Question

1) You will need to perform a melting point for the final product. Provide a step-by-step procedure for preparing, running, and interpreting a melting point.

Answer 1

Procedure to perform Melting Point(MP) of final product:

1.Sample preparation- Once the reaction is completed (indicated by progress of reaction using Thin Layer Charomatography single spot for the final product), work up of the reaction mixture is carried out including filtration (may be simple or vacuum filtration i would say vacuum is most appropriate one ), washing with different solvents in which our final product is insoluble so that impurity expelled along with solvents ,drying, and recrystallisation then approx 1 mg compounds which is completely dry is taken on watch glass and loaded in melting point capillary(one side closed). Once it is loaded it is ready for melting point.

2.Running -Before running the melting point machine it should be calibrated using standard compounds , Generally benzoic acid is used for the same( MP=122⁰C). Once it is calibrated it is ready to hold the already loaded sample in the capillary. Now put the loaded capillary in the melting point apparatus.If somebody was using the apparatus just before you, you must wait for temperature to be at room temperature and it is more easier to perform if you know the melting range. If the synthesised compound is not reported then move its parent molecules for literature.when apparatus started it need much attention till its melting otherwise may cause experimental error. Note down the first point when compound started melting and colse when its melting finished.

Melting point is taken by digitalised apparatus , it can be done manually using Thiele tube.

3. Interpretation - Melting point is also one of the technique to check the purirty of the compounds. If it is having wide range then it would contain impurity, There might be depression in the melting point which is also landmark of contamination. Sharp melting point is indication of pure compound.