Question

a. Based on the stereochemistry of the addition of bromine to trans-cinnamic acid, write the structure of the product(s) that will form when bromine reacts with (Z)-2-hexene.

b. Assume that you carried out separate reactions of bromine with (E)-2-pentene and (Z)-2- pentene. After isolating, purifying and determining the melting point of the product from each reaction, you found that the melting points were significantly different. Explain why.

c. Why did you dry your product in the oven before taking its melting point?

d. Do you think IR spectroscopy would be a better method than melting point for differentiating between the threo and erythro products in the bromination of trans-cinnamic acid? Explain briefly

Answer 1

c. Melting point is a physical constant which is the characteristic property of that particular compound i.e we can identify compound from its melting point but for this purpose, we need to get very sharp melting point and in order to get sharp melting compound has to be very pure and dry otherwise we will end up getting approximate melting point that won't help us identification of that particular compound.

d.IR or Infrared spectroscopy in organic chemistry is used for the identification of functional groups, in our case both erythro and threo compounds are having same functional groups, therefore, melting point determination will be a better method to differentiate between threo and erythro products in brominatio n of trans-cinnamic acid.