Clayton State University s1

CHEM2411L Clayton State University Dr. Susan F. Hornbuckle Experiment #2 Part 1 Melting points

A. Melting point of a pure known compound Fill capillary tube with a small amount of the sample. To fill the tube, press the open end of the tube into a mound of the sample. The sample should be packed tightly down into the capillary tube either by tapping the tube on the bench top or by dropping it through a piece of glass tubing onto either the floor or bench top. This may need to be done several times to make sure that the sample is packed tightly. Make sure you pack each sample the same way. After packing the sample insert the capillary tube into the Mel-temp and begin heating. The first trial is the “quick” or approximate trial in that the temperature should rise about 10C per minute. The sample should be watched carefully to see when it begins melting. Record the temperature when melting is first observed and record when the sample is melted completely. This is the melting-point range. Repeat this procedure with a new capillary tube, letting the Mel-temp cool to about 15C below the first recorded temperature. Then begin heating again, however the temperature should only rise 1 to 2C per minute. These are the “slow” trials and should give a more accurate range. Record the temperatures as before. These temperatures and ranges should agree within 1 to 2C. If you do not obtain these results you may need to complete more trials or check with your instructor.

Melting-Point Standards Compound MP (C) Compound MP (C) p-Dichlorobenzene 53 Salicylic Acid 159 m-Dinitrobenzene 90 Succinic Acid 188 Acetanilide 114 3,5-Dinitorbenzoic acid 205 Benzamide 130 p-Nitrobenzoic Acid 241 CHEM2411L Clayton State University Dr. Susan F. Hornbuckle B. Melting point of an unknown compound Obtain and unknown from your instructor and determine its melting- point range. The unknown will be one of the substances in Table 2.2. Determine the melting point the same way as before and compare the values to the known samples to identify the unknown. The results should be within 1 to 2C. You will have to complete multiple trials to ensure that it is the correct identification. You will also need to complete multiple trials with a mixture of the unknown and the known you think it matches. The results should be within 1 to 2C. Make sure you always use a fresh sample for each trial.

Compounds for Melting-point unknowns Compound MP (C) Compound MP (C) Benzhydrol 68 o-Anisic Acid 100 Phenyl benzoate 69 Phenanthrene 101 Biphenyl 70 o-Toluic Acid 105 Phenylacetic acid 78 Acetanilide 114 Naphthalene 80 Fluorene 114 Vanillin 81 Cholesteryl acetate 116