Physical Properties of Organic Compounds Ii: Refractive Index and Boling Point

Purpose:

The purpose of this lab was to identify an unknown compound (in our case an organic liquid sample) using the compound’s two important physical properties. These two properties are refractive index and boiling point.

Procedure:

The only thing that I did different from our listed procedure was during boiling point determination. For my second temperature determination (in step 4), I should’ve waited a little bit longer as the temperature was rising. Instead of waiting, I became impatient because I had still not done my refractive index determination and therefore, I believe my temperature reading is off.

Data:

Boiling point Determination:

Unknown # Organic Substance Structural Formula 1Color 2Color BP Range

6 Butyl Acetate

C6H12O2 clear and colorless clear and colorless 3125ºC - 126ºC

4115ºC - 121ºC

1. state of the original sample

2. state of the distillate

3. boiling point lit. value

4. boiling point experimental value

Refractive Index Determination:

nD20 = nDT + 0.00045(T - 20°C).

n=the refractive index

T = temperature observed in degrees C

Temperature 23ºC = 1.3905

nD20 = nD23 + 3 (0.00045) = 1.3919

Refractive Index

Lit Value Experimental

1.3951 1.3905 1.3919

Questions:

In deciding, which of the six compounds my unknown liquid (#6) was, I first looked at the literate value of the boiling point, since my refractive index (RI) was off by 0.0032 units. Even though my experimental boiling point was within the range of the literature value given for 1-Butanol in the table under part 3 of BP determination procedure, I decided to go with Butyl Acetate for my unknown sample because stated in our procedure, “the midpoint value is usually within 10˚C of the literature value” and my experimental midpoint was 118ºC. Furthermore, I was impatient with my reading as stated in the procedure. As for my RI value that was off by 0.0032 units, I believe it was due my initial...