Question

Question. A chemist is summoned to an abandoned waste-disposal site to determine the contents of a leaking, corroded barrel. The barrel reeks of an overpowering fishy odor. The chemist dons a respirator to approach the barrel and collect a sample, which she takes to her laboratory for analysis.

The mass spectrum shows a molecular ion at m/z101, and the most abundant fragment is at m / z86. The IR spectrum shows no absorptions above 3000 cm^-1, many absorptions between 2800 and 3000 cm^-1, no absorptions between 1500 and 2800 cm^-1, and a strong absorption at 1200 cm^-1. The proton NMR spectrum shows a triplet
(J = 7 HZ ) at 2.4, with integrals of 17 spaces and 11 spaces, respectively.

1. Show what structural information is implied by each spectrum, and propose a structure for the unknown toxic waste.
2. Current EPA regulations restrict the disposal of liquid wastes because they tend to leak out of their containers. Propose an inexpensive method for converting this waste to a solid, relatively odorless form for reburial.
3. Suggest how the chemist can remove the fishy smell from her clothing.

Short answer

(a)

(b)An inexpensive method for converting the waste to a solid, relatively odorless, is to react the trimethylamine with hydrochloric acid. The pure salt formed will be solid and odorless.

(c) Chemist can remove fishy smell from her clothing by washing her clothing in dilute acid like vinegar or dilute hydrochloric acid and this would form a water soluble salt.

Step-by-step solution

Step-1. Explanation of part (a):

Fishy odor indicates that the unknown compound must be an amine. It has molecular weight 101, means it has odd number of nitrogen atoms and if one nitrogen and no oxygen is present, the remainder is C₆H₁₅. From the mass spectrum data, fragment at 86 means M - 15 which indicates loss of methyl group. The compound is likely to have the following structural piece,

From IR spectrum data, no hydroxyl or no NH means that it must be a tertiary amine. Also, no C=O or C=C or cyanide is present. From NMR spectrum, only a triplet and quartet is observed and integration about 3:2, which indicates it has ethyl groups only. Thus, from all the given data, we can conclude that it has molecular formula C₆H₁₅N, tertiary amine and only ethyl in NMR. Thus, the structure will be as follows.

Structure of the unknown compound

Step-2. Explanation of part (b) and (c):

An inexpensive method for converting the waste to a solid, relatively odorless, is to react the trimethylamine with hydrochloric acid. The pure salt formed will be solid and odorless.

Chemist can remove fishy smell from her clothing by washing her clothing in dilute acid like vinegar or dilute hydrochloric acid and this would form a water soluble salt as shown above.