Question

Br KOH Triethylenegylcol heat KOH Triethylenegylcol heat Br Br Purpose: To generate diphenyl acetylene from the product of the previous experiment. Prelab: A standard prelab is expected. In addition, calculate the theoretical yield of alkyne based on a starting amount of 0.75 g of 1,2-dibromo-1,2-diphenyl ethane Procedure: Place a mass of KOH chips equivalent to the dry mass of 1,2-dibromo-1,2-diphenyl ethane into a 25 mL Erlenmeyer Flask (EF). Add 5 mL of triethylene glycol. Heat this reaction mixture on a prewarmed hot plate (~200°C) until all of the solid has dissolved in the solvent. DO NOT CHANGE THE SETTING. Add the 1,2-dibromo-1,2-diphenyl ethane obtained from the previous lab and swirl the contents in the flask periodically while heating the flask. Keep the flask on the plate for 30 min after all of the solid has dissolved. The reaction will darken as it proceeds. Once the time is up, remove the flask from the hot plate and let it cool for about 5 min, then carefully add a total of 10 mL of distilled water in ~2 mL portions; mix completely. Add an additional 5mL of water. Allow the solution to cool for another 10 min in an ice bath. Collect the solid by vacuum filtration. Wash the solid with water. Continue to vacuum until dry (at least 5 min) and calculate your percent yield for the reaction. Waste: Pour the filtrate waste into the appropriate waste container in the hood. Once you have taken the mass and melting point of your product you should place it in a clean, labeled vial. This product will be used the following semester. The 'H NMR spectra for the starting materials and products are included in this lab packet.

Br
KOH
Triethylenegylcol
heat
KOH
Triethylenegylcol
heat
Br
Br
Purpose: To generate diphenyl acetylene from the product of the previous experiment.
Prelab: A standard prelab is expected. In addition, calculate the theoretical yield of alkyne based
on a starting amount of 0.75 g of 1,2-dibromo-1,2-diphenyl ethane
Procedure:
Place a mass of KOH chips equivalent to the dry mass of 1,2-dibromo-1,2-diphenyl ethane into a
25 mL Erlenmeyer Flask (EF). Add 5 mL of triethylene glycol. Heat this reaction mixture on a
prewarmed hot plate (~200°C) until all of the solid has dissolved in the solvent. DO NOT
CHANGE THE SETTING. Add the 1,2-dibromo-1,2-diphenyl ethane obtained from the previous
lab and swirl the contents in the flask periodically while heating the flask. Keep the flask on the
plate for 30 min after all of the solid has dissolved. The reaction will darken as it proceeds. Once
the time is up, remove the flask from the hot plate and let it cool for about 5 min, then carefully
add a total of 10 mL of distilled water in ~2 mL portions; mix completely. Add an additional 5mL
of water. Allow the solution to cool for another 10 min in an ice bath. Collect the solid by vacuum
filtration. Wash the solid with water. Continue to vacuum until dry (at least 5 min) and calculate
your percent yield for the reaction.
Waste: Pour the filtrate waste into the appropriate waste container in the hood. Once you have
taken the mass and melting point of your product you should place it in a clean, labeled vial. This
product will be used the following semester.
The 'H NMR spectra for the starting materials and products are included in this lab packet.

Added by William H.

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