Lab #1 - Melting Points
Purpose:
a) Determine the melting points of two organic compounds known to have the same melting range when pure.
b) Determine the mixture melting point of a mixture of the two pure compounds.
c) Identify an unknown organic compound by determining its melting point and mixture melting point.
Procedure and Observations:
Using the procedure outlined in Appendix A of the Lab Manual, approximately equal samples of p-Nitrophenol and acetanilide, which are known to have the same melting range of 113-114 degrees Celcius, were taken and inserted into the melting point apparatus. The melting points of the compounds were noted and found to be very similar.
Next, approximately equal amounts of p-Nitrophenol and acetanilide were mixed on a clean watch glass. A sample of the mixture was placed in the Mel-temp apparatus as before and the mixture melting point was noted. The mixture melting point was found to be much lower than the melting point of each of the pure organic substances separately.
Following this, an unknown pure organic compound, was taken and melted following the steps of Appendix A and using the “Mel-temp” apparatus. It’s melting point was noted to be 129.6-132 degrees Celcius. Based on the melting range found, the unknown substance was narrowed down to be one of two known pure compounds – Urea or trans-Cinnamic Acid. The unknown was then mixed with approximately equal amounts of each of the two likely known compounds and the mixture melting point of each was noted. The melting range of the mixture of the unknown and Urea was unchanged and the mixture of the unknown with trans-Cinnamic Acid dropped drastically to 95.7- 97.2 degrees Celcius.
Compound/Unknown number Observed melting range (degrees Celcius) Literature melting range
(degrees Celcius) p-nitrophenol 114 – 115.3 110-115 acetanilide 111.7 – 115.7 113-115
Unknown #8 129.6-132 132-133 http://www.sigmaaldrich.com/catalog/product/fluka/1048?lang=en®ion=CA (p-nitrophenol)
a) Determine the melting points of two organic compounds known to have the same melting range when pure.
b) Determine the mixture melting point of a mixture of the two pure compounds.
c) Identify an unknown organic compound by determining its melting point and mixture melting point.
Procedure and Observations:
Using the procedure outlined in Appendix A of the Lab Manual, approximately equal samples of p-Nitrophenol and acetanilide, which are known to have the same melting range of 113-114 degrees Celcius, were taken and inserted into the melting point apparatus. The melting points of the compounds were noted and found to be very similar.
Next, approximately equal amounts of p-Nitrophenol and acetanilide were mixed on a clean watch glass. A sample of the mixture was placed in the Mel-temp apparatus as before and the mixture melting point was noted. The mixture melting point was found to be much lower than the melting point of each of the pure organic substances separately.
Following this, an unknown pure organic compound, was taken and melted following the steps of Appendix A and using the “Mel-temp” apparatus. It’s melting point was noted to be 129.6-132 degrees Celcius. Based on the melting range found, the unknown substance was narrowed down to be one of two known pure compounds – Urea or trans-Cinnamic Acid. The unknown was then mixed with approximately equal amounts of each of the two likely known compounds and the mixture melting point of each was noted. The melting range of the mixture of the unknown and Urea was unchanged and the mixture of the unknown with trans-Cinnamic Acid dropped drastically to 95.7- 97.2 degrees Celcius.
Compound/Unknown number Observed melting range (degrees Celcius) Literature melting range
(degrees Celcius) p-nitrophenol 114 – 115.3 110-115 acetanilide 111.7 – 115.7 113-115
Unknown #8 129.6-132 132-133 http://www.sigmaaldrich.com/catalog/product/fluka/1048?lang=en®ion=CA (p-nitrophenol)