 1.666 g x 1 mol / 130.23 g

=0.0127 mol

Now from the reaction we say that mol ratio between octanol : 2-octene is 1 : 1

Therefore ,

n 2-octene = n Octanol x 1 mol octane / 1 mol octanol

                =0.0127 mol 2-octene

Mass = mol x molar mass

Mass of 2-octene = 0.0127 mol x 112.226 g /mol

                =1.425 g

So the theoretical yield of the 2-octene would be 1.425 g

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