Question

1.) Which would have a longer effective chain length (ECL) 5,9,12,15-20:4 or 9,12,15-20:3? Why might this be?

2.) Draw methyl stearate, methyl oleate, and methyl linoleate. All double bonds are of the Z-configuration.

3.) Methyl linoleate has a boiling point of 192 °C at 4 mm Hg (0.005 atm); whereas, methyl stearate has a boiling point of 181 °C at 4 mm Hg. Why do you think this is? Discuss in terms of the possible intermolecular forces that dictate boiling points.

4.) Based on your answer above, which do you think would have a longer retention time, methyl linoleate or methyl stearate?

5.) Methyl stearate has a higher freezing point than methyl linoleate. Why might this be? (Hint: Think entropy of fusion (melting).)

Answer 1

1) Answer:

5,9,12,15-20:4 is the longer chain.

Explanation:

In the two chains one is the 20:4 and the another one is the 20:3. Here 20 indicates the number of the carbon atoms and the 4 and 3 are the number of the double bonds.

Double bonded carbon atoms are planar in nature, Hence the compound which containes the number of the carbon atoms its chain length is more.

2) Answer:

3) Answer:

Methyl linoleate is having the two double bonds. Due to the presence of the double bonds the temporary dipole formation takes place this leads to the formation of the attraction between the molecules. Hence the boiling point becomes more to break the attraction between the molecules.

4) Answer:

Which is having the more boiling point its retention time is more. Hence Methyl linoleate is more.